Leaf pretreatment with senescence retardants as a basis for oat protoplast improvement

Protoplasts obtained from oat leaves floated on buffer for 18 hr show high nuclease activity, low rates of incorporation of amino acids and nucleosides into macromolecules, and high rates of spontaneous lysis. Addition to the leaf flotation medium of the senescence retardants cycloheximide or kinetin, of the dibasic amino acids L-lysine or L-arginine, or of the diamines putrescine or cadaverine reduces the rise in nuclease activity and spontaneous lysis of protoplasts, and increases the rate or extent of presumptive protein and nucleic acid synthesis. The diamines, which also retard chlorophyll degradation in the excised leaves, appear to act both on the membrane and on systems controlling macromolecular synthesis and breakdown. By contrast, the senescence promoter L-serine hastens chlorophyll degradation from excised leaves and does not improve protoplasts derived from those leaves.