Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: in leaf development and thesis of Prunus serotina seedlings. | 490s Ann. Sci. For. 1989 46 suppl. 490s-492s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Ontogenetic changes in leaf development and photosynthesis of Prunus serotina seedlings . Horsley1 and . Gottschalk2 1 Northeastern Forest Experiment station USDA-Forest Service . Box 928 Warren PA 16365 and 2 . Box 4360 Morgantown wv26505 . Introduction Black cherry Prunus serotina Ehrh. is an important commercial hardwood species in the northeastern United States. The species is considered intolerant of overstory shade although young seedlings usually develop in the shade of an overstory or in partially cut stands. Leaf age and developmental stage are important determinants of many physiological processes in trees especially those with indeterminate growth. Net photosynthetic rate is a process that influences survival or death of young seedlings. Relationships between plant age leaf age and development and net photosynthesis have been investigated for only a few hardwood species. Materials and Methods Black cherry plants were raised from half-sib seed and grown in sand culture watered daily with a complete mineral nutrient solution. The plants were grown in growth chambers at 25 c during 16 h_d under approximately 335 Mmol PPFD from cool white fluorescent and incandescent lamps. Nights were 8 h at 18 c. Humidity was not regulated. We removed the cotyledons and first 4 leaves when plants reached the 8-10 leaf stage since these leaves often abscised. So the 5th true leaf produced was given the serial leaf number 1. We used the plastochron index of Erickson and Michelin 1957 to measure age of plants and of leaves on plants in units of developmental time. The index leaf length was set at 75 mm since smaller leaves were difficult to handle in our leaf chambers due to their short petioles. The plas-tochron index was calculated from measurements of the smallest leaf that had a leaf lamina at least 75 mm long and the next serial numbered leaf .
