Effect of Temperature of the Culture Medium on Growth and Nitrogen Fixation of Inoculated Legumes and Rhizobia

Abstract

Two pea (Pisum sativum L.) cultivars and a kidney bean (Phaseolus vulgaris L.) cultivars were grown in water cultures at different diurnal temperatures (15, 20, 24, 27, 30°C) or at 10°C night temperature combined with various day temperatures (20, 24, 27, 33 or 35°C) in the root medium. The inoculated plants were, more sensitive to the extreme temperatures than the plants supplied with combined nitrogen (KNO3). The middle‐European pea cv. Violetta was adapted to somewhat higher root temperatures than the northern one cv. Torsdag II, the latter showing better growth at lower temperatures, when the plants were inoculated with the same Finnish Rhizobinm strain (HA1). Especially at optimum day temperatures the nitrogen fixation and consequently the dry weights of the inoculated plants were greatly increased when the night temperature was lowered. The optimum temperature for the growth of free‐living Rhizobium strains (HA1 and H43) for peus was found to be 25°C and that of a strain (P103) for beans somewhat higher. Effective nitrogen fixation by nodulated legumes without a supply of combined nitrogen is achieved only when the optimum temperature range for root function is very close to the optimum for the rhizobia.

Carbon and nitrogen nutrition of nodulated roots of grain legumes

“…Obviously, more consideration should be given to variations in all these parameters in future studies. Temperature at night may be especially important: very warm temperate nights (18 C) reduce dinitrogen fixation rate in pea (Minchin & Pate, 1974), a crop known to grow well in cool (Roponen, Valle & Attala, 1970), whilst warm tropical nights (24 C) increase overall growth and dinitrogen fixation of soyabean and cowpea (Huxley, Summerfield & Hughes, 1976;Summerfield et ai, 1978a). Schweitzer & Harper (1980) have recently suggested that the release of stored photosynthates to support nodule activity at night is greater when nights are warm.…”