The effect of water deficit stress on chlorophyll fluorescence, photosynthetic pigments, trigoneline and grain yield in fenugreek in response to zeolite and nitrogen

In order to determine the effects of water deficit stress, nitrogen fertilization and zeolite on chlorophyll fluorescence, pigments, trigonelline content and seed yield in, a split factorial experiment was laid out in a randomized complete block design with three replications. Five irrigation regimes were randomly applied to the main plots. Subplots included six treatments and consisted of a factorial combination of three nitrogen fertilization (untreated plots, vermicompost 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 and 9 ton.ha-1). The results demonstrated that (Fm), (Fv), (Fv/Fm), chl a, b, total chl content and also seed yield were significantly reduced by water deficit stress, wheras minimum fluorescence (F0), carotenoid and trigonelline concentrations were increased. In addition, the highest Fv/Fm, chl a+b content and the lowest F0 and carotenoids were observed when irrigation was done after unloading 40% of ASW. In most treatments vermicompost increased the yield (by 25.51% and 98.32% in 2014 and 2015, respectively) and grain trigonelline concentration (7.46% in 2014) in Fenugreek. Mild water stress with vermicompost treatment is recommended for the production of trigoneline from Fenugreek seeds.