ISSN 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 3, pp. 309–313. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © E.L. Kaipiainen, P. Pelkonen, 2007, published in Fiziologiya Rastenii, 2007, Vol. 54, No. 3, pp. 350–355.
The ongoing improvement of instruments for gas
exchange measurements in plants has led to creation of
leaf chambers where climatic conditions distinct from
the ambient environment can be set and maintained
constantly. A Li-6400 gas analyzer (Li-Nor, United
States) is one of such devices. The artiﬁcial light source
placed in its leaf chamber can provide ﬂuence rates in a
very wide range. The built-in thermoelements allow the
adjustment of temperature inside the chamber and its
changes with respect to external environment. The
chemical desiccation system allows wide-range varia-
tions of relative air humidity (RH). Thus, an attached
intact leaf of a plant can be exposed to conditions,
which are either similar or quite different from the con-
ditions of ambient environment. The system maintains
constant conditions in the chamber as long as required
for gas exchange measurements. These facilities allow
researchers to study effects of natural wide-range vari-
ations of environmental conditions on gas exchange of
an individual leaf throughout one day.
The objective of this work was to develop experi-
mental conditions that would allow investigators to
measure photosynthesis and transpiration in an individ-
ual attached leaf, to study leaf responses to environ-
mental changes, to obtain photosynthesis and transpira-
tion indices most similar to their natural values, and to
use these indices for evaluation of the whole plant con-
dition at forest plantations for fast recovery of willow
MATERIALS AND METHODS
Conditions of experiments.
Some experiments were
performed in a greenhouse of University of Joensuu
(Finland) with rooted cuttings of willow (1999 and
2000, March–May); the other part of the study was
made under ﬁeld conditions, in the open plots with nat-
urally growing plants (1999 and 2002, June–August).
The experimental plot of 0.5 ha was located in the
eastern part of Finland near the town of Joensuu (lat.
E). Plants were planted in 1994.
In 1996 the shoots were pruned to increase their num-
ber. In 1998 the experimental plot was equipped with
an irrigational system that supplied water from the
nearest sewage disposal station. The amount of applied
water was equivalent to 10 mm/day. The residual con-
tent of nitrogen and other mineral salts in irrigation
water completely satisﬁed plant requirements for min-
eral supply and was not the limiting factor for plant
growth. The qualitative and quantitative laboratory
Requirements for Obtaining Maximum Indices of Photosynthesis
and Transpiration in Attached Leaves of Willow Plants Grown
in Short-Rotation Forest
E. L. Kaipiainen and P. Pelkonen
Faculty of Forestry, University of Joensuu, P.O. Box 111, Joensuu, FIN-80101 Finland;
Received May 10, 2006
—The results of multiyear studies of gas exchange in intact attached leaves of several willow species
) were analyzed. Measurements were performed with a portable Li-6400 infrared gas analyzer both
on plants in their natural environment and on rooted cuttings grown in a greenhouse. Individual attached leaves
were placed into the leaf chamber where climatic conditions were either similar to or different from those out-
side the chamber. The maximal rates of net photosynthesis (
) and transpiration (
) were only observed with
the provision that the environmental variables inside and outside the chamber were identical. On rainy or cloudy
values observed under optimum conditions inside the leaf chamber were lower than their
potential maxima by 12–18% and 35–45%, respectively. Deviation of temperature in the chamber by
from the external level and ﬂuctuations of ambient temperature affected
rates of tested leaves. Vari-
ations in relative air humidity in the chamber directly inﬂuenced
but had no effect on
of attached leaves.
It was shown that the maximum rates of gas exchange in the attached willow leaf could be only attained by
providing optimum conditions for the whole plant.
Key words: Salix sp. - net photosynthesis - transpiration - light - temperature - relative air humidity
PAR—photosynthetically active radiation; RH—relative humidity.