Muraoka H, Tang Y, Koizumi H, Washitani I
Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305 Japan Fax: (+81)-298-53-6614; e-mail:
Global Environmental Division, National Institute for Environmental Studies, Tsukuba, Ibaraki, 305 Japan, , , , , , JP.
Oecologia. 1997 Sep;112(1):26-34. doi: 10.1007/s004420050279.
Photosynthetic characteristics, leaf longevity and biomass accumulation of a threatened herb species, Arisaema heterophyllum, were studied in the understory of a riparian forest and at a neighboring deforested open site for 3 years in order to understand the combined effects of light and water availability. Light availability was 2- to 4-fold higher at the deforested than at the forest site during the growing season of the species, and precipitation varied considerably over the 3 years. Despite the difference in water availability among the years (dry in 1994 and 1996, and wet in 1995), the species showed a strong acclimation to the different light environments. Light-saturated assimilation rate on a leaf area basis, leaf mass area ratio (LMA), and relative growth rate (RGR) were all higher at deforested site. While a positive correlation between individual RGR and microsite light availability was found in the wet year, no correlation was found in the dry years, and mean RGR was significantly lower in the dry year at both sites. Leaf longevity, photosynthetic capacity on a leaf mass basis, dark respiration rate, and leaf conductance, varied considerably from year to year, especially in the plants at the open site, probably depending on water availability. In the dry years plants at the deforested sites showed a lower photosynthetic rate and leaf conductance under unwatered than under watered conditions. These results suggest that the water availability in a given year may strongly affect light acclimation and annual RGR of the herb species in natural habitats, even under mesic climate conditions.
为了解光照和水分有效性的综合影响，对一种濒危草本植物——异叶天南星的光合特性、叶片寿命和生物量积累进行了为期3年的研究，研究地点分别为河岸森林林下以及相邻的森林砍伐后的开阔地。在该物种生长季节，开阔地的光照有效性比森林地点高2至4倍，且3年间降水量变化很大。尽管不同年份的水分有效性存在差异（1994年和1996年干旱，1995年湿润），但该物种对不同光照环境表现出很强的适应性。基于叶面积的光饱和同化率、叶质量面积比（LMA）和相对生长率（RGR）在开阔地均较高。在湿润年份，个体RGR与微生境光照有效性呈正相关，但在干旱年份未发现相关性，且两个地点在干旱年份的平均RGR均显著较低。叶片寿命、基于叶质量的光合能力、暗呼吸速率和叶片导度每年变化很大，尤其是开阔地的植株，这可能取决于水分有效性。在干旱年份，开阔地未浇水的植株比浇水的植株光合速率和叶片导度更低。这些结果表明，即使在温和气候条件下，特定年份的水分有效性可能会强烈影响自然栖息地中该草本植物的光适应和年RGR。
