The role of calcium ions in phytochrome-controlled swelling of etiolated wheat (Triticum aestivumL.) protoplasts

摘要

Protoplasts from dark-grown wheat (Triticum aestivumL.) maintained at a constant osmotic potential at 22°C, were found to swell upon red irradiation (R) and the effect was negated by subsequent far-red light (FR), indicating phytochrome involvement. Swelling only occurred when Ca2+ions were present in the surrounding medium, or were added within 10 min after R. Furthermore, Mg2+, Ba2+or K+could not replace this requirement for Ca2+. The presence of K+did not enhance the Ca2+-dependent swelling response. When the Ca2+-ionophore A 23187 was added to the medium, protoplasts swelled in the dark to the same extent as after R. Both the Ca2+-channelblocker Verapamil and La3+inhibited R-induced swelling. It is proposed that R causes the opening of Ca2+-channels in the plasma membrane. Boyle-van't Hoff analyses of protoplast volume after R and FR are consistent with the conclusion that R irradiation causes changes in membrane properties