Agriculture Reference
In-Depth Information
H
20
18
H
16
L
H,L
H
14
L
H
L
12
H,L
L
H
10
L
2
5
8
Time (weeks after unfolding)
Figure 8.4
Net photosynthesis rates at light saturation of apple
leaves as affected by light regime during the preceding weeks.
H,full greenhouse sunlight; L,20% of full greenhouse sunlight. From
Barden (1974). Reproduced with permission.
mg CO
dm
−
h
−
changes in leaf structure and lower maximum rates, e.g.
by leaves from trees grown at
% full sunlight.
By comparing all sequences of sun versus heavy shade over three
-week
periods starting in April, Barden (
) showed that net photosynthesis at
saturating illumination was increased by exposure to high light even after leaf
expansion had ceased, although the effect of the light climate in the earliest
period of leaf development was greatest (Figure
.
). This is in keeping with
effects on specific leaf weight.
