GROWTH, GAS-EXCHANGE AND CARBON-ISOTOPE DISCRIMINATION IN YOUNG PRUNUS-AVIUM TREES GROWING WITH OR WITHOUT INDIVIDUAL LATERAL SHELTERS

One-yr-old wild cherry (Prunus avium L) plants were grown as follows: 1) in small cylindrical shelters (diameter 50 cm, treatment S); 2) in large shelters (diameter 100 cm, treatment L); or 3) without shelter ( control, treatment C) during 1 growing season. Treatment C was charact erized by higher values of photosynthetic photon flux density (I(p)) a nd of leaf-to-air water vapour pressure difference (DELTAW) than treat ments L and S. The plants were taller in treatments L and S than in tr eatment C but biomass production was higher in the latter treatment. T he plants of treatment C were also characterized by higher values of C O2 assimilation rate (A) and of leaf mass per unit area (LMA, ratio of leaf mass to leaf area). Relative carbon isotope composition (delta(p )) of the leaves was higher in treatment C than in treatments L and S, which expresses higher time-integrated values of plant intrinsinc wat er-use efficiency (Alg ratio) in the former treatment. There was a pos itive correlation between delta(p) and LMA. Thus, LMA, a readily measu rable parameter, is a relevant parameter for understanding and modelli ng water-use efficiency of canopies.