Our data (Fig.1) demonstrate an active growth of all soybean lines at the
beginning of the experiment (the third true leaf stage), which may be linked to the 10-
20-fold higher IAA level than the content of ABA (Table 1). The IAA/ABA ratio was
decreased in all the lines at the end of two-week experiment independently of a
daylength, whilst ABA was accumulated. However, the IAA/ABA dynamics was
different in various daylength conditions so as it depends on E genes.
No significant changes in the IAA/ABA ratio were observed in the leaves of the
SD lines under 16-hour photoperiod during the first week of the experiment, however
this ratio was significantly decreased in the leaves of the ND lines, especially in the
line е1е2Е3 (Fig. 1, A). It is explained by an accumulation of IAA in the leaves of the
SD lines against an insignificant increase of ABA content (Tab.1). Altogether, all the
ND soybean lines displayed the IAA content decrease against the ABA level increase,
which corresponds to the growth delay.
Figure 1. The IAA/ABA ratio in the leaves of soybean lines isogenic for E genes of
Clark cv. Average data for 2010-2012 growing seasons. (A) The IAA/ABA ratio of
the control plant group are shown at LD (16h); (B) the IAA/ABA ratio of the
experimental plant group, which were grown for 14d at SD (9h). Sampling points
were accordant to the experimental group: before daylength shortening (0), on the 7th
(7d) and 14th (14d) days of photoperiod shortening
Source: developed by the author
When photoperiod reduced, the IAA/ABA ratio was decreased, respectively (Fig.
1, B), in the first week of the experiment. It was mostly connected with the rapid
0,0
2,5
5,0
7,5
10,0
12,5
15,0
17,5
20,0
22,5
25,0
0d
7d
14d
0d
7d
14d
IA
A
/A
BA
ra
ti
o
Е1Е2Е3
Е1е2е3
е1Е2е3
е1е2Е3
е1е2е3
A
B
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