daylength shortening for both the experimental plant groups (short day) and the control
plant groups (long day) at the same period.
Plant hormones were extracted, purified and measured in accordance to protocols
published by Savinsky et al. (Savinskii et al, 1991). Chromatograms and hormone
contents were analyzed and calculated using ‘TotalLab 1.10’ software (Nonlinear
Dynamics, United Kingdom). The content of GAs was measured by biotesting assay
(Polevoi, 2001). The plant hormone contents (IAA, ABA and GAs) are presented as
μg per gram of dry weight of plant materials.
The data obtained were analyzed using the one-way analysis of variance
(ANOVA) by means of ‘Microsoft Office Excel 2003’. LSD (least significant
differences) test was applied to assess the significant differences between the groups.
Statistical significance was set at p<0.05. The mean and standard deviations within
2010-2012 average data are presented in this paper.
Research results. Maturity E genes influence plant physiological processes
mediating by endogenous regulatory systems of plants, e.g. hormonal system.
Gibberellins (GAs), indole-3-acetic acid (IAA) and abscisic acid (ABA) tightly control
flowering of SD plants. GAs are thought to be the most important hormone in flowering
control due to the fact that flowing from the leaf into the apex GAs are components of
a mobile floral signal, which may directly activate the SOC1 gene expression (Wong
et al., 2013). In addition, GA accumulation in the leaves against their low level in the
apexes may indirectly initiates flowering by inducing FT or TSF gene expression
(Hisamatsu et al, 2008; D’Aloila et al., 2011). ABA may be either an activator or an
inhibitor of flowering. Its effects depend on associated conditions, e.g. photoperiod and
plant age (Conti, 2017). IAA also affects flowering processes because it determines the
flowering initiation and reproductive competence of SAM controlling the growth of
flower parts (Vanneste et al, 2009). Moreover, an interaction of plant hormones
(hormonal balance) forms the complex floral signal in SAM, which ultimately leads to
flowering. Thus, both the ratio and dynamics of these hormones and their distribution
between the leaves and SAM may display plant growth processes and development
direction in different photoperiodic conditions.
The level and ratio of phytohormones in the leaves of soybean E-isogenic lines
under different photoperiodic conditions. The leaves are well known to receive a
photoperiodic signal and to form the floral stimulus (Jackson, 2009). Therefore, the
content and ratio changes of hormones in the plant leaves may characterize the effect
of a photoperiod on hormone metabolism or their signaling pathways involved in
photoperiodic signal transduction.
The IAA/ABA ratio in the soybean leaves is shown on the Figure 1. Both IAA
and ABA are involved in plant growth regulation and function as antagonists of each
other. Therefore, a decline of the IAA/ABA ratio is associated with growth retardation,
whereas an increase of the IAA/ABA ratio promotes growth processes.
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