Volin J C, Tjoelker M G, Oleksyn J, Reich P B
Department of Forestry, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI 53706, USA.
Department of Forest Resources, University of Minnesota, 1530 N. Cleveland Avenue, St. Paul, MN 55108-1027, USA.
New Phytol. 1993 Aug;124(4):637-646. doi: 10.1111/j.1469-8137.1993.tb03853.x.
Diagnostic gas exchange measurements and foliar chemical assays were conducted on hybrid poplar (Populus tristis Fisch. ×P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings grown under contrasting light and ozone treatments. Seedlings were grown in low irradiance (c. 2.5 mol m d ) and six-fold greater irradiance (c. 16.6 mol m d ) in combination with low (< 10 nl I ) and elevated (99-115 nl 1 ) ozone. Analysis of light response curves showed ozone-induced reductions in photosynthetic capacity and quantum yield for unshaded poplar and shaded sugar maple, but not the contrasting light treatments. Photosynthesis at saturating CO concentrations was decreased in the elevated ozone treatment in both the unshaded and shaded poplar and in shaded sugar maple. Poplar had significant reductions in chlorophyll concentration due to ozone exposure in both unshaded and shaded treatments. Older leaves of unshaded poplar plants had significantly greater reductions in chlorophyll levels due to ozone than older leaves of shaded plants. In maple, only shade-grown leaves had significant decreases in chlorophyll concentration due to ozone exposure. The diagnostic gas exchange measurements in conjunction with chlorophyll measurements indicate that in hybrid poplar, unshaded leaves may be more sensitive to ozone than shade leaves, while in sugar maple, shade leaves are more sensitive to ozone. For hybrid poplar a decrease in photosynthetic capacity, quantum yield and chlorophyll concentration in the unshaded, moderately high light environment due to elevated ozone is consistent with prior studies. The results indicating that sugar maple seedlings may be more detrimentally affected by elevated ozone in the lower light environment may have serious implications for this and other shade-adapted species with respect to their performance in an understorey environment.
对在不同光照和臭氧处理条件下生长的杂交杨树（Populus tristis Fisch. ×P. balsamifera L. cv. Tristis）和糖枫（Acer saccharum Marsh.）幼苗进行了诊断性气体交换测量和叶片化学分析。幼苗在低光照（约2.5 mol m² d⁻²）和高六倍的光照（约16.6 mol m² d⁻²）条件下生长，同时分别处于低臭氧（< 10 nl l⁻¹）和高臭氧（99 - 115 nl l⁻¹）环境中。光响应曲线分析表明，臭氧导致未遮荫的杨树和遮荫的糖枫的光合能力和量子产率降低，但不同光照处理之间没有差异。在高臭氧处理下，未遮荫和遮荫的杨树以及遮荫的糖枫在饱和CO₂浓度下的光合作用均降低。由于臭氧暴露，未遮荫和遮荫处理的杨树叶绿素浓度均显著降低。未遮荫杨树植株的老叶因臭氧导致的叶绿素水平降低幅度显著大于遮荫植株的老叶。在糖枫中，只有遮荫生长的叶片因臭氧暴露导致叶绿素浓度显著降低。诊断性气体交换测量结合叶绿素测量表明，在杂交杨树中，未遮荫的叶片可能比遮荫叶片对臭氧更敏感，而在糖枫中，遮荫叶片对臭氧更敏感。对于杂交杨树，在未遮荫、适度高光环境下，由于臭氧浓度升高导致光合能力、量子产率和叶绿素浓度降低，这与先前的研究一致。结果表明，在低光照环境下，糖枫幼苗可能受到臭氧浓度升高的更不利影响，这对于该物种以及其他适应遮荫的物种在林下环境中的表现可能具有严重影响。
