Ethylene Evolution from Bracts and Leaves of Poinsettia,Euphorbia pulcherrimaWilld

Abstract

Woodrow, L. and Grodzinski, B. 1987. Ethylene evolution from bracts and leaves of Poinsettia, leaves contained mainly sucrose for translocation. The total free alpha-amino nitrogen content of the bract tissue was twice that of the leaf tissue. The leaves contained more ACC (1-aminocyclopropane 1-carboxylic acid) and produced proportionally more endogenous C2H4 than either the red or white bracts. ACC-stimulated C2H4 release was also greatest from the green tissue indicating that the EFE (ethylene forming enzyme) was most active in the leaves. The specific activity of the 14C2H4/12C2H4 released from (2,3-14C)ACC confirmed ACC as the primary precursor of C2H4 in this tissue. Ethylene release from the non-photosynthetic, bract tissue was not markedly affected by alterations in C02 or light conditions. In green leaf tissue endogeneous ethylene release increased from 1-5 to 6 0 pmol C2H4 cm 2 h 1 while ACC-stimulated ethylene release increased from 10 to 35 pmol C2H4 cm2 h1 as the C02 partial pressure increased from 100 to 1 200 /tbar.