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Seasonal Changes in Plant Hydraulics and Drought Tolerance Strategies of Three Dominant Evergreen Tree Species in a Seasonally Tropical Limestone Rainforest of Xishuangbanna

Author: WangAiYing
Tutor: CaoKunFang
School: Xishuangbanna Tropical Botanical Garden
Course: Ecology
Keywords: Tropical monsoon forest Limestone Hydraulic conductivity Water Relations Season drought
CLC: Q945
Type: Master's thesis
Year: 2008
Downloads: 81
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Abstract

Southwest China is the world's largest contiguous distribution area of ??the karst area, limestone karst geology major type, limestone mountain consists mainly of carbonate rocks, strong chemical leaching, soil is thin and scarce soil. Limestone occupies a large area in Yunnan, in Xishuangbanna region accounted for about 19%. And one year in half a year of drought, the limestone plant suffered more severe drought stress. How to keep the plants under drought stress conditions is particularly important for effective moisture transport. The thesis evergreen species of Xishuangbanna limestone tropical monsoon forest three dominant oil Park (Celtis wightii), pointed leaves closed flowers (Cleistanthus sumatranus) and round leaves halberd (Lasiococca comberi var. Pseudoverticillata) as experimental materials to study their leaves anatomy The structure and xylem anatomical structures, as well as seasonal drought on tree branches moisture conductivity, xylem sap flow flux density, branches vulnerability curve, the maximum net photosynthetic rate (Anet), osmoregulation leaf physiological characteristics. Attempts to explore the physiological and ecological adaptability characteristics of the dominant tree species in this habitat this habitat seasonal drought. The results show that: (1) during the dry season the three species the blade early morning water potential (Ψpd) and noon water potential (Ψmd) have significantly lower that the habitat of the plant suffered a greater degree of soil drought stress during the dry season; (2) dry season turgor loss point water potential (π0) and saturation osmotic potential (π100) is significantly reduced, the average reduction of 69.2% and 69.8%, respectively, compared to its reduction and other arid habitat plants. Strong osmotic adjustment ability of the three species, and can better adapt to the Lime Hill season drought. (3) compared to the rainy season, the dry season oil Pu edge material than the conduction rate (Ks) without significantly with the sex change, while the closed flowers and round leaves halberd of Ks in the dry season significantly with decreases; leaves ratio conduction rate (Kl) the three species had no significant forward The sexual season changes. This result indicates that the oil Park catheter withstand cavitation ability closed flowers and vanes killer may have occurred in the dry season catheter cavitation leaving KS reduce shedding some leaves, but still in the dry season in order to adjust the hydraulic structure to maintain a higher per unit leaf area's water supply. (4) during the dry season of three species Anet had significant decreases. Rainy season three species Ks, Kl and Anet into a significant positive correlation; during the dry season three species π0 and Ψpd was significantly positive related (R2 = 0.63, P = 0.002), the rainy season Anet and Ψpd was significantly positive related (R2 = 0.92, P lt; 0.001). These results suggest that, have a direct impact on plant xylem hydraulic conductivity and leaf water status of the plant leaf photosynthesis. Although the plant is reduced during the dry season water potential, xylem cavitation occurs, maintain moisture balance and basic the photosynthetic physiological function of the three species by raising the osmotic adjustment to reduce the leaf area. (5) three limestone evergreen sap flow start time in the day during the rainy season than the dry season as early as the end of time late in the rainy season, the maximum flow flux density of the rainy season than the dry season large. Limestone in the dry season the soil water deficit limits plant transpiration water consumption. Different maximum flow flux density variation between the seasons between the three species, indicating possible tree roots deep into the soil depth. (6) of three lime Hill Evergreen dominant tree species wood density is relatively large by comparison with the the two symbiotic advantages of deciduous trees, we found three evergreen tree species in the loss of 50% water conduction capacity of the limestone in leaf water potential (P50) significantly lower than the other two symbiotic deciduous trees that evergreen species to resist cavitation was significantly higher than the symbiotic deciduous trees, the Lime Hill the Three Dominant Evergreen species Drought sexuality than symbiotic deciduous trees; through other xerophytic the habitat plants compared, we found that its P50 is much lower than the typical species S?o Bento Mine in Brazil Wang satisfied, xylem conduit resistance to cavitation ability. (7) the three dominant evergreen species leaves anatomic features, typical drought-resistant plants such as leaves, thick, double palisade tissue. These results come limestone three evergreen plants can adapt to the arid environment by adjusting the water relations, transpiration and osmotic adjustment during the dry season, has strong adapt to the arid environment and the ability to resist cavitation.

Seasonal Changes in Plant Hydraulics and Drought Tolerance Strategies of Three Dominant Evergreen Tree Species in a Seasonally Tropical Limestone Rainforest of Xishuangbanna

Abstract

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