SCREENING SALT-TOLERANT PLANTS FOR PHYTOREMEDIATION: EFFECT OF SALINITY ON GROWTH AND MINERAL NUTRIENT COMPOSITION
Keywords:biomass, growth, mineral nutrients, NaCl, Scirpus littoralis, Typha orientalis.
Scirpus littoralis Schrab and Typha orientalis C. Presl are cultivated in the paddy field and in the shrimp pond in the Mekong Delta of Viet Nam for human food and providing habitat for shrimp, respectively. They are recognized as phytoremediator in brackish shrimp aquaculture wastewater treatment system. However, information on effects of NaCl on plant growth and mineral concentrations of the two species is limited. Therefore, the present study was carried out to identify salt-tolerance between the two species. Six NaCl salinity concentrations (0, 5, 10, 15, 20, 30 ‰) and two plant species were arranged in a completely randomized factorial design with three replications. The plants were supplied full strength Hoagland’s solution as growth condition with an increment of NaCl 5 ‰ weekly for 6 weeks. T. orientalis had 65 % mortality at the high NaCl level of 20-30 ‰ while 100 % S. littoralis plant survived with only young shoots remained green. Fresh weight of T. orientalis at the 0 ‰ was 30.6 g FW/plant higher than those at the 20-30 ‰ (8.3-6.4 g FW/plant, respectively) leading to the same pattern in dry weight. The amount of Na+ accumulated in the shoots of T. orientalis at 30 ‰ (27.4 mg/g) higher than those at 0-5 ‰ (2.76-10.1 mg Na+/g). S. littoralis had a lower Na+ content in the shoots (20.1 mg Na+/g) than that of T. orientalis at 30 ‰. The Cl- concentration in the shoots of T. orientalis at 0 ‰ (19.7 mg Cl-/g) was significantly lower than that at 30 ‰ (83.3 mg Cl-/g) and was ~1.3 times higher than that of S. littoralis at 15-30 ‰. Between two studied plants, T. orientalis accumulated a higher Na+ and Cl- concentration in the roots and shoots especially at the high levels of NaCl of 15-30 ‰. That indicated S. littoralis are able to withstand salt stress and can be considered the best bio-filter candidate in the integration of constructed wetlands and marine shrimp culture towards sustainable aquaculture in the Mekong delta, Viet Nam.
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