Plants modify their carbon allocation as a response to low water availability. The objective of this study was to evaluate, using a 14 CO 2 pulse-chase analysis, the effect of moisture restriction on biomass production in common bean plants var. OTI. The plants were maintained with irrigation until the beginning of pods filling; then, three groups were formed, kept at 100%, 75% or 50% field capacity (FC). After 10 days, 14 CO 2 gas was supplied to the plants for 4 hr. The plants were harvested at 1, 3 and 7 days after applying the label. Ripe fruits imported more than 50% of the total 14 C.Particularly, the label presented greater changes in pericarps of stage III of pod development. The fructose concentration doubled that of the glucose and decreased with the pod age; sucrose concentration increased in pericarps in stages III and IV of pod development in relation to those in stage II. The sucrose decrease only in stage II pericarps on day 7, as well as the starch concentration that decreased by half in the 50% FC condition. The latter coincided with the highest amylolytic activity as evaluated in native gels. These findings open new opportunities to research the carbon allocation mechanism under moisture restriction.

The common bean (Phaseolus vulgaris L.) pod wall is essential for seed formation and to protect seeds. To address the effect of water restriction on sugar metabolism in fruits differing in sink strength under light–dark cycles, we used plants of cv. OTI at 100% field capacity (FC) and at 50% FC over 10 days at the beginning of pod filling. Water restriction intensified the symptoms of leaf senescence. However, pods maintained a green color for several days longer than leaves did. In addition, the functionality of pods of the same raceme was anatomically demonstrated, and no differences were observed between water regimes. The glucose and starch concentrations were lower than those of sucrose, independent of pod wall size. Remarkably, the fructose concentration decreased only under water restriction. The cell wall invertase activity was twofold higher in the walls of small pods than in those of large ones in both water regimes; similar differences were not evident for cytosolic or vacuolar invertase. Using bioinformatics tools, six sequences of invertase genes were identified in the P. vulgaris genome. The PvINVCW4 protein sequence contains substitutions for conserved residues in the sucrose-binding site, while qPCR showed that transcript levels were induced in the walls of small pods under stress. The findings support a promising strategy for addressing sink strength under water restriction.