Year: 1986
Type: conference-paper
Abstract: The acetylene-reduction assay for nitrogenase activity has shown that the roots ofsorghum and \npearl millet stimulate N,jixation. A soil-core assay usedfor measuring nitrogenase activity of \nfield-grown plants showed large planHo-plant variability. An improved core assay (planted core \nassay) developed at ICRISAT Center showed higher activity than that recorded by regular core \nassay. In greenhouse assay methods plants with shoots sustained higher activity than the ones \nwhose tops were cut before the assay. Nitrogen(Jse activity varied throughout the day, as well as \nover the season. Activity was maximum at the lateflowering or early grain:/illing stage and it was \nrelated to the ontogenetic development of the plant. Activity was favored in moist, warm (ca \n35° C) soil and decreased with high levels of fertilizer N. \nGenotypic variation in sorghum and pearl millet lines for stimulating rhizospheric nitrogenase \nactivity was observed. Out of 184 pearl millet lines tested, 18 lines stimulated high nitrogenase \nactivity (> 460 nmol C2H4 h-I 15 em diam core-I) in the rhizosphere. Two lines, Gam 73 and J \n1407, were consistently active over several seasons. Similarly, 28 of 334 sorghum lines tested had \nhigh nitrogenase activity (>460 nmol C2H4 h-I 15 cm diam core-I). \nAt ICRISAT Center, pot-culture experiments with sorghum and pearl millet grown in a \nlow-fertility Alflsol, or in unsterilized washed vermiculite, showed substantial positive balances \nfor N. Long-term N balance studies .in, 'the field with sorghum and pearl millet cultivars are \ncontinuing. \nUsing IS N2 it has been shown that 10-days-old sorghum seedlingsfix N2 in the rhizosphere, and \npart of it is taken up by the plant within 3 days after exposure. The 15 N isotope dilution technz'que \nhas been evaluated for studying genotypic variation in sorghum and pearl millet cultivars for N2 \nfixation. \nMany different kinds of bacteria closely associated with the roots of sorghum and pearl millet \nplants show nitrogenase activity. Responses to inoculation in terms of increased dry-matter \nproduction and N uptake have been observed in pot experiments with sorghum and pearl millet \ngrown in Alfisols and vermiculite. In five out of nine field trials with pearl millet cultivars, \ninoculations with N2:/ixing bacteria significantly increased the grain and plant dry-matter yields \nin all the cultivars.
Author: S P Wani
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2167661772