Helping Halophytes Combat Soil Salinization

Geissler et al. (2009) write that "desertification is often accompanied by soil salinization ... leading to growth conditions inacceptable for most conventional crops." However, they note that what they call "a promising solution" to the problem "is the desalinization and reclamation of degraded land by making sustainable use of naturally salt-tolerant halophytes under seawater irrigation (including drainage mechanisms which avoid salt accumulation in the soil)." What is more, they indicate that the leaves of certain halophytes "have a high nutritional value and can be eaten as salad or vegetable," making them "a promising potential cash crop."

In a study germane to both of these functions -- land reclamation and edible biomass production -- Geissler et al. grew well-fertilized two-month-old Aster tripolium L. plants for one additional month in a hydroponics system maintained at seawater salinity (sws) levels of 0, 50 and 100% within open-top chambers in northern Germany that were maintained at atmospheric CO₂ concentrations of either 380 ppm (ambient) or 520 ppm (elevated), during which time they measured several plant properties and processes.

In ambient air, the three researchers found that growing the plants with water of 100% sws (as opposed to 0% sws) resulted in "a significant decrease in photosynthesis [65%] and water use efficiency [33%] and to an increase in oxidative stress." But when the air's CO₂ concentration was raised by 37% (from 380 to 520 ppm), there was a subsequent increase of 84% in photosynthesis and 60% in water use efficiency. In addition, they determined that "the improved water and energy supply was used to increase the investment in mechanisms reducing water loss and oxidative stress."

In concluding their paper, Geissler et al. say that because "elevated CO₂ concentration enhances the energy and water supply of Aster tripolium, ameliorates oxidative stress, and thus enhances the survival of this plant in saline habitats," it (1) "seems to be a promising cash crop halophyte for a future with rising atmospheric CO₂ concentrations," and (2) "can help in desalinizing and reclaiming degraded land and sequestering CO₂, thus counteracting the greenhouse effect."