Effect of drought and salinity stress on flower quality, biochemical changes and ions concentration of Narcissus tazetta cv. ‘Shahla’

 Narcissus that is one of the most important ornamental and medicinal plants that its various species are grown in throughout the world except for tropical regions. Narcissus cv. Shahla is a perennial bulbous plants which is used as cut flower, garden and pot plant. Considering that the narcissus plant is one of the most important economic and cultivating crop in Iran. On the other hand, the drought crisis and salinity of water and soil are one of the serious problems of agricultural production. Knowledge of the tolerance of this plant to drought and salinity stresses in order to produce optimal product is essential. The aim of this study was to investigate the combined effect of drought and salinity stresses on some reproductive and biochemical chracteristics and sodium and potassium ion concentrations of N. tazzeta flower.

This pot research was conducted as factorial based on completely randomized design, with 3 replications. The first factor was drought stress at four levels of 90% (control), 70%, 50% and 30% field capacity (FC), and the second factor was salinity stress of irrigation water caused by sodium chloride at four levels of 0 (control), 20, 40 and 60 mM. Application of drought and salinity treatments lasted about 4 months and then the traits were measured. The investigated traits were included flower number, flower diameter, total chlorophyll content, carotenoid and total flavonoids of leaf, activity of catalase and guaiacol peroxidase enzymes of leaf, and the sodium and potassium elements of leaf and bulb.

The results showed that the effect of drought and salinity stresses and their interaction on flower number was not significant, but these stresses reduced flower diameter. The highest and lowest flower diameter was obtained from control and 60 mM NaCl × 30% FC treatments. The simple effects of salinity and drought stresses and their interaction on total chlorophyll content was significant and decreased, so that 60 mM NaCl × 30% FC treatment reduced total chlorophyll content by 72% compared to control. Salinity and drought stress reduced leaf carotenoid content, so that the amount of this trait at the highest levels of salinity and drought decreased by 26 and 25% respectively, compared with the control. The results showed that with increasing levels of salinity and drought stress, the activity of catalase and guaiacol peroxidase enzymes increased, so that the highest enzyme activity was obtained from the highest levels (salinity 60 mM and 30% field capacity). In the interaction of two stresses, the highest activity of catalase enzyme was obtained from 60 mM × 30% FC with a 4.5-fold increase compared to the control. With increasing salinity and drought stress, the amount of potassium in leaves and bulb decreased, but the sodium content of leaf and bulb increased with increasing stresses level, especially salinity stress.

The results showed that all levels of drought and salinity stress improved the antioxidant enzymes (catalase and guaiacol peroxidase) and non-enzyme (total flavonoid) of N. tazetta flower, but under drought and salinity stress conditions, flower diameter, carotenoid and total chlorophyll content decreased. Under the conditions of salinity and drought stresses, the amount of sodium accumulation in the leaves was higher than that of the bulb. The results showed that the sensitivity of N. tazetta plant to salinity stress was more than drought, which was exacerbated by simultaneous application of two stresses. In general, the results showed that cultivation of N. tazetta flower up to 70% FC and iriigation salinity about 3 dS/m did not have a significant negative effect on yield and plant quality and it is recommended.