EFFECTS OF METHANOL FOLIAR APPLICATION ON NUTRIENT CONTENT AND RWC OF SUGAR BEET UNDER WATER DEFICIT STRESS

To study the effect of methanol foliar application on sugar beet under water deficit stress an experiment was conducted. Treatments were water deficit stress in three levels, a1: mild stress (50% FC irrigation), a2 : fair stress (75% FC irrigation) and a3: normal irrigation (100% FC irrigation) and the foliar application of methanol in seven levels [b1 : 0, b2 : 5, b3 : 10, b4 : 15, b5 : 20, b6 : 25 and b7 : 30 (v/v)]. The analysis of variance showed significant effect of water deficit stress and methanol foliar application on concentration of α-amino N, Na, K, RWC and sugar content (p < 0.01). Results showed that α-amino nitrogen and K contents were the highest in mild stress and the lowest in 20% (v/v) methanol foliar application. However, Na content was the highest in normal irrigation and 30% (v/v) methanol foliar application. Sugar content was the highest in mild stress (16.40%) and the lowest in the normal irrigation (15.86%). Besides, the results also proved that 20% (v/v) and 30% (v/v) methanol foliar application had the highest (17.16%) and lowest (15/31%) sugar content, respectively. Introduction Water deficit is a major abiotic stress that adversely affects the crop growth and yield (Jaleel et al. 2008). It reduces plant growth and development by affecting various physiological and biochemical processes (Jaleel et al. 2008, Farooq et al. 2008). Plants use different mechanisms to cope with the drought stress. The first step to achieving high yield per unit area is to increase production of dry matter, because almost 90% of plant dry weight is resulted from CO2 assimilation during photosynthesis (Khalilvand and Yarnia 2013). Today in order to achieve this goal compounds such as methanol, ethanol and amino acids like glycine, glutamats and aspartate are used as C source for the most production. Recent investigation showed that C3 crops yield and growth increased via methanol spray and methanol may act as C source for these crops (Makhdum et al. 2002). Methanol (CH3OH) is the second most abundant organic gas in the atmosphere after methane (Hanson et al. 2000). Methanol metabolism in plants is poorly understood. Methanol is a naturally occurring, volatile organic compound emitted from the leaves of many plant species (MacDonald and Fall 1993, Nemecek-Marshall et al. 1995), but the origin of emission is uncertain. The diurnal pattern for volatile organic compounds (VOCs) and methanol suggests that accumulation of these substances is related to photosynthetic processes (Fall and Benson 1996). Interestingly, leaves typically harbor methylotrophic bacteria capable of metabolizing methanol (Corpe and Rheem 1989, Holland and Polacco 1994), and these bacteria may be associated with leaf surface methanol emission. Methylotrophic yeast is also capable of metabolizing methanol. Foliar applications of aqueous methanol have been reported to increase yield, accelerate maturity, and reduce drought stress and irrigation requirements in C3 crops grown in arid environments, under elevated temperatures, and in direct sunlight (Ramirez et al. 2006). Metabolism of methanol to sugars would change leaf osmotic potential, resulting in increased turgor and stomatal conductance. Keeping the stomata open would increase the assimilation rate and, subsequently, *Author for correspondence: < e.khalilvand@iaut.ac. ir>.