Final answer:
The ion channels involved in the leaf-closing response of the Mimosa plant are those that facilitate the movement of Calcium ions (Ca²⁺). These ion channels are part of a signaling pathway activated by mechanical stimulation, causing the leaves to droop and fold.
Step-by-step explanation:
The ion channels responsible for the leaf-closing response in the Mimosa plant, also known as the sensitive plant, are part of an intricate signaling process that includes the second messengers NO (Nitric Oxide) and Ca²⁺ (Calcium ions). When the leaves of the Mimosa pudica are touched, mechanical stimulation triggers an electrical signal, which is transmitted via calcium ion channels.
This rapid influx of calcium ions into cells results in a change in turgor pressure, causing the leaves to droop and fold. The movement is reversible and after a while, the plant returns to its normal state. The role of calcium ion channels in this process is analogous to their function in other plant movement responses, such as phototropism, where IAA (Indole Acetic Acid), a plant hormone, accumulates on the shaded side of the plant, inducing cell elongation.