Effects of drought stress on some phytochemical characteristics of rice cultivars under different chemical and organic nutritional sources

To study the phytochemical properties of rice cultivars using different nutrients (chemical and organic) under drought stress, a split-plot factorial experiment with randomized complete block design with three replications at Dasht-e-Naz field in Sari city, in the crop years 2016 and 2017 were repeated. The drought stresses were fully performed in three levels; stress on the time of tillering initiation (15 days after transplanting), in remobilization stage (the end of flowering and the beginning of grain filling stage), and no stress (control) as the main factors in terms of elimination of irrigation and re-irrigation after the appearance of hairy cleavage. The type of nutrition system was considered as the sub-factors in the factorial pattern in terms of four levels of vermicomposting and Azolla compost, in the quantities of 6 and 8 tons per hectare respectively, humic acid (4.5 per one thousand), the conventional chemical fertilizers (Nitrogen, Phosphor, and Potassium), and two cultivars (Shirodi and the local Tarom). The highest proline, CAT, POX, APX, and enzymes ABA were also carried out under drought stress conditions in the remobilization stage using conventional fertilizer (Nitrogen, Phosphor, and Potassium) in the local Tarom cultivar. Therefore, according to this experiment's results, the local Tarom cultivar, due to increased activity of enzymes under stress conditions, is a tolerant cultivar. One can also consider humic acid's role in increasing drought tolerance of rice cultivars by reducing the oxidative damage caused by active oxygen species created under drought stress and protecting plants' physiological processes.