Influences of Light Quality, Growth Regulators and Inhibitors of Protein Synthesis on Respiration of Protoplasts from Meristematic Cells in Barley Seedlings

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Abstract
The influences of light of different wavelengths and plant growth regulators on the respiration of protoplasts isolated from tissue 0 to 5 mm above the basal intercalary meristem of barley (Hordeum vulgare L. cv. Patty) leaves were studied. Respiration was measured using oxygen electrodes and a Cartesian-diver technique. Red, far-red and blue light all stimulated respiration in the protoplasts but not in mitochondria isolated from them. Gibberellic acid stimulated respiration in protoplasts but abscisic acid had the opposite effect. Physiological concentrations of indole-3-acetic acid and kinetin had no influence in either direction. Combinations of gibberellic acid with light of any wavelength always increased respiration. Red or far-red light treatments in the presence of abscisic acid decreased dark respiration and only blue light significantly reversed the inhibitory effect of abscisic acid. Cycloheximide markedly increased dark respiratory activity; chloramphenicol was without effect. These results indicate that mitochondrial activity in the leaf basal intercalary meristem was partially controlled through phytochrome and a blue light receptor, and by gibberellic and abscisic acids. Changes in cytosolic protein synthesis were important for the initiation of enhanced mitochondrial activity in meristems.