INTERSPECIFIC VARIABILITY OF PLANT WATER STATUS AND LEAF MORPHOGENESIS IN TEMPERATE FORAGE GRASSES UNDER SUMMER WATER-DEFICIT

Leaf water status and elongation rate (LER) of five forage grasses (Lo lium perenne, Lolium multiflorum, Festuca arundinacea, F.a. var. glaus cescens a wild species related to F.a., and a genotype derived from a hybrid between F.a. var. glauscescens and L.m. called L4F4) were compa red during two summer periods in the field in 1994 and 1995, Variation s in predawn leaf water potential (psi(d)) indicated differences betwe en genotypes in terms of water availability. This was consistent with neutron probe measurements which showed that L, multiflorum had a much shallower rooting system than L. perenne and Festuca arundinacea. Noo n leaf water potentials (psi(n)) of L. multiflorum remained at relativ ely high values despite that species' disadvantage in terms of rooting depth. The L4F4 hybrid exhibited higher psi(d), a greater depth of wa ter extraction than L. multiflorum and higher psi(n) than in F.a. var, glauscescens, The response of LER to psi(d) in the hybrid was similar to that of the Festuca and Lolium parents. By contrast with 1994, in 1995, even at high psi(d), LER Of rainfed Lolium perenne plants was on ly approximately 44% of the irrigated plants, To a lesser extent a sig nificant year effect could also be observed in the other species, The role of the partitioning of leaf elongation between day and night in d etermining these differences is discussed. (C) 1997 Elsevier Science B .V.