accumulation of ABA (3-3.5 times greater than the initial level), whereas the IAA
content was unaltered (Table 1).
We interpreted this data as a general primary reaction of plants (photoperiodic
sensitivity independent) to a decrease in the light amount and the plant adaptation to
new light conditions. The shortened time of photosynthesis in a short day decreased
the accumulation of assimilates and growth processes accordingly. Since the second
week of the experiment, the pattern of the IAA/ABA ratio has been mainly determined
by the photoperiod duration and the line genotypes.
Table 1. The contents of plant hormone in the leaves of soybean lines isogenic
for E genes of Clark cultivar, μg/g of dry weight. Average data for 2010-2012
growing seasons. Sampling points were accordant to the experimental group: before
daylength shortening (0), on the 7th (7d) and 14th (14d) days of photoperiod
shortening
Sampling
points
IAA content, μg/g
ABA content, μg/g
GA content, μg/g
Daylength, h
16
9
16
9
16
9
SD isoline / genotype Е1Е2Е3
0 d
8.5±0.6
8.5±0.6
0.88±0.04
0.88±0.04
3.7±0.4
3.7±0.4
7 d
11.5±0.8
9.4±0.7
1.53±0.10
3.16±0.20
46.3±1.4
66.0±1.9
14 d
9.9±0.6
5.3±0.4
2.25±0.11
1.61±0.07
8.6±0.9
84.6±2.3
SD isoline / genotype Е1е2е3
0 d
7.7±0.5
7.7±0.5
0.69±0.03
0.69±0.03
11.0±0.9
11.0±0.9
7 d
12.7±1.0
9.3±0.8
0.94±0.06
2.58±0.13
50.7±1.7
24.1±1.1
14 d
11.8±0.9
6.3±0.4
1.97±0.09
1.31±0.10
41.5±1.3
47.8±1.6
ND isoline / genotype е1Е2е3
0 d
9.0±0.7
9.0±0.7
0.91±0.07
0.91±0.07
24.9±1.1
24.9±1.1
7 d
8.0±0.6
7.1±0.6
2.52±0.11
2.97±0.12
36.8±1.2
68.1±1.9
14 d
6.5±0.4
7.5±0.7
1.60±0.13
1.73±0.14
43.5±1.6
51.6±1.8
ND isoline / genotype е1е2Е3
0 d
14.5±1.0
14.5±1.0
0.65±0.04
0.65±0.04
3.6±0.2
3.6±0.2
7 d
12.1±0.9
14.7±1.1
1.38±0.10
3.34±0.16
4.6±0.7
27.8±0.9
14 d
9.3±0.7
11.5±0.8
1.96±0.11
0.88±0.06
71.9±2.0
27.0±0.9
ND isoline / genotype е1е2е3
0 d
10.5±0.9
10.5±0.9
0.75±0.03
0.75±0.03
19.0±1.0
19.0±1.2
7 d
10.3±0.8
6.9 ±0.5
2.36±0.11
2.56±0.12
37.7±1.3
84.5±2.4
14 d
9.1±0.7
8.7±0.6
1.15±0.09
1.25±0.09
55.6±1.8
74.7±2.1
Source: compiled by the authors
The ND lines е1е2е3 and е1Е2е3 displayed higher IAA/ABA ratio in the leaves
at both 16h and 9h photoperiods than others (Fig.1, A and B), whereas the lines
carrying E1 and E3 dominant alleles (Е1Е2Е3, Е1е2е3, е1е2еЕ3) showed the inverse
IAA/ABA ratio on the 14th day of the experiment. The IAA/ABA ratio in the leaves
of Е1Е2Е3, Е1е2е3, е1е2еЕ3 lines was lower at 16h photoperiod (Fig. 1, А), mostly
due to further ABA accumulation in the leaves against IAA level declined (Tab. 1).
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