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| Photomorphogenesis and Phytochrome |
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nondirectional, light-triggered development
-red light wavelengths change Pr to Pfr and can trigger photomorphogenesis.
-Pfr is "biologically active" form of phytochrome |
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| involve bending of growing stems or leaves toward light sources-auxin most likely involved |
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the response of a plant to gravity
-auxins play primary role |
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1. gravity perceived by cells
2. signal is formed following a shift in position
3. signal is transduced intra- and inter- cellularly
4. causes greater cell elongation on one side |
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| auxin moves to lower side causing those cells to grow more than cells on upper side--stem bends upward (negative gravitropism) |
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| auxin is still moved to lower side but upper side of roots grow more rapidly than the lower side--roots bend downward (positive gravitropism) |
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| directional growth response to contact with an object (tendrils, vining stems) |
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| outside grows faster than inside of vine/tendril; caused by touch genes activated (up regulated) by touch |
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| pressure within a living cell resulting from water diffusion |
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| multicellular swellings located at base of leaves of leaflets; rapid loss of turgor pressure associated with changes in leaf orientation after exposure to a stimulus |
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| endogenous time keepers that keep plant responses synchronized with the environment |
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Definition
-Continue to run in absence of external signals
-about 24 hours in duration
-can be reset or entrained to external signals
-can compensate for effects of temperature
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Term
The ability to cease growth and enter a dormant stage provides_______.
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| environmental signals that initiate and terminate dormant phases: |
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changes in temperature
changes in soil moisture
changes in day length |
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| Chilling and freezing acclimation |
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Definition
| rely on high levels os unsaturated fatty acids, supercooling, and synthesis of antifreeze compunds |
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| Acclimation to high temperatures |
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| involves the development of heat shock proteins that stabilize other proteins at high temps to avoid folding errors (denaturation) |
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Many internal signaling pathways involve _____.
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| plant hormones (phytohormones) |
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-produced in small quantities, then transported elsewhere for use
-stimulate and/or inhibit physiological processes
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| 7 major types of phytohormones |
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Definition
| auxins, cytokins, gibberellins, brassinosteroids, oligosaccharins, ethylene, and abscisic acid |
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Definition
-increases plasticity of plant cell walls and involved in stem elongation
-Discovered by Went (1926)
-In addition to its roles in photo- and gravi- tropism, it promotes activity of the vascular cambium and vascular tissues
-Plays role in fruit development |
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| auxin may work by causing cells to actively pump H+ from the cytoplasm into the cell wall space (loosens cell wall allowing cell expansion) |
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in combination with auxins, stimulate cell division and differentiation.
-most produced in root apical meristems
-inhibit formation of lateral roots (auxins promote their formation)
-have been used against plants by pathogens
-Cause massive cell divii=sion and formation of an agrobacterium (crown gall) tumor |
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Term
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Definition
Named after fungus Gibberella fuji kuroi which causes rice plants to grow abnormally tall.
-126 different gibberellins found in plants synthesized in shoot and root apices
-causes stem elongation
-may hasten seed germination |
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Definition
-gas (H2C=CH2) is produced when auxin is transported down from the apical meristem of the stem.
-plays major role in fruit development and ripening
-production increases rapidly when the plant is exposed to toxic chemicals, temp extremes, drought, pathogens, and other stresses |
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produced chiefly in mature green leaves and fruits
-suppresses bud growth, promotes leaf senescence and seed nutritional uptake and dormancy
-helps control stomatal opening and closing |
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-have a broad spectrum of physiological effects, many similar to/synergistic with auxin
-can be triggered by chilling and drought stress
-can enter nucleus to directly influence gene expression (just like human steroidal hormones) |
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