Effects of deficit water stress in response to the zeolite, vermicompost and nitrogen fertilizer on number of physiological and biochemical traits of fenugreek

Water deficit stress is first limitation that cause crops yield reduction in dried and semi-dried regions. In addition to the physiological changes that occurs due to water deficiency in plants, oxidative damage is also an important factor limiting plant growth and production. Plants adopt to cope with water deficit stress to accumulate osmolytes such as proline, glycine betaine and soluble sugar and increased antioxidant compounds (enzymatic such as superoxide dismutase, catalase and non-enzymatic such as carotenoids and anthocyanins against oxidative stress. This study was designed to investigate the effects of deficit stress, nitrogen fertilizer and zeolite on some physiological traits, biological and Trigonelline yield in fenugreek (Trigonella foenum-graecum L.).
A split factorial experiment was laid out in a randomized complete block design with three replications in the research field of Tarbiat Modares University in 2014 and 2015. Five irrigation regimes (unstress at vegetative and reproductive stages, Irrigation at 60% FC; mild stress and irrigation at 40% FC during the vegetative and reproductive stages respectively; severe stress irrigation at 20% FC during the vegetative and reproductive stages respectively) were randomized to the main plots. Subplots were 6 treatments in number and consisted of a factorial combination of three nitrogen fertilization (untreated plots, vermicompost fertilizer at a rate of 2.7 ton ha-1 and nitrogen chemical fertilizer at a rate of 11 kg ha-1) and two zeolite rates, (0, 9 ton ha-1). Physiological traits of fenugreek were measured.
The results showed that irrigation regime had a significant effect on all traits. And water deficit stress in both years resulted in increased levels of proline, glycine betaine, soluble carbohydrates, malondialdehyde, superoxide dismutase, catalase, carotenoids and anthocyanin and also reduces leaves greenness (SPAD), biological and grain trigonelline yield in fenugreek. Increase in the activity of two enzymes superoxide dismutase, catalase, and carotenoids and anthocyanin to sort of indicate activation of both enzymatic and non enzymatic antioxidant system to deal with oxygen free radical production in fenugreek under water deficit stress. It also increases the amount of compounds proline, glycine betaine and soluble carbohydrates in the leaves is effective in osmotic adjustment and create good conditions for absorbing water from the soil. With increasing severe stress decreased the amount of soluble carbohydrates, biological and grain trigonelline yield in fenugreek. The highest and lowest biological and trigoneline yield was obtained in full irrigation and vermicompost fertilizer treatment and severe water deficit stress in reproductive stage (20% FC) and no fertilizer treatment in both years. Also significant statistical difference was observed in trigoneline yield between mild water deficit stresses in vegetative stage treatment (40% FC) with control treatment (full irrigation) in both years.
Based on the results in this study, it can be concluded that although the reduction in water consumption was reduced biological and trigonelline yield in fenugreek, But by using vermicompost fertilizer to some extent reduce (14% and 46%) the adverse effects of sever water deficit stress in during reproduction on biological and trigonelline yield in this plant in 2015, respectively. So that produced the least malondialdehyde content (as a marker of lipid peroxidation and membrane damage) with (8 µmol g-1) and the highest total antioxidant capacity (4/6 mg protein), biological and grain trigonelline yield in control treatment (60% FC).