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1. (a) Name the gaseous plant hormone. Describe its three different actions in plants.
i. is a gaseous plant hormone.
ii. It promotes the ripening of fruits such as tomato, apple, mango, banana etc.
iii. It induces the elongation of stems and coleoptiles, thereby stimulating them to grow.
iv. It accelerates the senescence of leaves and flowers.
1. (b) Which hormone is known as a stress hormone in plants? Why?
Abscisic acid improves plant tolerance to a variety of stresses. As a result, it's also known as a stress hormone.
2. Describe an experiment which demonstrates that growth-stimulating hormone is produced at the tip of the coleoptile?
i. The prevalence and effect of auxins in plants was first demonstrated by a Dutch biologist Frits Warmot Went.
ii. During his , he dissected the tips of Avena coleoptiles and observed that the tips did not grow due to the lack of an essential growth stimulator .
iii. In his , he inserted the detached coleoptile tips on agar blocks and left them for an hour.
iv. After an hour he separated the tips and placed the agar blocks on the decapitated coleoptile. As a result of this he observed that the growth stimulated in the decapacitated coleoptile was due to some chemical which diffused from the cut coleoptile tips into the agar block.
v. From these series of experiments Went concluded that the chemical diffusing from the tip of coleoptiles was responsible for growth, and he named it as “Auxin” meaning ‘to grow”.
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