EFFECTS OF LIGHT-INTENSITY ON GROWTH, ANATOMY AND FORAGE QUALITY OF 2TROPICAL GRASSES (BRACHIARIA-BRIZANTHA AND PANICUM-MAXIMUM VAR TRICHOGLUME)

Effects of light intensity on growth, histology and anatomy, and nutri tive value were studied in seedlings of two shade tolerant species: Br achiaria brizantha (A. Rich) Stapf and Panicum maximum var.trichoglume (K. Schum.) C.E. Hibbard. They were studied under greenhouse conditio ns in pots with sandy soil and sufficient N and cut after a growth per iod of 8 weeks. High light intensity stimulated growth, tillering and yield per tiller and increased stem proportion. It greatly increased n umber of sclerenchyma cells, their wall thickness in all organs and th e content of cell wall constituents. High light intensity also reduced concentrations of total N, NO3-N and ash appreciably. It reduced dige stibility of cell wall constituents in leaf blades but increased it in leaf sheaths and stem, especially in Panicum. Variation in sclerenchy ma tissue could be associated with variation In percentage of cell wal l constituents, but not with variation in cell wall digestibility. The resultant ot these effects of light intensity on composition of organ s was a higher digestibility of organic matter of the whole crop at lo wer light intensity. Brachiaria was more tolerant to shade than Panicu m with regard to growth, N-concentration and digestibility, but it acc umulated more nitrate. It was suggested that light intensity may affec t forage quality little under low nitrogen supply in the tropics, but effects may be larger at ample nitrogen supply. Individual species may partly divert from this general pattern.