Question

In his 1875 treatise on plant irritability, botanist Wilhelm Pfeffer investigated the mechanisms underlying pulvinar movement in Mimosa pudica and legume leaves. Contrary to the contemporary hypothesis that leaf droop resulted from passive mechanical exhaustion of cellular walls, Pfeffer demonstrated that rapid movement is driven by active, asymmetric changes in turgor pressure within specialized motor organs called pulvini. Specifically, Pfeffer observed that upon mechanical stimulation, parenchymal cells in the abaxial (lower) half of the pulvinus rapidly lose potassium ions and water to surrounding intercellular spaces, causing a sudden loss of cell turgor and volume. Simultaneously, cells in the adaxial (upper) half retain their turgor or undergo slight turgidity increases, creating a differential mechanical tension that forces the leaf downward. Furthermore, Pfeffer established that recovery of upright leaf posture requires an energy-dependent active transport mechanism to re-accumulate potassium ions back into the abaxial cells against a concentration gradient, a process that is significantly inhibited under hypoxic conditions or in the presence of metabolic toxins like cyanide.

According to the passage, which of the following statements regarding leaf movement in Mimosa pudica are explicitly supported? Select all that apply.