Question

Students testing the effects of solute concentration in soil on plant transpiration noticed a significant decrease in transpiration when abscisic acid was used as the solute. Even at molar concentrations less than 0.2 M, transpiration seemed to stop almost completely.
a) Make a claim as to which structural and/or physiological component of transpiration is affected by the presence of abscisic acid.
b) Explain the reasoning that supports your claim.

Answer 1

Answer:

look in textbook - concept 29.6

Explanation:

Drought stress can also cause stomata to close. A hormone called abscisic acid (ABA) is produced in roots and leaves in response to water deficiency and signals guard cells to close stomata. This response reduces wilting but also restricts CO2 absorption, thereby slowing photosynthesis. ABA also directly inhibits photosynthesis. Water availability is so tied to plant productivity not because water is needed as a substrate in photosynthesis but because freely available water allows plants to keep stomata open and take up more CO2.

abscisic acid (ABA): A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance.