Photosynthesis of Four Radish (Raphanus sativus L. var. sativus) Cultivars Grown in Controlled Cabinets under Varying Temperatures and Irrigation Levels

Abstract

Topsi, Famox F1, Corox F1, and Altox F1 radish cultivars grown in controlled 20 and 12oC cabinets and they subjected to 0, 33, 66, and 100% depletion of peat moss available water capacity (AWC). The objective of this experiment was to determine the performances of photosynthesis of four radish cultivars in response to varying temperature and irrigation. Low temperature slightly increased photosynthesis rate. Chlorophyll pigment percentage out of other pigments of cool cabinet highly exceeded that of warmer cabinet by 17.24% in chlorophyll content of radish leaves. 12oC highly reduced stomata conductance by 20.5% as compared to 20oC. The highest photosynthesis rate was found in the 0% AWC depletion (14.38µM CO2.m-2.s-1), and the lowest was confined to 100% AWC depletion (1.28µM CO2.m-2.s-1).The highest chlorophyll percentage detected in 66%AWC depletion 38.5063%, however, the lowest in 100%AWC depletion (33.73%). The highest stomata conductance observed in 0%AWC depletion (291.47 mM.m-2.s-1), and the lowest detected in 100%AWC depletion (20.95mM.m-2.s-1). Regression equations are Photosynthesis rate (µM CO2.m-2.s-1) = 14.3- 0.1238 %AWC; Chlorophyll percentage = 34.5=02915 %AWC; Stomata conductance (mM.m-2.s-1) = 290.7-2.638%AWC. Cultivar performance ordered as follow: AltoxF1> Corox F1> Famox F1> Topsi. Interaction results mentioned within the discussion section. It can be concluded that both 12 and 20oC temperatures were within the radish photosynthesis range and partially stomata aperture can sustain adequate carbon dioxides for reasonable photosynthesis rate accompanied by profound transpiration reduction.