Aharoni, N., Agricultural Research Organization, The Yolcani Center, Bet Dagan, Israel
Marco, S., Agricultural Research Organization, The Yolcani Center, Bet Dagan, Israel
Levy, D., Agricultural Research Organization, The Yolcani Center, Bet Dagan, Israel

Retardation of hypocotyl growth occurred in cucumber seedlings following infection with cucumber mosaic virus (CMV). This corresponded with a reduction in gibberellin-like substances (GA) and an increase in abscisic acid (ABA) and the inhibitor-β complex. The enhanced inhibitory effects of the latter were due mainly to the increase in ABA, as measured by gas-liquid chromatography (g.l.c.). Exogenous treatments with gibberellic acid (GA3) at concentrations of 5 parts/106 enhanced hypocotyl growth in healthy seedlings, but in virus-infected cucumbers the same concentration of the hormone was ineffective. ABA treatment markedly retarded the growth of healthy hypocotyls only when applied at the relatively high concentration of 250 parts/106, whereas it inhibited almost completely the growth of the infected hypocotyls even when applied at a lower concentration of 25 parts/106. While not excluding other contingencies, it is suggested that the suppression of hypocotyl growth induced by CMV is influenced by virus-induced changes in the endogenous levels of GA and ABA which are capable of antagonizing the effect of each other. © 1977.