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Carbohydrate Partitioning and Nodule Function in Common Bean after Heat Stress

Dep. of Vegetable Crops, Cornell Univ., Ithaca, NY 14853

A. R. J. Eaglesham

Boyce Thompson Inst. for Plant Res. at Cornell Univ.

^* Corresponding author.

Previous work has shown that daily temperature maxima of 38 °C eliminate N₂-fixing activity in common bean (Phaseolus vulgaris L.) in less than 3 d. The purpose of this work was to (i) determine if this response is related to diminished supply of C to nodules and (ii) investigate the recovery of nodule function following short-term heat stress. ‘Jutiapa’ was grown in sand culture at 26/22 °C (day/night) until 16 d after planting, then transferred to 38/22 °C for 6 d. Acetylene reduction activity (ARA) was eliminated at 38 °C, but nodule concentrations of sucrose and glucose at that temperature were equal or higher than at 26 °C throughout the 6-d period. Stressed nodules and controls had 127 ± 12 and 90 ± 10 mg of starch per g of dry weight, respectively, after 3 d of treatment, which was the largest difference observed. Treated plants tended to have higher levels of sucrose, glucose, and starch in shoots, particularly in stems, than did controls. In a similar experiment, cells of stressed nodules showed loss of cytoplasm and rupture of peribacteroid membranes after 6 d of heat. Recovery of ARA started 1 wk after the removal of the stress; at that point, treated plants and controls had shoot N contents of 30 and 118 mg plant^–1, respectively. This N deficiency caused long-lasting alterations of plant growth and development. The inhibition of nodule function by high temperature was not related to availability of carbohydrate, but to the breakdown of the bacteria-infected cells.

Received for publication October 24, 1988.