EFFECT OF LEAF ROLLING ON LEAF WATER LOSS IN Triticum spp.

The effect of leaf rolling on water loss by wheat (Triticum aestivum L. and T. turgidum L. var. durum) leaves and its relationship to yield and other parameters was studied in field-grown wheat in 1983 and 1984. The influence of rolling on water loss was estimated by measuring water loss from excised leaves held flat during wilting compared to that from control leaves allowed to roll during wilting. Leaf rolling was visually scored for both excised leaves and for intact plants growing in the field. Leaves which were held flat during wilting lost 9–46% more water than the controls, and there was evidence of genotypic variation in the effect of rolling on water loss. Complete rolling reduced leaf surface area by 41–48%. There were inter- and intragenotypic differences in the amount of water lost by excised durum leaves prior to reaching intermediate and high rolling scores. Percentage water loss before reaching an intermediate rolling score ranged from 20 to 84% across genotypes, and from 24 to 84% within the most variable genotype. There were no consistent correlative relationships between leaf rolling score in field plots and yield and other parameters, probably as a result of intragenotypic differences in expression or rolling. Leaf rolling is unlikely to be of adaptive significance to wheat in environments where stress develops rapidly, but could be of potential use where stress develops gradually or is of short duration. This potential could only be exploited if the low water loss prior to onset of rolling observed in some genotypes is heritable.Key words: Triticum aestivum L., T. turgidum L. var. durum, leaf rolling, leaf water loss, drought, wheat