Variation in Selection for. Leaf Water Conductance in Relation to Growth and Stomatal Dimensions in Lolium perenne L.

A simple, rapid technique for direct selection for leaf waterconductance (LWC) in two populations of Lolium perenne L. isdescribed. Measurements were made with a diffusion porometerin growth rooms on the youngest fully expanded leaf of eachtiller. Considerable variation in LWC was found between 100genotypes of each population. Most of the variation in totalLWC was attributed to variation in adaxial LWC and it was shownthat ignoring abaxial LWC gave very similar ranking of genotypesto those using total LWC. Selection criteria were then establishedwhich maximised the repeatability of LWC measurements and allowedselection of groups of plants significantly different from oneanother in LWC. The variation in LWC was not related eitherto stomatal length or number, or to growth rate. Lolium perenne L., perennial ryegrass, abaxial and adaxial, leaf water conductance, selection, diurnal rhythms, ontogenetic changes, growth, stomatal dimensions