Plant responses

Question 1

What are the 2 limitations of plant responces?

Answer 1

• rooted to the spot so aren’t mobile
• don’t have a rapidly responding nervous system

Question 2

How do plants respond to their environment?

Answer 2

produce hormones that are transported through the plant and affect different parts of the plant

Question 3

What is plant dormancy?

Answer 3

period of inactivity allowing the seed to withstand various adverse environmental condition

Question 4

What are the 2 key structures in initiating the germination process?

Answer 4

Embryo = the developing plant

Endosperm = an energy store that contains starch and surrounds the embryo

Question 5

What is the process of plant germination?

Answer 5

1) water enters the seed

2) absorption of water causes the embryo to synthesise gibberellins

3) in response amylase and maltase enzymes are synthesised

4) amylase enzymes hydrolyse the starch stored in the endosperm into maltose

5) this can then be broken down into glucose which provides the embryo with sugars that are essential for energy and growth

Question 6

What are plant growth factors?

Answer 6

chemicals that influence plant development mainly by modulating cell elongation and division

Question 7

What is synergistic plant hormone interaction?

Answer 7

when different hormones work together giving a greater response than on their own

Question 8

What is antagonistic plant hormone interaction?

Answer 8

different hormones have opposing effects like one promoting growth and one inhibiting it

the balance between them determines the response of the plant

Question 9

What are auxins and give an example of one?

Answer 9

Auxins are crucial plant growth factors

e.g indoleacetic acid (IAA) is synthesised in the growing tips of shoots and roots where cell division occurs

Question 10

What aspects of plant growth do auxins regulate?

Answer 10

• cell expansion + differentiation
• suppression of lateral bud growth (apical dominance)
• directional growth responses (tropisms)

Question 11

What are the 2 effects auxin has on plant tissue?

Answer 11

• high concentration inhibit root growth and promote shoot growth.
• low concentration promote root growth and inhibit shoot growth

Question 12

What is the role of IAA in shoot elongation?

Answer 12

• auxins are synthesised by the meristem cells in shoot tips
• auxins diffuse down the shoot away from the tip
• auxins bind to receptor sites on cell-surface membranes
• low pH develops in cell walls
• cells absorb water by osmosis forming vacuoles and increasing the internal pressure causing the cell walls to expand.
• cells elongate and the plant grows

Question 13

What are abiotic stresses?

Answer 13

non-living factors in the environment that can negatively affect an organisms survival

Question 14

What are examples of abiotic plant stresses?

Answer 14

• changes in day length
• excessive cold and heat
• lack of water or excess water
• high winds
• changes in salinity

Question 15

What is photoperiodism?

Answer 15

sensitivity of plants to the level of light in their environment

Question 16

How does photoperiodism align with the changing seasons?

Answer 16

Summer = daylight hours are maximum and trees are in full leaf maximising photosynthesis and growth

Autumn = lengthening of dark period triggers leaf fall in trees

Winter = daylight hours are at a minimum and trees maintain a period of dormancy

Spring = days lengthen and temp rises causing trees to come out of dormancy