Senescence of cut leaves of Zantedeschia aethiopica and Z. elliottiana. Part II. Free amino acids accumulation in relation to soluble protein content

Abstract

Proteolysis and free amino acid accumulation occur during leaf senescence. As senescence is under control of plant hormones leaves of Zantedeschia aethiopica Spr. and Zantedeschia elliottiana Engl., two species grown for the florists' green, were pulse treated 24 hours with solutions of benzyladenine or gibberellic acid (0.1 mmoldm -3 and 0.25 mmoldm -3 , respectively) in order to delay senescence and to prolong their vase life. GA3 but not BA retarded proteolysis in both species. A standard preservative solution used to prolong the longevity of cut (8-HQC + 2% S; 8-hydroxyquinoline citrate + 2% su- crose) accelerated proteolysis in the Z. aethiopica leaves but had no effect on leaves of Z. elliottiana. Soluble protein losses were accompanied by elevated levels of free amino acids, however, range of these increases did not correspond to decreases in protein con- tents. A massive accumulation of free amino acids occurred in the sugar-fed leaves of both species. Growth regulators somewhat limited free amino acid accumulation in leaves held in the preservative, BA being more effective in Z. elliottiana while GA3 in Z. aethiopica.