Variations in the growth, oil quantity and quality, and mineral nutrients of chamomile genotypes under salinity stress

Abstract

Understanding how plants respond to salinity, which severely restricts plant growth, productivity, and survival, is highly important in agriculture. Using three genotypes of Matricaria recutita L. (Shiraz, Ahvaz, and Isfahan) with different sensitivity to NaCl, the effect of long-term (about 110 days) NaCl treatments (2.5, 6, 9, and 12 dS*m-1) on crop growth, oil quality and quantity, and nutrient variations were investigated to underpin its agricultural management in the future. The adaptation strategy and plant responses were influenced by salinity level, genotype, and genotype × salinity interactions. With higher productivity compared to the Isfahan genotype, the Shiraz and Ahvaz genotypes had efficient Na+ exclusion at root surface as an avoidance strategy; however, under higher NaCl concentration, their higher performance were mainly attributed to the Na+ sequestration in root vacuoles and higher Ca2+/Na+, Mg2+/Na+, and root/shoot ratios as tolerance strategies. The higher oil yield and chamazulene percentage in the Isfahan genotype were not affected by salinity level and were only genotype dependent. Under 12 dS*m-1 NaCl, roots of the Shiraz and Ahvaz genotypes accumulated markedly higher Ca2+ (2.5% and 1.5% respectively) and Mg2+ (1.6% and 1.3% respectively), required for membrane stability and chlorophyll synthesis, respectively, more than the Isfahan genotype (0.2% Ca and 0.1% Mg2+) and considerably more than the control plants to keep low concentrations of ion toxicity of Na2+ and Cl- in shoots. Overall, greater salt tolerance found in the Shiraz and Ahvaz genotypes could be due to a variety of mechanisms, including higher efficiency of nutrient uptake (Ca2+, Mg2+, and Zn2+), utilization (N, P, Ca2+, and Mg2+), compartmentation (Na in roots), and maintenance of higher root/shoot ratios. Taking flower and oil yield as well as chamazulene percentage into consideration, the findings recommended cultivation of the Ahvaz genotype in the absence of salt stress (by 1.18 g*plant-1, 6.25 kg*ha-1, and 12.54% respectively), the Isfahan genotype under 6 dS*m-1 NaCl (by 0.73 g*plant-1, 4.84 kg*ha-1, and 11.66% respectively), and the Shiraz genotype under high salinity of 9 and 12 dS*m-1 NaCl (by 0.68 g*plant-1, 5.20 kg*ha-1, and 13.46% respectively under 12 dS*m-1 NaCl).