Physiological responses to saline irrigation in two summer mungbean [Vigna radiata (L.) Wilczek] genotypes
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Date
2013
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CCSHAU
Abstract
The effects of saline irrigation on morpho-physiological traits, antioxidant defense mechanism and protein rofile (SDS-PAGE) in two summer mungbean (Vigna radiata L.) genotypes viz. MH 421 and SML 668 differing in their sensitivity to salinity was investigated under natural conditions of screen house. At the flowering stage (30-35 DAS), plants were exposed to single saline irrigation (Cl-dominated) of levels 2.5, 5.0 and 7.5 dS m-1. Sampling was done after 7 and 14 days of treatment (DAT). The control plants were irrigated with distilled water. The water potential (Ψw) of leaf and osmotic potential (Ψs) of leaf and root decreases in both the genotypes. MH 421 showed more negative values Ψw of leaf i.e. from -0.20 to -0.46 MPa as compared to -0.18 to -0.40 MPa in SML 668, respectively. The Ψs of leaf decreased from -1.36 to -1.89 MPa in MH 421 and -1.36 MPa to -1.80 MPa in ML 668 with increase in salinity level from control to 7.5 dS m-1 at 7 DAT. A similar trend of change in the osmotic potential (Ψs) of root was observed. The proline content of leaf increased significantly from 11.4 to 144.5 % and 15.7 to 219.4 % and the total soluble carbohydrate (TSC) content from 16.6 to 79.8 % and 22.5 to 81.9 % in SML 668 and MH 421, respectively, with increasing level of saline irrigation from control to 7.5 dS m-1. A marked increase in hydrogen peroxide H2O2, lipid peroxidation (MDA content) and relative stress injury (RSI %) was noticed in leaf and root which was much higher in SML 668 than MH 421. A similar trend was observed at 14 DAT. Saline irrigation increased the Cl- and SO4 2- concentration in leaf by 2.8 and 3.1 fold in MH 421 and 3.0 and 3.6 fold in SML 668, respectively, at 7.5 dS m- 1. Moreover, MH 421 had overall lower Na+/K+ ratio than SML 668. More negative values of Ψw of leaf, Ψs of leaf and root and better accumulation of osmotically active solutes, i.e. proline, TSC and low Na+/K+ ratio in leaf and root of MH 421, helped in maintaining the higher RWC % of these organs than noticed in SML 668. ROS scavenging enzyme of leaves i.e. SOD, CAT, POD, APX, GR, GPX and GST increased by 296.7, 58.5, 146.3, 159.1, 125.8, , 95.9, 81.0 % in SML 668 and by 806.8, 180.3, 231.4, 174.9, 190.2, 112.6, 172.6 % in MH 421, respectively, upon increasing levels of saline irrigation from control to 7.5 dS m-1 after 7 days of treatment (DAT). Despite the increase in the activity of these enzymes AsA content decreased by 52.5 and 41.3%. Higher activities of antioxidant enzymes, lower accumulation H2O2, MDA and AsA content in MH 421 than in SML 668 indicated those enzymes play a key role in removal of ROS in MH 421 better than in SML 668, thus minimizing the cellular damage caused by ROS under saline irrigation. Pollen viability (%), in vitro pollen germination and tube growth were also adversely affected with increasing salinity; the effect being most pronounced in SML 668. SDS-PAGE revealed more deletion than addition of polypeptide bands in SML 668 than MH 421 with increasing levels of saline irrigation in leaf and root at both the stages. The yield parameters like number of pods plant-1, number of seeds plant-1, 100 seed weight and seed weight plant-1 decreased more in SML 668 with increasing salinity. Hence, the mechanism of salt tolerance was better in MH 421 than in SML 668 as found from physiological traits studied.
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Keywords
Irrigation, Genotypes, Planting, Food preservation, Vegetative propagation, Enzymes, Tolerance, Proteins, Sowing, Biological development