Plant Physiology

Step 1: Understand the functions of various plant hormones (phytohormones).
Plant hormones are chemical messengers that regulate various physiological processes in plants, including growth, development, and responses to environmental stimuli. Step 2: Evaluate the function of each hormone listed in the options.
(1) Auxin: Auxins are primarily involved in cell elongation, phototropism, gravitropism, and apical dominance. They generally promote growth.
(2) Gibberellin: Gibberellins play roles in stem elongation, seed germination, and flowering. They generally promote growth.
(3) Cytokinin: Cytokinins promote cell division and differentiation, delay senescence (aging) in leaves, and promote bud development. They generally promote growth.
(4) Abscisic Acid (ABA): Abscisic acid is a stress hormone. It plays a crucial role in regulating plant responses to environmental stresses, such as drought. ABA promotes stomatal closure to reduce water loss, inhibits seed germination, and plays a role in dormancy and leaf senescence (aging and detachment), which can lead to wilting. Specifically, during water stress, ABA levels increase, causing stomata to close, which reduces transpiration but also leads to wilting if water uptake is insufficient. Step 3: Identify the hormone associated with wilting.
Abscisic acid is known for its role in stress responses, including causing stomatal closure and promoting processes that lead to wilting and dormancy, especially under water deficit conditions. $ $

Step 1: Understand Transpiration.
Transpiration is the process by which plants lose water through their leaves, stems, or other parts. To measure the rate of transpiration, a device called a potometer is commonly used. Step 2: Analyze Each Option.
Option (1): Barometer — Incorrect, as a barometer measures atmospheric pressure, not transpiration.
Option (2): Potometer — Correct, as a potometer is specifically designed to measure the rate of water uptake by plants, which is directly related to transpiration.
Option (3): Hygrometer — Incorrect, as a hygrometer measures humidity, not transpiration.
Option (4): Galvanometer — Incorrect, as a galvanometer measures electrical current, not transpiration. Step 3: Final Answer. $ $