Carbohydrate Partitioning and Nodule Function in Common Bean after Heat Stress
- R. Hernandez-Armenta,
- H. C. Wien and
- A. R. J. Eaglesham
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.
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