Ethylene

Drought resulting from global warming destabilizes plant growth and development and also triggers premature and excessive abscission of organs from plants. During evolution, plants developed an informative system that warns them about stress. A key component of this mechanism is plant hormones, including ethylene (ET). Hormones not only participate in the transduction of signals but also influence molecular and biochemical changes and, in this way, regulate defense responses and adaptation to stress conditions. In this chapter, we present the most important facts about contribution of ET in the strategies of plants against drought. We describe in detail the changes regarding the formation and transport of ET precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in roost, which is the first place a water deficit is perceived. Then, we explain how ET influences the growth of the root system and the functioning of root nodules in a stress-dependent manner. We also focus on drought-evoked events related to the induction of ET biosynthesis in roots, which leads to several consequences in the aboveground parts of the plant, e.g. reduction of transpiration, disruption of cellular turgor, stomata movement, osmolyte production, and redox imbalance. The current knowledge about the specific elements of the ET signal transduction pathway and ET-responsive genes induced by drought stress is also summarized. We finally describe the crosstalk of ET and other hormones, including auxin, abscisic acid, and jasmonates, which mediates the response of plants to water deficits.