Chapter 24.3 Seeds and Fruit. Why? The seeds and fruits formed help ensure survival of the next...

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.