Halopriming of seeds imparts tolerance to NaCl and PEG induced stress in Vigna radiata (L.) Wilczek varieties

Abstract

The investigation was carried out to study the effect of halopriming on NaCl and polyethylene glycol-6000 (PEG-6000) induced stress tolerance potential of three Vigna radiata (L.) Wilczek varieties, with varied abiotic stress tolerance potential. Halopriming is a seed priming technique in which the seeds were soaked in various salt solutions (in this study NaCl was used). The results of the study indicated that the application of stresses (both NaCl and PEG) induced retardation of growth attributes (measured in terms of shoot length, fresh weight, dry weight) and decrease in physiological attributes like total chlorophyll content, metabolites, photosynthetic and mitochondrial activity of the seedlings in all three V. radiata (L.) varieties. However, halopriming of the seeds could reduce the extent of decrease in these biological attributes. NaCl and PEG stress also caused increase in MDA content (a product of membrane lipid peroxidation) in all the varieties studied and this increase was significantly minimized under halopriming. From the present investigation it was evident that among the green gram varieties studied, Pusa Vishal, a NaCl tolerant variety showed enhanced tolerance to NaCl and PEG induced stress, when the seeds were subjected to halopriming followed by Pusa Ratna (stress sensitive variety). Pusa 9531 (drought tolerant variety) also showed positive halopriming effects but it was less significant when compared to other two varieties. It could be concluded that halopriming improved the drought and salinity stress tolerance potential of all varieties and it was significantly higher in the Pusa Vishal as compared to Pusa 9531 and Pusa Ratna.

Keywords: Abiotic stress; Drought; Mitochondrial activity; Photochemical activity; Salinity; Seed priming.

Fig. 1

Percentage of increase in protein (a) and total carbohydrates (b) of seedlings raised from haloprimed seeds of three different varieties of V. radiata as compared to that of seedlings raised from non primed seeds. Total protein content in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl and PEG stress is 105, 231 and 186 mg/g dw, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 239, 241, 227 mg/g dw, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 258, 146 and 149 mg/g dw, respectively. Total carbohydrate content in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl and PEG stress is 145, 173, 187 mg/g dw, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 126, 124, 103 mg/g dw, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 161, 202, 204 mg/g dw, respectively. The vertical bars represent SE of the mean value of recordings from three independent experiments each with a minimum of three replicates. Values super scribed with same alphabet is homogenous for each stress at 1 % level significance (p < 0.01; ANOVA)

Fig. 2

Percentage of change in proline (a) and MDA (b) of seedlings raised from haloprimed seeds of three different varieties of V. radiata as compared to that of seedlings raised from non primed seeds. Proline content in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl, PEG stress is 634, 641, 778 μg/g dw, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 793, 1,384, 3,149 μg/g dw, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 1,237, 1,912, 1,896 μg/g dw, respectively. MDA content in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl and PEG stress is 117, 127, 133 μmol/g dw, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 61, 67, 66 μmol/g dw, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 92, 104, 103 μmol/g dw, respectively. The vertical bars represent SE of the mean value of recordings from three independent experiments each with a minimum of three replicates. Values super scribed with same alphabet is homogenous for each stress at 1 % level significance (p < 0.01; ANOVA)

Fig. 3

Percentage of increase in peroxidase activity of seedlings raised from haloprimed seeds of three different varieties of V. radiata as compared to that of seedlings raised from non primed seeds. Peroxidase activity in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl, PEG stress is 178, 433, 331 μmol guaiacol oxidized/min/g dw, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 473, 536, 963 μmol guaiacol oxidized/min/g dw, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 314, 353, 980 μmol guaiacol oxidized/min/g dw, respectively. The vertical bars represent SE of the mean value of recordings from three independent experiments each with a minimum of three replicates. Values super scribed with same alphabet is homogenous for each stress at 1 % level significance (p < 0.01; ANOVA)

Fig. 4

Percentage of increase in PS I (a) and PS II (b) activity of seedlings raised from haloprimed seeds of three different varieties of V. radiata as compared to that of seedlings raised from non primed seeds. PS I activity in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl, PEG stress is 116, 155, 101 μmol of O₂ consumed/mg chl/min, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 168, 165, 113 μmol of O₂ consumed/mg chl/min, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 127, 103, 105 μmol of O₂ consumed/mg chl/min, respectively. PS II activity in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl, PEG stress is 41, 14, 24 μmol of O₂ evolved/mg chl/min, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 30, 28, 24 μmol of O₂ evolved/mg chl/min, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 38, 26, 22 μmol of O₂ evolved/mg chl/min, respectively. The vertical bars represent SE of the mean value of recordings from three independent experiments each with a minimum of three replicates. Values super scribed with same alphabet is homogenous for each stress at 1 % level significance (p < 0.01; ANOVA)

Fig. 5

Percentage of increase in mitochondrial activity of seedlings raised from NaCl primed seeds of three different varieties of V. radiata as compared to that of seedlings raised from non primed seeds. Mitochondrial activity in seedlings raised from non primed seeds of Pusa Ratna in 0, NaCl, PEG stress is 44, 11, 27 μmol of O₂ consumed/mg protein/min, respectively; for Pusa 9531 in 0, NaCl, PEG stress is 40, 37, 22 μmol of O₂ consumed/mg protein/min, respectively and for Pusa Vishal in 0, NaCl, PEG stress is 40, 17, 30 μmol of O₂ evolved/mg protein/min, respectively. The vertical bars represent SE of the mean value of recordings from three independent experiments each with a minimum of three replicates. Values super scribed with same alphabet is homogenous for each stress at 1 % level significance (p < 0.01; ANOVA)