Relationship of excised-leaf water loss and stomatal frequency in wheat

Abstract

Rate of water loss from excised leaves of wheat (Triticum spp.) is associated with adaptation to dry growing conditions, but the causes of observed genotypic differences are not well understood. This study was conducted to determine the relationship between stomatal characteristics and excised-leaf water status in tetraploid (Triticum turgidum L. var. durum) and hexaploid (Triticum aestivum L.) wheat genotypes. Samples were taken from field and growth-room experiments to measure stomatal frequency (SF) and size, leaf water content at excision (WC0) and 30 min after excision (WC30), rate of water loss (RWL) 30-120 min after excision, epidermal conductance (ge), and relative water content (RWC). SF was not correlated with RWL in the field experiments and was negatively correlated with WC0 and WC30 in tetraploids but not in hexaploids. In the growth-room experiment, SF was positively correlated with ge 50 and 30 min after excision for tetraploid and hexaploid genotypes, respectively. SF was correlated with RWL in tetraploids (r = 0.64*, n = 12) and hexaploids (r = 0.81**, n = 12). However, there were no significant correlations between stomatal characteristics and WC0, WC30 or RWC. These results indicate that SF is perhaps one of several factors influencing genotypic differences in excised-leaf water loss. The inconsistency of this relationship may be due to the influence of other traits affecting RWL. Key words: Leaf water loss, stomata, drought, Triticum aestivum L., T. turgidum L. var. durum