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Abstract

Gibberellins (GAs) have been shown to be involved in the tolerance of plants to a range of environmental stresses. However, the physiological and metabolic implications of altered levels of GAs in plants under drought stress remain largely unknown. To understand the contribution of GAs for the responses to water deficit conditions, physiological and metabolic parameters were evaluated in tomato deficient mutants in GAs biosynthesis, gib1, gib2, and gib3. Interestingly, the mutants maintained leaf water content over a longer time period and recovered photosynthesis faster than wild-type (WT) plants. Furthermore, gib1 and gib2 plants showed no apparent wilt even after reaching low leaf water potential (-1.3 MPa). Additionally, mutants plants partitioned more biomass to the roots than shoots compared to WT. The maintenance of leaf water content and consequent increased water use efficiency observed in the mutants can be explained by the osmotic adjustment of leaf and root cells, mainly due to amino acid accumulation. Collectively, our results suggest that plants with reduced GAs content are able to cope with water deprivation by increasing proline and other amino acid levels. This response, alongside partitioning of carbon to roots allows GAs-deficient plants to maintain the leaf turgor for a longer time and thereby promotes water deficit tolerance.