GROWTH, DEVELOPMENT AND DRY-MATTER DISTRIBUTION OF A TOMATO CROP AS AFFECTED BY ENVIRONMENT

Greenhouse tomato plants, cvs Carmen and Diva, were grown during autum n and winter in two non-heated polyethylene greenhouses having similar values of incoming solar radiation and different air temperatures. Da ily radiation fell to values blow 8.4 MJ m(-2) day(-1) after the 131 d from sowing. Daily amplitude of air temperatures differed by 3.8 K be tween greenhouses when minimum air temperatures were higher than 18 de grees C. Periodically destructive measurements were conducted for a pe riod of 154 d from sowing to determine the number of leaves, trusses a nd developed fruits per plant, leaf area and dry matter of shoot organ s. The number of leaves preceding the first inflorescence varied betwe en 4 and 6, suggesting this variable is negatively correlated with rad iation, but positively with temperature. The number of leaves decrease d after the 130 d from sowing while the number of fruits per plant con tinued to increase during the same period. Total dry matter was simila r in both greenhouses, despite the differences in numbers of leaves an d fruits per plant. The fraction of dry matter in fruits was low, alwa ys below 40%. Exponential functions were fitted between vegetative dry matter and fruit dry matter and also between total and fruit dry matt er content. When radiation became low, growth of fruits was greater re lative to the vegetative plant parts. Growth of fruits was dependent o n assimilate supply by leaves, and this dependence should be considere d in modelling the assimilate partitioning of a tomato plant.