Interaction Between Different Levels of Nitrogen Fertilizer and Drought Stress on Photosynthetic Pigments and Yield in Four Wheat Cultivars

Effect of different levels of nitrogen fertilizer on chlorophyll a, chlorophyll b, carotenoid, flavonoid, yield and yield components of four wheat cultivars in two locations (Kudian and Nasrabad, Fars province, Iran) were investigated. The experiment was conducted as split plot in a randomized complete block design with two main irrigation levels (normal and interrupted irrigation at the stem stage). Four wheat cultivars (Shiroodi, Chamran 2, Chamran matri, and Siamran) and four levels of nitrogen fertilizer (0, 120, 240 and 360 kg ha-1) with three replications were used as sub-factors. Grain yield traits, number of grains per spike, number of spikes per square meter, 1000-grain weight, chlorophyll a, chlorophyll b, carotenoid and flavonoid pigments were evaluated. The results showed that drought stress reduced chlorophyll a, chlorophyll b, carotenoid, flavonoid, yield and yield components. Drought stress reduced grain yield by 29% but application of 120, 240 and 360 kg ha-1 nitrogen increased yield by 25, 32 and 15%, respectively. Therefore, the use of 240 kg nitrogen could be useful for these cultivars in both drought and non-stress conditions.