© 2007 Heron Publishing—Victoria, Canada
Induction of photosynthesis and importance of limitations during the induction phase in sun and shade leaves of five ecologically
contrasting tree species from the temperate zone
Otmar Urban (1, 2), Martina Košvancová (1), Michal V. Marek (1) and Hartmut K. Lichtenthaler (3)
1. Laboratory of Plant Ecological Physiology, Institute of Systems Biology and Ecology AS CR, Porící 3b, CZ-60300 Brno, Czech
Republic / 2. Corresponding author (otmar@brno.cas.cz) / 3. Botanical Institute (Molecular Biology and Biochemistry of Plants), University of Karlsruhe, Kaiserstrasse 12, D-76133 Karlsruhe,
Germany / Received June 26, 2006; accepted November 8, 2006; published online May 1, 2007
Summary
We examined the principal differences in photosynthetic characteristics between sun and shade foliage and determined the relative
importance of biochemical and stomatal limitations during photosynthetic induction. Temperate-zone broadleaf and conifer tree
species, ranging widely in shade tolerance, were investigated from one locality in the Czech Republic. The study species included
strongly shade-tolerant Abies alba Mill. and Tilia cordata Mill., less shade-tolerant Fagus sylvatica L. and Acer pseudoplatanus L. and sun-demanding Picea abies (L.) Karst.
In the fully activated photosynthetic state, sun foliage of all species had significantly higher maximum CO2 assimilation rates, maximum stomatal conductance and maximum rates of carboxylation than shade foliage. Compared with shade
leaves, sun leaves had significantly higher nocturnal stomatal conductances. In all species, shade foliage tended to have
higher induction states 60 s after leaf illumination than sun foliage. Sun and shade foliage did not differ in the rate of
disappearance of the transient biochemical limitation during the induction phase. Longer time periods were required to reach
90% photosynthetic induction and 90% stomatal induction in sun foliage than in shade foliage of the less shade-tolerant F. sylvatica and A. pseudoplatanus and in sun-demanding P. abies; however, in sun foliage of the strongly shade-tolerant species T. cordata and A. alba, the time needed for photosynthetic induction was similar to, or less than, that for shade foliage. Shade but not sun needles
of P. abies and A. alba had significantly slower induction kinetics than the broadleaf tree species. Among species, the sun-demanding P. abies exhibited the shortest stomatal induction times in both sun and shade leaves. Independently of shade tolerance ranking, the
transient stomatal and total limitations that characterize photosynthetic induction were relieved significantly earlier in
shade foliage than in sun foliage. Sun foliage generally exhibited a hyperbolic photosynthetic induction response, whereas
a sigmoidal induction response was more frequent in shade foliage. The different relative proportions of transient biochemical
and stomatal limitations during photosynthetic induction in sun and shade foliage indicate an essential role of stomata in
photosynthetic limitation during induction, mainly in shade foliage, with a consequent influence on the shape of the photosynthetic
induction curve.
Keywords:
dynamic light environment, gas exchange, photosynthetic limitations, sun/shade acclimation.
