EFFECT OF TWO GREENHOUSE COVERS ON GROWTH, DRY MATTER CONTENT AND TOMATO FRUIT QUALITY

The aim of this work was to evaluate the effect of two greenhouse cover (glass and plastic) and two crop season (autumn and winter) on growth, dry matter accumulation and fruit quality of Beefsteak type tomato cv. ‘7106’ grown in commercial greenhouses. The equatorial diameter of the fruit was measured to evaluate its growth over a seven week period; dry matter accumulation was measured for the same period of time while fruit quality was determined at the end of each season. Mean daily temperatures and overall radiation for each greenhouse were recorded. Daily temperatures in the greenhouses were higher for glass cover compared to those with plastic cover, although both were within the optimal range for tomato growth (20-24 °C). The amount of light was greater with plastic than glass during the two seasons. Fruit growth showed a sigmoid type curve and fitted the model proposed by Gompertz to predict population growth. Coefficient ‘a’ or maximum growth was not significantly affected by treatments. Coefficient ‘b’ or exponential growth rate, and final exponential growth (Coefficient ‘c’), were higher in tomato plants grown in a glass covered greenhouse during the autumn. The greater rate of growth in the glass cover was due to the fact that the mean temperatures were close to the highest optimal limit for the fruit growth and that the transmittance of the was also higher. Statistical analysis of dry matter content in the tomatoes indicated that the season factor was very significant, showing that winter fruit had higher content of dry matter during the final stages of growth. Production of high quality fruit (‘Premium’) was high in both types of cover; nevertheless, in the autumn both covers showed the same values for quality and in the winter, the plastic cover showed a higher percentage ‘Premium’ fruit quality.