Biology Chapter 24 Notes

Chapter 24: 

Chapter 24 Plant Reproduction

I. Sexual Reproduction in Flowering Plants: 

I. Sexual Reproduction in Flowering Plants A. Structure of Flowers – angiosperms – flowering plants 1. Structure of flowers – see figure 5-13 A. sepals – the leaflike structures at the base of a flower that enclose and protect the flower bud – in some species the sepal is green while in others it may be white or brightly colored

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B. petals – leaflike structures inside the sepals that surround the reproductive organs of the flower – may be brightly colored or white – often have a sweet fragrance C. stamens – male reproductive organ 1. Anther – contains the pollen grains which contain the monoploid sperm nuclei 2. Filament – or stalk – supports the anther

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D. pistils – the female reproductive organs 1. Stigma – knoblike sticky structure – allows the pollen to stick to it 2. Style – supports the stigma – a slender stalk that connects the stigma to the ovary 3. Ovary – monoploid egg cells

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B. pollination and fertilization – see figure 5-14 1. Pollination – transfer of pollen grains from an anther to the stigma a. Self-pollination – transfer of pollen from an anther to a stigma of the same flower or to a stigma of another flower on the same plant b. Cross-pollination – the transfer of pollen from an anther of one flower to the stigma of a flower on another plant – this increases the chances of genetic variation

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2. Pollination may be carried out by the wind, insects or birds 3. Germination – when a pollen grain reaches a stigma it sprouts – a pollen tube grows from the pollen grain down through the stigma and style to an ovule within the ovary – the growth of the pollen tube is controlled by the tube nucleus – two sperm nuclei and the tube nucleus pass down through the pollen tube – one sperm fertilizes the egg and the other fuses with polar nuclei to make a triploid endosperm nucleus (food) – the ovule ripens to form a seed and the ovary develops into a fruit

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C. structure of a seed 1. Seed coat – develops from the outer coverings of the ovule – surrounds and protects the embryo 2. Epicotyl – upper portion of the embryo – develops into the leaves and upper portion of the stem 3. Hypocotyl – lower portion of the embryo – develops into the roots and lower portion of the stem 4. Cotyledon – contains the endosperm – stored food for the developing plant

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D. plant growth 1. In flowering plants, only certain regions, called meristems, are able to undergo cell division A. apical meristems – found in the tips of roots and stems – bring about an increase in length B. lateral meristems – or cambiums – found between the xylem and phloem – bring about an increase in diameter