Soru

For decades, plant physiologists attributed rapid systemic signaling in response to mechanical wounding almost exclusively to chemical transport through the phloem. According to this traditional model, phytohormones such as jasmonic acid traveled passively along hydrostatic pressure gradients, initiating defensive gene expression in distant leaves only after a substantial temporal lag. However, recent electrophysiological studies utilizing microelectrodes inserted into vascular bundles have identified surface potential waves—propagated electrical transients—that traverse the plant stem at velocities exceeding 100 millimeters per second. These electrical signals arrive at uninjured distant tissue long before bulk flow could transport chemical elicitors. Curiously, when researchers artificially depolarized cell membranes while blocking phloem transport via localized cryo-ablation, target leaves still mounted a robust systemic immune response. This finding strongly suggests that electrical depolarization is not merely a byproduct of vascular pressure changes, but functions as an autonomous signal capable of directly activating calcium ion channels and downstream transcription factors. Nevertheless, some skeptics contend that electrical wave propagation relies on intact symplastic continuity through plasmodesmata, which might still permit microscopic cascades of signaling molecules. To resolve this ambiguity, investigators must isolate single-cell electrophysiological dynamics from multicellular symplastic pathways.

Based on the passage, which of the following can be inferred regarding the systemic defensive response in plants?