D. Janous et al., CHAMBER EFFECTS AND RESPONSES OF TREES IN THE EXPERIMENT USING OPEN-TOP CHAMBERS, Journal of plant physiology, 148(3-4), 1996, pp. 332-338
Chamber effects are unintentional concomitants of experiments using op
en-top field chambers (OTCs). Cylindrical OTCs were used in a mountain
Norway spruce stand. Chamber effects were investigated as well compar
ing samples in OTCs with ambient air and samples not enclosed in OTCs
(control). The OTCs were 2.5 m in diameter at the base, 6.0 m high and
the volume was 20 m(3). The iron frames were covered by transparent 0
.2 mm PVC film. Changes of growth conditions as follows: Transmission
of the chambers covered by a new clear film was 91 +/- 2% of the solar
photosynthetically active radiation (84 +/- 4% at the end of the grow
ing season). Mean air temperatures inside OTCs were 1.3 degrees C high
er than outside OTCs on sunny days. Inside there were decreases in rel
ative humidity during the sunny hours by as much as 10%.Responses of t
he trees as follows: Continual increase of chlorophyll content (a + b)
tvas recorded during the cultivation of the trees in the OTCs in comp
arison with the control (76%). A similar situation was observed for th
e carotenoids content. We recorded seasonal increases of F-v/F-max val
ues and the t(1/2) parameter in the OTCs in comparison with the contro
l treatment. At the beginning of the seasons (1993 and 1994) stem resp
iration was greater in the control than in the OTC (70% and 85% of the
control) but at the end of the seasons the situation was opposite (11
5% and 230% of the control). No differences were found in the developm
ent of apical shoots. Differences were found only in length increases
of whorl branches, in the season 1994 (p=0.01). The length increase in
the OTCs was greater by 38%.