Effects of water and salt stresses on growth, water relations and gas exchange in Rosmarinus officinalis

Plants of Rosmarinus officinalis were submitted to water and salt stress, independently. The effects of water or salt stress on growth, water relations and gas exchange were investigated in order to understand the tolerance and adaptative mechanisms of R. officinalis to these types of stress. Under both stress conditions, plants developed avoidance mechanisms to minimise water loss based on morphological and physiological changes (e.g., reduction of plant biomass and leaf area, stomatal closure). Only under salt stress conditions were treated plants able to maintain turgor via osmotic adjustment, which was achieved by the uptake of Na+ and Cl- ions. Osmotic adjustment was not observed in R. officinalis plants submitted to water stress. The results indicate that high accumulation of Na+ and Cl- ions was responsible for the growth reduction observed in salinised plants. However, the growth reduction observed in water-stressed plants was caused by a dehydration process.