chapter 24.3 seeds and fruit. why? the seeds and fruits formed help ensure survival of the next...
TRANSCRIPT
Chapter 24.3
Seeds and Fruit
Why?
The seeds and fruits formed help ensure survival of the next generation
Seed formation
After fertilization Zygote divides = embryo Triploid cell divides = endosperm Ovule wall = seed coat
Fruit formation
Fruit – the structure that contains the seeds of an anthophyte
Fruit – the enlarged ovary surrounding the seed
Can be made up of other organs as well.
Fruits
Fleshy fruits – apples, grapes, melons, tomatoes, cucumbers
Dry fruits – peanuts, sunflower seeds, walnuts. The ovary around the seeds hardens
Seed dispersal
Fruits aid in dispersal Dispersal reduces competition Animals – digestion and/or carrying
the seed on the body Wind – dandelion, tumbleweed Water – coconut and water lilies
Pictures – from flower to fruit
http://www.cas.vanderbilt.edu/bioimages/pages/fruit-devel.htm
What about seedless fruit?
Ex. Watermelon and bananas Triploid plants – prevents meiosis
from happening and no gametes are produced
So where do the plants come from if there are no viable seeds?
Bananas – vegetative reproduction Watermelons – Cross a diploid with a tetraploid
to produce a triploid seed Diploid (2) + Tetraploid (4) = 6 sets of
chromosomes Divide 6 by meiosis to get 3 sets of
chromosomes. Pollination triggers fruit formation – without
seeds. The plants must be grown with a diploid variety
for pollen
Seed germination
Dormancy – the period of inactivity in a mature seed
Varies greatly between species Ends when the seed germinates Germination – the beginning of the
development of the embryo into a new plant
Germination
Water – activates the metabolism Some seeds have specific
requirementsEx. Animals digestive system,
freezing temps, extensive soaking in saltwater, specific daylengths, exposure to fire.
Dicot germination
Radicle – embryonic root appears first
Hypocotyl – portion of stem nearest seed
Cotyledon – plants first leaves In monocots the cotyledon remains
below the surface
Vegetative reproduction
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
Tissue culture and/or cuttings.