Day 3 Wednesday: Pollination and Fruit Development - Cristina Zepeda (9/30)

Tapetum

The innermost layer of nutritive cells in the anther wall of flowering plants that surrounds and nourishes developing pollen grains: susceptible to heat and cold stress

Heat stress effect on pollen

Heat stress leads to premature degradation of the tapetum, which is important for nutrition of pollen

Cold stress effect on pollen

Cold stress leads to alteration or abnormal expansion in cell wall formation–leaky cells

Progamic phase

The period lasting from pollen landing and tube growth to fertilization

Egg development: where is it formed, and what are the 2 phases?

• Formed in the female gametophyte in 2 phases

  • Megasporogenesis

  • Megagametogenesis

Low light effect on pollen

Results in pollen grains starving and forming abnormally

Hermaphrodite

Contain both male and female reproductive organs

Monoecious

Male and female organs occur on the same plant

Dioecious

Only male or female flowers on one plant

Outcrossers

Need 2 separate plants to reproduce

Selfers

A plant capable of self-pollination (fertilizing its own stigma, or from another flower on the same plant)

Why is pollination difficult in closed environments?

Bees cannot see red, but can see UV. LEDs don’t have UV in their spectra

Parthenocarpy

Fruit set without the fertilization of ovules

Stenospermacarpy

A natural plant process where fruit develops with tiny, undeveloped seeds because the fertilized embryo stops growing and dies early

Seed effect on fruit development

Seeds are a source of hormones for initiation and stimulation of fruit growth, seed number correlates with final fruit size

When source strength decreases, what happens to the sinks (fruits)?

Abortion rate increases linearly

Competition

Increase in the seed number of the first fruit reduces growth of the second fruit because of competition for limited assimilate supply

Hard to differentiate from dominance

Dominance

Growth reduction due to hormones produced by older fruits

Hard to differentiate from competition