For the first time, carbon isotope discrimination 13C/12C is used for oil palm to investigate precisely carbon &location from source organs to sink 's one and to identify metabolites belonged to a reserve pool , involved in fine in the filling of the bunches. Isotope signature is measured first on organic matter which is supposed to integrate total metabolism pathways during the elaboration of the organs. Then, same processes are done on soluble sugars (sucrose, fructose, glucose), starch and lipids. This project IOPRI-CIRAD-UPS XI is composed by three main experimentations (i) the study of the link from heteretrophy to autotrophy during the leaves development (ii) the spatial and seasonal variations 'of metabolites and their isotope signatures on different parts of the trunk (iii) the study of the oleosynthesis during fruits maturation. Only the first part (i) is presented in this work which reveals that carbon isotope is a very pertinent tool to follow carbon assimilate inside each organs and may be of great help to found the main factor which is responsible for the sex ratio at individual scale including genetic and environment effects.