Endogenous signals may also be involved in flower initiation
during inductive conditions
RNA-seq 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 can
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 (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
RT-qPCR 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 accumulation of 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 maybe
still in the process of accumulating enough resources.