plant reproduction.pdf

Plant Reproduction The life cycle of flowering plants divide into two stages. Sporophyte: Diploid stage in the life cycle of a plant. Produces spores by osmosis. Gametophyte: Haploid stage in the life cycle of a plant. Produces male and female gametes. Flower...

Plant Reproduction The life cycle of flowering plants divide into two stages. Sporophyte: Diploid stage in the life cycle of a plant. Produces spores by osmosis. Gametophyte: Haploid stage in the life cycle of a plant. Produces male and female gametes. Flower Parts Structure of the flower part Function of the flower part Sepal protection Petal is brightly coloured part of the flower Attracts insect pollinators by colour and fragrance Stamen Male sexual organ of the plant. Produce the male gametes Filament thin stalk Brings food and water to the anther Anther Sac-like structure Pollen production because of meiosis Stigma Top of the carpel Receives pollen Ovary Site of fertilisation Carpel Female sexual organ The plant develops from a zygote (fertilised egg). The sporophyte stage is the adult plant with a root and shoot system. The sporophyte produces spores by meiosis which go onto develop into the gametophyte stage of the plant. Flowers have both male and female parts. The male and female parts contain gametes (haploid cells). The male gamete fuses with the female game to form a diploid zygote. Germination will occur in the seed and the seed will form a plant. A plant will spend most of its life in the sporophyte stage. Fertilisation: The fusion of a male gamete and female gamete form a diploid zygote. Pollen grain produced by the anther lands on the stigma of another plant. Pollination is the transfer of pollen from the anther of one flower to the stigma of another flower of the same species. Flowers are pollinated by wind or insects. - Pollination is vital for plants to reproduce sexually, Seed and fruit formation and Genetic variation After pollination, the tube nucleus goes down the style of the stigma and into the micropyle in the ovary. The nucleus divides by mitosis in the tube to form two male gametes. The tube disintegrates once the tube has reached the embryo sac. The two male gametes enter the embryo sac One male gamete fuses with the egg. The other fuses with the polar nuclei to form endosperm. This is called double fertilisation. zygote (2n) Methods of pollination Self-pollination: The transfer of pollen from an anther to a stigma on the same plant. Advantage: Guarantees reproduction if pollinating agent is absent or not efficient. Disadvantage: Lack of genetic variation. Cross-pollination: The transfer of pollen from an anther to a stigma on a different plant of the same species. Adaptations of wind-pollinated flowers: Long stamens, Long, feathery stigmas, large numbers of pollen grains, Light pollen, No showy colours or no scent or no nectar small petals or no petals Adaptations of insect-pollinated flowers Attraction of pollinators: brightly coloured petals and petal shape. Pollen collection by insect sticky pollen. Pollen capture by flower: sticky stigmas so pollen from insect will transfer to them. Seed dispersal Example Wind sycamore. Animal burdock seed head stuck in dogs hair. Self-dispersal pea plant exploding open. Water water. Dormancy is a period in the life cycle of a plant when growth is temporarily stopped. Dormancy is important to help ensure the survival of a plant by ensuring plants don’t begin to germinate in winter when it is very cold. Vegetative propagation this is asexual reproduction in plants. Gametes or fertilisation are not involved. Asexual reproduction involves Sexual reproduction involves: One parent Two parents No gametes Gametes involved No meiosis or fertilisation Meiosis occurs, fertilisation occurs Fast process Slow process Off-spring identical Offspring different A root tuber is a swollen, underground root that remains dormant during winter and from which new plants may grow. Artificial vegetative propagation a cutting is a portion of a plant that is removed from the parent plant and grown into a new, independent plant. Tropisms is a change in the growth of a plant in response to an external stimulus. Tropism occurs when the growth is towards the stimulus, e.g. phototropism, thigmotropism. Phototropism is the change in growth of a plant in response to light. Stems grow towards the light. Phototropism is vital to maximise the amount of photosynthesis for plants to produce more food. Geotropism is the change in growth of a plant in response to gravity. Roots grow towards gravity and shoots grow against gravity. Auxins are growth regulators a.k.a. plant hormones. Auxin is a chemical responsible for the growth of a plant. Identifying plant families ( All have Latin names.) Buttercup Daisy Violet Pansy Nettle Sunflower