Physiological response of halophytes to multiple stresses.

As halophytes grow vigorously in saline soils, they serve as extraordinary resources for the identification and development of new crop systems. Understanding the mechanisms of tolerance of halophytes to salinity in combination with other co-occurring constraints such as drought, flooding, heavy metals and nutrient deficiencies, would facilitate efforts to use halophytes for saline land revegetation, as well as provide new insights that might be considered in future breeding of plants for salt-affected agricultural lands. Recent results suggest that salinity may improve the response of halophytes to other stresses. Some physiological and biochemical mechanisms of tolerance to salinity are common to many halophytes when plants are subjected to salinity, whereas others are specifically amplified under a combination of stresses. Therefore, the response of halophytes to multiple stresses may not reflect an additive effect of these constraints, but rather, constitute specific response to a new situation where many constraints are operating simultaneously. Comparative studies between halophytes and glycophytes have shown that halophytes are better equipped with the mechanisms of cross-stress tolerance and are constitutively prepared for stress. Moreover, other data has shown that the pre-treatment of halophytes with salinity or other constraints in the early stages of development improves their subsequent response to salinity, which suggests the capacity of these plants to 'memorise' a previous stress allows them respond positively to subsequent stress.