Effect of Shade on Yield, Quality and Photosynthesis-Related Parameters of Sweet Pepper Plants

To avoid the problem of too high temperature and high radiation during late spring and summer period, growers reduce the incident radiation with several methods, like with the use of shading screens and whitening. To determine the effects of shade, simultaneous comparisons were carried out among greenhouses that were either not shaded (control treatment) or shaded with reflective aluminized shade cloth positioned below the roof, which attenuated 40 (T40) or 60% (T60) of direct sunlight. The shade was applied at the beginning of hot weather in early May. The shading screens were kept until the end of the crop cycle and fruit was picked until August. Leaf CO2 assimilation rate, relative (SPAD) and absolute chlorophyll content, F-v/F-m, transpiration rate, stomatal conductance, internal CO2 concentration and water use efficiency were measured. Plants cultivated under 40 and 60% of shading significantly decreased the net CO2 assimilation rate, stomatal conductance, and transpiration. Plants cultivated under 60% of shading had higher contents of chlorophyll a, b. Under 40% of shading, plants yielded 1.26 kg.m(2) more than under control. However, the yields of T60 and control treatment were similar (8.9 kg.m(2)). The use of shading decreased the unmarketable yield.