Exam 39: Plant Sensory Systems, signals, and Responses

You grew reed canary grass seedlings in the dark and cut off their tips.Then you placed tips on agar blocks,one in dark and one in light.Based on your knowledge of auxin movement and stability in light,predict the concentration of auxin in the agar blocks.

Put the following events of the acid-growth hypothesis in order. 1)Cell wall softens and expands. 2)Sugar enters the cell via proton cotransporters. 3)Protons are pumped out of the cell by H⁺-ATPases. 4)Positively charged ions enter the cell. 5)New cellulose microfibrils are produced to extend cell length. 6)Water enters the cell via osmosis,and the cell swells.

Use the following information when answering the corresponding question(s). The shade avoidance response is a plant's way of changing its growth pattern when it is being shaded by another plant.Upon exposure to shade,many plants will grow taller,flatten their leaf angle,and extend their leaves further from their stems in order to reach full sunlight.Research performed by Pierik et al.(Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco.2004.Plant Physiology 136:2928-36;online at http://www.plantphysiol.org/cgi/content/full/136/2/2928)examined the role of ethylene and gibberellins on the shade avoidance response in tobacco plants.The shade avoidance response is known to involve phytochromes. -Refer to the paragraph on the research done by Pierik et al.When tobacco plants were exposed to far-red light,they exhibited increased stem length,petiole length,and petiole angle.These three responses are part of the shade avoidance response.When the same plants were exposed to small concentrations of ethylene while being exposed to far-red light,they exhibited even greater increases in stem length,petiole length,and petiole angle.In a subsequent experiment,tobacco plants showed an increase in ethylene production in response to far-red light.Moreover,mutant plants that are insensitive to ethylene did not show a shade avoidance response when exposed to far-red light.Taken together,these data suggest that ethylene _____.

Table 39.1 -Refer to Table 39.1.Plant C is a long-day plant.

What will a plant sensitive to touch or vibration look like when it is repeatedly touched or exposed to wind?

What do abscisic acid and gibberellins have in common?

Figure 39.3 -Figure 39.3 is a Northern blot showing the expression of Myb mRNA in cultured aleurone layer cells that were treated with gibberellin versus control cells that were not treated with gibberellin.Only the gibberellin-treated cells expressed the Myb mRNA,but the Myb mRNA was not detectable until 6-12 hours after gibberellin application.Why did it take so long?

If a particular species of bacterium were able to produce a substance that breaks down reactive oxygen intermediates and inhibits the production of nitric oxide,it would be less effective at infecting plant cells.

Which of the following cell activity would not be triggered by a signal transduction cascade?

If a Venus flytrap were treated with a drug that inhibited the H⁺-ATPase,which of the following would likely happen?

What hormones are necessary for maintenance of plant tissue culture?

Upon exposure to blue light,plants not only begin to grow toward the light,but move their chloroplasts to the sunny side of each cell.Why would it be advantageous to move chloroplasts within cells?

Suppose a plant had a photosynthetic pigment that absorbed far-red wavelengths of light.In which of the following environments could that plant thrive?

To understand how plant phototropic responses are regulated,a researcher performed the following experiment.He exposed oat seedlings to light and then cut off tips of coleoptiles and placed them on agar blocks.Later the agar blocks were placed on decapitated coleoptiles of other individuals,and some seedlings were kept in the dark while others were exposed to light.Based on your knowledge of auxin synthesis and mode of action,predict in what cases the decapitated coleoptiles would bend to the right.

Use the following information when answering the corresponding question(s). The shade avoidance response is a plant's way of changing its growth pattern when it is being shaded by another plant.Upon exposure to shade,many plants will grow taller,flatten their leaf angle,and extend their leaves further from their stems in order to reach full sunlight.Research performed by Pierik et al.(Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco.2004.Plant Physiology 136:2928-36;online at http://www.plantphysiol.org/cgi/content/full/136/2/2928)examined the role of ethylene and gibberellins on the shade avoidance response in tobacco plants.The shade avoidance response is known to involve phytochromes. -Refer to the paragraph on the research done by Pierik et al.Ethylene's role in the shade avoidance response in tobacco plants is related to its role in fruit ripening,leaf abscission,and senescence.

Which of the following will occur when sensory hairs in a Venus flytrap are stimulated?

In lettuce seeds,blue light initiates germination.If you measured hormone levels within the seed,which hormone would be produced upon exposure to blue light?

A certain species of bacterium is not very effective at colonizing potato plants because the potato plants have a resistance gene that responds to the presence of the bacterium.Which of the following mutations would make the bacterium more successful at invading the potato plant?

Figure 39.1 -The data in Figure 39.1 were taken from a study on the effects of far-red light on stem elongation.The data indicate that plants from shady habitats do not respond to far-red light by growing taller.Which of the following would be a logical hypothesis for why these plants do not respond to far-red light?

What do phototropin and ABA have in common?