Influence of foliar application of triacontanol on growth attributes,gas exchange and chlorophyll fluorescence in sunflower (Helianthus annuus L.) under saline stress

To appraise the effect the foliar application of triacontanol (tria) on sunflower (helianthus annuus l.) under saline stress,a pot experiment was conducted under natural conditions. two sunflower cultivars (smh-907 and smh-917) were grown in sand culture medium supplemented with full strength hoagland's nutrient solution for 25 days,after which time,two saline regimes [control (0 mm) and saline (150 mm)] were applied. three tria levels [0 (water spray),50 and 100 μm] were applied as foliar spray on 44-day old plants. plants were harvested after 4 weeks of tria application. the root growing medium saline stress significantly reduced shoot and root fresh weights and their lengths,net co2 assimilation rate (a),transpiration rate (e),water use efficiency (wue),co-efficient of nonphotochemical quenching (qn) and non-photochemical quenching (npq) in both sunflower cultivars. foliar-applied tria markedly increased shoot and root fresh weights and lengths,a,e,stomatal conductance and wue in both cultivars under both saline and non-saline regimes. tria did not show prominent effect on chlorophyll fluorescence attributes such as electron transport rate and photochemical quenching of sunflower plants. the tria level 100 μm was more effective as compared to the others and sunflower cultivar smh-917 showed better performance than those of cv. smh-907 in terms of different attributes measured in this study.