PLANTS: REPRODUCTION, GROWTH & SUSTAINABILTY SBI3U1

PLANT REPRODUCTION

Plants can reproduce both sexually and asexually

Sexual Vs. Asexual Reproduction 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.

OVERVIEW Copy chart on pg. 583 (textbook) Plant Reproduction Sexual Seedless Plants Non-vascular Vascular Seed Plants Gymnosperms Angiosperms Asexual Natural Vegetative Propagation Artificial 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.  

Sexual Reproduction in Seed Plants 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.

Angiosperms

4 Basic Flower Organs sepals – protect the flower bud petals – attract pollinators stamens – male reproductive structure pistils – 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.

4 Pollinating Mechanisms 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.

Self Pollination vs. Cross Pollination

Label your diagram using handout

Seed & Fruit Development Fertilization 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 Seeds The 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

Asexual reproduction Produces genetically- identical clones from a parent Vegetative propagation – Involves growing a new individual from only a portion of the original plant

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 Hormones Hormone: 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

5 Main Plant Hormones: Auxins Cytokinins Gibberellins Ethylene Abscisic acid

Stimulatory Hormones: 1.Auxins: Principal plant hormone “to increase” stimulates elongation of plant cells Produced in developing leaves/seeds and shoot tips (apex) Controls upward growth – apical dominance

Stimulatory Hormones: 2. Cytokinis Promotes cell division & differentiation Stimulates the production of proteins required for mitosis and cytokinesis delays aging of leaves and fruit

Stimulatory Hormones: 3. Gibberellins Stimulates taller, stronger plant growth Stops dormancy in seeds Used in commercial crops to increase fruit size or larger cluster size in grapes

Inhibitory Hormones: 4. Ethylene Promotes ripening of fruit Gaseous hormone Diffuses through spaces in cells and transported within phloem

Inhibitory Hormones: 5. Abscisic Acid Induces seed dormancy Inhibits growth of buds in plant stems Closes stomata & blocks intake of CO2

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

Tropic Responses Phototropism Gravitropism Thigmotropism Growth responses to external stimulation coming from one direction in the environment. 3 main Types: Phototropism Gravitropism Thigmotropism

1) Phototropism 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

2) Gravitropism Growth response to gravity a “positive” growth response of the roots downward or a “negative” growth response of stems upward

3) Thigmotropism a growth response to mechanical stimuli Contact with another object Ie. Ivy growing on a fence or tree

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