Plant Structure, Growth, and Reproduction (Final) Flashcards
Explain apical growth in plant shoots, including phototropism and the role of auxin.
Apical meristems (for primary plant growth) occur at the apex (tips) of roots and stems. They contain totipotent cells. It allows plants to grow taller and gain more access to light and CO2. This, in turn, allows plants to produce new leaves, flowers, and fruits, and allow roots to extend towards the soil. This is due to cell elongation and mitosis.
Outline the relationship between flowers and pollinators (mutualistic).
Most flowering plants (-80%) use mutualistic relationships with pollinators in sexual reproduction. This means that both benefit from pollination, as the animal gets nectar or pollen and the flower is pollinated/fertilized. In fact, most plants have coevolved with pollinating species.
Distinguish between pollination and fertilization in flowering plants.
Pollination is the transfer of pollen (male gamete) to the stigma. Fertilization occurs after the pollen has traveled down the style, and is the formation of a zygote from the male and female gametes.
Describe how flowering is controlled in short-day plants.
With photoperiodism, short day plants require long days to flower. This is due specifically to phytochrome, a pigment which controls photoperiodism in plants. Phytochrome is split into two groups: Pr, the inactive form, and Pfr, the active form.
Pr absorbs red light (660 nm), which converts it to Pfr. Pfr absorbs far-red light, which converts it to Pr. However, as there is more red light than far-red light during the day, there is a build up of Pfr. During the night, Pfr slowly absorbs more far-red light and gradually converts back to Pr. The amount of Pfr left at the end of the day, which tells the plant how long the night was. When a specific amount of Pfr is reached, it activates specific genes that promote flowering.
