Influence of strigolactone (GR24) on growth, physiological and biochemical attributes of wheat (Triticum aestivum L.) under saline conditions

Abstract

In order to examine whether exogenous application of strigolactones (GR24) could mitigate the adverse effects of salt stress on spring wheat (Triticum aestivum L.), experiments were conducted under natural climatic conditions in a net-house of the Old Botanical Garden, University of Agricuture, Faisalabad Pakistan. Both wheat cultivars [S-24 (salt tolerant cultivar) and PARI-73 (moderately salt sensitive cultivar)] were grown in full strength Hoagland’s nutrient solution under non-stressed and salt stressed conditions. Experiment I was conducted to explore the effect of pre-seed treatment with strigolactone (GR24) for 16 h. on wheat under non-saline and saline conditions. There were four different levels of GR24 solution (Water (0), 0.001, 0.01 and 0.1 mg L-1). Salinity treatment applied through root growing medium to fifty day-old plants. There were two salt (NaCl) levels control (0 mM) and 150 mM (NaCl). Experimental design was completely randomized with four replicates. Data were recorded of 77 day old plants. In experiment I findings, root growing salinity (150 mM) significantly decreased growth attributes, photosynthetic efficiency of wheat plants, leaf water relations parameters except leaf turgor potential, activity of catalase enzyme, shoot and root K+ and shoot Ca2+ and yield attributes except 100-seed weight. However, concentration of ascorbic acid, activity of glutathione reductase, production of hydrogen peroxide, accumulation of organic osmotica (Proline and glycinebetaine contents) and uptake of shoot and root Na+ ion contents significantly increased under salt stress. Pre-soaking seed treatment with GR24 increased photosynthetic efficiency, only leaf water potential, enzymatic antioxidants (catalase and peroxidase) activities, accumulation of total soluble proteins, osmoprotectants like proline and glycinebetaine contents, non-enzymatic antioxidants (total phenolic contents and glutathione reductase activity) and production of hydrogen peroxide. Pre-soaking seed treatment with GR24 further slightly reduced growth and number of tillers per plant. Exogenous application of GR24 in experiment II was applied through foliar spray. In experiment II, imposition of salinity through root growing medium (150 mM) significantly reduced growth parameters, non-photochemical quenching (NPQ), electron transport rate (ETR) and co-efficient of non-photochemical quenching (qN), gas exchange characteristics, water relations parameters, ascorbic acid contents and shoot and root K+ and Ca2+ ions. Salinity increased accumulation of glycinebetaine and free proline, activities of enzymatic antioxidants and Na+ contents in both shoot and root of wheat plants. GR24 spray XV significantly increased gas exchange characteristics except transpiration rate (E), activities of enzymatic antioxidant, accumulation of free proline production but markedly increased the malondialdehyde and hydrogen peroxide (H2O2), root Ca2+ and K+ content. Overall, S-24 performed better than PARI-73 in all aspects and PARI-73 severely affected by salinity.