[Effects of canopy position and leaf age on photosynthesis and transpiration of Pinus koraiensis].
The photosynthesis and transpiration of Pinus koraiensis needles at different canopy positions and of different leaf ages were measured in the field with a Li-6400 portable CO2/H2O infrared gas analyzer. The results showed that canopy position and leaf age had significant effects on the maximum net photosynthetic rate (Pmax), light saturation point (LSP), light compensation point (LCP), maximum apparent quantum efficiency (alpha), transpiration rate (T(r)), and specific leaf area (SLA), but no effects on water use efficiency (WUE). The Pmax decreased with the decrease of canopy position and the increase of leaf age, ranging in 6.55-9.05 micromol.m(-2).s(-1) on average. There were great variations in LSP and LCP among different canopy positions and leaf ages. The needles at middle canopy position had the greatest capacity of utilizing both weak and strong radiation. The T(r) decreased with canopy position decreasing, and varied from 1.37 to 1.59 mmol.m(-2).s(-1) across different leaf ages. There was a significant positive correlation between T(r) and photosynthetically active radiation (R2 = 0.967), and between WUE and net photosynthetic rate (R2 = 0.860). The SLA decreased with canopy position and leaf age increasing, ranging in 6.61-8.41 m2.kg(-1) and 6.65-8.38 m2.kg(-1), respectively.
Huo
Hong
H
College of Forestry, Northeast Forestry University, Harbin 150040, China. huohong-00@163.com
Wang
Chuan-kuan
CK
D010788:Photosynthesis / Q000502:physiology*; D028223:Pinus / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology*; D013997:Time Factors