STUDIES ON THE GERMINATION OFPENSTEMON PARRYI GRAY SEED (GIBBERELLIC

ACID, TEMPERATURE, STRATIFICATION).

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Authors Reaber, Ann Catherine.

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University' Microfilms

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1325621

Raeber, Ann Catherine

STUDIES ON THE GERMINATION OF PENSTEMON PARRYI GRAY SEED

The University of Arizona M.S. 1985

University Microfilms

International 300 N. Zeeb Road, Ann Arbor, Ml 48106

STUDIES ON THE GERMINATION OF

PENSTEMON PARRYI GRAY SEED

by

Ann Catherine Raeber

A Thesis submitted to the Faculty of the

DEPARTMENT OF PLANT SCIENCES

In partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE WITH A MAJOR IN HORTICULTURE

In the Graduate College

THE UNIVERSITY OF ARIZONA

19 8 5

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the. head of the major department or the Dean of the Graduate College when in his or her judgement the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

U) ĉ e-e- )Da^,

CHI WON LEE Date Assistant Professor

This manuscript is affectionately dedicated to Orlou

Raeber, my mother, and Arthur Henkel, my fiance'. Without

their constant love and understanding this composition and

the work it represents would not have been possible.

\.

ACKNOWLEDGEMENTS

My sincere thanks are extended to Dr. Chi Won Lee

for his friendship and continual encouragement during the

course of this study. Additionally, I wish to thank Dr.

David A. Palzkill and Dr. Ronald C. Smith for their interest

and support throughout my graduate studies at the University

of Arizona.

I am especially indebted to Nancy Rue, her unmatched

and willing clerical support were deeply appreciated and

will not go unforgotten.

I would also like to extend my gratitude to all my

friends in the Plant Science departmental family— faculty,

staff, and fellow students. They have truly made Arizona to

be my "home away from home".

Finally, I owe great appreciation to the staffs of

the Arizona Crop Improvement Association and Agricultural

Communications for their time and generosity in my

endeavors.

iv

TABLE OF CONTENTS

Page

LIST OF ILLUSTRATIONS vii

LIST OF TABLES ix

ABSTRACT x

INTRODUCTION 1

LITERATURE REVIEW . 5

Effect of Temperature 5 Effect of Stratification 7 Effect of Light 9 Effect of Gibberellic Acid 11 Effect of Salinity 12

MATERIALS AND METHODS 14

Seed Collection and Handling 14 Germination Tests 14

Preliminary Greenhouse Tests 14 General Procedure 15 Gibberellic Acid Effects 16 KNO, Effects 16 Temperature and Light Influence 17 Stratification Studies 17 Post GA3~Treatment Storage Effects 18 Salinity Treatment 19

RESULTS AND DISCUSSION 20

Greenhouse Seed Germination Test 20 Effect of Gibberellic Acid 20 Effect of KN03 21 Effect of Temperature and Light 27 Effect of Stratification 33 Stratification and GA_ Interactions 36 Effect of Post GA_-Treatment 40 Effect of Salinity 40

v

vi

TABLE OF CONTENTS—Continued

Page

SUMMARY AND CONCLUSIONS 50

LITERATURE CITED 53

LIST OF ILLUSTRATIONS

Page

Figure

1. The Sonoran Desert and its vegetational subdivisions 3

2. Changes in percent germination of Penstemon parrvi seed as affected by planting date 22

3. Changes in percent germination of Penstemon parrvi seed as affected by 24 hour soak treatments with 7 different concentrations of

GA3 23

4. Changes in percent germination of Penstemon parrvi seed as affected by continuous application of 7 different concentrations of GA3 24

5. Changes in percent germination of Penstemon parrvi seed as affected by 24 hour soak treatments of 500 ppm GA.,, distilled water and 0.2 % KN03 f 28

6. Changes in percent germination of Penstemon parrvi seed as affected by 6 different temperatures under lighted conditions 29

7. Changes in percent germination of Penstemon parrvi seed as affected by 6 different temperatures under nonlighted conditions 30

8. Changes in percent germination of Penstemon parrvi seed as affected by stratification time 34

9. Changes in percent germination of Penstemon parrvi seed as affected by cold stratification and presoak seed treatments 35

10. Changes in percent germination of Penstemon parrvi seed as affected by prestratification soaks of various concentrations of GA^ 37

vx 1

viii

LIST OF ILLUSTRATIONS—Continued

Page

11. Changes in percent germination of Penstemon parrvi seed as affected by poststratification soaks of various concentrations of GA^..... 38

12. Changes in percent germination of GA., treated and nontreated Penstemon parrvi seed without storage 42

13. Changes in percent germination of GA., treated and nontreated Penstemon parrvi seed after storage for 15 days at 5° and 25°C 43

14. Changes in percent germination of GA^ treated and nontreated Penstemon parrvi seed~after storage for 30 days at 5° and 25°C 44

15. Changes in percent germination of GA^ treated and nontreated Penstemon parrvi seed~after storage for 45 days at 5° and 25°C 45

16. Changes in percent germination of GA., treated and nontreated Penstemon parrvi seed after storage for 60 days at 5° and 25°C 46

17. Changes in percent germination of GA3 treated and nontreated Penstemon parrvi seed as affected by various salinity (NaCl) levels 48

LIST CF TABLES

Page

Table

1. Effect of different gitberellic acid concentrations applied by two treatment methods on the germination of Penstemon parrvi seed in 5 and 10 days 25

2. Effect of different treatment methods of various concentrations of GA3 on the germination of Penstemon parFvi seed in 5 and 10 days 26

3. Effect of incubation temperature on the germination of Penstemon parrvi seed in 5 and 10 days in the presence and absence of light 31

4. Effect of light on the germination of Penstemon parrvi seed in 5 and 10 days at various incubation temperatures 32

5. Effect of various stratification periods and GA_ concentrations on the germination of Penstemon parrvi seed 39

6. Effect of length of storage at 25°C following GA_ treatment on the germination of Penstemon pafrvi seed 41

•7. Effect of various salinity (NaCl) levels on the germination of Penstemon parrvi seed 49

ix

ABSTRACT

The effects of gibberellic acid (GA_), temperature,

light, cold stratification, potassium nitrate (KNO^), and

salinity on the germination of Fenstemon parrvi Gray

(Scrophulariaceae) seed were investigated. Seed treatment

with 50-500 ppra 144-1-44 mM) GA-, for 24 hr greatly

enhanced germination. The GA^ treated seeds, after drying,

retained their initial enhanced germination potential over a

6 month period. The optimum temperature range for seed

germination was 15-20°C in both the light and dark.

However, light significantly reduced seed germination when

the temperature was below or above the optimum. Neither

seed stratification at 5°C nor seed soaking in 0.2 % KNO^

was as effective as GA^ treatment in inducing germination.

Imbibition of seed in sodium chloride (NaCl) concentrations

higher than 6000 ppra (102.6 mM) severely inhibited

germination.

x

IMTP.ODUCTIQW

Penstemon parrvi Gray (Scrophulariaceae), commonly

Jcnown as Parry penstemon or desert beardtongue, is a drought

tolerant wild flower native to the Sonoran desert and its

surrounding semi-arid regions. Its tall spikes of pink

tubular flowers contrast the dominantly yellow and orange

color of the spring flowers in the desert regions.

Depending on the elevation, desert beadtongue blooms from

early March until late June. A short-lived, herbaceous

perennial, Farryi penstemon has an erect growth habit

reaching up to 120 cm in height and produces one to several

flowering stems per plant. The plant has a variable leaf

shape depending on the location on the stem. Basal leaves

are elliptic, spatulate or oblanceolate, narrowing to a

winged petiole while leaves of the upper stem are lanceolate

and clasping to the stem. The paniculate infloresences are

10 to 50 cm long with few to many flowers per peduncle at

each node. The cup shaped calyx consisted of 5-parted sepals

with short acuminate tips is usually pubescent. The tubular

corolla is rose-magenta in color with 5-parted petals. The

length of the corolla is 13 to 21 mm with a diameter of 10

to 15 ram at the mouth. There are four stamens , 8 to 12 mm

long with glabrous and peltately explanate anther sacs. The

staminodium is dilated apically and retrorsely bearded with

1

stiff yellow hairs. The pistils are 8 to 12 mm long with 2-

celled carpels. The seed capsules are ovoid, 4 to 6 mm long

each containing 20 to 150 seeds. The crescent shaped seeds

measure 2 mm long and 1 mm thick,and have dark colored seed

coats at maturity (Kearney and Peebles, 1951; Shreve and

Wiggins, 1964).

The distribution of Fenstemon parrvi ranges from

southern Gila and Maricopa counties in Arizona to southern

Sonora, Mexico. Eased on the collection samples in the

University of Arizona herbarium, parrvi has been located

in Maricopa, Gila, Cochise, Santa Cruz, Pinal, and Pima

counties in Arizona. In Sonora, this species has been

identified in the Magdalena, Curcurpe, Bevispe, Banamichi,

Tesopaco, and San Bernardo regions. Roughly, this

represents the vegetative subdivision described as the

Arizona Uplands (Figure 1). The native stands of P.

penstemon range in elevation from 1,500 feet in the Sauceda

Mountains in Maricopa county to 5,200 to 5,400 feet at the

North fork of Big Casa Blanca Canyon in the Santa Rita

Mountains of Santa Cruz County. (Mason, 1985).

Penstemon parrvi thrives on hillsides, well drained

slopes and mountain canyons leading down to the desert.

Often, it is found growing under the protection of Acacia

crrecrcrii (catclaw acacia) and is commonly associated with

many desert cacti including Qpuntia spp., Ferocactus spp.,

and Carneqiea qicrantum, and many of the desert grasses.

NEE ILE5

OUAPTZSITE

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EL CfNTftC

SAN LUIS

rueSON y&'-. LSONSTTTA ENSENAOA V7

SASABE OOU61M

•zaisn

m A*MO HCRMDSt

mTHA

CA'.MALL'

TA ROSAUA SAN IGNACLO

MULEGT

' H i F O F T H E

S O N O R A N D E S E R T V/ / / l f )> IA LOWER COLORADO VALLEY I' '•••:'• ARIZONA UPLAND LLLLLLLLLLLLL PLAINS OF SONORA

FOOTHILLS OF SONORA w/ir/rri CENTRAL GULF COAST lllllllllllll VIZCAINO REGION FE——J MAGDALENA REGION

=3.

Figure 1. The Sonoran Desert and its vegetational

subdivisions (Shreve and Wiggins, 1964).

4

Parrvi penstemon is gaining popularity as a drought

tolerant, perennial flower used for desert landscaping in

southern Arizona (Duffield and Jones, 1981; NVCAC-SCS,

1973). Once established, it continues to proliferate,

adding vibrant color and beckoning hummingbirds to home

gardens in the spring. Pj_ parrvi also has the potential for

development as an attractive flowering potted plant or a cut

flower in commercial flower industry. A preliminary study

indicated that this species can produce flowering plants

throughout the year. However, the lack of seed germination

under greenhouse conditions was a major problem. The

objective of this study was to determine optimal conditions

for germination of P.;. parrvi seed. Parameters considered

were the effect of environmental conditions (temperature,

light and salinity) and the influence of chemical treatment

on seed germination.

LITERATURE REVIEW

Effect of Temperature

Temperature plays a significant role in germination

of seeds of many species. Many of the earliest temperature

studies focused on the determination cf optimum temperature

for seed germination.. The concept that every plant species

has an upper (maximal) and a lower (minimal) temperature

limit was identified as early as 1860 by Sachs. Seed

germination temperatures are usually well below that suited

for subsequent growth of the seedling (Toole et al., 1955).

According to Koller (1969), temperature dependence of seed

germination is related to differences in climatic conditions

in which plants are adapted. In his experiments, seed of

higher latitude plants germinated better at lower

temperatures (7-12°C) than at higher temperatures (27°C) as

compared to those of the lower latitude plants. As seeds

were collected progressively further south within the United

States, optimum temperatures for seed germination

increased.

Seeds of cool weather cocklebur remain dormant

during the high summer temperatures (Thornton, 1935). Once

the temperature decreases, as winter approaches, dormancy in

this plant is broken. High temperature inhibition of

germination may be due to lack of oxygen available to the

5

6

seed embryo (Come and. Tissaoui, 1973). The higher the

temperature in which the seeds are placed to germinate, the

smaller the quantity of oxygen available to the embryo since

oxygen becomes less soluble in water when temperature rises

and a smaller quantity reaches the embryo.

Unfortunately, most of the earlier work on

temperature studies focused on vegetable crops, (Kotowski,

1926; Edwards, 1332). Heit (1950), after recognizing the

paucity of previous concern for testing seed of flower

species, offered a guide to laboratory testing of several

flower seed sensitive to cool and warm temperatures. In

this guide, he identified several Penstemon cultivars as

being sensitive to warm temperature for germination.

Penstemon crloxinoides. P. hartweqii and other penstemon

mixtures showed a higher germination percentage (75-85 %) at

15°C than at 25° when scored for 28 days.

Maguire and Overland (1972) demonstrated varying

temperature responses among three Penstemon species.

Treatments included 15°C in darkness, 15° with alternating

light and darkness, 20° in darkness, 20° and 30°

alternating in darkness and 20° and 30° alternating with

alternating light and darkness. Penstemon procurus did not

germinate at 15° in darkness while the remaining treatments

gave 72 % germination. Penstemon wilcoxi did not germinate

at any of the treatments. Penstemon speciosa seeds

germinated 38 % at 20° and 30° alternating in darkness,

7

but no germination was observed when these alternating

temperatures were combined with alternating light and

darkness.

Asclepias tubsrosa. Liatrls pycnostachva, Liatris

aspera, and. Penstemon grandiflorus studied by Salac and

Hesse (1975) gave excellent germination when the day and

night temperatures were alternated between 33° and 19°C.

Kaspar and McWilliams (1982, 1983), and Kaspar, McWilliams,

and Grigg (1982) .also showed the varying temperature

responses of wildflower seeds for germination. Seeds of

Coreopsis tinctoria had an optimum germination temperature

of 30°, although they germinated over a temperature range of

20°-30° . Ipomosis rubra seed germination was less than 4 %

regardless of temperature. Linum perenne seeds germinated

optimally at 20° .

Effect of Stratification

In certain plants such as cocklebur, peach and plum,

seeds require a pregermination chilling treatment to

overcome their dormancy (Thornton, 1935; Lin and Boe, 1972;

Lipe and Crane, 1966). The optimal length of chilling time

and the optimal temperature to cool depend upon 'the native

climatic conditions for a given species. According to

Westwood and Bjornstad (1948), species from warm winter

climates required a shorter chilling time at a higher

optimum chilling temperature (7-10°C) than those from cooler

climates, which required chilling temperatures from 3 to

8

5°C. Lin and Boe (1972), studying the natural dormancy of

plum seeds, reported that low temperature seed

stratification reduced abscisic acid (ABA) concentration,

while increasing gibberellin (GA) substances in the tissue.

Villiers and Wareing (1965) reported similar findings in

Fraxinus excelsior. They found that cold treatment

increased the amount of growth promoter, notably GA or GA-

like substances.

In investigations by Lipe and Crane (1966), peach

seed dormancy was found to be due to a substance similar to

dormin which disappears or may be inactivated during

stratification of the seeds. Yet another explanation is

given by Bradbeer (1968) and Ross and Bradbeer (1968). They

hypothesized that chilling either overcomes a block to GA

synthesis or promotes the subsequent rate of GA synthesis to

exceed GA consumption. One additional point he made was

that, although chilling may activate the mechanism for GA

synthesis, synthesis will only occur at the germination

temperature and not at the chilling temperature.

In' studies on Penstemon, Nichols (1934) showed the

varying response of selected native American plants to cold

temperature exposure. Seeds of Penstemon spesiosa responded

favorably to a pre-germination cold storage treatment in a

study by Maguire and Overland (1972). Seeds stored for 1 to

4 weeks at 3°C showed a 50 to 70 % germination increase over

non-stratified seed under germination conditions of constant

9

20°. According to Blake (1935), Penstemon grandiflorus

seeds did not germinate after periods of dry storage at

freezing and room temperatures, but cool moist

stratification gave 38 % germination. Seeds of Penstemon

crrandif lorus. Asclepias tuberosa, and Liatris aspera

stratified at 4° showed a significant increase in

germination over dry storage at 4° or 20° in studies

presented by Salac and Hesse (1975). The requirement for

low temperature treatment for overcoming dormancy of

Penstemon crrandiflorus was also noted by Salac (1982) and

Salac and Traeger (1982). Their study revealed most

successful germination of this species in November.

Effect of Light

Exposure to light can stimulate or inhibit

germination of seeds, depending upon age, previous handling,

and accompanying temperature. Flint and McAlister (1935) and

Borthwick et al. (1954) discovered this phenomenon in their

classical studies with 'Grand Rapids' lettuce seed. They

noted that germination in imbibed seeds of some lettuce

varieties was promoted by irradiation with the red portion

of the light spectrum but inhibited by irradiation with the

infared portion. Further studies by Borthwick et al. (1954)

concluded that maximum sensitivity for promotion of

germination was found in the region 6400- 6700 A (red light)

and for inhibition in the range 7200-7500 A (infared light).

10

Phytochrome is the photoreceptor responsible for

light stimulus. Red light converts P , the probably

inactive form of phytochrome, to Pf , the active form, which

sets up a whole range of morphogenic responses, including

seed germination (Smith, 1973; Borthwick et al., 1954; Flint

and McAlister, 1935). Dark germinating seeds contained non-

limiting proportions of while light requiring seeds

contained limiting quantities of P^. (Smith, 1973). The

photoreaction, while possibly present in all seeds, was not

obligatory for germination of all seeds, according to Toole

et al. (1955). It controls the levels of two compounds

which are also under control by other reactions subject to

influence by temperature.

In studies on Penstemon species, Mitchell (1926)

showed that P^ digitalis gave 32 % germination under light

but no germination in the dark. Light is recommended for

germinating Pj. barbatus, Pj_ crrandif lorus, P. laevigata, and

P. hirsutus according to AOSA (Association of Official Seed

Analysts, 1981). Salac and Hesse (1975) reported that P.

crrandif lorus exhibited greatest germination under conditions

of alternating long days and short nights.

Other considerations for seed germination include

the sensitivity of seeds to light duration (Hammond, 1959;

Wareing, 1963) as well as sensitivity to light intensity

(Corbineau and Come, 1982).

11

Effect of Gibberellic Acid

It is well known that gibberellins, more than any

other hormone, are involved in the initiation of germination

(Hartman and Kester, 1959; Khan, 1971, Jacobsen and Varner

1967; Chrispeels and Varner 1967; Frankland and Wareing,

1962). Mayer and Shain (1974) described the physiological

enzymatic activities in the cotyledons and endosperm which

regulate the action of hormones and other growth substances

during germination. They found that, during germination of

pea seeds, an increasing amount of bound gibberellins is

converted into free gibberellins, which are then transported

from the cotyledons to the embryo. Gibberellic acid enables

the embryo to germinate by initiating the production of

amylolytic and other hydrolytic enzymes needed for the

utilization of the food reserve in the seed. Mathur et al.

(1971) showed that a conversion of GA7 to GA3 takes place

during the stratification of peach seeds which leads to

increased germination.

Exogenously applied GA3 was effective in breaking

dormancy in hazel (Corvlus avellena) seed (Bradbeer and

Pinfield, 1967). They found enhanced activities of certain

enzymes, particularly those involved with mobilization of

cotyledonary oil reserves in the GA3 treated seeds. Hammond

(1959) demonstrated that the embryo and inner seedcoat

dormancy of guayule achenes were completely broken by

treating the seed with GA^ or NaOCl (sodium hypochlorite)

12

when germinated under supplemental lighting for four days.

A study by Naqvi and Hanson (192C) showed that the best

germination of guayule seeds involved soaking the seeds

eight hours in distilled water and then treating with a

solution of GA^ and NaOCl. NaOCl increases the permeability

of the seed coat to oxygen and water and therefore improves

germination.

Seeds of some hybrids of Antirrhinum species

(Scrophulariaceae) have been shown to require treatments of

potassium nitrate (KN03> to overcome dormancy, according to

the AOSA (1981). However, no literature has been found on

the effect of chemical treatment on the germination of

Penstemon species.

Effect of Salinity

The effect of salinity on seed germination has been

studied by Ayers (1949). The kind and the amount of salt

may influence germination. According to Ayers, soil salinity

may affect the germination of seeds in two ways, either by

decreasing the ease with which seeds take up water or by

facilitating the entry of ions in sufficient amounts to be

toxic. These effects resulted in slower emergence of

germinating seeds as well as an overall decrease in total

germination (Uhvits, 1946 and Ayers and Hayward, 1949).

Another consideration is salt tolerance of plants at

various temperatures during seed germination. Ahi and

Powers (1938) found that temperature was a dominant factor

13

in the germination and growth cf plants under saline or

alkaline conditions. They summarised earlier work on salt

tolerance and presented tolerance levels for various crop

species. Upper limits of salt stress at which Suaeda

monoica seeds would germinate were 0.4 M NaCl at 20°C and

0.3 M at 30° (Waisel and Ovadia, 1972). Germination in S.

monoica occurred predominantly in the winter when soil

salinity stress was reduced by increased precipitation.

During the summer months, higher soil salinities in the

surface soil layers inhibited seed germination of this

species. Ungar (1978) determined fluctuations in the growth

regulator concentration to be directly affected by soil

stress. Soil salinities could therefore be considered an

important limiting factor in determining when germination

takes place. No literature on the effect of salinity on

Penstemon species has been found.

MATERIALS AMD METHODS

Seed Collection and Handling

Mature Penstemon parrvi seed was collected in June

from native stands in the Picture Rocks Pass area of the

Tucson Mountains west of Tucson. Seed was separated from

large stem pieces with the aid of grain sieves (Seedburo

Equipment Co., Chicago, ID. Further cleaning of the seed

was accomplished with a South Dakota Blower (E.L. Erickson

Products, Brookings, S.D.) to eliminate very light

impurities. Finally, an A'ooga Crafts (Brookings S.D.)

purity hoard was used to remove any seed-size debris

remaining. For each experiment seeds were counted using a

grain seed counter (The Old Mill Co., Savage, MD). The

cleaned seeds were stored at room temperature (22°-25°C) for

various lengths up to a year until use.

Germination Tests

Preliminary Greenhouse Tests

Monthly plantings of Penstemon parrvi seed were made

from August to March. Four hundred prestratified (4 weeks

moist, 5°C) seeds were planted in Peat-lite mix (1

vermiculite : 1 peat) contained in galvanized steel flats

(38 x 53 x 10 cm). Germination counts were checked

regularly for 3 months.

14

General Procedure

Eight replicates of the 100 seed samples were used

in the stratification studies. In all other experiments,

four replicates of the 100 seed samples were used. All

experiments were repeated once. Each 100 seed sample was

germinated in a plastic petri dish (Falcon 100 x 15 mm) on

top of 3 layers of Whatman No. 1 filter paper. The filter

papers were saturated with 7 ml of sterile distilled water

in all cases, except where GA3 solutions were applied

directly to the filter paper. In the latter case 7 ml of

the appropriate GA^ concentration was applied to the

germination paper. The petri dishes were sealed with a

strip of Parafilm (American Can Co., Greenwich, CT) to

maintain high moisture levels and placed in an incubator.

Unless mentioned otherwise, seed germinations were scored

daily for a 10 day period. In all experiments, treatments

as well as replications were completely randomized.

Seeds that produced visible radicles (1 mm long)

were considered as germinated. Results were scored in

percentages which were then transformed to arcsine values

for statistical analysis. The analysis of variance (ANOVA)

was performed by a computer using the Statistical Package

for the Social Sciences (SPSS) program and the mean

separations were made by Duncan's or Student-Newman-Keuls

multiple range tests on the transformed data.

16

Gibberellic Acid Effects

Each of the 100-seed samples was wrapped in a 5 x 5

cm Miracloth (Chilopee Mills, Milltown, N.J.) and was

treated in 250 ml of distilled water containing 0, 10, 50,

100, 200, or 500 ppm (0, 0.028, 0.144, 0.289, 0.577 or 1.444

mM, respectively) GA, for 24 hr at 25°C. Treated seeds were

removed from the solution, blot-dried in a paper towel and

uniformly spread on the surface of moistened filter paper in

a petri dish prepared as described above. In another

experiment, nonsoaked seeds were germinated on filter paper

moistened with 7 ml aliquots of 0, 10, 50, 100, 200, or 500

ppm (0, 0.028, 0.144, 0.289, 0.577 or 1.444 mM,

respectively) GA^ solutions. To each petri dish, an

additional 1 ml of each concentrate solution was applied

again on the 5th day.

KN03 Effects

The effect of KNO^ was evaluated under both lighted

and nonlighted conditions. Four 100 seed lots were soaked

in 0.2 % KN03 for 24 hr at 25°C. The treated seeds then

were germinated in a 15°C incubator under constant

fluorescent light. Dark treatment was provided by wrapping

the petri dishes with aluminum foil. Nontreated controls as

well as 0 and 500 ppm GA^ seed soaks were used for

comparison. Seed germination was scored for 12 days.

17

Temperature and Light Influence

The effect of incubation temperature on seed

germination was investigated at 5, 10, 15, 20, 25, and 30° C

in the presence and absence of light (intensity 17-69 uraol

-1 -2 s m ) using the seed soaked in 500 ppm GA^ for 24 hr.

For dark treatments, seeds were presoaked in the dark and

then placed in each petri dish under a 40-watt fluorescent

lamp filtered with a monochromatic green filter (No. CBS

Green 545, Carolina Biological Supply Co., Burlington,

N.C.). The petri dishes then were wrapped immediately with

aluminum foil and incubated with unwrapped petri dishes

(light treatment) in constantly lighted incubators having

the 6 diferent temperatures. Seed germinations were scored

on the 5th and 10th day. For the dark-treated seeds, counts

were made under the same green-filtered light described

above. These precautions were taken to eliminate red-far

red light effects on seed germination during counts.

Stratification Studies

For stratification studies, seeds were wrapped in

Miracloth and placed with moist Sphagnum peat moss in clear

polyethylene bags. Seeds were soaked in 0, 10, 50, 100, and

500 ppm GA3 for 24 hr prior to and after stratification.

Both GA^ soaked and nonsoaked seed were stored in the dark

at 5°C for one to four weeks. Sample preparation and

placement in storage was done weekly so that seed

germination tests for all treatments could be performed at

18

the same time, immediately after removing the seeds from

cold storage. Along with these stratified seeds,

nonstratfied seeds soaked in various concentrations of GA^

for 24 hr and non-soaked seeds were germinated for

comparison. All seeds were germinated at 15°C in the dark

for 10 days.

Post GA^-Treatment Storage Effects

The longevity of GA treatment effects was

investigated. Miracloth seed packages containing 100 seed

were treated with 500 ppm GA^ and distilled water for 24 hr.

Nonsoaked seeds were used as a control. The treated seeds

were allowed to air dry and then placed in Manila seed

envelopes. Seeds were kept in storage conditions of 5 and

25°C (room temperature). Four representative samples of

each treatment and each storage temperature were removed

after 15, 30, 45, and 60 days and allowed to germinate in a

non lighted 15°C incubator. Daily germination was scored

for 10 days.

In an additional experiment, GA^ (500 ppm) treated

seeds stored at room temperature (25°C) were allowed to

remain in storage up to 6 months. Seed samples were removed

and scored for germination as described earlier after 0, 15,

30, 45, 60, 75, 90, 120, 150, and 180 days in storage.

19

Salinity Treatment

The effect of salinity on seed germination was

studied by using 0-10,000 ppm (0-171 mM) sodium chloride

(NaCl) applied to the germination plates in place of water.

Salinity levels were checked with a Wescor Vapor Pressure

Osmometer (Wescor Co., Logan, UT). Seeds which were

presoaked in water and in GA3 for 24 hr and non-soaked seeds

were used to compare the interactions of these treatments

with salinity. The germination was scored throughout 12

days at 15°C.

RESULTS AND DISCUSSION

Greenhouse Seed Germination Test

A preliminary result showed that the germination of

Penstemon parrvi seed under greenhouse conditions was

erratic. As shown in Figure 2, percent seed germination

tested over a period of 8 months never exceeded 20 %. Seeds

planted during October gave the highest germination (20 %)

with a gradual decline in percent germination in later

plantings. Since the germination was scored 3 months after

seed planting, the highest germination was actually noticed

in January and the lowest germination in June.

The seasonal fluctuation of percent seed germination

indicates a possible influence of temperature. Although the

greenhouse was heated by a gas heater, the maximum

temperature during the daytime was lower in the winter

months than in spring and summer months. Hence, the trend

suggests that low temperature is favorable for seed

germination. The low and non-uniform germination

percentages found for E\>_ parrvi would make it difficult to

routinely produce as a flowering potted plant.

Effect of Gibberellic Acid

Gibberellic acid applications had a profound

influence on seed germination at 15°C. Percent seed

germination as affected by 6 concentrations of GA^ applied

21

for 24 hr as a presoak and. applied directly to the petri

dishes during germination are shown in Figure 3 and Figure

4, respectively. In both treatment methods, percent

germination increased with increasing concentrations of GA^

up to 500 ppm. Although the mean germination scores were

higher as GA^ concentrations increased, no statistical

difference was detected amcnrr the tre-atraent zneans for GA^

concentrations higher than 50 Fpm (Table l}. Seeds that

received 24 hr presoaking of GA, germinated earlier than

those seeds not presoaked but treated during germination

(Table 2). Generally, seeds presoaked in GA, reached a peak -J

germination one day faster than those seeds non-pretreated.

The relationship has not been studied at other temperature

ranges or various light conditions. Although both GA^

application techniques show high germination response, the

direct application technique of seed treatment is less

feasible in practice. Seed treatment at the time of

planting requires more time and a better controlled

germination environment to keep the seed in contact with GA^

solutions.

Effect Q£ KNO^

Effects of potassium nitrate (KNO^) treatment on the

germination of P^_ parrvi seed under light and dark

conditions are shown in Figure 5. In this figure, the

effects of GA^ and water soak on seed germination are also

22

50

40

P 30

Aug Sep Oct Nov Dec Jan Feb Mar

PLANTING MONTH

Figure 2. Changes in percent germination of Penstemon parrvi seed as affected by planting date. Germination was scored 3 months after planting.

23

100..

g50

1-NO TREATMENT 2-0 PPM GA 3-10 PPM GA 4-50 PPM GA 5-100 PPM GA B-200 PPM GA 7-500 PPM GA

DAYS AFTER TREATMENT

Figure 3. Changes in percent germination of Penstemon parrvi• seed as affected by 24 hour soak treatments with 7 different concentrations of GA-,.

24

100. .

90. .

230.1. u tr LLl £L

1-NO TREATMENT 2-0 PPM GA 3-10 PPM GA 4-50 PPM GA 5-100 PPM GA 6-200 PPM GA 7-500 PPM GA

2. 3. 4. 5. 6. 7. 8. 9. 10.

DAYS AFTER TREATMENT

Figure 4. Changes in percent germination of Fenstemon parrvi seed as affected by continuous application of 7 different concentrations of GA^.

25

Table 1. Effect of different gibberellic acid concentrations applied by two treatment methods on the gerrtinaticn of Penstemon parrvi seed in 5 and 10 days.

% Germination2

5 Days 10 Days

GA-, (pplti}

Direct treatment"

24 hr Direct Tr presoak treatment-'

24 hr presoak

0 0 . 0 + 0 . 0 w a 3. 3 + 2. 8 a 11. 8 + 4. 3 a 18. 0 + 7. 3 a

10 0 . 0 + 0 . 0 a 7. 0 + 4. 7 a 38. 0 + 2. 3 b 38. 5 + 9. 9 b

5 0 0 . 0 + 0 . 0 a 22. 8 + 5. 0 ab 74. 3 + 2. 9 r 83. 5 ± 2. 1 c

100 0 . 8 + 0 . 9 a 32. 8 + 4. "3 mJ b 75. 8 + 3. 8 c 92. 0 ± 0 . 8 c

200 0 . 6 + 0 . 6 a 53. 3 + 7. 8 c 86. 8 + 2. 1 c 94. 5 ± 2. 4 c

500 0 . 8 + 0 . 5 a 66. 5 + 4. 5 c 87. 3 + 3. 4 c 96. 5 + 2. 4 c

•" Seeds were germinated at 15° C in dark.

^ Seeds were germinated continuously in GA^ solutions

applied to filter paper.

x Seeds were soaked for 24 hr in GA^ solutions and then

germinated in sterile distilled water.

w Mean (+ SD) separation in each column was made by Duncan's

multiple range test at the 5% level, using arcsine

transformed data.

26

Table 2. Effect of different treatment methods of various concentrations of GA-, on the germination of F?nstemon carrvi seed in 5 and 10 days.

% Germination"

5 Days 10 •Days

GA_ Direct 24 hr Direct . 24 hr ( p p f l i ) treatment-' presoak treatment^ presoak

0 0 . 0 + 0 . 0 aw 3. 3 + 2. B a 11. 8 + 4. • 3 a M

CD

•

0 + 7. 3 a

10 0 . 0 + 0 . 0 a 7. 0 + 4. 7 b 38. 0 + 2. 9 a 38. 5 + 9. 9 a

50 0 . 0 + 0 . 0 a 22. 8 + 5. 0 b 74. 3 + 2. 9 a 83. 5 + 2. 1 b

100 0 . 8 + 0 . 9 a 32. 8 + 4. 3 b 75. 8 + 3. 8 a 92. 0 + 0 . 8 b

200 0 . 6 + 0 . 6 a 53. 3 + 7. 8 b 86. 8 + 2. 1 a 94. 5 + 2. 4 b

500 0 . 8 + 0 . 5 a 66. 5 + 4. 5 b 87. 3 + 3. 4 a 96. 5 + 2. 4 a

~ Seeds were germinated at 15° C in dark.

y Seeds were germinated continuously in GA^ solutions

applied to filter paper.

x Seeds were soaked for 24 hr in GA^ solutions and then

germinated in sterile distilled water.

w Mean (+ SD) separation in each row was made by Duncan's

multiple range test at the 5% level, using arcsine

transformed data.

V

27

presented for comparison. The KNO^ treated seeds gave

a higher germination percentage in the dark than in the

light.' While the KNO^ treated seeds gave a higher seed

germination as compared to the nonsoak control, maximum

germination reached only 35 %, much lower than that of GA^

treated seed (Figure 5). KN03 has been known to stimulate

seed germination in some Scrophulariaceae plants (AOSA,

19815. However, the results of this study show that the

influence of KNO^ is minimal as compared to that of GA^ in

inducing seed germination in P_s_ parrvi.

Effect of Temperature and Light

The changes in percent seed germination as

influenced by 6 different temperatures in the light and in

the dark are shown in Figures 6 and 7, respectively. Higher

germination was recorded in the dark throughout the interval

tested. This difference was not always significant, as seen

in Table 3. At five days, germination was the highest at

20° and 15° C in the light and the dark, respectively. No

statistical difference was found, however, among 15°, 20°,

and 25°C under light or dark conditions. Similarly, at ten

days, no statistical difference in % germination was found

between 15° and 20°C in either light or dark (Table 3).

Comparisons between light and dark treatments were made at

each temperature (Table 4). No statistical difference

between light and dark was found within the optimum

temperature range, although germination was constantly

28

100,

90, 1-NO TREATMENT 2-24 HR WATER SOAK 3-24 HR 500 PPM GA SOAK 4-24 HR 0.2% KN03 SOAK (DARK) 5-24 HR 0.2% KN03 SOAK CLIGHT)

80,

70,

60,

LD

t-30. L

10..

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12,

DAYS AFTER TREATMENT

Figure 5. Changes in percent germination of Penstemon parrvi seed as affected by 24 hour soak treatments of 500 ppm GA^, distilled water and 0.2 % KNO^.

29

100.

90. 1-5 DEGREES CELSIUS 2-10 DEGREES CELSIUS 3-15 DEGREES CELSIUS 4-20 DEGREES CELSIUS 5-25 DEGREES CELSIUS 6-30 DEGREES CELSIUS

80,

70.

60.

20.

10,

1. 2. 3. 4. 5. 6. 7, 8, 9, 10.

DAYS AFTER TREATMENT

Figure 6. Changes in percent germination of Penstemon parrvi seed as affected by 6 different temperatures under lighted conditions.

30

100. ̂

1-5 DEGREES CELSIUS 2-10 DEGREES CELSIUS 3-15 DEGREES CELSIUS 4-20 DEGREES CELSIUS 5-25 DEGREES CELSIUS 8-30 DEGREES CELSIUS

90,

80.

70. L

60,

<

20.

10. .

1. 2. 4. 3. 5. 7. 6. 8.

DAYS AFTER TREATMENT

Figure 7. Changes in percent germination of Penstemon parrvi seed as affected by 6 different temperatures under nonlighted conditions.

31

Table 3. Effect of incubation temperature on the germination of Penstemon parrvi seed in 5 and 10 days in the presence and absence of light.

% Germination"

5 Days 10 Days

I CIUP •

(°C) Light' Darkx Lighty Dark

5 o

o

+

o •

o aw o

• o

+ 0.0 a

o •

o + o

o

a

o •

o +

o •

o a

10 0.0 + 0.0 a 0.0 + 0.0 a 49.5 + 14.2 c 73.5 + 5.1 b

15 22.5 + 5.2 b 64.0 + • 12.7 b 91.0 + 1.4 d 95.0 + 1.6 c

20 30.8 + 8.5 b 58.0 + 6.5 b 80.5 + 10.8 d 90.8 + 5.9 c

25 24.5 + 7.6 b 60.0 + 7.9 b 33.0 + 7.2 b 80.5 + 5.4 be

30 0.5 + 0.6 a 0.3 + 0.5 a 0.8 + 0.5 a 0.5 + 0.6 a

" A l l see d s w e r e p r e s o a k e d i n 5 0 0 p p m G A ^ f o r 2 4 hr pr i o r

to germination.

v -1 -n J Light intensity varied 17-69 AIE S M " under cool-white

fluorescent lamps.

x Seeds were incubated in petri dishes wrapped in aluminum

f oi 1»

w Mean (+ SD) separation in each column was made by Duncan's

multiple range test at the 5% level, using arcsine

transformed data.

Table 4. Effect of of light on the germination Penstemon parrvi seed in 5 and 10 days at various incubation temperatures.

% Gerirnnation

5 Days 10 Days

Temp. (°C) Light" Dark* Light^ Darkx

5 o

o

+

o •

o aw 0.0 4 -

o

d a

o

o + 0.0 a

o

d + o

o

3

10 0.0 + 0.0 a 0.0 + 0.0 a 49.5 + 14.2 a 73.5 + 5.1 t

15 5 + 5.2 a 64.0 + 12.7 b 91.0 + 1.4 a 95.0 + 1.6 a

20 30.8 + 8.5 a 58.0 + 6.5 b eo.5 + 10.8 a 90.8 + 5.9 a

25 24.5 + 7.6 a 60.0 + 7.9 b 33.0 + 7.2 a 80.5 + 5.4 b

30 0.5 + 0.6 a 0.3 + 0.5 a 0.8 + 0.5 a 0.5 + 0 . 6 a

" A l l see d s w e r e p r e s o a k e d i n 5 0 0 p p m G A ^ f o r 2 4 hr p r i o r

to germination,

v -1 J Light intensity varied 17-69 AIE s m " under cool-white

fluorescent lamps.

x Seeds were incubated in petri dishes wrapped in aluminum

foil.

w Mean (+ SD) separation in each row was made by Duncan's

multiple range test at the 5% level, using arcsine

transformed data.

33

better under dark conditions. This difference was only

statistically different under suboptimal temperatures (10°

and 25°C). Since little or no germination occured at 5° and

30°C no comparison was made. The influence of light and

temperature interaction on seed germination is not

conclusive, since temperature was not precisely controlled

inside wrapped and unwrapped petri dishes. Hence, the

clarification of light effect requires further

investigation.

Effect of Stratification

Seed stratification generally increased percent

germination as compared to the control. Figure 8 shows the

cumulative percent germination over a 12-day period as

affected by stratification time. When seed germination was

compared between stratification times, a highest percent

germination (59.5 %) was obtained from 2-3 week treatments.

Seeds stratified for 1 week or 4 weeks gave percent

germination as low as those nonstratified. Stratified

seeds, especially those stored for 2-3 weeks in cold started

to germinate earlier than those of the control or the 500

ppm GA^ treatment. The highest germination percentage (59.5

%) in stratified seed was much lower than that in GA^

treated seed (Figure 9).

Unlike seeds of other species responsive to

stratification, P^. parrvi seeds seem to require a shorter

period of cold storage for maximum germination. A drastic

34

100

90

80

70

60 •

50 •

40

30 •

20 •

0 1 2 3 4 S T R A T I F I C A T I O N T I M E ( w e e k )

Figure 8. Changes in percent germination of Penstemon parrvi seed as affected by stratification time.

35

1-NO TREATMENT 2-24 HR WATER SOAK 3-24 HR 500 PPM GA SOAK 4-1 WK STRATIFICATION 5-2 WK STRATIFICATION 6-3 WK STRATIFICATION 7-4 WK STRATIFICATION

2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

DAYS AFTER TREATMENT

Figure 9. Changes in percent germination of Penstemon parrvi seed as affected by cold stratification and presoak seed treatments.

36

drop in percent germination in 4 week stratification

treatment may have been due to deterioration of the seed

cotyledon tissues caused by microorganisms. The fact that

stratification alone is not as effective as GA^ treatment in

inducing seed germination is especially interesting. The

endogenous chemical regulation involved in the control of

seed dormancy in this species awaits further investigation.

Stratification and GA-, Interactions

As discussed earlier, seed stratification alone gave

generally lower germination percentages than GA^ treatments.

The highest germination percentage was obtained at 3 week

stratification with a decline in germination at 4 week

treatments (Figure 10). The changes in percent seed

germination as influenced by the interactions of various

concentrations of GA^ applied prior to and after

stratification are illustrated in Figures 10 and 11,

respectively. Again, as GA3 concentrations increased

percent germination increased concomitantly regardless of

stratification in both pretreated and posttreated seeds.

Generally, GA^ treatment prior to stratification was more

effective in inducing seed germination when the

stratification time was more than 2 weeks. Germination of

seed treated with GA^ after stratification was significantly

reduced as compared to that of nonstratified seed (Table

5). This indicates that GA^ treatment and stratification do

not augment each other in terms of stimulating germination.

37

-*

5 0 0 p p m G A 3 l O O p p m G A 3 5 0 p p m G A 3 1 0 p p m G A 3 O p p m G A 3

br 60

20 -

0 1 2 3 STRATIFICATION TIME (week)

Figure 10. Changes in percent germination of Penstemon parrvi seed as affected by prestratification soaks of various concentrations of GA^.

38

• • 500ppm GA3 * * 100ppmGA3 * A 5 0 p p m G A 3 a • l 0 p p m G A 3 * • 0 ppm GA3

100

9 0

80 -

z 7 0 -O

5 60 -

£ 4 0

20 •

J 1 1 I I 0 1 2 3 4

STRATIFICATION TIME (week)

Figure 11. Changes in percent germination of Penstemon parrvi seed as affected by poststratification soaks of various concentrations of-GA^.

39

Table 5- Effect of various stratification periods and GA^ concentrations on the germination of Penstemon parrvi seed.'"

% Germination

Treatment GA- 'ppm)

0 10 50 100 500

No Strat. 25. 5 d? 38. 5 f S3. 5 PS 92.0 : r-s 96. 7 s

1 Week Strat. Presoak 12. 0 ab 37. 4 f 84. 0 pq 75.0 m-p 96. 4 s Postsoak 21. 6 be 25. 1 cd 73. 4 m-p 70.3 l-o 96. 3 s

2 Week Strat. Presoak 9. 1 a 53. 5 h-j 82. 3 o-q 82.8 o-q 94. 5 s Postsoak 13. 8 ab 13. 5 ab 58. 5 h-1 54.3 h-k 95. 1 s

3 Week Strat. Presoak 56. 1 h-k 32. 4 f 67. 5 k-n 81.6 o-q 97. 0 s Postsoak 75. 1 m-q 57. 1 h-1 67. 1 i-n 52.3 h 81. 0 O-q

4 Week Strat. Presoak 32. 1 cd 40. 8 fg 79. 5 n-q 91.8 rs 87. 3 qr Postsoak 49. 0 gh 65. 5 h-m 74. 5 m-p 78.1 m-q 79. 3 n-q

z Average values of 8 replications determined after 10 days

from seed placement. Mean separation by Student-Newman-

Keuls procedure at the 5 % level.

^ Mean separation letters are inclusive ranges.

40

The drop in percent gemination in seeds treated with GA^

after stratification may hc.ve been due to reduced GA^ uptake

caused bjT seed imbibition from stratification.

Effect of Fost GAj-Treatment

Sa^ds which have been stored at 25°C after GA^

treatment showed no significant decrease in initial percent

germination over ISO days tested (Table 6). Seeds which

were treated with 500 ppm GA^ retained their initial GA^

induced germinability in both cold (5°C) and room

temperature (25°C) storage over 60 days monitored (Figures

12-16). No difference in percent seed germination was

detected among any storage length. Similar conclusions can

be made among water soaked and nontreated seeds. The

maintainance of high germination potential induced by GA^

treatment over an extended period of posttreatment seed

storage will greatly benefit the practical handling of seeds

for crop programming and scheduling.

Effect of Salinity

The effects of 7 different salinity levels on the

germination of P. parrvi seed treated with and without 500

ppm GA^ are presented in Figure 17. A stimulatory effect of

salinity for germination occured at 100 ppm NaCl in both GA^

treated and control seeds. NaCl concentrations above 5000

ppm were inhibitory to germination. Seed soaked in 500 ppm

GA^ had consistently higher germination than nontreated

41

Table 6. Effect: of length of storage at 25 C following*- » GA-, treatment on the germination of Penstemon parryi seed.2

z

Days in Storage % Germination

15 94.5 + 1.3 a

30 95.B + 2.6 a

45 95.5 + 3.3 a

60 95.3 + 1.3 a

75 95.0 + 2.2 a

90 93.5 + 1.3 a

120 94.0 + 2.1 a

180 95.8 + 0.5 a

Average values (mean + SD) of 4 replications. Mean

separation was made by Duncan's multiple range test at

the 5 % level.

42

90. 1-DRY, 5C

2-0 PPM GA, 5C 3-500 PPM GA, 5C

4-DRY, 25C

5-0 PPM GA. 25C 6-500 PPM GA, 25C

80.

60,

S50. .

<

5 40. .

20.

1. 2. 3. 4. 5. 7. 6. 8. 9. 10.

DAYS AFTER TREATMENT

Figure 12. Changes in percent germination of GA- treated and nontreated Penstemon parrvi seed without storage.

43

100,

90. . 1-DRY, 5C 2-0 PPM GA, 5C 3-500 PPM GA, 5C

4-DRY, 25C

5-0 PPM GA. 25C

6-500 PPM GA, 25C

80. .

70. .

60. .

Q.

20.

1. 2. 4. 3. 5. 7. 8. 9. 10. 6.

DAYS AFTER TREATMENT

Figure 13. Changes in percent germination of GA^ treated and nontreated Penstemon parrvi seed after storage for 15 days at 5° and 25°C.

44

100.

90. 1-DRY, 5C 2-0 PPM GA, 5C

3-500 PPM GA, 5C

4-DRY, 25C 5-0 PPM GA. 25C 6-500 PPM GA. 25C

80.

70. .

60.

<

5 40. m

30.

20.

10.

1. 2. 3. 10. 4. 5. 6. 7. 8. 9.

DAYS AFTER TREATMENT

Figure 14. Changes in percent germination of GA-, treated and nontreated Penstemon parrvi seed^after storage for 30 days at 5° and 25°C.

90. 1-DRY, 5C 2-0 PPM GA, 5C

3-500 PPM GA, 5C

4-DFY, 25C 5-0 PPM GA. 25C

6-500 PPM GA, 25C

80.

70. .

60.

aE 40. . on ui u

30. .

UJ a.

20. .

10.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

DAYS AFTER TREATMENT

Figure 15. Changes in percent germination of GA^ treated and nontreated Penstemon parrvi seed after storage for 45 days at 5° and 25°C.

46

100.

90. 1-DRY.5C

2-0 PPM GA, 5C 3-500 PPM GA, 5C

4-DRY, 25C 5-0 PPM GA, 25C

6-500 PPM GA, 25C

80.

70.

60.

20.

10.

0. 1 10.

DAYS AFTER TREATMENT

Figure 16. Changes in percent germination of GA^ treated and nontreated Penstemon parrvi seed after storage for 60 days at 5° and 25°C.

47

seeds at all NaCl concentrations that allowed germination.

No statistical differences were observed among the seed

germination percentages in treatments with 0-1000 ppm NaCl

(Table 7). The results of this study indicate that seed

germination in Penstemon parrvi is moderately tolerant to

NaCl-induced salinity.

48

100

9 0

80

Z O 7 0 -»-< 60 -

C 5 0 Ul

° 4 0

3 0

20

10

d—o 500 ppm GA, 24 hrs

m-m H20, 24 hrs

Control

2 3 4 NaCl (9/1 iter)

Figure 17. Changes in percent germination of GA3 treated and nontreated Penstemon parrvi seed as affected by various salinity (NaCl) levels.

49

Table 7. Effect of various salinity (NaCl) levels on the germination of Fenstarrton parrvi seed.2

% Germination

NaCl Control H90-soaked GA.,-soaked (Fprn)

0 to

00

+ 1.7 c 28.0 + 1.1 d 95.8 +

O «

i—1

d

10 4.0 + 2.2 c 29.5 + 1.0 d 95.3 + 2.8 d

100 4.5 + 1.3 c 35. 0 + 3.6 d 95.8 + 2.2 d

1000 3.0 + 2.8 c 29.5 + 6.2 d 95.3 + 4.2 d

2000 1.0 + 0.8 b 27.5 + 2.4 d 70.0 + 4.2 c

4000 0.0 + 0.0 a 13.8 + 7.1 c 20.0 + 9.9 b

6000 0.0 + 0.0 a 0.8 + 0.5 b 0.0 + 0.0 a

8000 0.0 + 0.0 a 0.0 + 0.0 a 0.0 + 0.0 a

10,000 0.0 + 0.0 a 0.0 + 0.0 a 0.0 + 0.0 a

** Average values (mean + SD) of 4 replications determined

after 10 days from seed placement. Mean separations

were made by Student-Newman-Keuls procedure at the 5 %

level.

SUMMARY AND CONCLUSIONS

The influences of GA_, temperature, light,

stratification and salinity on the germination of P^_ parrvi

were investigated. Gibberellic acid treatment as well as a

relatively low temperature were found to be essential for

seed germination under laboratory conditions. Without GA^

treatment, little germination occurred even in the optimum

temperature range. Additionally, GA-, treated seeds, after

drying, retained their enhanced germination potential.

While seed germination took place equally well in both light

and dark when the temperature was optimal, the absence of

light was favorable when the temperature was above or below

optimal. Although low temperature seed stratification

improved germination as compared to that of the control, the

best percent germination (59.5 %) in the stratified seed was

never as high as that of the GA^ treated seeds (93 %). In

addition, a prolonged (4 weeks) stratification resulted in a

drastic reduction in the germinability.

The interdependence of GA^ treatment and the low

incubation temperature as well as ineffectiveness of strati

fication in parrvi differ from the results of seed

germination reported for other plant species in which a

single GA3 treatment or stratification completely breaks

seed dormancy (Blake, 1935; Bradbeer and Pinfield, 1967;

50

51

Koller, 1969). However, hi.jh.er concentrations of GA^ may be

necessary for germination at less optimum temperatures

(Khan, 1968).

P. parrvi showed a moderate level of salt tolerance

for seed germination. The results of this study suggest

that the seed germination would not be affected by salinity

in most desert conditions where the concentration of total

soluble salts in the soil is less than 1500 ppm.

In its natural habitat, parrvi disseminates a

large number of seeds (5,000-50,000 seeds/plant) following

the maturation of seed capsules in the late spring to early

summer. These seeds are highly viable (90-95 % germination

when GA^ treated) and did not not lose their initial

viability when tested for two years at room temperature.

Although not determined, the viability of seed is expected

to remain high in the natural conditions at least one year.

Like crrandiflorus (Salac and Hesse, 1975) and many

prairie plants (Blake 1935), P^. parrvi seeds stay dormant

through the summer and fall until favorable temperature and

optimum soil moisture trigger germination. Once the seed

lings are established after germination, they grow rapidly

through the cool winter months, resulting in a colorful

display of flowers during the spring months (February-May).

Although P^. parrvi produces abundant seed each year,

most natural stands are sparcely populated. Whether this is

due to poor seed germination or due to high seedling

52

mortality after germination is not known. Since only a very

low seed germination was induced by low temperature and

stratification without GA^ treatment in this study, one may

speculate that seed germination in the natural habitat can

be sporatic even under the most favorable temperature and

moisture conditions. Further investigation is needed to

illucidate the endogenous control cf seed dormancy as it

relates to the adaptation of this species to the harsh

desert environment.

The practical aspect of this work relates to the

production of desert beardtongue as a new floral crop. GA3

treatment of seeds and germination at a cool temperature

(15°C) should assure seedling supplies needed for year-round

production of the crop. Further work is needed to monitor

the effects of GA^ treatment on seedling establishment and

subsequent growth of the plant.

LITERATURE CITED

Ahi, S.M. and W.L. Powers. 1538. Salt tolerance of plants at various temperatures. Plant Physiology 13:767-789.

AOSA (Association of the Official Seed Analysts). 1981. Rules for testing seeds. Journal of Seed Technology 6(2) : 71-72.

Ayers, A.D. 1949. Seed germination as affected by soil moisture and salinity. Agronomy Journal 44:82-84.

Ayers, A.D. and H.E. Hayward. 1949. A method for measuring the effects of soil salinity on germination with observations on several crop plants. Soil Science Society of America Proceedings 13:224-226.

Blake, A.K. 1935. Viability and germination of seeds and early life history of prairie plants. Ecological Monographs 5(4):405-460.

Borthwick, H.A., S.B. Hendricks, E.H. Toole, and V.K. Toole. 1954. Action of light on lettuce seed germination. Botanical Gazette 115:205-225.

Bradbeer, J.W. 1968. Studies in seed dormancy. IV. The role of endogenous inhibitors and gibberellin in the dormancy and germination of Corvlus avellana L. seeds. Planta 78:266-276.

Bradbeer, J.W. and N.J. Pinfield. 1967. Studies in seed dormancy. III. The effects of gibberellin on dormant seeds of Corvlus avellana L. New Phytologist 66:515-523.

Chrispeels, M.J. and J.E. Varner. 1967. Control of enzyme synthesis: On the mode of action of gibberellic acid and abscisin in aleurone layers of barley. Plant Physiology 42:1008-1016.

Come, D. and T. Tissaoui. 1973. Interrelated effects of imbibition, temperature and oxygen on seed germination. In "Seed Ecology" Pennsylvania State University Press, University Park. pp. 157.

53

54

Corbineau, F. and D. Come. 1962. Effect of the intensity and duration of light at various temperatures on the germination of Cldenlandia corvmbosa L. seeds. Plant Phvsi^lDay 70:1518-1520.

Crocker, W. 193B. The life spar, of seeds. Botanical Review 4:235-274.

Duffield, M.R. and CC.D. Jones. 1981. "Plants for dry climates" Fisher Publishing Inc., Tucson, AZ. p. 29.

Edwards, T.J. 1932. Temperature relations of seed germination. Quarterly Review of Biology 7:428-443.

Flint, L.H. and E.D. McAlister. 1935. Wavelengths of radiation in the visible spectrum inhibiting the germination of light sensitive lettuce seed. Smith Miscellaneous Collection 94:1-11.

Frankland, B. and P.F. Wareing. 1962. Changes in endogenous gibberellins in relation to chilling of dormant seeds. Nature (London) 194:313-314.

Hammond, B.L. 1959. Effect of gibberellin, sodium hypochlorite, light, and planting depth on germination of guayule seeds. Agronomy Journal 51:621-623.

Hartman, H.T. and D.E. Kester. 1959. Plant Propagation: principles and practices. Third edition. Prentice-Hall Inc., Englewood Cliffs, N.J.

Heit, C.E. 1950. Germination of sensitive flower seed kinds and varieties with suggested methods for testing in the laboratory. Proceedings of the Association of Official Seed Analysts 40:107-117.

Jacobsen, J.V. and J.E. Varner. 1967. Gibberellic acid-induced synthesis of protease by isolated aleurone layers of barley. Plant Physiology 42:1596-1600.

Kaspar,. M.J. and E.L. McWilliams. 1982. Effects of temperature on the germination of selected wildflower seeds. HortScience 17(4 5:595-596.

Kaspar, M.J. and E.L. McWilliams. 1983. The effect of temperature and light on the germination of scarified and unscarified seeds of Lupinus-Texensis Hook, HortScience 18(4):574.

55

Kaspar, M.J., E.L. McWilliams, arid S.L. Grigg. 1982. Effects of temperature and light on the germination of 5 prairie wildflower species. HortScience 17(3):484.

Kearney, T.H. and R.H. Peebles. 1951. "Flora of Arizona" University of California Press, Berkeley, pp. 768-779.

Khan, A.A. 19£8. Inhibition of gibberellic acid-induced germination by abscisic acid and reversal by cytoKinins. Plant Physiology 43:1463-1465.

Khan, A.A. 1971. Cytokinins: Permissive role in seed germination. Science 171:853-859.

Koller, D. 1969. Environmental control of seed germination. Seed Biology 2:2-201.

Kotowoski, F. 1926. Temperature relations to germination of vegetable seed. Proceedings of the American Society of Horticultural Science. 23:176-184.

Lin, C.F. and A.A. Boe. 1972. Effects of some endogenous and exogenous growth regulators on plum seed dormancy. Journal of the American Society for Horticultural Science 97(1):41-44.

Lipe, W. and J.C. Crane. 1966. Dormancy regulation in peach seeds. Science 153:541-542.

Maguire, J.D. and A. Overland. 1972. Laboratory germination of weedy and native plants. Washington Agricultural Experiment Station Circular No. 349.

Mason, C.T., Jr. 1985. Distribution of Penstemon parrvi in southern Arizona. (Personal communication).

Mathur, D.D., G.A. Couvillon, H.M. Vines, and C.H. Hendershott. 1971. Stratification effects on endogenous gibberellic acid in peach seeds. HortScience 6(6):538-539.

Mayer, A.M. and Y. Shain. 1974. Control of seed germination. Annual Review of Plant Physiology 25:167-193.

Mitchell, E. 1926. Germination of seeds of plants native to Dutchess County, New York. Botanical Gazette 81:108-112.

Naqvi, H.H. and G.P. Hanson. 1980. Recent advances in guayule seed germination procedures. Crop Science 20:501-504.

NVCAC-SCS (Natural Vegetation Committee, Arizona Chapter, Soil Conservation Society of America). 1973. Landscaping with native Arizona plants. University of Arizona Press, Tucson.

Nichols, G.E. 1934. The influence of exposure to winter temperatures upon seed germination in various native American plants. Ecology 15(4 5:364-373.

Ross, J.D. and J.W. Bradbeer. 1968. Concentrations of cribberellin in chilled hazel seeds. Nature (London) 229:85-86.

J. i860. Physiolcgische Untersuchurgen uber die Abhangigkeit der Keimung von der Temperature. Jahrb. wiss Bot. 2:338-377.

S.S. 1982. Effect of seeding date cn field establishment of 12 species of wildflowers. HcrtScience 17(3-2):525.

S.S. and M.C. Hesse. 1975. Effects of storage and germination conditions of the germination of four species of wild flowers. Journal of the American Society for Horticultural Science 100(4 5:359-361.

S.S., and J.M. Traeger. 1982. Seeding dates and field establishment of wildflowers. HortScience 17(5): 805-806.

Shreve, F. and I.L. Wiggins. 1964. "Vegetation and Flora of the Sonoran Desert, Vol 1" Stanford University Press.

Smith, H. 1973. Light quality and germination: Ecological implications. Xo. "Seed Ecology" Pennsylvania State University Press. University Park. pp. 219-231.

Thornton, N.C. 1935. Factors influencing germination and development of dormancy in cocklebur seed. Contributions of the Boyce Thompson Institute 7:477-496.

Toole, E.H., V.K. Toole, H.A. Borthwick, and S.B. Hendricks. 1955. Interaction of temperature and light in germination of seeds. Plant Physiology 30:473-478.

Sachs,

Saiac,

Salac,

Salac,

Uhvits, R. 1946. Effects of osmotic pressure on water absorption and germination of alfalfa seeds. American Journal of Botany 33: 278-285.

57

Ungar, I.A. 197B. Halophyte seed germination. Botanical Review 44:233-264.

Villiers, T.A. and P.F. Wareing. 1965. The growth-substance content of dormant fruits of Fraxinus excelsior L. Journal of Experimental Botany 16:534-544.

Waisel, Y. and S. Ovadia. 1972. Biological flora of Israel 3. Suaeda aoncica Forsic. Israel Journal of Botany 21:42-52.

Wareing, P.F. 1963. The germination of seeds. In "Vistas in Botany" W.B. Turrill, ed. pp. 195-227.

Wareing, P.F. and P.F. Saunders. 1971. Hormones and dormancy. Annual Review of Plant Physiology 22:261-288 .

Westwood, M.N. and H.O. Bjornstad. 1948. Chilling requirements of dormant seeds of fourteen pear species as related to their climatic adaption. Proceedings of the American Society of Horticultural Science 92:141-149.