JXB Advance Access originally published online on November 26, 2008
Journal of Experimental Botany 2009 60(1):137-151; doi:10.1093/jxb/ern271
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Elevated atmospheric CO2 concentration ameliorates effects of NaCl salinity on photosynthesis and leaf structure of Aster tripolium L.
Institute of Plant Ecology, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
* To whom correspondence should be addressed: E-mail: Nicole.Geissler{at}bot2.bio.uni-giessen.de
This study investigated the interaction of NaCl-salinity and elevated atmospheric CO2 concentration on gas exchange, leaf pigment composition, and leaf ultrastructure of the potential cash crop halophyte Aster tripolium. The plants were irrigated with five different salinity levels (0, 25, 50, 75, 100% seawater salinity) under ambient and elevated (520 ppm) CO2. Under saline conditions (ambient CO2) stomatal and mesophyll resistance increased, leading to a significant decrease in photosynthesis and water use efficiency (WUE) and to an increase in oxidative stress. The latter was indicated by dilations of the thylakoid membranes and an increase in superoxide dismutase (SOD) activity. Oxidative stress could be counteracted by thicker epidermal cell walls of the leaves, a thicker cuticle, a reduced chlorophyll content, an increase in the chlorophyll a/b ratio and a transient decline of the photosynthetic efficiency. Elevated CO2 led to a significant increase in photosynthesis and WUE. The improved water and energy supply was used to increase the investment in mechanisms reducing water loss and oxidative stress (thicker cell walls and cuticles, a higher chlorophyll and carotenoid content, higher SOD activity), resulting in more intact thylakoids. As these mechanisms can improve survival under salinity, A. tripolium seems to be a promising cash crop halophyte which can help in desalinizing and reclaiming degraded land.
Key words: Aster tripolium, cash crop halophyte, elevated CO2, gas exchange, oxidative stress, photosynthesis, salt tolerance, ultrastructure, water use efficiency
Received 29 July 2008; Revised 8 October 2008 Accepted 9 October 2008