Stomatal Response to Drought is Modulated by Gibberellin in Tomato

It has been shown that gibberellin (GA) perception is part of root-to-shoot communication in plants during drought. However, it is not clear how GA content interferes with long-distance drought response signaling. Thus, in this study, the tomato ( Solanum lycopersicum L.) cultivar Micro-Tom (MT) was treated with 50 mM acid gibberellic, while the control plants were sprayed with water. After treatment, tomato plants were reciprocally grafted (i.e., MT/MT, MT + GA/MT + GA, MT + GA/MT, MT/MT + GA; within each pair, the first indicates the scion, and the second indicates the rootstock). Therefore, to evaluate the role of GA in root-to-shoot communication during drought stress, plants were grown under well-watered or drought conditions. Height, leaf and root area, dry weight, malondialdehyde content, relative water content and stomatal conductance were measured. It was verified that the MT + GA/MT and MT + GA/MT + GA plants were taller than the grafted plants without GA treatment. Furthermore, non-treated plants (MT/MT) exhibited a reduction in root area due to water-deficit. Regarding water relations, under drought, the greatest reduction in stomatal conductance was observed in plants grafted onto rootstocks treated with GA, which favored the maintenance of an increased relative water content. This demonstrates an important role of GA in root-to-shoot communication to induce stomatal closure during water-deficit conditions.