Exam 37: Plant Sensory Systems, Signals, and Responses

An eccentric millionaire botanist has offered a $25,000 scholarship to anyone who can successfully get a plant to grow through a vertical maze in complete darkness. The maze is not in a box; the maze is simply drawn on the wall, and the contestants must get their plant to grow in a pattern that matches the path through the maze. You need the money and feel confident that you can accomplish this task. Which of the following techniques will help you succeed?

Why does Arabidopsis have 5 genes that code for phytochrome?

Figure 37.2 -Suppose you laid a seedling on its side so that the root was parallel to the ground. Immediately after the change in position, where in the root cells position A, B, or C in the figure above) would you find the amyloplasts? The answer should be one of the positions show in Figure 37.2.

Mammalian eyes sense light because they have cells containing molecules called opsins, which change structure when exposed to light. Which of the following plant molecules) would be analogous to mammalian opsins in their light- sensing ability?

Lettuce seeds need full sunlight to germinate; therefore, germination is inhibited when their phytochrome molecules are in the Pfr conformation.

Which of the following signals indicates shade to a plant?

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.

In the fall, the leaves of some trees change colour. This happens because chlorophyll breaks down and the accessory pigments become visible. What hormone is responsible for this?

When Charles and Francis Darwin first documented phototropism, why was it important that they germinated the grass seeds in the dark before beginning the experiment?

Use the following information when answering the corresponding questions). Some plants continually produce secondary defense compounds. Other plants are induced to form secondary defense compou when they are injured. Corn seedling leaves that are chewed on by the caterpillars of a type of cutworm moth emit immediate chemicals LOX products), and, after six hours, large amounts of terpenoid compounds are released into the air. The terpenoid are released not only from the leaf being chewed, but from all leaves of the plant. The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the caterpillar. When the wasp larvae hatch, they eat and kill the moth caterpillar. T.C.J. Turlings, J. H. Loughrin, P. J. McCall, U. S. R. Rose, W. J. Lewis, and J. H. Tumlinson. 1995. How caterpillar- damaged plants protect themselves by attracting parasitic wasps. Proceedings of the National Academy of Science 92:4169- 74.) -How could you test the hypothesis that caterpillar saliva and a wound are both necessary to attract the parasitoid wasps?

Figure 37.3 -Figure 37.3 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?

Which of the following is the correct sequence of events after a receptor perceives a signal?

Antisense gene sequences can be used to block the transcription of specific genes in a cell or group of cells. Suppose you treated a seed with an antisense sequence that blocked the transcription of GAMyb transcription factor. What would happen to the seed?

Plant A B C Growth Conditions 14 hours of darkness 14 hours of darkness, interrupted by 10 minutes of light during the fifth hour 14 hours of light, interrupted by 10 minutes of darkness during the fifth hour Result Flowers or no flowers) No flowers No flowers Flowers Table 37.1 -Plant C is a long- day plant.

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

You grew reed canary grass seedlings in the dark and cut off their tips. You then placed the 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.

A population of plants experiences several years of severe drought. Much of the population dies due to lack of water, but a few individuals survive. You set out to discover the physiological basis for their adaptation to such an extreme environmental change. You hypothesize that the survivors have the ability to synthesize higher levels of than their siblings do.

prevents seeds from germinating until conditions are favourable for the growth of the plant.

Use the following information when answering the corresponding questions). Some plants continually produce secondary defense compounds. Other plants are induced to form secondary defense compou when they are injured. Corn seedling leaves that are chewed on by the caterpillars of a type of cutworm moth emit immediate chemicals LOX products), and, after six hours, large amounts of terpenoid compounds are released into the air. The terpenoid are released not only from the leaf being chewed, but from all leaves of the plant. The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the caterpillar. When the wasp larvae hatch, they eat and kill the moth caterpillar. T.C.J. Turlings, J. H. Loughrin, P. J. McCall, U. S. R. Rose, W. J. Lewis, and J. H. Tumlinson. 1995. How caterpillar- damaged plants protect themselves by attracting parasitic wasps. Proceedings of the National Academy of Science 92:4169- 74.) -What can you conclude based only on the information in the preceding paragraph?

You are out working in your garden, and you notice that one of your favorite flowering plants has black, dead spots on the leaves. You immediately suspect that the plant has been invaded by a pathogen and has initiated a