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 plants confronted with low root zone temperatures was explored by using signal blockers in root medium with (or without) low temperatures, and examining changes in root hydraulic conductivity. EGTA, lanthanum, and verapamil did not block this root response suggesting that Ca2+ exchanges with the apoplast on the plasmalemma were not strictly required for signal transfer. In contrast, treatments with lithium ions or neomycin blocked the reestablishment of root hydraulic conductivity during cold acclimation. This result is consistent with the involvement of IP3 signaling in the response, and suggests the role of Ca2+ ions from internal stores as secondary messenger. The effect of t-BHQ (modulator of Ca2+ exchange between internal stores and protoplast) reinforces this hypothesis of IP3 intervention in delivering Ca2+ ions on the endomembrane system. The target of the Ca2+ ions would be enzymes (such as protein kinases) rather than calmodulin itself.