Growth periodicity in trees of Coffea arabica L. In relation to nitrogen supply and nitrate reductase activity

Vegetative growth of branches and leaf area gain in field-grown Arabica cof fee trees in Vicosa, southeastern Brazil, exhibited active and quiescent ph ases. Nitrogen supplementation during the cool season did not prevent growt h decline, nor did it alter the overall pattern of the tree growth; however , it enabled the plants to grow faster following the quiescent growth phase . Growth was related poorly to both nitrate content and nitrate reductase a ctivity in leaves. In roots, N-fertilization in addition to accounting for greater content of nitrate, amino acids and ammonium was also associated wi th the maintenance of the nitrate reductase activity, but nitrate reduction was apparently nil in leaves during most of the cool season. (C) 1999 Else vier Science B.V. All rights reserved.