In a climate chamber experiment, sorghum cv. Venturoli Aralba plants were grown in pots under constant temperatures of 15, 21, 24, 27, 30 or 35°C and given 0 or 150 mg P/pot. The shortest biological cycle was obtained at 24°C. With increasing temperature from 21° to 30°C, days from sowing to panicle initiation decreased, and days from panicle initiation to anthesis and from anthesis to physiological maturity increased. Grain yield was highest at 24°C, and was reduced at 21°C by the lower weight per seed and at 27 and 30°C by the lower number of seeds per plant. P supply increased grain yield by increasing the number of seeds per plant, while there was no effect on seed weight. Optimal growth temperature was 27°C for leaves and stems, and 21-24°C for panicles and roots. Up to anthesis, the optimum temperature for whole plant growth was 27°C, since the plant was composed mainly of leaves and stems. After anthesis, optimum temperature dropped to 24°C, on account of extensive panicle and root development. The higher absolute growth rate value was due to greater leaf area development and duration. The P rate induced a slightly increased growth rate in all plant parts.
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