Chinese Journal of Applied Ecology
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ZHAO Ping, SUN Gu-chou, NI Guang-yan, ZENG Xiao-ping
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Abstract: In this study, measurements were made on the leaf water potential (Ψl), stomatal conductance (gs), transpiration rate, leaf area index, and sapwood area of mature Acacia mangium, aimed to understand the relationships of the leaf hydraulic conductance (Kl) with the leaf water use and photosynthetic characteristics of the A. mangium in wet season (May) and dry season (November). The ratio of sapwood area to leaf area (Asp/Acl) of the larger trees with an average height of 20 m and a diameter at breast height (DBH) of 0.26 m was 8.5% higher than that of the smaller trees with an average height of 14.5 m and a DBH of 0.19 m, suggesting that the larger trees had a higher water flux in their leaf xylem, which facilitated the water use of canopy leaf. The analysis on the vulnerability curve of the xylem showed that when the Kl decreased by 50%, the Ψl in wet season and dry season was -1.41 and -1.55 MPa, respectively, and the vulnerability of the xylem cavitation was higher in dry season than in wet season. The Kl peak value in wet season and dry season was 5.5 and 4.5 mmol·m-2·s-1·MPa-1, and the maximum transpiration rate (Tr max) was 3.6 and 1.8 mmol·m-2·s-1, respectively. Both the Kl and Tr max were obviously higher in wet season than in dry season. Within a day, the Kl and Tr fluctuated many times, reflecting the reciprocated cycle of the xylem cavitation and refilling. The leaf stomatal closure occurred when the Kl declined over 50% or the Ψl reached -1.6 MPa. The gs would be maintained at a high level till the Kl declined over 50%. The correlation between the hydraulic conductance and photosynthetic rate was more significant in dry season than in wet season. The loss of leaf hydraulic conductance induced by seasonal change could be the causes of the decrease of Tr and CO2 gas exchange.
ZHAO Ping, SUN Gu-chou, NI Guang-yan, ZENG Xiao-ping. Seasonal differences in the leaf hydraulic conductance of mature Acacia mangium in response to its leaf water use and photosynthesis.[J]. Chinese Journal of Applied Ecology.
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URL: http://www.cjae.net/EN/abstract/abstract10527.shtml
http://www.cjae.net/EN/Y2013/V24/I1/49