From individual leaf elongation to whole shoot leaf area expansion:: A comparison of three Aegilops and two Triticum species

Background and Aims Rapid leaf area expansion is a desirable trait in the early growth stages of cereal crops grown in low-rainfall areas. In this study, the traits associated with inherent variation in early leaf area expansion rates have been investigated in two wheat species (Triticum aestivum and T durum) and three of its wild relatives (Aegilops umbellulata, A. caudata and A. tauschii) to find out whether the Aegilops species have a faster leaf area expansion in their early developmental stage than some of the current wheat species. Methods Growth of individual leaves, biomass allocation, and gas exchange were measured on hydroponically grown plants for 4 weeks. Key Results Leaf elongation rate (LER) was strongly and positively correlated with leaf width but not with leaf elongation duration (LED). The species with more rapidly elongating leaves showed a faster increase with leaf position in LER, leaf width and leaf area, higher relative leaf area expansion rates, and more biomass allocation to leaf sheaths and less to roots. No differences in leaf appearance rate were found amongst the species. Conclusions Aegilops tauschii was the only wild species with rapid leaf expansion rates similar to those of wheat, and it achieved the highest photosynthetic rates, making it an interesting species for further study. (C) 2004 Annals of Botany Company.