CONCLUSION
Studies conducted both on long-day plants and short-day plants indicate that plant
hormonal system plays a significant role in the regulation of flowering. Some of
phytohormones stimulate while others inhibit the flowering (King et al. 2001,
Wilmowicz et al., 2011, Campos-Rivero et al., 2017). There is a cross-talk amongst
different hormonal pathways to modulate growth and differentiation processes in
different photoperiodic conditions (Conti, 2017). Therefore, a proper balance between
them decides the direction of plant differentiation. On the other hand, the certain level
and ratio of each group hormones may characterize the effect of a photoperiod on their
metabolism or their signaling pathways involved in photoperiodic signal transduction
(Davis, 2009). Meanwhile, the transduction of this signal involved a complex genetic
network, that trigger the formation of a floral stimulus in the leaves (Jackson, 2009).
Maturity E genes participate in photoperiodic signaling pathways of soybean flowering
initiation, so they can effect on both growth process regulation and plant hormonal
networks.
The obtained results confirm the involvement of E-genes in regulation of
hormonal level and ratio in the leaves and in the SAM of soybean isogenic lines. But
their effects on these indicators depended on photoperiodic conditions.
Thus, the lines carrying one of or both E1 and E3 dominant alleles (Е1Е2Е3,
Е1е2е3, е1е2еЕ3) showed the accumulation of all investigated hormones in the leaves
at 16h (long) photoperiod, but especially of GAs. It suggests that a high level of GAs
against lower level of ABA in the leaves of these lines play an important role in the
intensification of growth processes, that can lead to flowering delay.
Under short-day conditions, the ratio of IAA/ABA decreased in leaves of all
soybean lines and the ratio of GAs/ABA, on the contrary, increased. Moreover, such
dynamic of these ratios was observed in the leaves of the lines carrying e1 and e3
recessive alleles (e1E2е3 and е1е2е3) at both short (9h) and long (16h) photoperiod
equally. The results shown indicate that a decrees of IAA/ABA ratio in the leaves
towards the end of the inductive 14 short days is needed for deceleration of growth
processes and generative induction. A high GAs/ABA ratio in the leaves indicate that
accumulation of GAs may indirectly initiates flowering by inducing FT or TSF gene
expression and that process is under the photoperiodic control. Also, it has been
reported that GA could play a role in the facilitating the transport of FT from the leaf
vasculature to the SAM (Corbesier et al., 2007). In a short day, IAA and ABA levels
were almost equal in SAM of the SD lines and the DN line (e1e2E3), that carrying one
of or both E1 and E3 dominant alleles. However, they contain an elevated GAs level.
On the other hand, regardless photoperiodic conditions, hormonal balance in SAM of
two DN lines (e1E2e3 and e1e2e3) was shifted towards GAs and IAA accumulation.
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