Institutional Repository of Xishuangbanna Tropical Botanical Garden
| 西双版纳石灰山三种常绿优势树种水力特征的季节变化及其对干旱胁迫的适应机制 | |
| 王爱英 | |
| Thesis Advisor | 曹坤芳 |
| 2008-06 | |
| Degree Grantor | 中国科学院研究生院 |
| Place of Conferral | 北京 |
| Degree Discipline | 生态学 |
| Keyword | 热带季雨林 石灰岩 水分传导 水分关系 季节干旱 |
| Abstract | 我国西南地区是世界上连片分布面积最大的岩溶地区，石灰岩是岩溶地质的主要类型，石灰岩山体主要由碳酸盐岩石组成，化学淋溶强烈，土层很薄，土壤稀少。石灰岩在云南占有较大的面积，在西双版纳地区约占19%。而且该地区一年有半年的干旱，石灰山植物遭受的干旱胁迫更加严峻。在干旱胁迫条件下植物如何保持有效的水分运输显得尤为重要。本论文以西双版纳石灰岩热带季雨林三种优势常绿树种油朴（Celtis wightii）、尖叶闭花木（Cleistanthus sumatranus）和轮叶戟（Lasiococca comberi var. pseudoverticillata）为实验材料，研究了它们的叶片解剖结构和木质部解剖结构，以及季节性干旱对树木枝条水分传导、木质部液流通量密度、枝条脆弱性曲线、最大净光合速率（Anet）、和渗透调节相关的叶片的生理特征等的影响。试图探讨此生境下的优势树种对该生境季节性的干旱的生理生态适应性特征。结果表明：（1） 旱季三树种叶片凌晨水势（Ψpd）和正午水势（Ψmd）都有显著降低，表明该生境的植物在旱季遭受较大程度的土壤干旱胁迫；（2） 旱季膨压丧失点的水势（π0）和饱和渗透势（π100）均显著降低，其平均降低幅度分别为69.2%和69.8%，与其他干旱生境植物相比其降低幅度较大。表明三树种有较强的渗透调节能力，能较好地适应石灰山的季节干旱。（3） 较雨季，旱季油朴的边材比导率（Ks）无显著性变化，而闭花木和轮叶戟的Ks在旱季显著减小；叶比导率（Kl）三树种均无显著性的季节变化。该结果表明油朴导管耐受气穴化的能力较强，而闭花木和轮叶戟在旱季可能发生了导管气穴化而使Ks降低，但仍能在旱季通过脱落部分叶片以调整其水力结构来保持较高的单位叶面积的水分供应。（4） 旱季三树种Anet都有显著性减小。雨季三树种Ks、Kl与Anet均成显著正相关；旱季三树种π0和Ψpd呈显著正相关(R2=0.63, P=0.002)，雨季Anet与Ψpd呈显著正相关(R2=0.92, P<0.001)。由以上结果表明，植物木质部的水分传导和叶片的水分状态对植物叶片光合作用有直接的影响。尽管植物在旱季水势降低，木质部发生气穴化，三树种通过提高渗透调节，减少叶面积维持水分平衡和基本的光合生理功能。（5） 三种石灰山常绿树种木质部液流在一天中开始的时间在雨季比旱季早，结束的时间在雨季较晚，最大液流通量密度雨季比旱季的大。说明石灰山旱季的土壤水分亏缺限制了植物的蒸腾用水量。三个树种之间最大液流通量密度在季节间的变化幅度不同，说明可能三树种的根系深入土壤的深度不同。（6） 三种石灰山常绿优势树种的木材密度比较大，通过与两个共生优势落叶树种的比较，我们发现石灰山三种常绿树种丧失50% 水分传导能力时的叶片水势（P50）明显低于另外两个共生的落叶树种，表明常绿树种抵抗气穴化的能力明显高于共生落叶树种，石灰山三种常绿优势树种抗旱性能力较共生落叶树种强；通过与其他旱生生境植物相比较，我们发现其P50比典型的巴西萨王纳树种还要低很多，其木质部导管抵抗空穴化的能力较强。（7） 三种优势常绿树种具有典型抗旱植物的叶片解剖结构特征，如叶片较厚，双层栅栏组织等。由以上结果得出石灰山三种常绿植物能够在旱季通过调整水分关系、蒸腾量以及渗透调节等适应干旱环境，具有较强的适应干旱环境和抵抗气穴化的能力。 |
| Other Abstract | Southernwest China is characterized by extensive limestone landscape, which is the largest limestone area in the world. Due to the strong weathering and eluviation of carbonate rocks in this region, the soil developed from the limestone is very thin and infertile. In Xishuangbanna, the limestone area accounts for 19% of the total area. The limestone substrates quickly leak water through the crackles and holes among the rocks. Moreover, there is a distinct dry season that lasts for half of a year in this area so that the trees in limestone hills suffer severe drought. Therefore, the maintenance of effective water transport in the dry season is important for the growth and survival of the trees on the limestone hills. We chose three dominant evergreen tree species (Celtis wightii, Cleistanthus sumatranus and Lasiococca comberi var. pseudoverticillata) in tropical seasonal rain forest of a limestone habitat in Xishuangbanna, Yunnan province. To investigate the adaptive mechanisms of three dominant evergreen tree species to limestone seasonal dry habitat, we investigated ecophysiological traits including the changes of stem hydraulic conductivity, sapflow, xylem vulnerability to drought induced cavitation, the maximum net photosynthetic rate during dry and wet seasons, and leaf and stem xylem anatomical characteristics to try to identify the major adaptive traits contributing to the drought tolerance. The results indicate that: (1) During the dry season, predawn leaf water potential (Ψpd) and midday leaf water potential (Ψmd) were significantly lower compared to those of the wet season in all the three species suggesting a significantly lower soil water potential during the dry season. (2) Leaf water potential at turgor loss point (π0) and saturated leaf water potential (π100) all decreased in all the three tree species during the dry season. Compared to values of the wet season, π0 and π100 decreased by 69.2% and 69.8%, respectively, which were much larger than the decrease found in species of similar environment during the dry season. These findings suggested that the species in the limestone mountain have relatively strong osmotic adjustment ability to seasonal drought. (3) The specific hydraulic conductivity (Ks) of Cleistanthus sumatranus and Lasiococca comberi var. pseudoverticillata both decreased in dry season, but there were no such a significant seasonal change in Celtis wightii; however, there is no significant changes in leaf-specific conductivity (Kl) in all of the three species. These results may indicate that Celtis wightii xylem is resistant to drought induced loss of xylem misfunction, while the Ks of Cleistanthus sumatranus and Lasiococca comberi var. pseudoverticillata may decreased due to cavitation. But both the later two species can keep high Kl by the reduction of total leaf area during the dry season. (4) In dry season, the maximum net photosynthetic rate (Anet) decreased significantly in all the three species. Ks and Kl are positively correlated to Anet in all three species during the wet season. There was a strong correlation between Ψpd and π0 in the dry season and Ψpd was highly correlated to Anet in the wet season. These suggested that the xylem conductivity and leaf water status have important effects on photosynthesis. (5) The sap flow measurements indicated that in all three species, the amount of water used by trees during the dry season was significantly decreased. However, the magnitude of decrease was different among the three species, which may indicate the differences in their rooting depth. (6) The leaf water potential at 50% loss of xylem conductivity (P50) of three evergreen tree species was significantly lower than the co-occurring deciduous tree species, which may suggest evergreen tree species in limestone area have a stronger tolerance to drought induced xylem cavitation than deciduous tree species; the average P50 of the 3 limestone species was more negative compared to that of the species growing in other dry habitat indicating the strong resistance to drought induced xylem cavitation. (7) The three evergreen tree species shows typical leaf characteristics of drought tolerant species, such as thick leaf and double mesophyll layers of the leaves. All the results indicate that the three evergreen tree species in limestone area in Xishuangbanna can adapt to drought environment through adjust water relations, transpiration and osmotic regulation. They have a strong drought tolerance and a strong ability to resist cavitation. |
| Document Type | 学位论文 |
| Identifier | https://ir.xtbg.ac.cn/handle/353005/494 |
| Collection | 西双版纳热带植物园毕业生学位论文 |
| Recommended Citation GB/T 7714 | 王爱英. 西双版纳石灰山三种常绿优势树种水力特征的季节变化及其对干旱胁迫的适应机制[D]. 北京. 中国科学院研究生院,2008. |
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| 西双版纳石灰山三种常绿优势树种水力特征的（588KB） | 开放获取 | CC BY-NC-SA | Application Full Text | |||
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