Notes 10

Question 1

Plant behaviours are defined as what?

Answer 1

Plant Behaviors are defined as rapid morphological or physiological responses to events, relative to the lifetime of an individual. Since Darwin, biologists have been aware that plants behave but it has been an underappreciated phenomenon.

Question 2

Plants respond to what?

Answer 2

Their environment, often rapid and over short intervals. Difficult to observe. Could be light stimulus, environmental stimulus or hormones

Question 3

What is the point of auxin?

Answer 3

Auxin promotes cell elongation and helps in cell division and growth.

Question 4

What was the experiment that the Darwins’ did?

Answer 4

The darwins looked at the plants and saw that they bent toward the light. They cut the tip and found it did not bend, and an opaque cap that didn’t make the plant bend. Thought it needed to hit the tip. Made a transparent tip and it bent. Put an opaque shield over the curve, and it is still bent.

Question 5

How did Boysen-Jensons change the Darwins experiment?

Answer 5

Boysen-Jensons added a gelatin barrier across the stem which was permeable to the top and allowed it to still bend. When he added mica (impermeable) to top it didn’t bend. He knew something was traveling from tip to stem.

Question 6

Auxin is also known as what?

Answer 6

indoleacetic acid (IAA)

Question 7

What is the rate which auxin is produced?

Answer 7

Produced primarily in shoot tips, can be transported at a rate of 1 cm/hr.

Question 8

what direction is auxin transport?

Answer 8

Transport is stem tip to base only (aka “polar
transport”)

Question 9

How were cytokinins discovered?

Answer 9

Cytokinins were discovered because people figured out coconut milk and meat (endosperm) stimulated plant embryo growth. They added degraded DNA to cultured tobacco cells and induced them to divide. They found a modified form of adenine which they called cytokins because it stimulated cytokinesis (cell division)

Question 10

Where are cytokinins produced?

Answer 10

Cytokinin is produced actively in growing tissue (roots, embryos, fruits). It moves up from the plant from roots via xylem. Controls apical dominance.

Question 11

How were gibberellins discovered?

Answer 11

Farmers in Asia in the 1900s noticed some rice plants grew tall and toppled over before they could mature. In the 1920s it was discovered that fungus in the genus Gibberella was caused through the secretion of a chemical called gibberellin. Becomes infected and bolts, puts out flowers and leaves

Question 12

What are gibberellins?

Answer 12

Gibberellin is produced in young roots and leaves as well as embryos, promoting cell elongation and division. IN most plants you need both auxins and gibberellins need to be present for fruit to develop. Also regulate seed development, germination and sex determination.

Question 13

How does germination work?

Answer 13

A seed absorbs water which triggers the embryo to release gibberellin. This sends a signal to the aleurone (thin outer layers of endosperm). Then the aleurone responds to gibberellin by synthesizing a secreting enzyme that can digest nutrients stored in the endosperm. (alpha-amylase which breaks down starch). And last sugar in the cotyledon along with other nutrients are consumed by the seedling and sustain it until it can produce its own leaves and photosynthesize.

Question 14

T or F: Abscisic Acid (ABA) is synthesized in almost all plant cells.

Answer 14

Abscisic Acid (ABA) is synthesized in almost all plant cells. This is the hormone that slows growth to hibernate, basically to wait until conditions are favorable.

Question 15

How does aba slow a plants growth?

Answer 15

As seeds mature, plants want to make sure they do not germinate until growing conditions are right. ABA levels might increase 100% during seed maturation. Allows seeds to stay dormant for long periods of time. ABA also helps with drought tolerance by controlling stomata (high ABA level=closing of stomata)

Question 16

Seeds know when to grow based on the ratio of ____ to _____.

Answer 16

Seeds know when to grow based on the ratio of ABA to gibberellins. When ASBA is washed out of seed (desert plants). ABA inactivation is triggered by light or temp,when conditions are good can “Turn off ABA ‘’, and low ABA triggers precious germination which is where things germinate when they shouldn’t.

Question 17

What is the effects of life on plant morphology?

Answer 17

Photomorphology is the effects of life on plant morphology.

Question 18

Plants are most responsive to _____ and ____ lights.

Answer 18

Plants are most responsive to red and blue lights. Led researchers to identify blue light photoreceptors and phytochromes (red light photoreceptors)

Question 19

What are phytochromes?

Answer 19

Phytochromes are red light absorbing pigments and come in different forms. Pr= red light absorbing and Prfr= far red light absorbing. Converts back and forth. Conversion back to red form from far red form is more slow. Converts due to darkness (far is when dark).

Question 20

T or F: The first flash of light determines response

Answer 20

False. The last flash of light determines response. response is reversible.

Question 21

How does red light and far red light determine if germination occurs?

Answer 21

The seed germination is responding to the far red light. the pr form of phytochrome can be converted to the pfr form and vice versa. the plant will not germinate if only pfr or just in the dark, germinates if last flash is pr.

Question 22

Sunlight has what types of red light?

Answer 22

Sunlight is mostly red and far red light but the conversion of Pr to Pfr is faster so germination is triggered.

Question 23

What are the responses to pfr?

Answer 23

Pfr inhibits vertical growth and stimulation and branching, sets internal clocks and controls flowering.

Question 24

Canopy absorbs more _____ light than ____ light.

Answer 24

Canopy absorbs more red light than far red so forest floor trees have more far red increases Pr relative to Pfr, simulates the plant to invest in resources to grow tall.

Question 25

Why should plants keep track of time?

Answer 25

Plants keep track of time because of flowering or germinating at the same time every year to sync with the cycle of pollinators, and need to have good temp for growing. Needs a daily clock to keep track of things like humidity or light. 26 hour cycle

Question 26

What is photoperiodism?

Answer 26

Photoperiodism is how plants change with periods of time. Length of day changes with latitude and flowering is controlled by night length instead of day.

Question 27

Short day (long night) plants need nights to be ___ than day to flower. Long day (short night) flowers need nights to be ___ to flower.

Answer 27

Short day (long-night) plants need nights
to be longer than day to flower
Long day (short) plants need nights to be
shorter than day to flower

Question 28

What are some stimuli/plant stressors?

Answer 28

Other stimuli and plant stressor can be gravity, mechanical stimuli, and environmental stress like floods, drought, salt, and heat.

Question 29

How does gravity affect plants?

Answer 29

Roots grown down (positive gravitropism), shoots grow up (negative gravitropism). It knows this because structures called statoliths that slide to the lowest side of root and triggers gravity sensing mechanism that develops auxin and allows cell elongation and bending of plants.

Question 30

How does mechanical stimuli affect plants?

Answer 30

Mechanical stimuli: Touching plants can inhibit growth

Question 31

What is thigmomorphogenisis?

Answer 31

Thigmomorphogenisis: changes in growth form as a result of mechanical perturbation.
Thigmotropism are plants that are adapted to touch and grow in response to touch. Important for climbing plants.

Question 32

How does environmental stress affect plants?

Answer 32

Environmental stress: Over water can make roots soggy and rotten or underwatered.

Question 33

How does flooding affects plants?

Answer 33

Too much water means there is no space for oxygen, the plant roots will suffocate. In continually wet habitats plants develop aerial roots. In other cases root cells deprived of oxygen die and create tubes that function as snorkels to provide oxygen to the root.

Question 34

How do drought affects plants?

Answer 34

Less water stimulates production of ASA which helps keep stomata closed. Wilted leaves form tubes that reduce SA and reduce water loss by evapotranspiration. Plants may communicate about stresses with neighbors.