26

KIWIFRUIT DEVELOPMENTTHE EFFECT OF TEMPERATUREON BUDBURST AND FLOWERING

M. J. Morley-BunkerDepartment of Horticulture

Landscape and ParksLincoln College

Canterbury

INTRODUCTIONCrop farmers, horticulturalists a n d r e -

searchers are aware o f weather differencescausing large variations in the dates o f plantevents — for example the dates of flowering.Plant growth and development has two aspects.Plant growth is commonly expressed quanti-tatively as the incremental change in plant drymatter. Plant development is taken here asbeing the observable progress towards maturitythrough a series of morphological stages. Theseexternal changes a r e cal led phenologicalphases. The time interval between morpho-logical stages is commonly referred to as aphenological phase duration o f " d " days. I fthe interval " d " is short then development israpid.

Kiwifruit development is influenced by sev-eral environmental factors, the most significantbeing air and soil temperature and daylength(photoperiod). Some o f these factors varyfrom year to year in a district and betweendistricts; therefore t h e da tes f o r t h ephenological phases also varies. The variationin timing of phenological phases has importantconnotations fo r orchard management. The

Weather and Climate (1987) 7:26-30

M. J. SalingerNew Zealand

Meteorological ServiceP.O. Box 722

WellingtonABSTRACT

During the 1985/86 growing season kiwifruit flowering dates and otherphenological events have been monitored from Kerikeri in the north toBlenheim in the south. The phenological observations have been made athorticultural research orchards and b y growers. The results show thatbudburst differed by as much as two weeks between districts. Budburst datesrange from mid September to the beginning of October. Flowering dates showa similar spread from mid to late November. The number of days betweenbudburst and flowering diminishes wi th increasing temperature. Theserelationships are quantified by a thermal time model. Examples are given ofthe prediction o f flowering dates at Te Puke once budburst is known.

timing of flowering affects the time at whichbeehives should be moved into an orchard orspray pollination applied.

Published research indicates that temper-ature is a key variable controlling kiwifruitdevelopment. Brundell (1976) concluded therewas little, i f any chilling requirement needed toreinduce budbreak i n cuttings o f Actinidiadeliciosa cv. "Hayward" cuttings. However,chilling enhanced f loral development. Sub-sequently Lionakis and Schwabe (1984) suggestthat true bud dormancy can be accelerated incuttings by short days at warm and constanttemperatures. This dormancy can be brokenquantitatively by chilling. Controlled environ-ment work has shown that the duration frombudbreak to flowering varies by about 5 to 7days for every 1°C change in mean temperatureover the period (Warrington and Stanley,1986). The duration from budbreak to firstflower decreased f rom 80 days a t a meantemperature o f 12°C to 50 days at a meantemperature of 16°C.

During the 1985/86 growing season kiwifruitflowering dates and other phenological eventshave been monitored from Kerikeri in the north

Kiwifrui t Development, Effect o f Temperature

to Blenheim i n the south a t horticultural re-search orchards and by growers. Th is reportdiscusses t he t im ing o f budburst a n d openflowering a n d relates t h e dura t ion o f t h ephenological phase t o a thermal t ime model.The results are then applied to the prediction offlowering.

MEASUREMENTS

DISTRIBUTION OF OBSERVATION SITES

A w i d e nat iona l range o f phenologicalobservation sites f r o m Keriker i t o Blenheimwas obtained by requesting the co-operation ofkiwifruit growers and the technical s ta ff andscientists at six MAF and DSIR research centres(Fig. 1). Seventeen growers were recruited i nHawkes Bay, Golden Bay and Tasman Bay dis-tricts. T h e large range o f di fferent cl imaticconditions fac i l i ta tes t h e invest igat ion o frelationships between temperature and pheno-logical development.C L I M AT E OBSERVATIONS

All grower observations were allocated NewZealand Meteorological Service cl imate sitesclose t o t h e o rcha rd s i t e f o r compar ingphenological dates w i t h c l imate da ta . A l lresearch centres have a climate station on site.Growers were allocated the most typical NewZealand Meteorological Service station site fortheir orchard. T h e greatest distance f r o m agrower's orchard was 5km. Da i l y maximum,minimum a i r temperature, m i n i m u m grasstemperatures and rainfall were measured at allclimate sites and sunshine, solar radiation, soiltemperatures, w ind and evaporation a t someclimate sites.

P H E N O L O G I C A L OBSERVATIONS

Two sets o f instructions were prepared: onefor growers and another fo r research centres.However the procedures described were similar,the two recording formats producing a com-mon record . F i v e phenological stages a sdescribed b y Brundell (1975) were chosen fo rrecording. These were bud swell, bud burst lcmprojection, bud burst open cluster, calyx splitand open flower.

Five p lants were observed a t each s i te .Observers chose plants from a block on T-barsunder standard management techniques and ofplants producing fruit of uniform character andperformance. A l l p lants were t h e selectionHayward, except a t Rukuh ia where i t wasKramer. Plants were visually assessed at regular

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Fig. I . Climate and Kiwifruit phenological observationsites. Closed circles represent phenological and climate sitesat research centres, open circles climate sites and squaresgrower observation sites. The number o f growers in eacharea is given in the square.

intervals, and observed as a whole to determinethe phenological phase and the degrees of phasedevelopment. Commercial growers recordedthe progress of each plant for each phase at firstoccurrence, 5 0 % a n d 9 0 % occurrence. R e -search centres examined plants thrice weeklylooking f o r beginning (25070 o r less) o r massoccurrence (5007o o r more) o f the condition.The occurrence o f any damage f rom adverseweather o r pests a n d diseases, a n d imp le-mentation o f cultural treatments together withyields were noted.

RESULTSP H E N O L O G I C A L DATES

1985 was by repute a late season.The f i rstobservations o f bud development came f rombud burst observations at the research centresites. Blenheim and Rukuhia were f i rst , f o l -lowed a day later by Levin and Riwaka DSIR.Kerikeri was much later (13 days).

A common record of all observers was avail-able fo r the condition bud burst open cluster.

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Bud burst B u d burstSite ( l c m projection) open cluster

5007oFlowering

Kerikeri 3 Oct 10 Oct 25 Nov

Te Puna 4 Oct

Hastings

3 DecRukuhia 19 Sept 26 Sept 22 NovNapier

60

29 Sept 25 Nov*Hastings

67

29 Sept 27 NovLevin 20 Sept 27 Sept 30 Nov

*Takaka 25 Sept 30 NovRiwaka DSIR 20 Sept 30 Sept 29 Nov

*Riwaka 22 Sept 30 Nov*Motueka 21 Sept 27 NovAppleby 15 Sept 27 NovBlenheim 19 Sept 27 Sept 30 Nov

Site Time (days)

Kerikeri 46Rukuhia 60Napier 57Hastings 59Levin 64Takaka 65Riwaka DSIR 60Riwaka 69Motueka 67Appleby 73Blenheim 699

Table 1 records the mass occurrence dates. Thesequence, nationwide, began with the orchardtypified b y A p p l e b y c l imate d a t a o n 1 5September, followed by Motueka, Riwaka andTakaka. Rukuhia then interrupts the gradualsouth t o north trend (26 September). Kerikeriwas the latest on 10 October. The nationwidespread was 25 days.

The mass occurrence of open flower occurredwithin a 5 day nationwide span, but northernlocations were a day or so earlier. The trend inflowering time is not as notable as the north tosouth trend in the time taken f rom bud burstopen cluster to open flowering (Table 2). Ken-ken i took 46 days to flowering and Appleby 73days, a range o f 27 days.

TA B L E 1: D AT E S O F P H E N O L O G I C A L EVENTS I NK I W I F R U I T DURING 1985.

* A v e r a g e o f more than one observer's record.

TA B L E 2 : D U R AT I O N O F P H A S E B U D B U R S T —OPEN CLUSTER TO FLOWERING.

Kiwifrui t Development, Effect o f Temperature

TEMPERATURE A N D D E V E L O P M E N T

The relation between the duration from budburst to open flower (9 days) and mean temper-ature from research centre data is shown in Fig.2. The 1985 data shows a hyperbolic decreasewith mean temperature over the phase.

This can be conveniently treated by defininga rate for the phase bud burst to open flower(1/d) a t each temperature, as th is increaseslinearly with temperature. The temperature at

80 9\ •

•\11

50

40

2.00

1.75-0CDCD 1.50curu

—4—

CU 1.250

1.00

101 1 1 1 1

11 1 2 1 3 1 4 1 5Mean temperature (c)(

10 1 1 1 2 1 3 1 4 1 5Mean temperature (c)C)

Fig. 2(a): The relation between the duration from budbreak to flowering (d) and temperature for kiwifruit.

Fig. 2(b): The relation between development rate (100/d)and temperature.

Open circles represent DSIR climate laboratory results.

Kiwifrui t Development, Effect o f Temperature 2 9

which development stops, t h e base temper-ature, is 7.5°C for the phase burst to flowering.

The base temperature is derived f r o m theregression equation be low b y solving f o r adevelopment rate (1/d or y) o f zero.

The equation for the fitted line in Fig. 2b isy = -2.11 + 0.281 x

where y_ is the development rate and x is themean temperature for the phase, explaining 940/oof the variance.

From the relation

1/d b (T - Tb)

b is a constant, T the mean temperature duringthe phase a n d T b t he base temperature, i tfollows that

d (T - Tb) 1 /bwhere 1 / b i s t he thermal durat ion, degreesdays. For kiwifrui t the time from bud burst toopen flower at research centres was 359 ± 13°Cdays above a base of 7.5°C.

The combinat ion o f un i t s i s sometimesreferred to as "accumulated temperature" or asa "temperature sum" o r even a "heat un i t " ,which is not, as temperature is not, a measureof energy. We adopt the expression o f thermaltime (hence thermal durat ion) o f Monte i th(1981) a n d Gallagher, T h o r n e a n d Ta y l o r

Bud-Burst F l o w e r i n g B u d - B u r s t F l o w e r i n g

1 Sep 8 Nov 1 6 Sep2 Sep 8 Nov 1 7 Sep3 Sep 9 Nov 1 8 Sep4 Sep 9 Nov 1 9 Sep5 Sep 1 0 Nov 2 0 Sep6 Sep 1 0 Nov 2 1 Sep7 Sep 1 1 Nov 2 2 Sep8 Sep 1 1 Nov 2 3 Sep9 Sep 1 2 Nov 2 4 Sep

10 Sep 1 2 Nov 2 5 Sep11 Sep 1 3 Nov 2 6 Sep12 Sep 1 3 Nov 2 7 Sep13 Sep 1 4 Nov 2 8 Sep14 Sep 1 4 Nov 2 9 Sep15 Sep 1 5 Nov 3 0 Sep

15 Nov16 Nov16 Nov17 Nov18 Nov18 Nov19 Nov19 Nov20 Nov21 Nov21 Nov22 Nov23 Nov23 Nov24 Nov

(1981), as i t emphasizes the fact that time, as itis perceived by a developing kiwifruit, dependson temperature.

Similar relationships between temperatureand development existed f o r bud burst opencluster to open f lower f rom data collected atboth grower a n d research centre sites. D e -velopment increased l inear ly above a basetemperature o f 7.5°C, w i t h t h e regressionequation,

y = -2.42 + 0.313 xexplaining 8 4 % o f the variance. 334'Cdaysare required for the phase to be completed.

APPL ICAT IONS OF T H E R M A L T I M E

The thermal time relationship for the phasebud burst to open flower in k iwi frui t is a veryvaluable predictive aid. Thermal time averageswere calculated above a base o f 7.5°C for TePuke f r o m 13 years o f climate records. F o reach b u d b u r s t da te , a tab le o f averageflowering dates i s derived b y summing thethermal t ime requirements (Table 3). Thus i fbud burst is as early as 1 September, 50% openflower wi l l occur on 8 November. A late budburst o f 15 October gives an average 50% openflower date of 4 December. Such information isextremely u s e f u l f o r schedul ing c u l t u r a lactivities for kiwifruit.

The v a l u e compares w e l l w i t h c l ima telaboratory results (Warr ington a n d Stanley,

TA B L E 3: AV E R A G E FLOWERING DATES FROM BUDBURST: T E PUKE.

Bud-Burst F l o w e r i n g B u d - B u r s t F l o w e r i n g

1 Oct2 Oct3 Oct4 Oct5 Oct6 Oct7 Oct8 Oct9 Oct

10 Oct11 Oct12 Oct13 Oct14 Oct15 Oct

25 Nov25 Nov26 Nov27 Nov27 Nov28 Nov28 Nov29 Nov30 Nov

1 Dec1 Dec2 Dec2 Dec3 Dec4 Dec

16 Oct 4 Dec17 Oct 5 Dec18 Oct 6 Dec20 Oct 7 Dec20 Oct 7 Dec21 Oct 8 Dec22 Oct 8 Dec23 Oct 9 Dec24 Oct 1 0 Dec25 Oct 1 0 Dec26 Oct 1 1 Dec27 Oct 1 1 Dec28 Oct 1 2 Dec29 Oct 1 3 Dec30 Oct 1 4 Dec

30

1986) for plants grown at a mean temperatureof 12°C (363°C days) bu t no t a t a meantemperature o f 16°C (429°C days). The dif-fering environmental conditions between theclimate laboratory and field conditions mayexplain the discrepancy in the thermal timerequirements for the high mean temperature.

CONCLUSION

The results from phenological monitoring in-dicate that temperatures during late winter toearly summer directly effect the phases o fkiwifruit development. Bud burst is earlier inthe cooler southern districts (mid September)compared with Northland (early October) in1985 probably as a consequence o f vernalis-ation requirements being satisfied earlier i ncolder locations. The duration of the phase budburst t o 50% flowering decreases wi th in -creasing temperature. The phase requires 359°C-days above 7.5°C to be completed. This thermaltime requirement is constant between districts.

The strong relationship between temperatureand development with definite thermal timerequirements has beneficial applications. Fromdata at climate stations with a long record,average flowering dates from bud burst can becalculated. A further application is the fine

Kiwifruit Development, Effect of Temperature

tuning of the average prediction as the growingseason progresses. By monitoring temperaturesafter budbreak and using extended rangetemperature forecasts actual thermal time canbe calculated as the phenological phase pro-gresses. Adjustment forecasts can then be madeto the climatological flowering date based onwhether the growing season has been average,warm or cold. Thus management plans can bemade to arrange beehives o r organise spraypollution for the predicted 50% flowering date.

REFERENCES

Brundell, D. J. , 1975: Flower Development o f the ChineseGooseberry (Act in iodia chinesis Planch). I . Develop-ment o f the Flowering Shoot, New Zealand Journal o fBotany, 13, 485-496.

Brundell, K. J., 1976: The Effect of Chilling on the Termin-ation o f Rest and F lower B u d Development o f theChinese Gooseberry, Scientia Horticultural, 4, 175-182.

Gallagher, J. N . , Thorne, G. N . and Taylor, P. J. , 1981:Development o f Win te r Wheat , Rothamsted Experi-mental Station, Report for 1980, Part 1, 53-54.

Lionakis, S . M . and Schwabe, W . W. , 1984: B u d Dor -mancy in K iw i f ru i t , Act in id ia chinesis Planch. Annulsof Botany, 54, 467-484.

Monteith, J. L . , 1981: Cl imatic Variation and the Growthof Crops, Quarterly Journal o f the Royal Metero-rological Society, 107, 749-774.

Warrington, I . J . and Stanley, C. J. , 1986: The Influenceof Pre- and Post-Bud Break Temperatures on Flower-ing in Kiwi f ru i t , Ac ta Horticulture, 175, 103-107.