A new insight into foliar applied methanol influencing phylloplane methylotrophic dynamics and growth promotion of cotton (Gossypium hirsutum L.) and sugarcane (Saccharum officinarum L.)

Foliar applied methanol has been purported to enhance growth and yield of cotton and sugarcane possibly by stimulation of plant hormone production mediated by pink-pigmented facultative methylotrophic (PPFMs) bacteria. In vitro studies were performed on the relations between leaf methanol and pectin methylesterase (PME: EC 3.1.1.11) in young and old leaves of cotton and sugarcane. Results of field trials and pot culture studies of cotton showed that application of 30% methanol or PPFMs as foliar spray significantly increased plant height, plant dry weight, leaf area, boll number, and boll dry weight, leading to an increase of seed cotton yield (SCY) over control. Foliar application of PPFMs increased plant height and specific leaf area of sugarcane and led to a cane yield increase of 9.8% over control. The overall PPFMs population in the phyllosphere of cotton remained higher than sugarcane. Applications of methanol or PPFMs increased the total cytokinins in cotton and sugarcane. The methanol emission process, regulated by PME activity that catalyzes demethoxylation of pectins, could trigger PPFMs population on the leaf surface and subsequent cytokinin production in plants, and might play a role in plant growth promotion. In our study, the foliar applications of methanol or PPFMs increased the PPFM populations and cytokinin production resulting in increased yield in cotton and sugarcane.