IIX Reproduction in Flowering Plants Reproduction in Angiosperms

IIX. Reproduction in Flowering Plants Reproduction in Angiosperms

A. Structure of the Flower

A. Structure of the Flower 1. Filament 2. Anther 3. Stamen 4. Stigma 5. Style 6. Ovary 7. Pistil 8. Ovule 9. Receptacle 10. Petal 11. Sepal

1. Essential Flower Parts a) Stamen- male reproductive structure consisting of two parts: 1) Anther- pollen producing structure 2) Filament- structure which supports the anther b) Pistil- (carpel) female reproductive structure 1) Stigma- sticky tip of the pistil which captures the pollen 2) Style- supports the stigma 3) Ovary- swollen base of the pistil with ovules that produce eggs

2. Non essential Flower Parts a) Receptacle- holds the flower on the stem b) Sepals- tiny leaves that form the calyx c) Petals- help attract insects for pollination. Together, the petals form the corolla

B. Kinds of Flowers 1. Complete flower- contains all essential and nonessential parts. 2. Incomplete Flower- lacks one or more flower part 3. Perfect Flower- contains both pistil and stamen 4. Imperfect Flower- contains pistil or stamen, but not both.

C. Formation of Gametes 1. Pollen grain formation a) Anthers have 4 pollen sacs which contain microspore mother cells which undergo meiosis and produce 4 haploid microspores b) Microspores divide by mitosis and form a pollen grain consisting of a generative cell and a tube cell

2. Egg Cell Formation a) Ovules contain megaspore mother cells which undergo meiosis and produce 4 haploid megaspores of which only one survives b) The surviving megaspore undergoes mitosis producing 8 haploid nuclei c) 3 nuclei migrate to each end of the cell and 2 move to the center (these are the polar nuclei) d) Cell walls form around each group of cells forming a structure called the embryo sac or female gametophyte e) The cell nearest the ovule opening is the egg cell

D. Pollination and Fertilization Pollen grain Stigma Style Ovary Ovule 1. Pollination- transfer of pollen from the anther to the stigma by animals, wind or water.

2. Fertilization- Union of Sperm and Egg a) When the pollen lands on the stigma, the tube cell starts to form a tube down to the ovule. b) The generative cell divides and forms two sperm which go down the pollen tube. c) One sperm fertilizes the egg forming a zygote while the other sperm fertilizes the polar nuclei forming the endosperm (nutritive tissue)

E. Fruits and Seeds 1. Seed and Fruit Development a) The outer tissue of the ovule hardens forming the seed coat containing the endosperm and the zygote which will undergo mitosis until it forms the embryo b) The ovary swells and becomes the fruit while the reproductive structures wither and fall off

Fruit Development in Apples

Fruit Development in Strawberries

c) Types of Fruit 1) Simple Fruit- forms from a single ovary. (Beans, Peaches, tomatoes) 2) Aggregate Fruit- forms from flower with many pistils (strawberries, blackberries, raspberries) 3) Multiple Fruit- forms from many individual fruits growing together forming one structure (pineapples & figs)

2. Seed Dispersal

3. Seed Germination A) Germinationprocess in which the seed starts to grow after a period of dormancy. Moisture and warmth are two factors which start the process

b) Seed Structure- the embryo possesses all the basic plant organs in embryonic form 1) Epicotyl- part of the stem above the cotyledon where the first leaves grow 2) Hypocotyl- below the cotyledons. Becomes the stem 3) Radicle- becomes the roots 4) Cotyledon- contains endosperm which will feed the plant until it can carry on photosynthesis 5) Seed Coat- protective covering

Can you name the parts of the seed?

F. Asexual Reproduction- reproductive process that results in offspring that are genetically identical to the parent

1. Natural Propagation a) Vegetative propagation- producing new individuals from the leaves, roots or stems b) Runner or Stolon- low running modified stems that start adventitous roots and start new plants c) Rhizomes- underground modified stems that produce new plants d) Tuber- thick stem for food storage that have “eyes” capable of producing a new plant e) Bulbs- stems with layered leaves that produce new plants

2. Artificial Propagation a) Cuttings- pieces of stem cut from a plant that develop new roots when placed in water b) Grafting- buds or sections of stem called scions are attached to another plant called the stock c) Tissue culturing and layering 1) tissues are removed from a plants pith and are grown in culture dishes 2) Layering involves folding a branch down and covering it with soil. Some plants grow new roots at the nodes

IX. Plant Growth and Response

A. Factors Affecting Growth 1. Influences from the Environment

a) Light 1) Supplies energy for photosynthesis 2) Photoperiodism- plant response to changing light and dark periods. Often triggers budding, flowering and dropping leaves 3) Short day plants- produce flowers in spring or fall 4) Long day plants- produce flowers in summer 5) Day neutral plants- light doesn’t determine when they flower

b) Moisture 1) Xerophytes- Need very little water 2) Hydrophytes- thrive in wet conditions 3) Mesophytes- need an intermediate amount of water c) Temperature- plants grow best in temperature between 50 -100 o F 1) When temperatures drop below 50 o. F the metabolism of a plant slows and it enters a period of dormancy 2) Some seeds must go through a period of chilling called vernalization before they grow

2. Internal Factors (Hormones)Powerful chemicals that cause most internal changes a) Auxins- stimulate elongation of cell, promote meristematic growth and inhibit abscission b) Gibberellins- stimulates growth of leaves and stems c) Cytokinins- stimulate cell division without differentiation d) Abscissic Acid- inhibits growth causing dormancy in seeds e) Ethylene- stimulates fruit ripening

B. Plant Movements (Tropisms)occurs when one part of a plant organ grows faster than another causing bending 1. Phototropism- movement towards light 2. Geotropism or Gravitropism - movement towards the ground 3. Thigmotropism- curving response to contact with a solid object. (Ivy) 4. Hydrotropism- movement toward water 5. Nastic Movements- movement not related to a direction of a stimulus (opening and closing of petals, venus fly trap capturing prey