Journal Article

Gas exchange and hydraulics in seedlings of <i>Hevea brasiliensis</i> during water stress and recovery

Jun-Wen Chen, Qiang Zhang, Xiao-Shuang Li and Kun-Fang Cao

in Tree Physiology

Volume 30, issue 7, pages 876-885
Published in print July 2010 | ISSN: 0829-318X
Published online June 2010 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpq043
Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery

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The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (gs-max) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, gs-max was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of gs-max and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors.

Keywords: drought; embolism; hydraulic conductivity; photosynthesis; recovery

Journal Article.  7312 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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