Abstract: The investigation is a comparative study of heat stress on cherry tomato cultivated in different substrate systems (soil, peat moss, peat/perlite (1/2), perlite and a recirculation system) during summer time. The study was undertaken in a greenhouse during July, August and September 2002. The cherry tomatoes were transplanted in three different rooms (1, 2, 3) with different temperature regimes: 25/20℃, 35/25℃, and >35/>25℃ day/night temperatures respectively. The interaction between environmental factors and gas consistence was studied. There was a negative linear relationship between temperature and RH (R²: 0.894～0.972), and also between temperature and CO₂ consistence in all the rooms (R²: 0.668～0.786). The growth rate was assessed, which shows the stem elongation was specifically related to the growing media. The effect of heat stress on plant water status was evaluated using the leaf water potential and leaf temperature. The analysis of variance shows that the growing media and heat stress significantly affect leaf water potential either at predawn or at midday. This result allowed to determine effective growth stages of the heat stress precisely and to guide us to choose the effective growing media suitable during summer.