JXB Advance Access originally published online on July 12, 2006
Journal of Experimental Botany 2006 57(11):2687-2695; doi:10.1093/jxb/erl040
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RESEARCH PAPER |
Relationships between leaf conductance to CO2 diffusion and photosynthesis in micropropagated grapevine plants, before and after ex vitro acclimatization
1Consiglio per la Ricerca e Sperimentazione in Agricoltura–Istituto Sperimentale per le Colture Industriali, via di Corticella 133, I-40128 Bologna, Italy
2Potsdam Institute for Climate Impact Research (PIK), PO Box 601203, D-14412 Potsdam, Germany
3Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079, Bât. 362, UFR scientifique d'Orsay, Université de Paris-XI, F-95401 Orsay Cedex, France
*To whom correspondence should be addressed. E-mail: gianni.fila{at}entecra.it
In vitro-cultured plants typically show a low photosynthetic activity, which is considered detrimental to subsequent ex vitro acclimatization. Studies conducted so far have approached this problem by analysing the biochemical and photochemical aspects of photosynthesis, while very little attention has been paid to the role of leaf conductance to CO2 diffusion, which often represents an important constraint to CO2 assimilation in naturally grown plants. Mesophyll conductance, in particular, has never been determined in in vitro plants, and no information exists as to whether it represents a limitation to carbon assimilation during in vitro growth and subsequent ex vitro acclimatization. In this study, by means of simultaneous gas exchange and chlorophyll fluorescence measurements, the stomatal and mesophyll conductance to CO2 diffusion were assessed in in vitro-cultured plants of the grapevine rootstock ‘41B’ (Vitis vinifera ‘Chasselas’xVitis berlandieri), prior to and after ex vitro acclimatization. Their impact on electron transport rate partitioning and on limitation of potential net assimilation rate was analysed. In vitro plants had a high stomatal conductance, 155 versus 50 mmol m–2 s–1 in acclimatized plants, which ensured a higher CO2 concentration in the chloroplasts, and a 7% higher electron flow to the carbon reduction pathway. The high stomatal conductance was counterbalanced by a low mesophyll conductance, 43 versus 285 mmol m–2 s–1, which accounted for a 14.5% estimated relative limitation to photosynthesis against 2.1% estimated in acclimatized plants. It was concluded that mesophyll conductance represents an important limitation for in vitro plant photosynthesis, and that in acclimatization studies the correct comparison of photosynthetic activity between in vitro and acclimatized plants must take into account the contribution of both stomatal and mesophyll conductance.
Key words: Acclimatization, chlorophyll fluorescence, cuticular conductance, gas exchange, grapevine, in vitro culture, mesophyll conductance, photosynthesis, stomatal conductance