Cytokinins growth regulator for improving the number of

Cytokinins
have proven to be the most promising growth regulator for improving the number
of female flowers and seed yield. Benzyl adenine (BA) and thidiazuron treatment
resulted in a drastic increase in number of flowers and female flowers along
with induced bisexual flowers in Jatropha (Pan et al. 2011; Pan et al. 2016).
However, the fruiting rate
was relatively low i.e. 2-3 folds as compared to increased female flowers with
upto 9-10 folds. Also, there was a reduction in 100 seed weight in fruits
formed after cytokinin treatment (Pan et al. 2011; Chen et al. 2014). This
reduction in seed weight led to compromised seed yield even after the
application of phytohormones such as cytokinins. Apart from Jatropha, reduction
in seed yield after cytokinin application has also been reported in other plant
species such as soybean, jojoba and lupin (Ma et al. 1998; Nagel et al. 2001; Prat et al. 2008). However, the reasons for reduction in
seed yield have not been investigated. We hypothesize that the compromised seed yield could be a
consequence of the inability of the photosynthetic source to fully support sink
i.e. seed development in spite of having significantly increased number of
flowers. The reduction in final seed formation is also due to
abortion of floral buds in cytokinin treated plants at later stages of
development because all female flowers do not transit to formation of fruits
due to higher flower abortion rate, which may be due to non-fulfillment of
increased requirement of sink (Pan et al. 2016; Yashima et al. 2005). Limited
supply of photo assimilates to increased flowers is due to increased
competition among leaves, stems, nodules and reproductive organs which might be
the possible reasons for flower abortion (Brun and Betts 1984; Antos and
Wiebold 1984).  Also, the negative
correlation between fruiting rate and seed formation with the number of female
and bisexual flowers per inflorescence on plants treated with cytokinins, may
be a result of either the shortage of photosynthetic products or reduced source
to sink strength (Pan et al. 2011; Pan et al. 2016).