FORMATION OF INDIGESTIBLE MATERIALS FROM DIGESTIBLE MATERIALS AND PHOTOSYNTHATES IN THE GROWTH OF RHODES GRASS (CHLORIS-GAYANA KUNTH)

This study was conducted to analyze the formation of indigestible mate rials from digestible materials and new photosynthates in the growth o f Rhodes glass, using the following equation. 1/W - dI/dt = D+dW/dt/W - (1/D+dW/dt - dL/dt) - dI/dL, where W = forage dry weight (W-1 not eq ual W-2), I = dry weight of indigestible materials, L = amount of lign in, D = dry weight of digestible materials (D-1 not equal D-2), dW/dt = new photosynthates, (D + dW/dt) = amount of source materials [S] for I formation, (1/W).(dI/dt) = formation rate of I [FRI], (D + dW/dt)/W = the ratio of S to W [S ratio], {1/(D + dW/dt)}.(dL/dt) = lignificat ion rate of S [LRS], dI/dL = formation of I per unit increase in L [FI L]. This equation was applied to samples from Rhodes grass (Rg) cut at 25, 41 and 74 days of regrowth. Each attribute in the equation was gi ven a bar on it to show mean value over the Ist interval of 16 days an d over the 2nd interval of 33 days, respectively. The following result s were obtained: Higher (FRI) over bar in the 1st interval than in the 2nd interval was mainly due to higher (LRS) over bar in the Ist inter val with some contribution by higher <(S ratio)over bar>. This suggest ed that lignification of source materials composed of digestible mater ials and new photosynthates was the main factor promoting the formatio n of indigestible materials in the comparison between the 1st and 2nd intervals. It was suggested that tile new equation presented in this s tudy gave a macro analysis of the formation of indigestible materials from digestible materials and new photosynthates with growth of tropic al grasses.