چكيده انگليسي :
Safflower (Carthamus tinctorious L.) is an annual crop species from the Asteraceae. Owing to its deep root system, safflower indicates resilience toward environmental hardships, including drought and salinity. Salinity is amongst the most serious environmental stresses, suppressing grain yield and productivity of crop plants, worldwide. Salt-induced suppressions in the grain yield and quality are particularly notable in the arid-semiarid regions of the world. Application of some micronutrients may ameliorate the adverse effects of salinity on plants. Zinc (Zn) deficiency in agricultural crops and hence dietary Zn deficiency in humans’ nutrition is a real concern world-wide, necessitating Zn fortification of crop plants and alleviate Zn deficiency of humans particularly in semiarid regions. Though, there is a narrow gap between Zn essentiality and toxicity in plants, making Zn amendment to be a puzzling question, particularly under alkaline-saline conditions. Thus, two pot experiments were conducted to shed light on the negative and positive responses to different methods of Zn application of safflower genotypes. Two soils with different physicochemical properties, namely a more calcareous soil with less available Zn (i.e. deficient in Zn) and a less calcareous soil with more available Zn (sufficient in Zn) were used in the two experiments. In the first experiment six genotypes were exposed to four levels of Zn amendment (i.e. no Zn application, foliar-applied Zn, soil-applied Zn, and foliar-applied + soil-applied Zn) in a Zn-deficient soil. In the second experiment three selected genotypes were exposed to four levels of Zn amendment (i.e. no Zn application, foliar-applied Zn, soil-applied Zn, and foliar-applied + soil-applied Zn) in a Zn-sufficient soil in the presence (i.e. 120 mM NaCl) or absence (control=0 mM NaCl) of saline water. Each experiment was conducted as a factorial three-replicate randomized complete block design. Results of the first experiment were suggestive of some genotypic differences though commonality of improvement in leaf chlorophylls and carotenoids concentrations, leaf area, leaf Zn concentration, plant height, achenes/plant, 100-achenes weight, capitula/plant, achene weight/plant, and plant above-ground dry mass (SDM) in response to Zn amendment. Results of the second experiment were, in contrast, indicative of commonality of suppressions in the leaf chlorophylls and carotenoids concentrations, maximum efficiency of photosystem II, leaf area, relative water content, K concentration, plant height, achenes/plant, 100-achenes weight, capitula/plant, achene weight/plant, and plant above-ground dry mass (SDM), despite increases in Na/K, proline, Na, malondialdehyde, hydrogen peroxide, and grain Zn concentrations, and antioxidative enzymes activities upon exposure to saline soil and Zn amendment, particularly in the form of foliar application + soil application of Zn. The results of the two experiments, taken together, depict Zn application as a double-sward practice, benefiting safflower growth, physiology, and grain yield in Zn-deficient soil
but contrastingly, exerting phytotoxic effects on this oilseed crop in Zn-sufficient soil and saline water conditions.
