PLANTS: REPRODUCTION, GROWTH & SUSTAINABILTY

SBI3U1

PLANT REPRODUCTION

Plants can reproduce both sexually and asexually

Sexual reproduction is by sporic reproduction (alternation of generations).

Haploid gametophyte cells (1n) produce gametes

Diploid sporophyte cells (2n) produce spores.

Male and female gametes unite to form the sporophyte that continues the life cycle.

Sexual Vs. Asexual Reproduction

Plant Reproduction

Sexual

Seedless Plants

Non-vascular Vascular

Seed Plants

Gymnosperms Angiosperms

Asexual

Natural Vegetative

PropagationArtificial

Propagation

OVERVIEW

Copy chart on pg. 583 (textbook)

Sexual Reproduction in Seedless Plants

-Fertilization -> the sperm swims from the male gametophyte to the egg in the female gametophyte.

-Water must be present & sperm must have a flagellum.  

 

Ex. gymnosperms and angiosperms Male gametophytes called a microspore,

develop into a pollen grain and sperm. Female gametophyte, called a macrospore,

develops into an egg cell. In order for pollination to occur; male gametophyte must be transferred to the female reproductive structure.

Sexual Reproduction in Seed Plants

Angiosperms

sepals – protect the flower budpetals – attract pollinators

4 Basic Flower Organs

stamens – male reproductive structurepistils – female reproductive structure

• The reproductive structures are in the flowers.

• Fertilization & seed development occur within the ovule.

• Pollination takes place on the stigma.

• Female gametophytes develop in the ovules, where eggs are formed.

Variations Among Flowers◦ Complete flowers – Contain all four flower organs◦ Incomplete – Missing one or more flower organs

Grass flowers lack sepals and petals. They are incomplete.

Self-pollination: Plants pollinate themselves Cross-pollination: Plants receive pollen from another plant.

Animal Pollination: Insects and other small animals move from flower to flower collecting nectar and moving pollen. Bright, sweet-smelling flowers attract these pollinators.

Wind Pollination: Wind carries pollen and it lands on a receptive reproductive organ.

4 Pollinating Mechanisms

Self Pollination vs. Cross Pollination

Label your diagram using handout

Seed & Fruit DevelopmentFertilization is one long process that ends with the formation of a seed.A seed is part of a fruit, developed from the ovary

Monocot vs. Dicot SeedsThe outside layers of the ovule form a protective cover called the seed coat. Ex:Beans or peas have seed coats that can easily be peeled off

Seed germination A Seed may remain dormant for a period of time and then resumes growth

Produces genetically-identical clones from a parent

Vegetative propagation – Involves growing a new individual from only a portion of the original plant

Asexual reproduction

8 Types of Vegetative Propagation

1.Division Splitting 2.Grafting

8 Types of Vegetative Propagation

3. Leaf Cutting 4. Stem Cutting

8 Types of Vegetative Propagation

5. Root Cutting 6 Simple Layering

8 Types of Vegetative Propagation

7. Air Layering 8. Cell Culturing

PLANT GROWTH & DEVELOPMENT

Plant HormonesHormone: chemical compound produced in one part of the plant that controls growth in another part of that plant

act as chemical signals between cells and tissues

Some stimulate growth, others inhibit growth

1. Auxins2. Cytokinins3. Gibberellins4. Ethylene5. Abscisic acid

5 Main Plant Hormones:

“to increase” stimulates elongation of plant cells Produced in developing leaves/seeds and

shoot tips Controls upward growth – apical

dominance

Stimulatory Hormones:1.Auxins

Promotes cell division & differentiation Stimulates the production of proteins

required for mitosis and cytokinesis delays aging of leaves and fruit

Stimulatory Hormones:2. Cytokinis

Stimulates taller, stronger plant growth Stops dormancy in seeds Used in commercial crops to increase fruit

size or larger cluster size in grapes

Stimulatory Hormones:3. Gibberellins

Promotes ripening of fruit Gaseous hormone Diffuses through spaces in cells and

transported within phloem

Inhibitory Hormones:4. Ethylene

Induces seed dormancy Inhibits growth of buds in plant stems Closes stomata & blocks intake of CO2

Inhibitory Hormones:5. Abscisic Acid

Nastic response: a movement of the plant that is reversible, repeatable, and does not include growth. Ex: the opening & closing of flower petals as light conditions change.

Plant Responses to Environmental StimuliUNIT 5 Chapter 14: Plants: Reproduction, Growth, and Sustainability Section 14.2

Tropic Responses

3 main Types:

Growth responses to external stimulation coming from one direction in the environment.

1)Phototropism2)Gravitropism3)Thigmotropism

a growth response to light produced by an unequal distribution of auxin.

More auxin on the side with less light causes those cells to elongate and bend the plant toward the light

1) Phototropism

Growth response to gravity a “positive” growth response of the roots downward or

a “negative” growth response of stems upward

2) Gravitropism

a growth response to mechanical stimuliContact with another object Ie. Ivy growing on a fence or tree

3) Thigmotropism

Other Factors that Affect Plant Growth

Nutrients Soil pH

Nutrients needed in large amounts are called macronutrients (ie.N, K, Ca, Mg)

Nutrients needed in small amounts are called micronutrients

( ie. Cl, Fe, B, Zn)

Optimal soil pH is slightly acidic ( pH 6-7) or slightly basic ( pH 7-8)

Any extremes in pH will inhibit normal plant growth