Growth and gas exchanges of red pitaya under different shading conditions

Plants with yellow cladodes are commonly present in commercial red pitaya orchards, in Ceara, mainly during the warmer seasons of the year. Therefore, this study aimed to evaluate the effect of shading on the growth and gas exchanges of red pitaya. We tested five shading levels on stock plants (full sunlight, 35, 50; 65 and 80% shading) via randomized block design (RBD), with five replications and two plants per plot. After 180 days, the following characteristics were evaluated: sum of the length of the axillary shoots, number of axillary shoots, diameter, thickness of secondary shoots, photosynthetic rate, stomatal conductance of water vapor, transpiration, internal carbon dioxide concentration, ratio of internal to external CO2 concentration, instantaneous and intrinsic water use efficiency, and instantaneous carboxylation efficiency. The plants presents large and thin cladodes, apparently blanching under 80% shading; therefore, we concluded that cultivation in full sunlight caused a negative effect on gas exchanges and growth of red pitaya. . The use of 35% shading at 180 days increased the photosynthetic rate, water use efficiency and carboxylation, with increase vegetative growth.