Plants

Question 1

Describe autotrophs and their role in plant growth.

Answer 1

Autotrophs are organisms that manufacture their own food, usually through photosynthesis, by absorbing carbon dioxide, water, and trace minerals.

Question 2

Define primary growth in plants.

Answer 2

Primary growth refers to the elongation of plant cells at the tips of roots and shoots, involving cell multiplication through mitosis and growth in both length and width.

Question 3

How do cells grow during primary growth?

Answer 3

Cells grow by filling their vacuoles with water, which causes elastic cell structures to stretch, leading to elongation.

Question 4

What is the role of phytohormones in plants?

Answer 4

Phytohormones control various aspects of the plant life cycle, including growth, germination, and responses to environmental stimuli.

Question 5

Explain the function of abscisic acid (ABA) in plants.

Answer 5

Abscisic acid (ABA) prevents germination within the fruit, helping to maintain seed dormancy during fruit maturation.

Question 6

How do gibberellins (GA’s) affect seed germination?

Answer 6

Gibberellins initiate germination by promoting water absorption and breaking the dormancy of seeds.

Question 7

What is the role of cytokines in plant growth?

Answer 7

Cytokines work with auxins to stimulate cell division and promote the growth and development of chloroplasts responsible for photosynthesis.

Question 8

Describe the effect of ethylene on plants.

Answer 8

Ethylene stimulates the ripening of food and the abscission, or falling, of fruit and leaves.

Question 9

How do plants respond to changing conditions without moving?

Answer 9

Plants respond to changing conditions by moving their organs in response to stimuli, a process known as tropism.

Question 10

Define tropism in the context of plant growth.

Answer 10

Tropism is a directional growth response of plants to external stimuli.

Question 11

Describe the long-term changes in plant cells due to environmental conditions.

Answer 11

Long-term changes in plant cells involve permanent alterations to the size and shape of the cells, allowing plants to adapt to favorable conditions for growth, such as high light intensity for photosynthesis, while avoiding unfavorable conditions.

Question 12

Define auxins and their role in plant growth.

Answer 12

Auxins are water-soluble plant hormones produced in the tips of stems, shoots, and roots that promote cell growth by facilitating cell elongation, making cell walls more stretchable.

Question 13

How do different concentrations of auxins affect plant growth?

Answer 13

Different concentrations of auxins result in varying rates of cell elongation on different sides of the plant, causing the plant to bend in one direction.

Question 14

Explain the nastic response in plants.

Answer 14

The nastic response is a rapid, reversible change in turgor pressure of specific cells, resulting in non-directional movements that occur faster than tropic responses.

Question 15

What is the role of K+ ions in the turgor pressure of guard cells?

Answer 15

K+ ions are pumped into guard cells, increasing turgor pressure, which controls the movement of water across the concentration gradient.

Question 16

How does photoperiodism affect plant activity?

Answer 16

Photoperiodism is the regulation of plant activity based on the length of daylight, controlled by the phytochrome system.

Question 17

Define phytochromes and their significance in plants.

Answer 17

Phytochromes are light-sensitive protein pigments in plants that exist in two forms and play a crucial role in regulating growth and development in response to light.

Question 18

Describe the inactive form of phytochrome and its light absorption characteristics.

Answer 18

Pr (phytochrome red) is the inactive form that strongly absorbs red light.

Question 19

How does sunlight affect the conversion of Pr to Pfr?

Answer 19

Sunlight, which contains a lot of red light, rapidly converts Pr to Pfr.

Question 20

Define the role of Pfr in plant responses.

Answer 20

Pfr is the biologically active form that induces gene expression and the production of hormones for processes like flowering, bulb formation, and germination.

Question 21

What happens to Pfr when it is exposed to far-red light?

Answer 21

When Pfr is exposed to far-red light, it absorbs it and gets converted back to Pr.

Question 22

Explain the accumulation of Pfr during the day.

Answer 22

There is more red light than far-red light in sunlight, so more Pfr accumulates during the day compared to Pr.

Question 23

How does the conversion of Pfr to Pr occur during the night?

Answer 23

During the night, active Pfr is slowly converted back to inactive Pr, allowing Pr to accumulate only if there is a long period of darkness.

Question 24

Define photoperiod in the context of plant flowering.

Answer 24

Photoperiod is the length of the period of continuous darkness that determines whether or not a plant will flower.

Question 25

What are the characteristics of short day plants (SDP)?

Answer 25

Short day plants require a photoperiod less than the critical day length to flower and cannot flower in tropics due to insufficient day length.

Question 26

Describe the requirements for long day plants (LDP) to flower.

Answer 26

Long day plants need a photoperiod that exceeds the critical day length to flower.

Question 27

How does Pfr influence flowering in long day plants?

Answer 27

Pfr induces flowering in long day plants, which require high levels of Pfr.

Question 28

What is the effect of Pfr on flowering in short day plants?

Answer 28

Pfr inhibits flowering in short day plants, which prefer shorter photoperiods with less Pfr.

Question 29

Summarize the relationship between Pfr levels and flowering in plants.

Answer 29

High levels of Pfr promote flowering in long day plants, while low levels of Pfr inhibit flowering in short day plants.

Question 30

Describe the adaptive advantage of photoperiodism in plants.

Answer 30

Photoperiodism ensures that flowers can provide and receive pollen effectively, allowing their sexual maturity to align with the activity of pollinators, which maximizes the chances of cross-pollination for asexual reproduction.

Question 31

How does photoperiodism affect the energy expenditure of plants?

Answer 31

Plants expend significant energy and resources in producing leaves and photosynthetic pigments for growth and reproduction as a result of photoperiodism.

Question 32

Define photoperiodism and its role in plant reproduction.

Answer 32

Photoperiodism is the physiological reaction of organisms to the length of day or night, which plays a crucial role in synchronizing flowering and reproductive processes with pollinator activity.

Question 33

Do plants benefit from synchronizing their flowering with pollinator activity?

Answer 33

Yes, synchronizing flowering with pollinator activity maximizes the chances of cross-pollination, which is essential for successful reproduction.