Wudpecker Journal of Agricultural Research
Vol. 2(7), pp. 200 - 205, July 2013
ISSN 2315-7259
2013 Wudpecker Journals
Magnesium and nitrogen contents variation in
Sphenostylis stenocarpa Hochst. Ex. A. Rich
1
Ogbemudia F.O., 1Ubom R.M and 2Ekwere O.J.
1
2
University of Uyo, Akwa Ibom state, P.M.B, 1017, Uyo, Nigeria.
Department of Crop Science, Akwa Ibom State University (Obio Akpa Campus) Oruk Anam, Nigeria.
*Corresponding author: Email:[email protected].
Accepted 17 June 2013
The seeds of Sphenostylis stenocarpa Hochst. ex. A. Rich from three sites Ibiono, Ikono and Itu were
individually analyzed for nitrogen and magnesium contents. The results from Sphenostylis stenocarpa
show that individual seeds vary in nitrogen and magnesium contents (coefficient of variation = 8.54%
Mg and 983.7% N, respectively). The seeds from Ibiono have greater absolute quantities of magnesium
than nitrogen. Differences between seeds from the different sites explained the largest amount of
variation in Mg and N. Soil nitrogen and magnesium were not closely related to seed nitrogen or
magnesium at a site, suggesting that decisions on how much nitrogen or magnesium to allocate to
seeds are not entirely based on supply. The seeds of the plants were not of uniform colour. Differences
in seed mineral content between the three sites (Ibiono, Ikono, and Itu) suggest the possibility for
natural selection to operate, though research to determine heritability of that character will be
necessary to confirm how much of these observation.
Key words: Akwa Ibom state, magnesium, nitrogen, Sphenostylis stenocarpa.
INTRODUCTION
African yam bean (Sphenostylis stenocarpa Hochst ex. A.
Rich.) is an underutilized tropical African tuberous
legume. It belongs to family Fabaceae, (Potter and Doyle,
1994). African yam bean (AYA) is the most valuable
arable tuberous legume that is important in most
indigenous African food cultures and in peasant
agriculture.
African yam bean is a vigorously climbing herbaceous
vine whose height can reach 1.5-3m or more. The main
vine/stem produces many branches which also twine
strongly on available stakes. The vegetative growing
stage is characterized with the profuse production of
trifoliate leaves (Milne-Redhead and Polhill, 1971). The
pods which may sometimes be flat or raised in a ridgelike form on both margins are usually pruned to
shattering, they dehisce along the dorsal and ventral
sutures when dry. Each pod can yield up to 20 seeds
which may be round, oval, oblong or rhomboid. There are
varieties of seed colour (Oshodi et al., 1995) and size
(Adewale et al., 2010) with mono-coloured or mosaic
types. Mono-coloured seeds are white, grey, cream, light
or dark brown purple or black.
African yam bean is usually grown in mixtures with yam
and cassava. Protein content is up to 19% in the tubers
and 29% in the seed grain. The crop has medicinal
importance (Adewale et al., 2010). Assefa and Kleiner
(1997) remarked that African yam bean has very high
nitrogen-fixing ability. It has remarkably low susceptibility
to most field and storage leguminous pests (Omitogum et
al., 1999).
The seeds and tubers are the two organs of economic
importance providing food for both humans and livestock.
However, there is a cultural and regional preference for
each. West Africans prefer the seeds to the tubers, while
tubers are highly relished by the east and central
Africans. This exceptional nutritional pulse has a very
significant link with African socio-cultural life for instance;
there are times in Ghana when they prepare a special
meal from African yam bean seeds during the celebration
of puberty rites in adolescent girls (Potter, 1992).
The chemical composition and nutritional values of
African yam bean have been studied. The crude protein
level and quality of tuberous roots determined by
chemical methods showed that African yam bean have
crude protein levels ranging from 21 to 29% which is
lower than soybean (38%), but the amino acid analysis
indicated high level of methonine and lysine, equal to or
better than those of soybean and corresponding to
WHO/FAO recommendation (Evans et al., 1997) and
showed that the average composition of the whole seeds
are as follows: 20 to 50% protein, 8.2 to 5% fat, 59 to
72% total carbohydrates, 3 to 26% total ash and 8 to 10%
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Wudpecker J. Agric. Res.
moisture.
The seeds of African yam bean are cooked and eaten
as food. However, it is sometimes neglected in most
Nigerian homes because of long hours of cooking (4 to
6hours) after tedious removal of skin coat and soaking in
water.
The tubers are cooked and eaten in the same manner
as potatoes which it resembles in flavour. Extract of
African yam bean also have medicinal values such as its
ability to inhibit haemoglobin polymerization and improve
2
3+
the Fe /Fe ratio of sickle cell blood (Potter, 1992). The
protein in the tuber of African yam bean is more than
twice the protein in sweet potato (Ipomoea batatas) or
Irish potato and cassava. Moreover, the amino acid
values in African yam bean seeds are higher than those
in pigeon pea, cowpea, and bambara groundnut (Evans
et al., 1997). The content is up to 19% in the tuber and
29% in seed grain. The content of crude protein in African
yam bean seed is lower than that of soybean, but the
amino acid spectrum indicated that the level of most of
the essential amino acids especially lysine, methionine,
histidine and iso-leucine in African yam bean is higher
than those in other legumes including soybean. African
yam bean is rich in minerals such as K, P, Mg, Ca, Fe,
and Zn but low in Na and Cu.
African yam bean as a crop is less susceptible to pests
and diseases compared with most legumes. This quality
may undoubtedly be due to the inherent lection in the
seed of the crop. (Potter and Doyle, 1994). The inclusion
of the lectin extract from African yam bean in the meal for
three cowpea insect pests namely Maruca vitrata,
Callosobruchus maculates and Clavigralla tomentosicollis
gave a mortality rate greater than 80% after 10 days
(Potter, 1992).
MATERIALS AND METHODS
Study area
This research was carried out in Ibiono, Ikono and Itu in
Akwa ibom state, Nigeria. Akwa Ibom state lies between
latitudes 4o 30 i and 5o 30i N and longitudes 7o 31i and 8o
20i E within south –south, Nigeria. It has an average
temperature of 25.1-27.8o C and an annual rainfall range
2
of 2000 to 3000mm with the land mass of 8412km .
Relative humidity is usually high and ranges between 30
and 75%. There are two main seasons; dry and rainy.
The former starts from November and ends in April while
the latter begins in may and ends in October though there
may be a slight variation (Enwezor et al., 1981).
Sample collection
The seeds and sands of Sphenostylis stenocarpa were
obtained from Ikono, Itu and Ibiono local government
areas of Akwa Ibom State. The plants materials were
identified and authenticated by Dr. (Mrs) M. E. Bassey, a
plant taxonomist in the Department of Botany and
Ecological Studies, University of Uyo, Uyo, Nigerian.
Laboratory procedures for soil analysis and tissue
The soil samples were air-dried, crushed with mortar and
passed through a 2mm sieve and stored in polythene
bags for chemical and physical analysis. The soil
analyses for the macronutrients were carried out in the
soil science Department of University of Uyo and
micronutrients in ALSCON laboratory Ikot Abasi, Akwa
Ibom state.
Physicochemical analysis of soil samples
Soil samples were analyzed following the standard
procedures outlined by the Association of Official
Analytical Chemist (AOAC, 1975). Soil pH was measured
using Beckman’s glass electrode pH meter (Meclean,
1965). Organic Carbon by the Walkey Black wet
oxidation method (Jackson, 1962), available Phosphorus
by Bray P-1 method (Jackson, 1962). The total Nitrogen
content was determined by Micro-Kjeldahl method
(Jackobson, 1992). Soil particle size distribution was
determined by the hydrometer method (Udo and
Ogunwale, 1986) using mechanical shaker, and
sodiumhexametaphosphate as physical and chemical
dispersant. Exchange Acidity was determined by titration
with 1N KCL (Kramprath, 1967). Total Exchangeable
Bases were determined after extraction with 1M NH4OAc
(One molar ammonium acetate solution). Total
Exchangeable Bases were determined by EDTA titration
method while sodium and Potassium were determined by
photometry method. The Effective Cation Exchange
Capacity (ECEC) was calculated by the summation
method (that is summing up of the Exchangeable Bases
and Exchange Acidity (EA). Base Saturation was
calculated by dividing total Exchangeable Bases by
ECEC multiplied by 100.
RESULTS
Table 1 shows the chemical properties of Sphenostylis
stenocarpa. This result shows that individual plants i.e.
Sphenostylis
stenocarpa
differs
significantly
in
magnesium and nitrogen contents at p = 0.01.
Magnesium contents of Sphenostylis stenocarpa in
Ibiono (372.50) were higher than that of Ikono and Itu
(305.80 and 305.4). Nitrogen contents in Ikono (3.22)
were higher than that of Itu (2.94) and Ibiono (2.38) while
that of Itu (2.94) was higher than that of Ibiono (2.38).
There was a significant difference (p =0.01) among the
Ogbemudia et al.
202
Table 1. Chemical properties of Sphenostylis stenocarpa.
Molybdenum
Copper
Zinc
Cobolt
Calcium
Magnesium
Nitrogen
Phosphate
Sulphate
IBIONO
0.90
8.60
18.20
0.50
478.00
372.50
2.38
816.00
230.00
IKONO
0.80
7.70
6.60
0.30
372.10
305.80
3.22
608.00
460.00
ITU
0.50
8.90
16.0
0.70
492.05
305.4
2.94
544.00
115.00
Table 2. Physical properties of soils of Sphenostylis stenocarpa.
Ph
Electrical conductivity
Organic matter
Total nitrogen
Available phosphorus
Calcium
Magnesium
Sodium
Potassium
Exchangeable acidity
Effective cations exchange capacity
Bases saturation
Particle size analysis:
Sand (%)
Silt (%)
Clay (%)
Molybdenum
Copper
Zinc
Cobalt
Sulphate
magnesium contents as well as the nitrogen contents
from the different sites.
Table 2 shows the physical properties of soils of
Sphenostylis stenocarpa. This results showed that soils
of Sphenostylis stenocarpa did not differ significantly in
magnesium and nitrogen contents. The soil from Ikono
(0.10) had more nitrogen content than in soil from Ibiono
(0.05) and Itu (0.06) but seed produced in Ikono had
more amount of nitrogen than the other sites (Itu and
Ikono). The two sites with the lowest amount of nitrogen
(Itu and Ibiono) produced seeds with the lowest nitrogen
contents.
The soil from Ibiono (3.10) had more magnesium
contents than soil from Ikono (1.20) and Itu (1.40) but
seed produced in Ibiono had more amount of magnesium
than the other sites (Ikono and Itu). The two sites with the
lowest amount of magnesium (Ikono and Itu) produced
seeds with the lowest amount magnesium contents.
Therefore, sites that produced seeds with high
IBIONO
6.20
0.052
2.11
0.05
19.61
11.52
3.10
0.09
0.14
1.60
16.45
90.27
IKONO
5.50
0.020
3.78
0.10
27.70
2.88
1.20
0.10
0.17
1.80
6.15
70.73
ITU
5.20
0.043
2.55
0.06
29.83
4.80
1.40
0.08
0.16
1.92
8.36
77.03
73.40
1.20
5.40
0.45
4.10
9.05
0.35
57.0
83.40
7.20
9.40
1.20
2.80
6.10
0.25
57.0
87.20
5.40
7.40
1.00
3.70
8.10
0.45
57.0
magnesium content did not necessarily produced seeds
with high nitrogen contents.
There was a significant difference (P = 0.01) among the
magnesium contents as well as the nitrogen contents
from the different sites. Magnesium and nitrogen contents
pooled together also showed a significance (P = 0.01) for
the different sites.
Figures 1, 2 and 3 showed the relationship between the
magnesium and nitrogen uptake in Sphenostylis
stenocarpa and the soil of Sphenostylis stenocarpa. The
result obtained from the graphs showed that magnesium
and nitrogen uptake in plants (Sphenostylis stenocarpa)
increased as the magnesium and nitrogen contents in soil
increases.
DISCUSSION
Very little of the variation in nitrogen and magnesium
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Figure 1. Soil-Plant Mg and N contents relationships in Ibiono.
Figure 2. Soil-Plant Mg and N contents relationships in Ikono.
content was attributed to different sites. Hence the
potential for natural selection to operate on this character
is not great. Seed mass was by far the most important
variable determining seed mineral content. Larger seeds
grow into seedlings that are competitively superior to
seedlings from small seeds (Black, 1958). The greater
nutrient reserves of larger seeds may assist developing
seedlings to outcompete those with fewer mineral
reserves, though the relative contributions of seed size
and mineral content are difficult to separate. For example
Ogbemudia et al.
204
Figure 3. Soil-Plant Mg and N contents relationships in Itu.
Abutilon theophrastic plants grown at higher nutrient
concentrations produced heavier seeds with greater
concentrations of nitrogen that were able to grow to a
larger adult size in competition with Setaria than plants
grown from smaller and nitrogen-depauparate seeds
(Parrish and Bazzaz, 1985).
In this case the large seed size might have been more
important for competition than greater nitrogen content.
The highest nutrient environment produced seeds on
Abutilon theophrastic plants that were the heaviest and
the most competitive, but that did not have the highest
concentration of nitrogen. In contrast, experiments with
Trifolium subterraneum showed that seed phosphorus
content was more important than seed size in
determining final plant dry mass (Bolland and Paynter,
1990).
The small amount of variation in seeds of nitrogen and
magnesium content attributed to different sites and the
high degree of variation between seeds on each sites
suggest that plants vary in the allocation of mineral
nutrients, but that decision on how much to allocate are
not entirely based on supply. This is similar to previous
results for Senecio vulgaris L. in which added nitrogen
fertilizer did not result in greater seed nitrogen content,
even though it did result in greater shoot nitrogen content
(Fenner, 1986).
In contrast, however, Abutiloin theophrastic seeds
increased in nitrogen concentration with an increase in
nutrient application (Parrish and Bazzaz, 1985). Whereas
the magnesium content of Abutilon theophrastic seeds
was not affected by external nutrient supply, the
magnesium seed content of Senecio vulgaris actually
decreased significantly with increasing magnesium
supply (Fenner, 1986). In Sphenostylis stenocarpa, seed
contents did not increase with decreasing external
magnesium supply, but remained constant despite
differences in soil magnesium. Nitrogen supply might not
be as crucial for Sphenostylis stenocarpa as it is for most
species because of the association with frankia nodules
that fix atmospheric nitrogen (Dalton and Zobel, 1977).
However, the two most nitrogen-depauperate sites
(Ibiono and Itu) also had minimal seedling establishment
and seeds that had the least amount of nitrogen in their
seeds, suggesting that nitrogen might be important in
seedling establishment in Sphenostylis stenocarpa.
Magnesium has been shown to be one of the most
important minerals for ungulate health and productivity
(Jones and Hanson, 1985). The reason why the seeds of
Sphenostylis stenocarpa has greater quantities of
magnesium is that magnesium is found in thylakoids
which is one of the organelles that is host by chloroplast
and thylakoids are the Mg-containing compartments
where light energy is converted to chemical energy
through the process of photosynthesis.
It is possible to dissect the genetic and environmental
components of variation in seed mineral content in wild
outbreed species, but the significant differences found
between Sphenostylis stenocarpa sites may be at least
partially attributed to the underlying differences in the
maternal genetic component.
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Wudpecker J. Agric. Res.
Conclusion
This study revealed that there were variation in seeds of
Sphenostylis stenocarpa magnesium and nitrogen
attributable to different sites and this knowledge of
variation of seed mineral contents of individual sites
(Ibiono, Ikono and Itu) is necessary to assess the
potential for natural selection to operate. As a result,
there is a need to improve the crop and genetic studies
will help to elucidate whether selection on seed mineral
content alone is possible.
RECOMMENDATION
It is recommended that more research should be carried
out on Sphenostylis stenocarpa in other to dissect the
genetic and environmental components of variation in
seed mineral contents.
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