Growth Physiology and Membrane Permeability of Okra (Abelmoschus esculentus L.) Seedlings as Affected by Salinity

Abstract

Aims: Among the abiotic stresses, salinity is one of the most important environmental constraints which provokes grave threats for agriculture and environment. It is a growing threat to agricultural crops and its impacts have already started becoming visible as expansion in the affected areas and deteriorating soil fertility and crop productivity. By considering this feature, a study was conducted to determine the salinity responses of selected okra cultivars on certain physiological and biochemical attributes. Study Design: The experiment was laid out in a Completely Randomized Design with six treatments and four replications. Place and Duration of Study: A study was conducted at the crop farm of the Eastern University, Sri Lanka during the yala season of the year 2014. Methodology: The seeds of okra cultivar “Haritha” were surface sterilized with sodium hypochlorite 0.5% (v/v) and were allowed to germinate in petri dishes having filter papers saturated with distilled water as control and NaCl solutions of 25, 50, 75, 100 and 125 mM. The germinated seeds in distilled water and in saline solutions were transferred to plastic pots filled with soil/compost mixture (2:1V/V). The pots were irrigated with distilled water or saline solution for two weeks. The response of okra plants to salinity stress with respect to physiological growth attributes, water content and membrane permeability were investigated. Results: Salinity stress did not show significant (P > 0.05) effect on shoot dry weight. However, root dry weight decreased with an increase of NaCl concentration. The root water content and shoot/root ratio increased significantly (P < 0.05) with an increase of salt concentration (25, 50, 75, 100 and 125 mM). It was observed that there was an increase in membrane permeability with associated electrolyte leakage when okra seedlings were exposed to high levels of salt particularly 100 and 125 mM NaCl. Conclusion: The property of salinity tolerance depends on different physiological interactions. The growth physiological attributes presented by the plant in response to salinity may not be enough to determine its effect.