Different Strategies to Tolerate Salinity Involving Water Relations

Salinity is one of the main limiting factors in agriculture, which can affect plants growth and development, as a result of a disruption of homeostasis. Because of that, to understand the plants resistance mechanisms in response to salinity stress is essential in order to develop new techniques that may improve tolerance and, in this way, optimize crops yield. In this paper we compare the response of Cucumber (Cucumis sativus L.) and tomato (Solanum lycopersicum L.), grown by hydroponic culture, to a moderate salinity of NaCl 60 mM. For that, root hydraulic conductivity, leaves relative water content (RWC), stomatal conductance, fresh weight and dry weight relation and Na⁺ concentration in aerial part and root were measured. The results showed a significant decrease of root hydraulic conductivity in both species treated with NaCl, revealing a higher resistance to water passage from root to aerial part, probably influenced by the increase of Na content after the treatment. In addition, stomatal conductance in cucumber was reduced, accompanied with a decrease of fresh/dry weight relation in root. Conversely, neither of those parameters changed in tomato. These experiments confirm the evidence that cucumber and tomato follow different strategies in the adaptation to salinity, being tomato more resistant probably due to the role of membrane water transporters. Despite that, more specific studies would be needed in order to support this conclusion.