Tjoelker M G, Volin J C, Oleksyn J, Reich P B
Department of Forest Resources, University of Minnesota, 1530 N. Cleveland Avenue, St. Paul, Minnesota 55108-1027, USA.
Department of Forestry, University of Wisconsin-Madison, 1630 Linden Drive, Madison, Wisconsin 53706, USA.
New Phytol. 1993 Aug;124(4):627-636. doi: 10.1111/j.1469-8137.1993.tb03852.x.
Hybrid poplar (Populus tristis Fisch. ×P. balsamifera L., cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings were grown under contrasting light and ozone treatments to investigate the role of the light environment in their response to chronic ozone stress. In consecutive growth chamber experiments, cuttings of shade-intolerant poplar and 3-yr-old seedlings of shade-tolerant sugar maple were grown in pots for 6 and 10 wk, respectively, under shaded, low light irradiance (c. 2.5 mol m d PPFD or 7% of full sunlight) and six-fold greater irradiance (c. 16.6 mol m d PPFD or 45% of full sunlight) in combination with low (< 10 nl 1 ) and elevated levels of ozone (c. 99-115 nl 1 ). In unshaded poplar plants, ozone exposure reduced root dry mass by 33% at final harvest, while shaded plants had no such response. By comparison, sugar maple root dry mass was reduced by ozone in shaded plants by 10%, but was unaffected by ozone in unshaded plants. In poplar, leaf area: plant dry mass ratios were unaffected by ozone, whereas in sugar maple ozone-exposed plants had a 24% lower leaf area: plant dry mass ratio in the shaded treatment. In shade-grown sugar maple, ozone doubled dark respiration rates of leaves, but in unshaded seedlings ozone had no effect on respiration. In comparison, in poplar plants ozone exposure resulted in greater increases in dark respiration under unshaded than shaded conditions. In unshaded plants, ozone treatment resulted in lower in situ net photosynthesis in poplar, but not in sugar maple. Overall, shade-grown sugar maple appeared more sensitive to ozone stress than unshaded plants in terms of lower leaf area: plant dry mass ratio and root growth and higher leaf respiration. In poplar on the other hand, root growth, leaf respiration and photosynthesis were more affected by ozone in unshaded than in shaded plants. These findings suggest that shade-grown sugar maple and unshaded poplar may experience greater reductions in carbon gain and growth under elevated levels of ozone than plants under the opposite light conditions.
将杂种杨树（Populus tristis Fisch.×P. balsamifera L.，品种Tristis）和糖枫（Acer saccharum Marsh.）幼苗置于不同的光照和臭氧处理条件下，以研究光照环境在其对慢性臭氧胁迫响应中的作用。在连续的生长室实验中，不耐荫的杨树插条和耐荫的糖枫3年生幼苗分别在遮荫、低光照强度（约2.5 μmol m⁻² s⁻¹光合光子通量密度或全日照的7%）和高6倍的光照强度（约16.6 μmol m⁻² s⁻¹光合光子通量密度或全日照的45%）条件下，与低浓度（<10 nl l⁻¹）和高浓度（约99 - 115 nl l⁻¹）的臭氧组合，盆栽培养6周和10周。在未遮荫的杨树植株中，臭氧暴露使最终收获时的根干重减少了33%，而遮荫植株则没有这种反应。相比之下，糖枫遮荫植株的根干重因臭氧减少了10%，但未遮荫植株的根干重不受臭氧影响。在杨树中，叶面积与植株干重之比不受臭氧影响，而在糖枫中，经臭氧处理的植株在遮荫处理下叶面积与植株干重之比降低了24%。在遮荫生长的糖枫中，臭氧使叶片的暗呼吸速率增加了一倍，但在未遮荫的幼苗中，臭氧对呼吸没有影响。相比之下，在杨树植株中，臭氧暴露导致未遮荫条件下的暗呼吸增加幅度大于遮荫条件。在未遮荫植株中，臭氧处理导致杨树的原位净光合作用降低，但糖枫没有。总体而言，就较低的叶面积与植株干重比、根生长和较高的叶呼吸而言，遮荫生长的糖枫似乎比未遮荫植株对臭氧胁迫更敏感。另一方面，在杨树中，未遮荫植株的根生长、叶呼吸和光合作用受臭氧的影响比遮荫植株更大。这些发现表明，与处于相反光照条件下的植株相比，遮荫生长的糖枫和未遮荫的杨树在臭氧浓度升高时，碳获取和生长可能会有更大幅度的降低。
