Reproduction | Plant Physiology - Biology IB23

Pollination

Pollination

The male gamete/pollen getting transferred from the anther to the female gametes/ovules in the ovary.

Wind Pollination

For barely seen flowers.

ADVANTAGES: Does not require energy to make large, colourful flowers, smells or nectar to feed the pollinator.
DISADVANTAGES: Requires production of big amounts of pollen and the probability of it landing on another flower of the same is species is low.

EX:
1. Trees such as birch and hazelnut.
2. Grains such as grasses, wheat and oats.
People are allergic to these pollen as they’re easily carried by natural causes and produced heavily.

Animal Pollination

For large, showy or smelly flowers to attract pollinators.

ADVANTAGES: Less pollen is required as it’s brought directly from one plant to another of the same species.
DISADVANTAGES: Energy costly to produce the flower, colour pigments, chemicals for the smell and food for organisms.

EX:
1. Pollinators are usually insects like flies and bees.
2. Pollinators can be mammals.
3. Night pollinated flowers are brown and smell rotten to attract night-active organisms.

Cross-Pollination

Pollination of another species for genetic variation.

Methods to Avoid Self-Pollination

1. There are flowers with separate male and female plants so they can’t self-pollinate.

2. Different parts of the flower will not mature at the same so pollen can’t fertilize its own eggs.

Fertilization

Male gametes have to reach the ovule and fertilize it to produce a new zygote which becomes an embryo in the seed. A pollen tube will grow down the style of the flower to make it possible for the male gamete to reach the ovule in the ovary.

Seed Dispersal

Seeds moving away from the parent plant.

Seed Dispersal Reasons

1. To avoid competition with the parent plant with light from the sun and soil nutrition.

2. To colonize new and more areas.

Wind Seed Dispersal

Some seeds have wings or hairs which the wind can use and distribute them with, like dandelions or maple trees.

Water Seed Dispersal

Some seeds have pods that fall into water and float away.

Animal Seed Dispersal

1. Birds or mammals will eat sweet and nutritious fruit while the seeds will come out as feces deposited away from the parent plant.

2. Seeds can attach to animals.

Seed Germination

The embryo in the seed will break out of it and grown into an adult.

Starch within a starchy bean will be used as food reserve until the seed can photosynthesize on its own.

Seed Germination Steps

1. The seed will absorb water through a hole called micropyle.

2. Gibberellin will be produced and makes amylase.

3. The amylase will break down starch into maltose.

4. The maltose moves to the growing embryo root and shoot and gets broken down into glucose as required for cell respiration so the embryo can grow.

5. The testa will open for new roots and shoots to emerge from it.

6. The root will grow downward due to positive gravitation and the shoot grows upward in search of sunlight.

7. Once the shoot finds sunlight the two leaves of a dicotyledonous plant are gonna photosynthesize and make energy for the plant.