JXB Advance Access originally published online on October 24, 2005
Journal of Experimental Botany 2005 56(422):3093-3101; doi:10.1093/jxb/eri306
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RESEARCH PAPER |
Water stress-induced modifications of leaf hydraulic architecture in sunflower: co-ordination with gas exchange
Dipartimento di Biologia, Università di Trieste, Via L. Giorgieri 10, 34127 Trieste, Italia
* To whom correspondence should be addressed. Fax: +39 040 568855. E-mail: nardini{at}univ.trieste.it
The hydraulic architecture, water relationships, and gas exchange of leaves of sunflower plants, grown under different levels of water stress, were measured. Plants were either irrigated with tap water (controls) or with PEG600 solutions with osmotic potential of 0.4 and 0.8 MPa (PEG04 and PEG08 plants, respectively). Mature leaves were measured for hydraulic resistance (Rleaf) before and after making several cuts across minor veins, thus getting the hydraulic resistance of the venation system (Rvenation). Rleaf was nearly the same in controls and PEG04 plants but it was reduced by about 30% in PEG08 plants. On the contrary, Rvenation was lowest in controls and increased in PEG04 and PEG08 plants as a likely result of reduction in the diameter of the veins' conduits. As a consequence, the contribution of Rvenation to the overall Rleaf markedly increased from controls to PEG08 plants. Leaf conductance to water vapour (gL) was highest in controls and significantly lower in PEG04 and PEG08 plants. Moreover, gL was correlated to Rvenation and to leaf water potential (
leaf) with highly significant linear relationships. It is concluded that water stress has an important effect on the hydraulic construction of leaves. This, in turn, might prove to be a crucial factor in plantwater relationships and gas exchange under water stress conditions.
Key words: Gas exchange, leaf hydraulic architecture, sunflower, water relations, water stress
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