Effects of Ca-signalling inhibitors on short-term cold-acclimation of hydraulic conductivity in roots of Brassica rapa plants

The signal transmission during short-term acclimation in Brassica rapa plan ts confronted with low root zone temperatures was explored by using signal blockers in root medium with (or without) low temperatures, and examining c hanges in root hydraulic conductivity. EGTA, lanthanum, and verapamil did n ot block this root response suggesting that Ca2+ exchanges with the apoplas t on the plasmalemma were not strictly required for signal transfer In cont rast, treatments with lithium ions or neomycin blocked the reestablishment of root hydraulic conductivity during cold acclimation. This result is cons istent with the involvement of IP3 signaling in the response, and suggests the role of Ca2+ ions from internal stores as secondary messenger. The effe ct of t-BHQ (modulator of Ca2+ exchange between internal stores and protopl ast ) reinforces this hypothesis of IP3 intervention in delivering Ca2+ ion s on the endomembrane system. The target of the Ca2+ ions would be enzymes (such as protein kinases) rather than calmodulin itself.