Notes 10 Flashcards
Plant behaviours are defined as what?
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.
Plants respond to what?
Their environment, often rapid and over short intervals. Difficult to observe. Could be light stimulus, environmental stimulus or hormones
What is the point of auxin?
Auxin promotes cell elongation and helps in cell division and growth.
What was the experiment that the Darwins’ did?
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.
How did Boysen-Jensons change the Darwins experiment?
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.
Auxin is also known as what?
indoleacetic acid (IAA)
What is the rate which auxin is produced?
Produced primarily in shoot tips, can be transported at a rate of 1 cm/hr.
what direction is auxin transport?
Transport is stem tip to base only (aka “polar
transport”)
How were cytokinins discovered?
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)
Where are cytokinins produced?
Cytokinin is produced actively in growing tissue (roots, embryos, fruits). It moves up from the plant from roots via xylem. Controls apical dominance.
How were gibberellins discovered?
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
What are gibberellins?
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.
How does germination work?
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.
T or F: Abscisic Acid (ABA) is synthesized in almost all plant cells.
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.
How does aba slow a plants growth?
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)
Seeds know when to grow based on the ratio of ____ to _____.
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.
What is the effects of life on plant morphology?
Photomorphology is the effects of life on plant morphology.
Plants are most responsive to _____ and ____ lights.
Plants are most responsive to red and blue lights. Led researchers to identify blue light photoreceptors and phytochromes (red light photoreceptors)
What are phytochromes?
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).
T or F: The first flash of light determines response
False. The last flash of light determines response. response is reversible.
How does red light and far red light determine if germination occurs?
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.
Sunlight has what types of red light?
Sunlight is mostly red and far red light but the conversion of Pr to Pfr is faster so germination is triggered.
What are the responses to pfr?
Pfr inhibits vertical growth and stimulation and branching, sets internal clocks and controls flowering.
Canopy absorbs more _____ light than ____ light.
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.
