Activation of growth and nodulation in a symbiotic system between pea plants and leguminous bacteria by near-UV radiation

The effects of near-UV (300-400 nm) radiation on shoot length, fresh weight , photosynthesis, respiration, nodulation (nodule formation), N-2-fixation (nitrogenase activity) and flavonoid level have been examined in the symbio tic combination between pea plants (Pisum sativum L. cv. Sparkle) and legum inous bacteria (Rhizobium leguminosarum by. Viciae strain 128c53). The grow th (shoot length and fresh weight) of pea plants is enhanced by near-UV rad iation. The net photosynthesis and dark respiration are also significantly promoted. The nodulation and symbiotic N-2-fixation are enhanced about two and eight times, respectively, by near-UV radiation. The content of flavono ids in pea roots, which may promote nodulation, is increased 46% by near-UV radiation. A possible mechanism for the action of near-UV radiation on the symbiotic system between leguminous plants and leguminous bacteria is disc ussed. (C) 1999 Elsevier Science S.A. All rights reserved.