Abstract: Photosynthetic rate in leaves of Rhodimyrtus tomentosa decreased by 43.7 as leaf water potentential declined from -1.25 MPa to -2.0 MPa at lower light intensity. The relation-ship between photosynthetic rate (PN, umol.m-2s-l) and light intensity (PAR, m mol • m-2s-l) was PN=2.13+17.96 PAR, r2=0.89 in leaves of Rhodomyrtus tomentosa with leaf water poten-tial -1.25 MPa. While the correspondencing relationship was PN= 0.37+15.49 PAR, T2=0.9 as leaf water potential decreased to -2.0 MPa. Ardisia quinquegona had lower photosynthetic rate and it decreased by 69.6% as leaf water potential declined from -1.06 MPa to -1.9 MPa.

Key words: Rhodomyrtus tomentosa

摘要： 叶片水势(ψ)为-1.2MPa的桃金娘叶片光合速率(PN,μmo1.m-2s-1)与光强(PAR,mmo1.m-2s-1)关系曲线的最初直线部分PN=2.13+17.96PAR,r2=0.89。当ψ降至-2.0MPa,相当关系为PN=0.37+15.49 PAR,r2=0.9。最大PN降低43.7%,罗伞叶片ψ从-1.06MPa降至-1.9MPa,最大PN降低69.6%,较桃金娘大。桃金娘叶片有较高气孔传导率(g,mmo1.m-2s-1)。ψ降低引起桃金娘叶片g的降低较罗伞少。叶片ψ降低使PN与细胞北京时间CO2浓度(Ci,μ1.1-1)关系曲线的直线部分斜率变小。低g和当Ci高于外界CO2浓度时表现低羧化能力可能是罗伞光合速率低的原因。自然林被破坏后，土壤和空气水分善变化可能在林分更替中起作用。

关键词: 桃金娘, 罗伞, 光合速率, 水分胁迫, 植物演替