Higher stability in leaf water status in heat-tolerant cultivars of snap bean (Phaseolus vulgaris L.)
2006
Tsukaguchi, T.(Niigata Univ. (Japan). Faculty of Agriculture) | Egawa, Y.
Snap bean (Phaseolus vulgaris L.) is a heat-sensitive crop. A snap bean cultivar Haibushi, which was developed from an accession collected in Southeast Asia, shows higher heat tolerance than other cultivars or lines. For an effective breeding program, elucidation of the mechanism controlling the heat tolerance in Haibushi is necessary. A high temperature often coincides with intensive solar radiation, which causes excessive transpiration and temporal water deficit in plants in the daytime, even when soil moisture content is adequate. In snap bean cultivars, leaf water status declined at mid-day and there was a cultivar difference in mid-day depression of leaf water status. In heat-tolerant cultivars including Haibushi, mid-day depression in leaf water status was smaller and stomatal conductance was higher than those in heat-sensitive cultivars. Higher stability in leaf water status of Haibushi was due to higher water uptake rate in the morning. Under high temperature conditions leaf temperature of heat tolerant cultivars was lower than that of heat-sensitive cultivars, well reflecting stomatal conductance and growth. However technical hurdles should be cleared to use cool leaf as a selection criterion. We conclude that daily stability in leaf water status could be a reliable characteristic to estimate heat tolerance in Phaseolus vulgaris.
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