Hydrogen peroxide is involved in drought stress long-distance signaling controlling early stomatal closure in tomato plants

It has long been hypothesized that hydrogen peroxide (H2 O2) may play an essential role in root-to-shoot long-distance signaling during drought conditions. Thus, to better understand the involvement of H2 O2 in drought signaling, two experiments were carried out using tomato plants. In the first experiment, a split-root scheme was used, while in the second experiment, the tomato plants were grown in a single pot and subjected to drought stress. In both experiments, H2 O2 and catalase were applied together with irrigation. Control plants continued to be irrigated according to the water loss. In the split-root experiment, it was verified that the application of H2 O2 to roots induced a clear reduction in plant transpiration compared to untreated or catalase-treated plants. In the second experiment, we observed that H2 O2-treated plants exhibited similar transpiration when compared to untreated and catalase-treated plants under drought stress. Similarly, no difference in water use efficiency was observed. Thus, we conclude that the increase in H2 O2 in the root system can act as a long-distance signal leading to reduced transpiration even when there is no water limitation in the shoot. But it has little effect when there is a reduction in the shoot water potential.