Environmental Engineering Reference
In-Depth Information
14
a
12
10
8
6
4
2
0
-2
-4
b
200
150
100
50
0
c
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
4
8
12
16
20
Time (h)
Figure 1
.
In situ
diurnal trends in net CO
2
assimilation rate (
A
) (a), stomatal conductance (
g
s
) (b) and
quantum efficiency of PSII photochemistry (I
PSII
) (c) in the field throughout a sunny day of summer
1997. Values given are the means and standard errors of four replicate blocks for AMBIENT UV
(white circles), UV-A (grey triangles) and UV-B (black circles) treatments. Measurements were
made on the youngest fully expanded leaf. Data partially from Allen et al.
23
Photosynthetic productivity
Sudden exposure of plants to high UV-B irradiance for a few hours has no effect
on plant productivity. However, pea plants grown under high UV-B exposure for 24 d
had reduced plant height, leaf area, and total, leaf and root dry weights
14
, but the
number of leaves was not significantly affected. This is important since two factors
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