The effect of water deficiency and salinity on the growth and quality of fresh dill (Anethum graveolens L.) during autumn and spring cultivation

The aim of this experiment was to determine the response of dill (Anethum graveolens L.) to water deficiency and salinity. In spring, dill biomass decreased with increasing water deficiency due to a reduction in the number and mean weight of leaves per plant. The concentrations of chlorophyll, carotenoids, vitamin C and total phenolics within the leaves were unaffected by water stress, but the Cl, Na and K content decreased. Salinity had no effect on plant growth in the spring, except at the highest level (8 dS/m-1), where a decrease in biomass occurred. The chlorophyll and total phenolics content of leaves rose in the autumn with increasing salinity, whereas vitamin C and carotenoids were unaffected. In spring, increasing salinity caused fluctuations in the chlorophyll and vitamin C content of the leaves and a decrease in total phenolics. The concentrations of chlorophyll and antioxidants were higher in spring than in autumn at all levels of salinity. The essential oil content was also higher in the spring than in the autumn, irrespective of salinity. A relative decrease in dill ether within the herb oil under increasing salinity was compensated for by an increase in α-phellandrene. In the flower oil, increasing salinity caused a decrease in the relative concentrations of both α-phellandrene and dill ether, which was compensated for by an increase in carvone. Overall, dill appears more resistant to salinity than to water stress, but the season of cultivation has the most important effect on both yield and quality.