Gas exchange and leaf specific mass of different foliar cohorts of the wintergreen shrub Aristotelia chilensis (Mol.) stuntz (Eleocarpaceae) fifteen days before the flowering and the fall of the old cohort

摘要

In the beginning of the spring Aristotelia chilensis sheds the old cohort, forms a new one and flowers. Fifteen days before the flowering and the fall we measured net photosynthesis (A), transpiration (E), water use efficiency, (WUE), specific leaf mass (SLM) and area and mass of leaves per branch in old and new cohorts. Under low irradiance the old cohort exhibited higher mean values of A and WUE on area bases (P<0.05). Under high irradiance A and WUE on mass bases were higher in new cohort due toits lower SLM (42.10 gm~(-2)) in relation to old cohort (79.53 gm~(-2)). Because old cohort showed 3.7 times more dry mass per branch it was able to counterbalance its lower performance on mass bases. It was concluded that old cohort was an important source of carbon during two powerful sink processes in the beginning of the spring: new leaves cohort construction and flowering.