Chapter 24.3 Seeds and Fruit

Why? The seeds and fruits formed help ensure survival of the next generation The seeds and fruits formed help ensure survival of the next generation

Seed formation After fertilization After fertilization Zygote divides = embryo Zygote divides = embryo Triploid cell divides = endosperm Triploid cell divides = endosperm Ovule wall = seed coat Ovule wall = seed coat

Fruit formation Fruit – the structure that contains the seeds of an anthophyte Fruit – the structure that contains the seeds of an anthophyte Fruit – the enlarged ovary surrounding the seed Fruit – the enlarged ovary surrounding the seed Can be made up of other organs as well. Can be made up of other organs as well.

Fruits Fleshy fruits – apples, grapes, melons, tomatoes, cucumbers Fleshy fruits – apples, grapes, melons, tomatoes, cucumbers Dry fruits – peanuts, sunflower seeds, walnuts. Dry fruits – peanuts, sunflower seeds, walnuts. The ovary around the seeds hardens The ovary around the seeds hardens

Seed dispersal Fruits aid in dispersal Fruits aid in dispersal Dispersal reduces competition Dispersal reduces competition Animals – digestion and/or carrying the seed on the body Animals – digestion and/or carrying the seed on the body Wind – dandelion, tumbleweed Wind – dandelion, tumbleweed Water – coconut and water lilies Water – coconut and water lilies

Pictures – from flower to fruit s/fruit-devel.htm s/fruit-devel.htm s/fruit-devel.htm s/fruit-devel.htm

What about seedless fruit? Ex. Watermelon and bananas Ex. Watermelon and bananas Triploid plants – prevents meiosis from happening and no gametes are produced Triploid plants – prevents meiosis from happening and no gametes are produced So where do the plants come from if there are no viable seeds? So where do the plants come from if there are no viable seeds?

Bananas – vegetative reproduction Bananas – vegetative reproduction Watermelons – Cross a diploid with a tetraploid to produce a triploid seed Watermelons – Cross a diploid with a tetraploid to produce a triploid seed Diploid (2) + Tetraploid (4) = 6 sets of chromosomes Diploid (2) + Tetraploid (4) = 6 sets of chromosomes Divide 6 by meiosis to get 3 sets of chromosomes. Divide 6 by meiosis to get 3 sets of chromosomes. Pollination triggers fruit formation – without seeds. Pollination triggers fruit formation – without seeds. The plants must be grown with a diploid variety for pollen The plants must be grown with a diploid variety for pollen

Seed germination Dormancy – the period of inactivity in a mature seed Dormancy – the period of inactivity in a mature seed Varies greatly between species Varies greatly between species Ends when the seed germinates Ends when the seed germinates Germination – the beginning of the development of the embryo into a new plant Germination – the beginning of the development of the embryo into a new plant

Germination Water – activates the metabolism Water – activates the metabolism Some seeds have specific requirements Some seeds have specific requirements Ex. Animals digestive system, freezing temps, extensive soaking in saltwater, specific daylengths, exposure to fire. Ex. Animals digestive system, freezing temps, extensive soaking in saltwater, specific daylengths, exposure to fire.

Dicot germination Radicle – embryonic root appears first Radicle – embryonic root appears first Hypocotyl – portion of stem nearest seed Hypocotyl – portion of stem nearest seed Cotyledon – plants first leaves Cotyledon – plants first leaves In monocots the cotyledon remains below the surface In monocots the cotyledon remains below the surface

Vegetative reproduction A new plant is produced from a stem, root or leaf A new plant is produced from a stem, root or leaf This is essentially cloning – producing new plants that are genetically identical to their parents This is essentially cloning – producing new plants that are genetically identical to their parents Tissue culture and/or cuttings. Tissue culture and/or cuttings.