In order to obtain equations which make feasible the leaf area estiomate from linear measures of the leaf blade, correlation studies were done involving the real leaf blade area and main vein leaf lenght (C), maximum leaf width (L) and C*L. All the equations, linear, geometric and exponential, provide good leaf area estimate for both species. In the practical sense, it is suggested the use of the simple linear equation of the regression model using the C*L parameter and taking the linear coefficient equal zero. Then, the Brachiaria decumbens leaf area can be estimate using the equation Sf = 0,9810 (C*L) and the Brachiaria brizantha by using the equation Sf = 0,7468*(C*L).
Weed physiology; grass weeds