Plant Reproduction - 9.4

Question 1

Outline the relationship between animals and the flowers they pollinate.

Answer 1

Mutualistic relationship, both species benefit, flower gets pollinated / fertilized and animal gets nutrients / pollen.

Question 2

Describe the adaptations of flowers to attract animal pollinators.

Answer 2

Adapted plants have large, brightly colored (“showy”) AND scented flowers (to attract birds, bats, bees/ other insects etc.), and “sticky” pollen grains (to adhere to pollinator bodies)

Question 3

List and describe the vectors for seed dispersal.

Answer 3

Water carries aquatic plant seeds, wind carries plants with lighter & smoother seeds, animals can consume seeds and excrete them.

Question 4

Outline why seed dispersal is important in the survival of a plant species.

Answer 4

Seed dispersal allows plants to spread out into a wide area and avoid competing with one another for the same resources (such as light, water, nutrients from soil).

Question 5

List and describe the environmental conditions necessary for seed germination.

Answer 5

• Water rehydrates the seed, triggers gibberellin production, and triggers further metabolic reactions.
• Oxygen is for aerobic respiration which produces ATP.
• Optimum pH in soil / surrounding area for enzyme function.
• Ideal temperature for optimal enzyme activity, warmer temps indicate optimal germination (spring)
• BONUS: fire / digestion to break down seed coat

Question 6

Explain the steps of seed germination after favorable environmental conditions are encountered.

Answer 6

1. Water enters the seed, triggers synthesis of gibberellin (GA)
2. GA (plant growth hormone) turns on genes to make enzyme amylase
3. Amylase hydrolyzes (breaks down) starch (stored in the seed) into the sugar maltose
4. Maltose is hydrolyzed into glucose (for cellular respiration) or condensed/ polymerized (for production of cellulose to build cell walls in new cells being formed)
5. Seed is metabolically active, seed coat (testa) ruptures and the radicle grows into the ground (water, nutrients, and minerals)
6. The cotyledon emerges and produces the shoot’s first leaves

Question 7

Explain how you would design and carry out an experiment to test the effect of a factor on seed germination.

Answer 7

By altering the amount of water (5mL, 10 mL, 15mL) each group of germinating seeds gets every day. You would control the amount of oxygen, pH level in the soil, and temperature. You measure the amount (as a calculated percentage) of seeds that produce radicals over a month.

Question 8

Explain the role of phytochrome in flowering in both short day and long day plants.

Answer 8

• Phytochrome exists in 2 forms
  - Pfr = active form & absorbs FAR-red light
  - Pr = inactive form & absorbs red light
• Flowering is controlled by the absence of light / length of night BECAUSE Pfr turns into Pr in the darkness
  - Long-day plants = flowering activated by nights SHORTER than critical length (more Pfr)
  - Short-day plants = flowering activated by nights LONGER than critical length (less Pfr)
• This is because SID the LAD
  - Short-day plants INHIBITED by Pfr
  - Long-day plants ACTIVATED by Pfr

Question 9

Describe and identify the conditions necessary to induce flowering in long-day plants out of season.

Answer 9

Plants are purposefully exposed to a light source during the night (lengthening light exposure and minimizing time of darkness), results in more Pfr which activates flowering.

Question 10

Describe and identify the conditions necessary to induce flowering in short-day plants out of season.

Answer 10

Plants are purposefully covered with a black cloth for 12-15 hours a day until flower buds begin to grow/ show color. This results in less Pfr, which inhibits flowering.