Jatropha the possibility of the development of females

Jatropha
is a monoecious plant bearing male and female flowers on the same plant. It has
racemose inflorescence in a dichasial cyme pattern. Inflorescences are formed
at the terminal or axis of the branches with higher number observed in the
areas exposed to sun (Carels 2009). Inflorescences are formed by the grouping of 6 or 10
individual cymes, resulting in secondary inflorescences. These secondary
inflorescences are located at the base of the main inflorescence with tertiary
inflorescences attached to it (Burger and Huft 1995). Length of the
inflorescences varies
from 5 to 25. Jatropha flowers are pale green in color, with a
pedicle measuring 0.6cm to1 cm in length. Male flowers (Fig.)
measure around 0.75cm to 0.9cm in length and 0.3cm to 0.4cm in width, while the
female flowers (Fig.) measure about
0.7cm to 0.9cm in length and 0.3cm to 0.4cm in width. Flowers have five sepals;
with each sepal ranging from 0.40cm to 0.60cm in length and 0.20cm to 0.30cm
width in the male flower (Fig.), and
approximately 0.45cm to 0.75cm in length and 0.20cm to 0.40cm in width in the
female flower (Fig.).

Both
sexes (male and female) are present at the same inflorescence with single
female flower present at the top surrounded by male flowers. First sub-branch
may produce female flower at the second joint of dichotomous branching (Luo et
al. 2007). There are three types of flowering sites in the inflorescence:
female flowering sites where female flower forms, male flowering sites where
only male flowers are formed and the intermediate flowerings sites where both
male and female flowers are formed. Jatropha is a male dominant plant with a
ratio of male to female flower 25:1. Male can develop at the female flowering
sites whereas the possibility of the development of females at male sites is
zero. This shows the inflorescence has lesser number of female flower (average
8-10) despite of having 18 female flowering site (Wu et al 2010). The female
flower consists of stigma, style and ovary, which are green in color. The ovary is glabrous (ca. 2.5×2 mm), comprises of three
ovules with stylar columns (0.5 mm in length) and style branches (1.5 to 2 mm
in length). There are three stigmas and styles. The bifid stigmas are green in
color and are darker than petals and ovary. The floral base consists of five
flat square yellow glands (0.02 mm in lengths) (Luo et al. 2007). The male
flowers are greenish yellow in color having 10 stamens. The stamens are diadelphous
(fused by filaments in two separate bundles). The outer tier of stamens is free, while the inner tier
is united. The stamens are dicyclic (occur in two whirls) and are 2 to 7
mm in length. Each stamen has four microsporangia arranged in two thecae (Liu
et al. 2007).
Anthers are yellow in color and 10 in number and are 1 to 2.2 mm in length. They
are dithecous (two anther lobes), dorsifixed (attached dorsally to the filament), and
dehisce by the longitudinal slits. At the floral base of male flowers, five oval-shaped yellow glands are
present0.03 mm long and 0.02 mm wide. Pollen are globular, verrucated and
binucleate averaging 57 ?m in diameter (between 52.5 and 70?m) (Dehgan and
Webster 1979; Luo et al 2007). Pollen becomes nonviable after 48 hours and their
abortion may occur in one/two microsporangia per anther (Liu et al. 2007; Luo et al 2007).
Presence of hermaphrodite flowers have also been reported, which are
similar to female flowers with 8-10 stamens. Pollens of hermaphrodite are weak
and less viable with lower germination rates (Abdelgadir
et al. 2010).

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2.3.2 Sex determination

The
floral development of Jatropha has been divided into 12 phases starting from
vegetative to reproductive transition resulting the formation of inflorescence
meristem. During the first five phases no sexual differentiation occurs and the
females are present as bisexual tissue. Further development causes the abortion
of male tissue allowing the development of female flower. No traces of female
tissues were found in the male flowers. Thus, there are two modes of
development in Jatropha: formation of female flowers after the abortion of male
tissues and the other is the formation of male flowers with early adolescence
and no occurrence of female primordia (Wu et al 2012). As male can occupy
female flowering site, causing the decreased ratio of female to male flowers. Thus,
to increase the number of female flowers, the most effective approach is either
to transform male type inflorescences to middle of intermediate type or by
increasing the male abortion rate, allowing female flowers to develop. This
would only be possible by having the knowledge of genetic switches causing the
transition towards female flowers. This is one of the method to increase seed
yield, as fruits are formed from the female flowers only.

 

 Jatropha
is a monoecious plant bearing male and female flowers on the same plant. It has
racemose inflorescence in a dichasial cyme pattern. Inflorescences are formed
at the terminal or axis of the branches with higher number observed in the
areas exposed to sun (Carels 2009). Inflorescences are formed by the grouping of 6 or 10
individual cymes, resulting in secondary inflorescences. These secondary
inflorescences are located at the base of the main inflorescence with tertiary
inflorescences attached to it (Burger and Huft 1995). Length of the
inflorescences varies
from 5 to 25. Jatropha flowers are pale green in color, with a
pedicle measuring 0.6cm to1 cm in length. Male flowers (Fig.)
measure around 0.75cm to 0.9cm in length and 0.3cm to 0.4cm in width, while the
female flowers (Fig.) measure about
0.7cm to 0.9cm in length and 0.3cm to 0.4cm in width. Flowers have five sepals;
with each sepal ranging from 0.40cm to 0.60cm in length and 0.20cm to 0.30cm
width in the male flower (Fig.), and
approximately 0.45cm to 0.75cm in length and 0.20cm to 0.40cm in width in the
female flower (Fig.).

Both
sexes (male and female) are present at the same inflorescence with single
female flower present at the top surrounded by male flowers. First sub-branch
may produce female flower at the second joint of dichotomous branching (Luo et
al. 2007). There are three types of flowering sites in the inflorescence:
female flowering sites where female flower forms, male flowering sites where
only male flowers are formed and the intermediate flowerings sites where both
male and female flowers are formed. Jatropha is a male dominant plant with a
ratio of male to female flower 25:1. Male can develop at the female flowering
sites whereas the possibility of the development of females at male sites is
zero. This shows the inflorescence has lesser number of female flower (average
8-10) despite of having 18 female flowering site (Wu et al 2010). The female
flower consists of stigma, style and ovary, which are green in color. The ovary is glabrous (ca. 2.5×2 mm), comprises of three
ovules with stylar columns (0.5 mm in length) and style branches (1.5 to 2 mm
in length). There are three stigmas and styles. The bifid stigmas are green in
color and are darker than petals and ovary. The floral base consists of five
flat square yellow glands (0.02 mm in lengths) (Luo et al. 2007). The male
flowers are greenish yellow in color having 10 stamens. The stamens are diadelphous
(fused by filaments in two separate bundles). The outer tier of stamens is free, while the inner tier
is united. The stamens are dicyclic (occur in two whirls) and are 2 to 7
mm in length. Each stamen has four microsporangia arranged in two thecae (Liu
et al. 2007).
Anthers are yellow in color and 10 in number and are 1 to 2.2 mm in length. They
are dithecous (two anther lobes), dorsifixed (attached dorsally to the filament), and
dehisce by the longitudinal slits. At the floral base of male flowers, five oval-shaped yellow glands are
present0.03 mm long and 0.02 mm wide. Pollen are globular, verrucated and
binucleate averaging 57 ?m in diameter (between 52.5 and 70?m) (Dehgan and
Webster 1979; Luo et al 2007). Pollen becomes nonviable after 48 hours and their
abortion may occur in one/two microsporangia per anther (Liu et al. 2007; Luo et al 2007).
Presence of hermaphrodite flowers have also been reported, which are
similar to female flowers with 8-10 stamens. Pollens of hermaphrodite are weak
and less viable with lower germination rates (Abdelgadir
et al. 2010).

 

2.3.2 Sex determination

The
floral development of Jatropha has been divided into 12 phases starting from
vegetative to reproductive transition resulting the formation of inflorescence
meristem. During the first five phases no sexual differentiation occurs and the
females are present as bisexual tissue. Further development causes the abortion
of male tissue allowing the development of female flower. No traces of female
tissues were found in the male flowers. Thus, there are two modes of
development in Jatropha: formation of female flowers after the abortion of male
tissues and the other is the formation of male flowers with early adolescence
and no occurrence of female primordia (Wu et al 2012). As male can occupy
female flowering site, causing the decreased ratio of female to male flowers. Thus,
to increase the number of female flowers, the most effective approach is either
to transform male type inflorescences to middle of intermediate type or by
increasing the male abortion rate, allowing female flowers to develop. This
would only be possible by having the knowledge of genetic switches causing the
transition towards female flowers. This is one of the method to increase seed
yield, as fruits are formed from the female flowers only.