Photosynthetic efficiency in Gymnema sylvestre (Retz.) R.Br. genotypes

Abstract

Leaves of Gymnema sylvestre (Retz.) R.Br. ex SCHULT plants are used to cure the most prevalent and important life style disease, the diabetes mellitus. Gymnema is a slow growing plant genotype with the requirement of higher photosynthetic rate. Presently, there is no report available on gaseous exchange and chlorophyll fluorescence parameters in gymnema. Total 44 genotypes were evaluated for their physiological efficiencies during post rainy season in sub-tropical region of Gujarat.The light curve studies indicated the light requirement of the plants to be between 1000 and 1250 µ mol (photons) m−2 s−1. Genotypes were categorized into low, medium and high groups considering over all mean values of different parameters ± standard deviation. Seven genotypes showed higher photosynthetic rate (PN), nine genotypes showed higher stomatal conductance (gs), six genotype exhibited higher transpiration rate (E), five genotypes revealed higher intrinsic water use efficiency (WUEint), eight genotypes manifested maximum photochemical efficiency (Fv/Fm), seven genotypes reached maximum actual efficiency of PSII (\\({\\text{F}}_{\\text{v}}^{{\\prime }}\\)/\\({\\text{F}}_{\\text{m}}^{{\\prime }}\\)), six genotype showed maximum quantum yield of PSII (ɸPSII) and electron transport rate (ETR) and seven genotypes exhibited higher open PS II centers (qP). The correlation matrix revealed that the PN was strongly positively correlated with gs, \\({\\text{F}}_{\\text{v}}^{{\\prime }}\\)/\\({\\text{F}}_{\\text{m}}^{{\\prime }}\\), ΦPSII and ETR. DGS-2 and DGS-18 were physiologically most efficient genotypes having high values in seven common parameters. These parameters were PN, gs, Fv/Fm, \\({\\text{F}}_{\\text{v}}^{{\\prime }}\\)/\\({\\text{F}}_{\\text{m}}^{{\\prime }}\\), ΦPSII, qP and ETR will be very useful in crop improvement program focused on biomass maximization in Gymnema sylvestre.