PHOTOSYNTHESIS AND ABSORPTION OF MINERAL NUTRIENT IN TOMATO PLANTS UNDER VARIOUS ROOT ZONE TEMPERATURE AND LIGHT CONDITIONS
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Effect of various light and temperature regimes in the root zone on the light stage of photosynthesis, gas exchange, growth processes and absorption of mineral nutrients by tomato plants were studied. Optimum temperatures for dry matter accumulation and absorption of mineral nutrients were found to be shifted when the irradiation condition were changed. A shift of optimum temperatures for dry matter accumulation and absorption of mineral nutrients was found to be due to a change in irradiation conditions. It was 1.6℃ per 70 Wm^<-2> within the range of 50-175 Wm^<-2>. The maximum absorption of mineral nutrients did not always coinside with the optimums of dry matter accumulation. For example, at 50 Wm^<-2> the maximum amounts of P, Ca and Mg were absorbed at higher temperatures as compared with the optimum temperatures for dry matter accumulation. Only for N and K these temperatures coinsided. At 175 Wm^<-2> the maximum absorption of N, P, K, Ca, Mg was at the temperatures corresponding to those optimal for dry matter accumulation. These data are of particular importance for precise regulation of temperatures and concentrations of mineral nutrients under controlled conditions of the hydroponic green houses.
BIOTRONICS (17), 21-28, 1988-12
Biotron Institute, Kyushu University