Mise en évidence d'une régulation de l'efflux de NO3– racinaire par la partie aérienne chez quatre cultivars de blé tendre (Triticum aestivum L.), Sais, Jouda, Marchouch et Khair : influence de la lumière

Abstract

Nitrate exsorption in relation to light was studied in four wheat (Triticum aestivum L.) cultivars, Sais, Jouda, Marchouch, and Khair, using four experimental treatments: intact plants, excised roots, defoliated plants, and decapitated plants. Data show that nitrate exsorption was dramatically reduced from excised roots compared to controls. This efflux reduction was also observed from the roots of decapitated plants. On the contrary, defoliation triggered a significant increase in the quantity of exsorbed NO3–, as compared to intact plants. This increased efflux was much more dramatic when defoliated plants were exposed to darkness; nitrate exsorption from roots was then 8 to 10 times larger than from excised roots. In 21-day-old wheat plantlets, the aboveground parts are the main site for efflux regulation at the root level. Both leaves and apex are the aboveground organs responsible for this regulation. Indeed, the efflux was reduced by the leaves and, on the contrary, stimulated by the apex. Light was involved in controlling this efflux. This control involves a flow, between the aboveground parts and the roots, of two types of factors, one of which (or both) being sensitive to light. The first factor is of apical origin, whereas the second is of foliar origin. However, the chemical nature of these two types of photosensitive factors involved in NO3– ions efflux regulation remains to be determined.Key words: nitrate, efflux, light, darkness, common wheat.[Journal translation]