Heat tolerance in English ivy as measured by an electrolyte leakage technique

SummaryIdentification of heat-tolerant English ivy (Hedera helix L.) genotypes for commercial production in hot areas is desirable. The extent to which electrolyte leakage from English ivy leaf discs, measured using a test for cell membrane thermostability (CMT), could be related to the reduction to shoot dry weight induced by heat in the greenhousegrown plants was determined. A curved relationship existed between the relative injury (RI) value occurring in leaf tissue discs of English ivy cultivars and treatment temperature. A single temperature treatment at 50°C resulted in injury values near the midpoint of the response curve and showed the greatest sensitivity in detecting genotypic differences in heat tolerance. The cultivars with a high RI value are those with the lesser CMT and more reduction in shoot dry weights by high day/night temperature at 35/30°C.