1 A) With the extra energy provided by the light, the plant can grow selectively in the direction with more light. B) Light causes a hormone, auxin, to migrate away from the light side to the dark side into darker tissue where it promotes cell elongation. C) Light causes inhibition of growth in the cells closest to it by creating a conformational change in a steroid receptor. D) Cells closest to the light become photobleached, making them unable to grow as fast as cells farther from the light. E) Blue light receptors in tissue near the light signal gene activation that changes the plant's growth aspect. 2 A) It causes apoptosis (programmed cell death) in cells, which therefore causes bending toward the region where auxin has accumulated. B) It seems to be involved with the transmission of a signal arising from the gravity sensing cells that contain amyloplasts and the site of growth. C) Auxin causes mutations in genes, making target cells less efficient in growing. As auxin accumulates at the tops of horizontal branches, it stimulates bending upwards. D) All of these possibilities are being investigated as to the role of auxin in gravitropism. E) Two of the above are valid explanations for the effect of auxin in plant growth. 3 A) It generates a charge in the plant's nervous system, which is transduced to distant cells in leaves. These cells lose water rapidly through their stomata thereby collapsing. B) Genes in the pulvinus are stimulated for rapid cell growth in the side farthest from the stimulation. C) Apoptosis (programmed cell death) occurs in cells nearest the stimulation. D) An electrical stimulation of cell membranes causes pumping of ions from one side of the pulvinus to the other. This causes the depleted cells to collapse while the other cells swell. E) None of the above explain the function of a pulvinus. 4 A) temperatures becoming more favorable for germination B) availability of water and moisture C) changes in day length D) All of the above factors have been shown to allow seeds to break dormancy. E) Only appropriate temperatures and inhibitory chemicals have been demonstrated to terminate dormancy. 5 A) It undergoes a conformational change which allows it to be ubiquitinated and subsequently destroyed by a proteasome. B) It can either move from the cytoplasm into the nucleus and bind other proteins that form a transcription complex or work through protein kinase-signaling pathways that lead to the transcription of light-regulated genes.
It binds to promoters of specific genes to turn them on C) It binds to promoters of specific genes, preventing RNA polymerase from binding and therefore blocks expression. D) It binds to chlorophyll to improve its ability to absorb light. E) It blocks the Calvin cycle, allowing the plant's metabolism to concentrate on signal transduction. 6 A) amyloplasts, plastids that contain starch B) auxins C) gravoliths D) mitochondria E) vesicles containing iron granules 7 thigmotropism ?A) specific responses caused by hormone accumulation in plant tissues B) reversible changes in tissue structure due to physical stimulus C) vertical growth caused by repeated, regular contact with a stimulus D) spontaneous coiling of plant tissues around nearby, cylindrical objects E) directional growth of a plant or plant part in response to contact with some thing -- animal, another plant, the wind 8 A) true B) false 9 A) auxin B) cytokinin C) ethylene D) gibberellin E) brassinosteroid 10 A) dormant B) dehydrated C) photoperiodic D) thigmonastic E) gravitropic 11 A) adenine B) thymine C) guanine D) cytocine E) uracil 12 A) gravitropism B) thigmotropism C) dormancy D) phototropism E) thermotropism 13 A) gravitropism B) circadian rhythms C) phototropism D) heat shock E) thermotropism 14 A) brassinosteroids B) oligosaccharides C) cytokinins D) auxins E) abscisic acids 15 A) They were first discovered in pollen. B) They are released from the cell wall by enzymes secreted by pathogens. C) Their functions overlap with those of auxins and gibberellins. D) Their characteristics are similar to animal steroids. E) They may have evolved before the evolutionary divergence of plants and animals. 16 A) ABA plays a role in seed dormancy. B) ABA is antagonistic to gibberellins during germination. C) Abscisic acid is known to stimulate fruit abscission. D) ABA promotes senescence by counteracting auxin. 17 A) gibberellin B) ethylene C) cortisol D) auxin 18 A) true B) false 19 A) The gene for ethylene synthesis is blocked from being transcribed. B) The gene for the ethylene enzyme is transcribed with another organic that, upon translation, combines with the ethylene enzyme to form a protein for ethanol production. C) Antisense mRNA is transcribed with sense mRNA for ethylene. The two hybridize; thereby blocking the sense mRNA from translating the gene for the ethylene synthesis enzyme. D) Antisense mRNA is transcribed while sense mRNA transcription is blocked. 20 A) cell division B) membrane polarization C) elongation of hypocotyls in reduced levels of red light D) reproductive development 21 A) auxin B) ethylene C) gibberellins D) oligosaccharins
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