Biology: Reproduction in Plants

asexual reproduction

process of production of genetically identical offspring from one parent

Characteristics of Asexual Reproduction

-no sex cells or fertilization

-no fusion or gametes

-no mixing of genetic variation

Binary fusion

happens in bacteria

Budding

done by yeast produce chain of buds

spore formation

done by fern/fungi

Stem tuber

-underground storage system

-buds grow into plants by using the food stored

Rhizomes

-underground storage system

-buds grow into plants by using the food stored

Runner

-Slender roots grow horizontally at soil surface

-each bud along runner develops into a new plant

Advantages of population of species in the wild and crops plant

-faster than growing from seeds

-rapidly colonise new areas

-maintain the desirable quantaties

sexual reproduction

-two parents required

-Offspring are genetically different

-Fertilization when gametes fuse to form zygote

nuclei of gametes

haploid (half set of chromosomes)

nuclei of zygote

diploid (full set of chromosomes)

advantages of sexual reproduction

-produce different varieties of plants with good quality

-Grow/mature faster
-higher resistance to disease

-better adapted to different environmental conditions

disadvantages of sexual reproduction

-dependent on pollination/pollinators

-slower method

-wastage of energy and pollen grains

structure of insect pollinated plants

Carpel (male)

-filament

-anther

Stamen (female)

-stigma

-style

-ovary

-ovules

Others

-petal

-sepal

-receptal

Stigma

-secretes sucrose so protein grains stick to it

Style

holds stigma where it can best get pollen

Ovary

contains ovule

Ovules

Contain egg cells

Filaments

holds anther where it can best deliver protein

Anther

makes pollen

Petal

provides color,scent and sometimes nector to attract nector to attract pollinators

Sepal

protects bud

Receptacle

flower stalk to attach flower to the stem

pollen grains insects pollinated flowers

-larger in diameter

-heavier in weight

-fewer numbers of grains produced

-Contains spikes or hooks on the outside of grain

pollen grains of wind pollinated flowers

-fewer in diameter

-lighter in weight

-greater numbers of grains produced

-No spikes or hooks on the outside of grain

Stigma of wind pollinated flowers

Extends outside the plant and is feathery to catch pollen easier

Anther of insect pollinated flowers

Hang outside the flower so the wind can carry more pollen grains

Pollination

Transfer of pollen grains from anther to stigma

Self pollination

pollen grains from same flower/plant

Self pollination characteristics

-little or no genetic variation

-less well adapted to changing conditions

-less wastage of pollen grains

Cross pollination

pollen grains between 2 points of the same species

Cross pollination characteristics

-produce genetic variation

-lwell adapted to changing conditions

-higher wastage of pollen grains

fertilization

occurs when a pollen nucleus fuses with a nucleus in the ovule

What happens when a pollen grain lands on the stigma?

It sticks to the stigma and begins to germinate, forming a pollen tube.

Where does the pollen tube grow?

Down through the style toward the ovary.

How does the male gamete travel to the ovule?

The male nucleus moves down the pollen tube into the ovule.

What happens when the male nucleus reaches the female nucleus in the ovule?

They fuse together in fertilization to form a zygote.

After fertilization, what does the ovule and ovary become?

Ovule → seed; Ovary → fruit.

What is germination?

The process by which a seed develops into a new plant.

Why is water important for germination?

It activates enzymes that break down stored food in the seed.

Why is oxygen important for germination?

It allows respiration to release energy for growth

Why is warmth important for germination?

It provides the optimum temperature for enzyme activity.