Endogenous signals are also necessary to initiate flowering
during inductive conditions
Transcriptomic analysis also showed an increased expression of genes
involved in gibberellin synthesis in the leaf samples associated with
flowering tillers. Previous studies have already shown that gibberellin
is able to initiate and accelerate flowering in Chionochloa sp.in
the glasshouse (Martin, Jameson, Mark, Yeung, & Pharis, 1993) and the
field (Turnbull et al., 2012). Gibberellin has also been shown to
upregulate the expression of FT and SOC1 independently of
the photoperiodic pathway in Arabidopsis and several temperate cereals
as well (Yu et al., 2012). Greater expression of gibberellin synthesis
gene(s) may have promoted flowering in C. pallens by escalating
the expression of CpATFL1 and CpMADS1 as observed in the
transcriptomic studies. Along with gibberellin, expression of the sugar
signalling genes, CpUGT87A2 , CpTPS1 and CpHXK1 , was
found to be significantly greater in the leaves of the tillers that
flowered in the next season. Appropriate sugar levels are required as an
internal standard for a plant to respond to environmental signals to
induce the floral transition (Yang, Xu, Koo, He, & Poethig, 2013).
These data emphasise that, along with the external signals, C.
pallens may require sufficient internal signals to respond and initiate
the floral transition. This may explain why certain tillers in the
experimental transplants did not undergo flowering even following the
perception of an external cue such as warm summer temperatures. These
vegetative tillers may be either too young or may be still in process of
accumulating enough resources.