Effect of defoliation stress on regrowth and some nodule biochemical characteristics of "copada”

Abstract

The effects of defoliation stress on regrowth vigor, nodulation and nitrogenase activity, along with some nodule cytosol components of Cratylia floribunda Mart ex-Benth were evaluated. Plants clipped 5 to 7 cm above the ground, at fourteen-day intervals, yielded more dry matter herbage than plants never clipped. Clipped plants had increased number of stems from 11.0 to 19.5, and folair, 48.6% to 54.2%, whereas nonclipped plants had decreased foliar fraction, 55.4% to 29.4%, and stem protein, 8.2% to 6.2%. Neither clipping treatments nor plant age influenced percent leaf protein between 70 days after emergence (DAE), and 154 DAE. Plants clipped four times (126 DAE) had a larger number of mature and immature nodules, as well as higher immature nodule weight than plants with the same age, but never clipped. Nonclippled plants showed decreasing percent nodulation, 21.8 to 14.4, and nitrogenase activity, 46.5 to 32.5 μmoles C₂H₄g^-1fresh nodule h^-1 between 70 and 154 DAE. The activity of aspartate transaminase (AST) and levels of  α-Ketoglutarate (αKG) increased in mature nodules of nonclipped plant, but the activity of alanine transaminase (ALT) and glutamate dehydrogenase (GDH) in these nodules were not influenced either by clipping treatment or plant age between 98 DAE and 154 DAE.