High-Q | סימולציה 3

40

סימולציה מס' 3

פרק שני

– אנגלית

Raskin studied tobacco plants infected with tobacco mosaic virus, which forms dark blisters on leaves and causes them to pucker and yellow. The sick plants produce salicylic acid in large quantities. He and his colleagues found that some of the acid turns into methyl salicylate, a volatile chemical, that evaporates from diseased parts of plants. When the 15 researchers pumped air from infected tobacco plants over healthy ones, the healthy plants absorbed the methyl salicylate and turned it back into salicylic acid. That triggered the production of immune-system proteins, making the healthy plants more resistant to the disease. On the other hand, when the researchers removed the methyl salicylate first, the rest of the air caused no increase in the healthy plants' immunity. 20 Raskin sees crops one day being treated with aspirin instead of pesticides. In the case of fruits and vegetables, which are still alive long after their harvest, salicylic acid could even help them resist disease while they are being stored. “Instead of spraying toxic chemicals and poisons to kill pathogens,” Raskin says, “this is supplying the plants with a natural substance to boost their own immunity.” 25

Questions

13. The production of salicylic acid by tobacco plants proves that they -

(1) signal when in distress (2) cannot make sounds (3) are spiritually inclined (4) absorb aspirin

14. “…aspirin can also take to the air…” (line 8) in order to -

(1) destroy the pests that infect the aspirin producing plant. (2) produce salicylic acid (3) activate the immune system of nearby plants (4) fertilize other plants

15. The conversion of methyl salicylate into salicylic acid -

(1) helped heal infected plants (2) is effective in the fight against blisters in plants (3) eventually had no effect on the plants in the experiment (4) enabled healthy plants to better defend themselves against the disease

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