African Journal of Agricultural Research Vol. 6(2), pp.

275-284, 18 January, 2011

Available online at http://www.academicjournals.org/AJAR
DOI: 10.5897/AJAR09.727
ISSN 1991-637X ©2011 Academic Journals

Full Length Research Paper

A study on structural features in early flower

development of Jatropha curcas L. and the
classification of its inflorescences
Jun Wu, Yuan Liu, Lin Tang, Fuli Zhang and Fang Chen*
College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, China.
Accepted 26 November, 2010

Jatropha curcas L. produces seed oil that is viewed as having tremendous potential as an economical
alternative for diesel fuel. Seed yield, the main factor determining jatropha oil production, is highly
associated with flower development, especially with the number of female flowers. However, little was
known regarding floral development in this species. Accordingly, studies were undertaken to develop
more information on the developmental process of floral organs. The early floral development was
divided into 12 phases. The present study illustrated that, the sex differentiation of male or female
flowers occurred in phase-VII; earlier phases presented unapparent structural differences. The male
flowers always had unisexual tissues during floral development. In contrast, early development of
female flowers presented bisexual tissues, with male sexual degradation occurring at the later
developmental phases. There was significant location specificity with respect to the inflorescence of
male and female flowers. Based on this, the present study combined the total number of female flowers,
and divided the inflorescence into three types, which had significant differences in the number of
female flowers; they likewise presented different probabilities of occurrence in terms of different
growing seasons.

Key words: Biofuel, flower, inflorescence, Jatropha curcas, sex differentiation, scanning electron microscopy.

INTRODUCTION

It has been increasingly apparent that the production of non-domesticated nature. Thus, although jatropha grows
biofuels must originate from non-food crops dedicated abundantly in the wild, its seed and oil yields are
solely to energy production. These crops should not considered unpredictable for production. The conditions
compete with food crop production. Genetic improvement that best suit its growth remain largely undefined, and the
of such potential bio-energy-producing crops, such as potential environmental impacts of large-scale cultivation
switchgrass, poplar, and Jatropha curcas L. (jatropha) is are not at all fully understood (Chikara, 2007).
currently being pursued (Koonin, 2006; Kaushik, 2007; J. curcas L. (Euphorbiaceae) originated in Central
Ranade et al., 2008). Many countries hold high America. It is a perennial softwood shrub or small tree
expectations for jatropha as a biofuel source, as it grows that is now fairly well established in most tropical and
well on lands poorly suited for cultivation of food crops. subtropical areas of the world. The vegetable oil from the
However, although there is reason to be enthusiastic oil-rich seeds produced by this plant is known for its
about jatropha’s potential as a biodiesel feedstock, one medicinal value (Wei et al., 2005), and has long been
major obstacle to its current widespread cultivation is its used around the world as a source of lamp oil and for
producing soap (Chikara, 2007). Recently, jatropha oil
has been recognized for its suitability for conversion into
biodiesel (Solomon, 2002). The plant thrives in a wide
*Corresponding author. E-mail: wqh1019@yahoo.cn. Tel: +86 range of environmental conditions, from eroded land to
28 8541 7281. Fax: +86 28 8541 7281. reclaimed land. It likewise grows well with limited
276 Afr. J. Agric. Res.

amounts of water, nutrients, and capital inputs. J. curcas RESULTS

can be used to rehabilitate wastelands and improve the
environment. It can also enhance the quality of rural life Flower structure and location features
by providing new economic resources for marginal
farmlands (Openshaw, 2000; Francis et al., 2005). To study the structural features of the development
A number of industrial companies have launched plans process of early flowers of J. curcas and the structural
and have started to develop new industries based on the differences in their sex differentiation, it is first necessary
jatropha oil (e.g., biofuel production). For instance, China to clarify the structural features of mature flowers.
National Offshore Oil Corporation, one of the largest Typically, mature flowers are unisexual, both male and
state-owned oil companies in China, has begun to build a female flowers having five sepals, five petals, and five
six-ton biodiesel factory in the country’s Hainan province glands (Figures 1A, B, C and D). In addition, male flowers
based on the use of jatropha material. Recently, Air New have 10 stamens divided into upper and lower layers
Zealand has completed a two-hour test flight powered by (Figure 1A), while female flowers have three carpels and
a 1:1 blend of biodiesel made out of jatropha oil and two split stigmas (Figure 1C).
conventional jet fuel The jatropha plant produces flowers on a racemose
(http://www.bloomberg.com/apps/news?pid=20601081&si inflorescence with a dichasial cyme pattern (Solomon and
d=aMBr28xXRhTE&refer=australia). Ezradanam, 2002). A study of the inflorescence of J.
From a botanical perspective, the production of seed oil curcas has shown that the rachis of J. curcas develops its
depends on flower production and seed set. However, in branches several times and, in an inflorescence, female
jatropha, seed yield, which is highly correlated to the flowers would be located between two branches of their
number of female flowers, is currently considered as a inflorescence, while male flowers flourish at ends of the
limiting factor. The ratio of female to male flowers is low in plants’ branches (Figure 1E).
most of the available germplasm. Therefore, increasing
the number of female flowers through breeding and
management is essential for the success of seed oil Different structural characteristics of flowers in
production on a large scale. The aim of the present study different phases
is to further investigate the morphological development of
the male and female flowers, the number of female When the plants of J. curcas grow into a flower-matured
flowers per inflorescence, and the types of state, under appropriate environmental conditions, their
inflorescences. This information would help in the genetic inflorescence meristem would be differentiated at the top
improvement for oil yield and the mechanism studies of of their branches, which begin their reproductive growth.
sex differentiation and the objective setting of breeding For a better analysis of the structural characteristics of
and cultivating in this plant. male and female flowers, the present paper divides the
early flower development into 12 phases in accordance
with the early or late developmental time of calyx, petal,
MATERIALS AND METHODS glands, stamen, and pistil, taking note of the division
system established in Arabidopsis (Smyth et al., 1990)
The experiment was conducted in the provinces of Sichuan, Yunan,
and Silene latifolia (Grant et al., 1994).
and Hainan of China (26°56 N, 101°68 E; 19°25 N, 110°18 E;
N22°95 , E104°29 ) from 2007 to 2008, with two observation sites
located in each province. The trees for this study were 5 to 8 year
old. The reproductive body samples (about 300) were collected Phase-I to phase-II
every two days, from floral tissue emergence to the flower
senescence. Flowers were divided into male and female, and were In the first two phases, young inflorescences of J. curcas
then analyzed by scanning electron microscopy (SEM).
cannot be seen from the plant surface, since they are
For SEM, fresh flower tissue was fixed overnight in 2%
glutaraldehyde in phosphate buffer, pH 7.2 to 7.4 (Wang, 2006), enveloped by young leaves. When the meristem at the
dehydrated in a graded ascending ethanol series, and dried at the top of the branches forms a rounded protrusion, plants
critical point with CO2. Samples were mounted onto SEM stubs with begin to shift from vegetative growth to reproductive
epoxy or carbon-coated tape, and sputter-coated with a 25 nm layer growth. Such meristem would further elongate to form the
of gold or gold-palladium in a sputter coater. They were then viewed inflorescence primordia (Figure 2A), indicating the
with an S-450 SEM (Hitachi, Japan) running at an accelerating
voltage of 5 to 20 kV. To reveal the organs developing underneath,
beginning of phase-I. Then, further differentiation and
floral structures were dissected. development of inflorescence primordia would proceed;
A total of 5,000 J. curcas inflorescences were observed. that is, a number of young inflorescence branches are
Observations were initiated in mid-March when inflorescences differentiated on the inflorescence rachis, the completion
started to form, and ended in mid-December when new of which sets off phase-II (Figure 2B). At this phase, each
inflorescences had ceased to occur from 2007 to 2008. The branch is composed of the central flower primordium and
number, location, and array of female and male flowers in the
inflorescence were recorded for all of the observed inflorescences.
the inflorescence meristem on both sides, which is
Data were statistically analyzed using variance analysis of differentiated once again by the number of new
Statistical Analysis System (Meyes et al., 2009). inflorescences in the branches. Such developmental
 Wu et al. 277

Figure 1. The character of J. curcas flowers. (A) and (B) A male flower: ten stamens
(s), five petals (p), five sepals (se) and five glands (g). (C) and (D) A female flower:
ovaries (o), three styles, two splits each (arrowhead) five petals (p), five sepals (se)
and three of five glands (g). (E) Structure of an inflorescence (arrowheads show the
pedicels of the fallen male flowers, :female flower, :male flower )

process forms a number of branches when the female structure (Figures 3A and B). Therefore, the
inflorescences are matured (Figure 1E). formation patterns of female and male organs in phase-III
and phase-VI are the same, specifically, from the calyx to
the petal and stamen gland formation.
Phase-III to phase-VI

Along with the further development of flower primordia of Phase-VII to phase-XII

phase-II, the sepal primordia begin their formation. When
the primordia of five calyxes appear without the Immediately after phase-VI, female and male flowers
occurrence of petal primordia, it is then defined as phase- begin to show their developmental differences, mainly, in
III (Figure 2C). In phase-III, inflorescence tissues are the form of changes in the flower apical meristem. If such
visible at the top. When the primordia of five petals are apical meristem undergoes further differentiation and
formed at the base of the pentagram-like flower tissues, it protuberance, then female flowers are formed, and the
is referred to as phase-IV (Figure 2D). formation of protuberance of the apical meristem is
Then, at the base of the flower tissues and the inner defined as phase-VII of the female flowers (Figure 3A). In
part of petal primordia, further differentiation and growth this period, the apical meristem of male flowers no longer
out of five gland primordia are seen. This stage is now exhibits differentiation or elongation, but its stamen
defined as phase-V (Figure 2E). At this phase, the primordia continue to develop, with their top surrounded
elongated flower meristem appears like a circular by nearly oval-shaped stamen primordia and the center
truncated cone. Here, the five petal primordia can be taking a planer shape (Figure 3D). Carpel tissues are
observed as having a slower growth just prior to the likewise differentiated, developed, and formed from the
formation of the pistil or stamen primordia. At phase-VI, top protrusion of the meristem. The carpel primordia
there is a formation of ten nearly oval-shaped stamen emergence represents phase-VIII of the female flower
primordia divided into upper and lower layers, with each development (Figure 3B), while the structural emergence
layer having five oval-shaped stamen primordia (Figure of heart-shaped stamen primordia coming from a nearly
2F), which is consistent with the structure of mature male oval-shaped form is defined as phase-VIII of male flower
flowers (Figure 1A). SEM has shown that the early development (Figure 3E).
development of female flowers also presents 10 stamen Then, carpel tissues further differentiate and develop to
primordia, which is followed by further development of the form ovule primordia, now referred to as phase-IX of the
278 Afr. J. Agric. Res.

Figure 2. Scan of J. curcas L. flowers of phase-I to phase-VI. (A) The main inflorescence
primordia emerges, bracketed by a pair of stipules in phase-I. (B) A branch of inflorescence
composed of two lateral inflorescences (arrowheads) and a central flower (*) in phase-II. (C)
Sepal primordia enclose a near spheroid meristem in phase-III. (D) Reproductive meristem like
pentagram as five-petal primordia (*) arise in phase-IV. (E) Five glands primordia (*) arise at the
base of circular-truncated-cone-like floral meristem in phase-V. (F) Stamen primordia arise in
phase-VI. a: apical meristem, st: stipule primordium, se: sepal primordium, p: petal primordium.
Bars = 50 m.

female flowers (Figure 3C). This period is defined as the Sexual differentiation
formation of ovule primordia, and a female flower usually
is shown to have three ovules. In phase-IX, male flowers According to the above-mentioned division of
transform their stamen primordia from heart-shaped to developmental phases of early flowers of J. curcas, no
shallow cleft-shaped (Figure 3F). The formation of each obvious structural difference between male and female
carpel’s top central protuberance (developing into style in flowers can be observed before phase-VII, as similar
the future) is defined as phase-X of female flowers tissues and organs are formed, such as the sepals,
(Figure 4A). In this period, the stamens of male flowers petals, glands, and stamen primordia. In the latter period
develop from shallow cleft-shaped into strips, while their of phase-VI, the flowers whose top starts to elongate
pollen sac begins to take shape and each stamen takes (Figure 3A) will grow as female flowers, while those
on the formation of four pollen sacs (Figure 4D). without further differentiation and development (Figure
At phase-XI, a distinctive developmental feature of both 3D) will grow into male flowers. Thus, in the early stage of
female and male flowers emerges, particularly, their development of female flowers, bisexual tissues are
quickly growing glands (Figures 4B and E). The female prominent (Figure 3A, B and C). In the subsequent
flowers’ stigma is formed and carpel development allows development, male tissues undergo abortion (Figure 4A
the relative separation of the ovule and the surrounding and B), and traces of the stamens of abortion can still be
tissues (Figure 5A). Meanwhile, each anther of the male seen in the nearly mature female flowers (Figure 4C).
flowers is divided into two parts, each part having two Since there is no emergence of female tissues in male
rooms with pollen grains separated from each other flowers, their development process has always been
(Figures 4E and 5B). Growing to phase-XII, the female unisexual (Figures 1A, 3D, E, F; 4D, E and F). Thus,
flowers’ stigma is observed to grow towards development there are mainly two modes for the formation of unisexual
and maturation (Figure 4C), while the male flowers’ flowers of J. curcas: one is the formation of female
filament grows toward elongation and most pollen grains flowers after the later abortive development of male
present are round (Figures 4F and 5C). Not long after this tissues, and the other is the formation of male flowers
period, elongation of flowers, maturity of gametophytes, subject to the early adolescence when there is no
and blossoming of flowers occur. occurrence of female primordia.
 Wu et al. 279

Figure 3. Sex differentiation of J. curcas L. flowers in phase-VII to phase-IX. (A) The apical
meristem is elongated during phase-VII of a female flower. (B) Three carpels are established with
ten stamens on the base in phase-VIII of a female flower. (C) Three ovule primordia (arrowhead)
emerge in phase-IX. (D) The apical meristem (asterisk) is arrested and only stamen primordia exist
of the two gender organs in phase-VII of a male flower. (E) The heart-shaped stamen primordia are
formed in phase-VIII of a male flower. (F) Stamen primordia are transformed from heart-shaped to
shallow cleft-shaped structure in phase-IX of a male flower. a: apical meristem, p: petal, s: stamen,
c: carpel. Bars = 50 m

Figure 4. The development of J. curcas L. flowers of phase-X to phase-XII. (A)

The carpel’s top protuberances (bold arrowhead) indicate the formation of
style primordial with the undeveloped gland (thin arrowhead). (B) Stigma is
formed (thin arrowhead); the glands grow up in a short period; the aborted
stamen (bold arrowhead) is visible. (C) The floral stigma (thin arrowhead)
develops further to be ready to receive the pollens in phase-XII with the trail of
aborted stamen (bold arrowhead). (D) The stamens develop from shallow cleft-
shaped into strips with the undeveloped glands (bold arrowhead). (E) The
glands grow up quickly in phase-XI of male flowers. (F) The filament (bold
arrowhead) grows toward elongation in phase-XII. s: stamen, gl: gland. Bars =
50 m in A and D, bars = 500 m in B, C, E and F.
280 Afr. J. Agric. Res.

Figure 5. The sections of J. curcas L. flowers in phase-X and phase-XI. (A) The stigma is formed and the ovule
(the future seed) is relatively separated from surrounding tissues; the aborted stamen is visible at the base of the
ovary outside. (B) The pollen grains (arrowhead) start to be formed in phase-X of male flowers. (C) Most pollen
grains (arrowhead) develop into round shape in phase-XI of male flowers. p: petal, s: stamen, gl: gland, ov:
ovule bars = 500 m.

Figure 6. The configuration of J. curcas inflorescences. (A) male-type inflorescence: all flowers are male. (B) A
middle-type inflorescence. (C) A female-type inflorescence: all the places of female sites are occupied by
female flowers. : female flower, : male flower.

Inflorescence classification and ratio The top of the main inflorescence rachis and the central
location where the first and second sub-branches start
As mentioned above, male and female flowers of J. may form the female flowers (Figures 1E and 2B), and
curcas have their significant location features with are thus defined as the female sites. Based on the
respect to their distribution on inflorescence. For the early gender of female sites of inflorescence, the present paper
inflorescence development, the main inflorescence rachis divides inflorescence into three types that can, to some
is divided into a few branches, with each branch extent, reflect the proportion of male and female flowers
composed of a central flower and two sub-branches of of inflorescence, especially the number of female flowers,
inflorescence meristem generated in their maturation as well as reflect the number of their final fruits. When all
(Figure 2B). Then, sub-branches of inflorescence are the female sites of inflorescence are presented as female
differentiated into another central flower and lower sub- flowers, then such inflorescence should be divided into
branches of inflorescence meristem, which no longer female-type inflorescence (Figure 6C). When all of these
appears to be differentiated in inflorescence branches; its sites are presented as male flowers, then all the flowers
end part presents the formation of three to six flowers of such inflorescence are male flowers, referred to as
(Figures 1E and 6B). In this way, mature inflorescence is male-type inflorescence (Figure 6A). When the number of
developed with obviously branched inflorescence rachis. female flowers at the female sites is between the female-
A large number of observations indicate that, the flowers type inflorescence and the male-type inflorescence (that
formed on the third branch of the sub-branched is, the female sites of female flowers at an inflorescence,
inflorescence rachis would only grow into male flowers do not grow all female flowers or male flowers), then such
(Figures 1E, 6B and C), and the locations of intermediate type is called middle-type inflorescence
inflorescence growing flowers are defined as male sites. (Figure 6B).
 Wu et al. 281

Table 1. Variance analysis of the female flower number per inflorescence between the
female-type and middle-type inflorescences.

Source DF Type III SS Mean square F value Pr > F

Inflorescence type 1 518.57 518.57 8418.31 <.0001**
Site 5 0.27 0.054 0.88 0.56
Year 1 0.024 0.024 0.39 0.56
Inflorescence type × site 5 0.023 0.005 0.08 0.99
Inflorescence type × year 1 0.018 0.018 0.29 0.61
Site × year 5 0.296 0.059 0.96 0.52
Error 5 0.308 0.062
Corrected total 23 519.51
×: interact, **: significantly different, DF: Degree of freedom.

Table 2. Variance analysis of the male: female flower ratio per inflorescence between the
female-type and middle-type inflorescence.

Source DF Type III SS Mean square F-value Pr > F

Inflorescence type 1 1976.9 1976.9 42295.6 <.0001**
Site 5 0.097 0.019 0.41 0.82
Year 1 0.014 0.014 0.3 0.61
Inflorescence type × site 5 0.069 0.014 0.29 0.9
Inflorescence type × year 1 0.025 0.025 0.54 0.49
Site × year 5 0.276 0.055 1.18 0.43
Error 5 0.23 0.047
Corrected total 23 1977.61
×: interact, **: significantly different.

For ease of calculation, the branching inflorescence flower number is zero and the proportion of staminate
generated from the sub-branches of the main flowers and female flowers is infinity. Therefore, there is
inflorescence rachis is called secondary inflorescence extremely remarkable difference with respect to a single
(Figure 1E), which can further branch several times inflorescence’s female flower number and the proportion
during the development. Each secondary inflorescence of female and male of the three types of inflorescences.
has three female sites (Figures 1E and 6C), while the The female flower number and the proportion of female
number of the secondary inflorescence’s male sites are and male flowers for three types of inflorescences are
different on different inflorescences. The statistical shown in Table 3. Herein, the proportion of male and
analysis of the present study has indicated that, the female flowers is 25:1 on average. The proportion of male
secondary inflorescence has an average of 20 male sites. and female flowers and the female floral number of the
Statistics also show that a single inflorescence has an female-type inflorescence are about 15:1 and 16.5,
average of six secondary inflorescences. The variance respectively, while these are 20:1 and 7.2 for the middle-
analysis indicated that there are great differences, type inflorescence.
reaching to an extremely remarkable level (Pr > F, Through the observation for more than two years, it has
<0.0001), between the female-type and the middle-type been discovered that different types of inflorescences
inflorescences with respect to the number of female have different proportions (Table 3). To illustrate, female-
flowers and the proportion of female and male flowers of type inflorescence presents the smallest (0.09%)
a single inflorescence (Tables 1 and 2). However, for proportion, while middle-type presents the largest
different years and different sites, there is no obvious (74.9%). Moreover, different proportions occur in different
difference (Pr > F = 0.56 and 0.56) between the female- seasons for the same type of inflorescence. Since
type and the middle-type inflorescences with respect to jatropha is expected to blossom several times in a year,
the number of female flowers and the proportion of for ease of research, the average of three times of
female and male flowers per inflorescence (Tables 1 and blossoms per year was assumed for the analysis. Based
2). Meanwhile, the male-type inflorescence’s female on this assumption, it is found that female-type and
282 Afr. J. Agric. Res.

Table 3. Number of male and female flowers in three types of inflorescences.

Female Male Male: Average female flower

Inflorescence The ratio in all
Types flower flower female number per
number inflorescences
number number ratio inflorescence
Female-type
450 0.09 7425 65295 8.79 16.5
inflorescence

Middle-type
3475 0.749 25020 674100 26.94 7.2
inflorescence

Male-type
1075 0.215 0 218225 0
inflorescence

Figure 7. Different inflorescence types at different flowering stages in J. curcas.

middle-type inflorescences reach the highest proportion functions (Dellaporta and Calderon-Urrea, 1993). Such
of “one-time blossom” during the middle period, while the as in Spinacia oleracea, Mercurialia annua and Pistacia
proportion for the “first-time blossom” reaches the highest vera, only one kind of sex primordia are formed during
for the male-type inflorescence (Figure 7). the flower development process (Durand and Durand,
1984; Sherry et al., 1993; Wannan and Quinn, 1991).
Our results show that there are two modes of formation
DISCUSSION of unisexual flowers in jatropha. In female flowers,
bisexual tissues are present and the androecium
The development of flowering plants is an orderly selectively arrests its future development. In male
progression from the embryo to the mature plant through flowers, only one kind of sex tissue is present, and thus,
continuous organ formation from meristems (Krizek and there is no selective arrest of stamens or pistils. Besides,
Fletcher, 2005). Most studies indicate that both sex organ male and female flowers have similar tissues and organs
primordia occur in the early developmental stages in before female primordia emergence, and these
unisexual flowers (dioecious or monoecious); the development characteristics were also reported in Clusia
selective developmental arrest of preformed organ valerioi (Hochwallner and Weber, 2006). Based on this
primordia is the most common method for generating organization of the flower sexes in jatropha, we propose
unisexual flowers (Delong et al., 1993; Grant et al., that there are factors that regulate sex differentiation in
1994). However, some studies do not support the idea this plant, which may selectively affect the action of
that the production of unisexual flowers is controlled by homeotic genes in one whorl, such as only restraining the
selectively activating or inactivating homeotic gene initiation of a gynoecium meristem in male jatropha
 Wu et al. 283

flowers. since the first occurrence of blossom is within the period

Previous studies have shown that the pollination in of February to March, right after the end of the previous
jatropha flower is done by insects that are attracted by year and at a time of low temperature dormancy. The
the nectar produced by the flower (Bhattacharya et al., third occurrence of blossoms (possibly the fourth or fifth
2005; Solomon and Ezradanam, 2002). The nectar time in some places) occurs in the period of October to
secretion coincides with the time when pollens have November when temperature gradually drops. We have
developed in the anthers and the stigma has become also observed that the right amount of rainfall may
receptive, which is important for pollination. However, the possibly enhance the number of female flowers for each
structural basis for this to happen has not been clarified. inflorescence, while too much or too less would not favor
During floral development, glands emerge at phase-V, the occurrence of female flowers (data not shown).
but they only mature at phase-XI when the flowers are In conclusion, the present study provides new details
ready to open. Therefore, just before the flower opens, regarding floral development and inflorescence types
glands mature to release an aroma to attract insects. If (related with the female number) in J. curcas L. The
glands were to mature and release scent at an earlier findings reported here would be useful in bringing this
stage, the attracted insects would be blocked by the species into domestication, thus improving the production
petals enclosing the reproductive organs. By the time of biodiesel and extending its application to other uses.
flowers do open, the release of scent from the glands
would have ceased, and insects are then less attracted to
the flowers. As such, it is essential that the glands do not ACKNOWLEDGMENTS
mature and release scent until the flowers open,
especially since insects are attracted at a correct time in We are grateful to Qun Sun, Thomas Keeling and Yi He
order to complete the pollination. (analytical and testing center of Sichuan university) for
The present research has shown that the female and advice, encouragement, and helpful suggestions. This
male flowers of J. curcas have remarkable position research work was funded by the Cooperation Project
location features; that is, female flowers are located at Foundation of China and Holand (No. 2004DFB00300)
the female sites, male flowers are located at the male and the National Science Foundation (No. 30670204).
sites and the proportion of an inflorescence’s male sites
and female sites is approximately 20:1. Therefore, for J.
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