植物生态学报 ›› 2004, Vol. 28 ›› Issue (6): 803-809.DOI: 10.17521/cjpe.2004.0105

• 论文 • 上一篇    下一篇

水分胁迫对羊草光合产物分配及其气体交换特征的影响

王云龙1 许振柱1 周广胜1,2*   

  1. (1 中国科学院植物研究所植被数量生态学重点实验室, 北京 100093)(2 中国气象局沈阳大气环境研究所,沈阳 110016)
  • 出版日期:2004-11-10 发布日期:2004-11-10
  • 通讯作者: 周广胜

CHANGES IN BIOMASS ALLOCATION AND GAS EXCHANGE CHARACTERISTICS OF LEYMUS CHINENSIS IN RESPONSE TO SOIL WATER STRESS

WANG Yun-Long1 XU Zhen-Zhu1 and ZHOU Guang-Sheng1,2*   

  1. (1 Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China)
  • Online:2004-11-10 Published:2004-11-10
  • Contact: ZHOU Guang-Sheng

摘要: 通过对典型草原优势植物种羊草(Leymus chinensis)的盆栽实验,模拟5个土壤水分梯度(分别为土壤持水量的75%~80%(对照)、60%~65%、50%~55%、35%~40%和25%~30% )对羊草叶片相对含水量、光合速率、光合产物分配和种群CO2交换速率的影响。结果表明:随着土壤水分胁迫的增加,羊草叶片相对含水量呈先增加而后下降的单峰型变化,且在50%~55%处理下达到最大;叶片光合速率随着水分胁迫的增加而减小,且75%~80%、60%~65%、50%~55%的水分处理与35%~40%、25%~30%的水分处理的叶片光合速度日动态规律不同。羊草总生物量及根、鞘、叶生物量均随着水分胁迫的增加呈下降趋势。干旱促进早期羊草根的分配和根冠比增加, 但到后期却使它们降低, 表明羊草在受到较长期的持续干旱后通过增加根部的比重来提高抗旱性的能力逐渐降低。羊草根茎的生物量和分配随着土壤水分含量降低均呈现出先增加而后下降的趋势,羊草根茎的生物量在50%~55%处理下达最大(1.28 g·株-1),而羊草根茎的分配在35%~40%处理下达最大(48.5%)。羊草种群CO2的净交换速率随着水分胁迫的增加而减小,其日交换量随着水分胁迫的增加而增加,且在60%~65%处理下达到最高,而后呈下降趋势,并在25%~30% 处理下为负值。研究结果表明,土壤持水量的40%可能是羊草对于水分变化响应的阈值。

Abstract: Global environmental change has already been and will continue to reallocate water and heat resources at a global scale, and, as a result, will affect the structure and function of terrestrial ecosystems. For temperate zone steppe ecosystems, aridification currently is the most significant environmental problem and this may be intensified due to global warming. The responses of the dominant species of these ecosystems to water stress will be important for understanding how terrestrial ecosystems will respond to global change and how species will adapt to the aridification under the backdrop of global warming as well as the impact on the global carbon budget. The response of leaf relative water content, leaf photosynthetic rate, biomass allocation and net population CO2 exchange rate of Leymus chinensis to soil water stress were studied using a pond cultivation experiment from May to July 2002. Five soil water treatment levels were used: 75%-80% (control), 60%-65%, 50%-55%, 35%-40% and 25%-30% of soil water holding capacity. The results are summarized below. 1) The relationship between leaf relative water content of L. chinensis and soil water stress could be expressed as a single peak curve with its maximum value appearing in the 50%-55% soil water treatment. 2) Leaf photosynthetic rates decreased with an increase in soil water stress, and the diurnal pattern of leaf photosynthetic rates in the soil water treatments of 75%-80%, 60%-65% and 50%-55% were different than that under the drier conditions of 35%-40% and 25%-30%. 3) The total biomass, root biomass, sheath biomass and leaf biomass of L. chinensis decreased with an increase in soil water stress. 4) Soil water stress promoted the allocation of carbon to roots and increased the root to shoot ratio of L. chinensis at the early growth stage but not at late growth stages. These results imply that increasing the root to shoot ratio is an adaptive strategy for tolerating drought conditions. The relationship between the biomass of roots and sheaths and the percent of carbon allocation to soil water stress could also be expressed as a single peak curve with the maximum value of root and sheath biomass (1.28 g·plant-1) appearing at the 50%-55% soil water treatment and the maximum allocation to root and sheaths (48.5%) at 35%-40% soil water content. 5) The net population CO2 exchange of L. chinensis decreased with an increase in soil water stress. The relationship between daily net population CO2 exchange of L. chinensis and soil water stress showed a single peak with the maximum value occurring at 60%-65%. Negative values of daily net population CO2 exchange of L. chinensis occurred at 25%-30% soil water content. Moreover, the results indicated that 40% soil water holding capacity might be the tolerance threshold for L. chinensis below which this species is not able to survive.