Exam 39: Plant Sensory Systems, signals, and Responses

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

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

Which of the following is not a characteristic of plant hormones?

How does auxin binding to the auxin receptor trigger cell elongation?

To find the gene that encodes for the blue-light receptor,researchers inserted the gene for the PHOT1 protein into insect cells growing in culture.When they exposed the transgenic cells to blue light,they found that the PHOT1 protein became phosphorylated.No other plant proteins were present in the insect cells.Which of the following is a reasonable conclusion from this result?

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.Some seedlings were kept in darkness,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.

Antisense gene sequences can be used to block the transcription of specific genes in a cell or group of cells.Suppose you took a cutting from a plant and treated it with an antisense gene that would block the transcription of an enzyme involved in auxin production.What would happen to your cutting?

Which of the following signals indicates shade to a plant?

When the researchers inhibited the synthesis of gibberellins in the tobacco plants,neither ethylene nor far-red light could trigger a shade avoidance response.Taken together with the data presented above,these data suggest that gibberellins

What hormones are necessary for maintenance of plant tissue culture?

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

Mammalian eyes sense light because they have cells containing molecules called opsins,which change structure when exposed to light.Which of the following plant molecule(s)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.

________ in concentration of auxin in shoot cells and ________ in concentration of auxin in root cells lead to cell elongation.

Which of the following cannot be sensed by plants' senses?

Plant A is diploid and is homozygous for all of the resistance loci.Plant B is tetraploid and is heterozygous for all of the resistance loci.Which is better able to respond to infection?

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?

What do phototropin and ABA have in common?

How could you test the hypothesis that caterpillar saliva and a wound are both necessary to attract the parasitoid wasps?

Figure 39.1 -The data in the figure above 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?