Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Gas exchange and water relations of 3 sizes of containerized Picea mariana seedlings subjected to atmospheric and edaphic water stress under controlled conditions. | Ann Sci For 1995 52 1-9 Elsevier INRA 1 Original article Gas exchange and water relations of 3 sizes of containerized Picea mariana seedlings subjected to atmospheric and edaphic water stress under controlled conditions JD Stewart1 PY Bernier2 Centre de Recherche en Biologie Forestiere Faculte de Foresterie et de Géomatique Université Laval Sainte-Foy Quebec G1K 7P4 2 Natural Resources Canada Canadian Forest Service-Quebec Region PO Box 3800 Sainte-Foy Quebec G1V4C7 Canada Received 12 April 1994 accepted 17 August 1994 Summary Containerized black spruce Picea mariana Mill BSP seedlings of 3 sizes heights of 18 35 and 45 cm were placed in growth chambers and subjected to conditions of low evaporative 20 C 60 RH or high evaporative 30 C 40 RH demand with 3 levels of soil water availability in each environment. The large seedlings had the highest rate of net photosynthesis in the cooler environment but showed the greatest reduction in net photosynthetic rate in the warmer and drier environment under conditions of limited water supply. The small seedlings were least affected by the warmer and drier environment in which they maintained photosynthetic rates higher than those of the larger seedlings. The decrease in net photosynthesis experienced by the large seedlings in the warmer and drier environment under conditions of limited water availability was associated with a large decrease in stomatai conductance. However the maintenance of a high level of intercellular co2 concentration suggests that most of the limitations to net photosynthesis were of non-stomatal origin. Water content of the root plug was also reduced by increased seedling size but the differences were least evident under conditions that produced the largest differences in net photosynthetic rates. These results obtained under controlled conditions suggest that after outplanting large seedlings would experience greater reduction in growth than smaller ones only under conditions of high evaporative demand
