Physiological response of fennel (Foeniculum vulgare Mill.) related to methyl jasminate, uniconazole and proline + triton X-100 spraying under water-deficit stress conditions

In order to study the effects of the application of two-plant growth regulators/proline on some physiological characteristics in fennel under water-deficit stress conditions, an experiment was conducted as a split-plot based on a randomized complete block design with three replications at the research farm, agricultural faculty of Azarbaijan Shahid Madani University, Tabriz-Iran, in 2019. Factors were three irrigation regimes (irrigation at the field capacity (I1), irrigation after depleting 65 (I2) and 85% (I3) of the available water capacity) as the main plot and four foliar spraying (control, exogenous application of methyl jasmonate, uniconazole and proline + triton X-100) as a subplot. Results indicated that the minimum relative water content, membrane stability index, chlorophyll a, b, total (chl.), carotenoids and maximum proline, total soluble sugars, and malondialdehyde contents in leaves were obtained from severe water-deficit stress conditions. Maximum membrane stability index, chlorophyll a, total (chl.), carotenoids, and total soluble sugars were related to plant growth regulator application, especially methyl jasmonate. Interaction effects revealed that physiological growth characteristics were significantly reduced in the control treatment (except for proline and total soluble sugars) compared to foliar spraying treatments by increasing water-deficit stress conditions in the soil. The spraying with methyl jasmonate had a better effect on reducing the effects of water deficit stress on the physiological characteristics of the fennel by regulating of internal reactions and induction of antioxidant defenses. Therefore, methyl jasmonate can be used in water-deficit stress conditions in arid and semi-arid areas and reduce its harmful effects on the fennel plants.