The effects of molybdenum oxide nanoparticles on some physiological and agronomic characteristics of oilseed rape under drought stress

Water deficit stress is one of the most common abiotic stresses that reduce the growth, and development, and yield of crops such as oilseed rape. The Utilization of micronutrients in oilseed crops is one of the most valuable and practical approaches for improving grain yield and plant tolerance under drought stress conditions. Accordingly, this study aimed to investigate the effect of foliar application of molybdenum oxide nanoparticles on the physiological and agronomic characteristics of winter oilseed rape under the end season drought stress.

To investigate the effect of molybdenum oxide nanoparticles on the physiological and yield characteristics of oilseed rape under the end season drought stress, a split-plot experiment based on randomized complete block design (RCBD) was conducted with three replications at the research farm station of University of Mohaghegh Ardabili in 2018-2019. The experimental factors were irrigation (regular irrigation and omitting irrigation at the flowering stage) as main plots and molybdenum oxide nanoparticles foliar application ((0 (control), 25 and 50 mg/L) as sub-plots. The measured traits include the chlorophyll index, relative water content (RWC), electrical conductivity (EC), malondialdehyde (MDA) content, plant height, number of branches, number of pods per plant, number of grains per pod, 1000-grain weight, grain yield, oil percentage, and oil yield.

The results showed that the drought stress during the flowering stage significantly decreased the chlorophyll index, leaf relative water content and increased the electrolyte leakage and MDA content in the leaves, which resulted in a significant decrement of the yield and yield components of oilseed rape. Under the end season drought stress conditions, the foliar application of 25 and 50 mg/L molybdenum oxide nanoparticles significantly increased the grain yield and yield components of oilseed rape compared to the control treatment, mainly through improving the chlorophyll index and leaf relative water content and decreasing the membrane lipid peroxidation. Under the end season drought stress conditions, foliar spraying with 25 mg/L molybdenum oxide nanoparticles caused about 31.6 percent increase in the number of pods per plant, 10.09 percent in 1000-grain weight, 28.37 percent in grain yield, and 27.71 percent in oil yield of oilseed rape as compared to no spraying treatment. Under regular irrigation conditions, the highest plant height, number of branches, and number of pods per plant were obtained with foliar application of 25 mg/L of molybdenum oxide nanoparticles.

The results showed that the irrigation omitting at the flowering stage (the end season drought stress) negatively affected the growth and yield of winter oilseed rape. The foliar spraying of oilseed rap plants with molybdenum oxide nanoparticles had positive and significant effects on the physiological and agronomic traits of oilseed rape under favorable and unfavorable environmental conditions. So that, foliar spraying improved the grain yield and oil yield and reduced the harmful effects of drought stress. In general, the foliar application of 25 mg/L molybdenum oxide nanoparticles had a positive and significant effect, on the physiological and agronomical characteristics of oilseed rape, and can be used to reduce the destructive effects of drought stress and improve the grain and oil yield of this plant.