INFLUENCE OF LEAF-AREA INDEX AND CARBOHYD RATE RESERVES AT CUTTING ONTHE LEAF GROWTH OF 2 FORAGE GRASSES (DACTYLIS-GLOMERATA L AND FESTUCA-ARUNDINACEAE SCHREB)

Leaf growth of two forage grasses (Dactylis glomerata L. and Festuca a rundinacea Schreb.) was studied as a function of the sward state after a cut. Two heights of cut (3 and 6 cm) and a variable number of previ ous cuts were used to reach different residual leaf area index (IFr), and non-structural carbohydrate (CNS) concentration and quantity. For both species, four treatments were studied in 2 consecutive years. In mid-May for each of the species, the IFr ranged from 0 to 1, and the q uantity of CNS varied from 12 to 25 g 100 g(-1) DM according to the tr eatments. Over the 3 wk of regrowth, the IF reached values ranging fro m 1 to 7 and its increase depended on the IFr and the quantity of CNS. Among the three components of the quantity of CNS (weight of sheath p er tiller, tiller density and CNS concentration), only the first two h ad a significant effect on the IF increase. Tiller mortality occurred when the quantity of CNS or the IFr were the lowest and it contributed little to the growth of lower leaves. No significant differences were found between the two species.