ABSTRACT
The study investigated the growth characteristics and chemical composition of Gnetum africanum and G. bulcholzianum in different ecosystems in Nigeria lowland rainforest. The experiment consists of a 4x2 factorial experiment in RCBD for measurement of growth rate in rubber plantation and a 2x2 factorial experiment in RCBD for laboratory analysis. The results were expressed as mean standard Deviation and Standard Error. Duncan multiple range test was adopted to separate means and test for significant differences among means at (P>0.05). There was a significant difference (P>0.05) in growth rate of G. africanum and G. bulcholzianum but no significant difference in their girths. Gnetum as a shade loving plants experienced absolute shade in both environments. Dry matter and carbohydrate were higher in G. africanum (RF) 93.20±0.011% and G. bulcholzianum (rubber plantation) 93.16±0.075%. Least mean proximate compositions was found to be in G. bulcholzianum (RB) 1.77±0.125%, phenol was the least phytochemical with no significant difference (P>0.05) Alkaloid showed significant difference (P>0.05) with highest mean value of phytochemical composition and was higher in G. bulcholzianum 5.60±0.112mg/100g (RF) and G. africanum 4.75±0.050mg/100g (RB) than G. africanum of RF 3.83±0.887mg/100gm and RB 3.40±0.011mg/100g. Chromium and cadmium were significantly different with least mean values of heavy metal compositions. Chromium had values ranging from 0.08±0.003mg/100g in Gnetum africanum (RF) to 0.11±0.011mg/100gm G. bulcholzianum (RB), also cadmium had mean values of 0.24±0.152mg/100gm Gnetum africanum (RF) to 0.44±0.017mg/100gm G. bulcholzianum, (RF) which shows that gnetum is less toxic to human health. The two species of gnetum showed high significant amount of vitamin c component and least mean values of Vitamin B2 ranging from 0.56±0.011mg/100gm in Gnetum africanum (RB) to 0.63±0.011mg/100gm G. africanum (RB), it was higher in G. africanum 42.98±0.376mg/100gm (RB). Exchangeable cations needed for plant growth was significantly higher (P>0.05) in RB compared to RF. Na+ was the most limiting exchangeable cations in both top soils of rubber plantation and relic forest with values 0.13cmol/kg and 0.144cmol/kg respectively. Soil pH above 4.00 in both RF and RB shows favorable acidic nature for gnetum growth. Fe, Mn and S showed high significant difference and mean values in sub soils of RF than in RB. Gnetum species leaves have high nutritional value, phytochemical contents and medicinal values and it is recommended as cheap sources of plant proteins, materials for the synthesis of new drugs in pharmaceutical industries.
TABLE
OF CONTENTS
Title
Page i
Declaration ii
Certification iii
Dedication
iv
Acknowledgements v
Table
of Contents vi
List of
Tables viii
List of
Plates ix
List of
Figures x
Abstract xi
CHAPTER 1: INTRODUCTION
1.1
Background of the Study 1
1.2
Statement of the Problem 6
1.3
Aim of the Study 7
1.4
Objective of the Study 7
1.5
Justification of the
Study 8
CHAPTER 2:
LITERATURE REVIEW
2.1 Description of Gnetum Plants 10
2.1.1 Management 10
2.1.2 Growth and development 11
2.1.3 Climate 11
2.1.4 Habitat of gnetum 12
2.1.5 Anatomy of gnetum 13
2.1.6 Pollination 13
2.1.7 Method of propagation 14
2.2
Economic Importance of Gnetum 17
2.3 Nutritional
and Health Benefits 19
CHAPTER 3:
MATERIALS AND METHODS
3.1.2 Study Area 24
3.2 Methodology 26
3.2.1 Experimental design 27
3.2.2 Soil Sampling 27
3.2.3 Preparation of soil samples for analysis 28
3.2.4 Soil laboratory analysis 28
3.4 proximate analysis 34
3.5 Mineral analysis 44
3.6 Heavy metal determination 45
3.7 Determination of phytochemicals 38
`3.8 Statistical
analysis 46
CHAPTER 4:
RESULTS AND DISCUSSION 47
CHAPTER 5:
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 77
5.2 Recommendations 79
References 80
Appendices
LIST OF TABLES
2.3.1 Micro and macro element composition of
Gnetum leaves. 20
2.3.2 Essential and non-essential amino acid
composition of gnetum leaves. 20
4.1.1 Mean growth characteristics of two gnetum
species in rubber plantation. 49
4.1.2 Mean leaf biomass of gnetum species
harvested from rubber plantation
and relic forest, Michael Okpara University of agriculture,
Umudike. . 52
4.1.3 Proximate composition of gnetum species from
rubber plantation
and
relic forest, Michael Okpara University of agriculture, Umudike. 56
4.1.4 Phytochemical composition of gnetum species
from two ecosystems
(Rubber plantation and relic forest). 58
4.1.5 Macro elements composition of Gnetum species
from two ecosystems. 59
4.1.6 Micro nutrients composition of Gnetum
species from two ecosystems. 62
4.1.7 Vitamin composition of Gnetum leaves. 64
4.1.8 Moisture content, Bulk density and Total
porosity of soil samples from
rubber
plantation and relic Forest. 66
4.1.9 Physicochemical composition of soil samples 71
4.2.0 Extractible micro-nutrients and total
elements of soil samples 74
LIST OF PLATES
1: Picture
showing leaf of Gnetum bulcholzianum 16
2: Picture
showing leaf of Gnetum africanum 16
3: Harvesting
gnetum leaves in rubber plantation, Michael Okpara
University of Agriculture, Umudike. 70
4 Harvesting
gnetum leaves in relic forest, Michael Okpara
University of Agriculture, Umudike. 70
5 Gnetum stand with numeric
inscription at Michael Okpara
University of Agriculture, Umudike. 70
6 Digging
a profile pit at rubber plantation at Michael Okpara
University of Agriculture, Umudike. 70
7 Vertical
view of soil profile pit (50cm x 40cm x 85cm) 70
8 Weighing
of soil samples at National Soil, Plant, Fertilizer
and
Water Laboratory, Umudike. 76
9 Samples
for total elements and extractible nutrients at National
Soil, Plant, Fertilizer and Water Laboratories,
Umudike. 76
10 Laboratory
analysis carried out on soil samples at National
Soil, Plant, Fertilizer and Water Laboratories,
Umudike. 76
LIST OF FIGURES
1: Map showing the study area. 25
2: Growth characteristics of
gnetum species in relic forest, Michael Okpara University of Agriculture,
Umudike. 51
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Gnetum
species is a tropical wild climbing vegetable plant found in Nigeria, Cameroun,
Gabon, Congo (Eyo, et al., 1988). The vegetable has a place with the
family Gnetaceae which develops unexpectedly in the timberlands (Schippers,
2000). Gnetum africanum and Gnetum bulcholzianum are vine gymnosperm
species found locally all through Africa (Mialoundama, 1993), however bearing
leaves, the variety gnetum are gymnosperms, identified with pine and different
conifers (Chaw et al., 2000, Bowe et al., 2000). Gnetum, spoken to by
around 80 species is limited to the tropical and sticky locales of the world.
In Nigeria, it is significantly found in Abia, Akwa Ibom, Anambra, Cross River
and Imo State.
Almost
all species with the exception of G.
microcarpum, happen underneath an elevation of 1500 meters above ocean
level. In Africa, Gnetum africanum
and G.bulcholzianum exist while in
Asian nations like India, four species have been accounted for specifically G. contractum, G. gnemon, G. montanum, G.
trinerve , larger part of the gnetum species are climbers aside from a
couple of bushes and trees. Gnetum
trinerve is clearly parasitic, two sorts of branches are available on the
fundamental stem of the gnetum plant specifically parts of constrained
development and parts of boundless development. Each branch contains hubs and
internodes. Stems of a few types of gnetum are enunciated. In the climbing
species, for example, G. africanum
and G. bulcholzianum the branches are of constrained development or short
shoots are commonly unbranched and bear the foliage leaves of Gnetum africanum and Gnetum bulcholzianum
are of extraordinary financial significance in west and focal Africa (Fuashi et al., 2010, Shiembo 1996). It is a
lasting harvest that develops around 10 meters in length, with thick papery
like leaves developing in gathering of threes. The shade tolerant vine does not
develop well in direct daylight and can be discovered getting on center and
under story trees.
Edible
leaves of Gnetum species are sold in markets. It is for its food value that Gnetum is most prized. The leaves are
harvested and sold in local and international markets. Gnetum africanum
and Gnetum bulcholzianum value chain study gathered information on
stakeholders involved in the chain from forest to consumer (small scale
harvesters, traders, transporters, exporters and consumers) in Cameroun and
Nigeria revealed that at least two thousand five hundred and fifty people work
across the chain (Fuashi et al., 2010). Dependence upon gnetum based
incomes increased from those away from the forest, providing an average of 75%
of retailers (1,268US$) and 56% of exporters annual income of 7000US$ in Congo
(Ingram and Bongers, 2012).
The
seeds are specifically use as fungicides and in dressing fresh septic wounds
(Keatinge, 2012). It is also chewed raw in the administration of exorbitant pee
in juvenile diabetic patients in traditional medicine practice. Antioxidants
are believed to protect cells by mopping up excess free radicals in the human
body which otherwise could lead to oxidative stress (Isong et al., 2013).
Gnetum leaves have been reported to contain high levels of nutrients, minerals
and phytochemicals. Ekpo et al., (2011) reported that Gnetum
africanum contained 26.5% crude protein, 2.75% crude fat and 19.34%
carbohydrate, the levels of P, K, Mg, Ca and Fe were 0.14%, 0.1%, 0.925, 0.45%
and 1.15% respectively. The phylate and oxylate content of the gnetum leaves
were: 3.51mg/100g HCN, 6.12mg/100g phylate and 2.80 mg/100g tannin (Ekpo et
al., 2011). Leaves of gnetum have also been found to contain antioxidants
such as polyphenols, flavonoids, and carotenoids. Antioxidants are believed to
protect cells by mopping up excess free radicals in the body which otherwise
could have resulted in oxidative stress. The phytochemicals contained in gnetum
provide health benefits beyond normal health maintenance and nutrition, for
examples some of the antioxidants in gnetum such as the carotenoids are capable
of slowing down aging and preventing certain diseases such as cancer in humans.
Attah – Krah and Reynolds (1994) found that the chemical composition of
vegetables is dependent on the inherent genetic physiological difference
between vegetable species and the physico-compound properties of the earth on
which the vegetables were grown.
Antioxidants which occur in most leafy
vegetables slow down aging process and
prevent diseases such as cancer, Gnetum also is an important source of fiber,
essential amino acids, vitamins and minerals (Fadi et al., 2011).
According to El-Qudah (2008), Gnetum contain phytochemicals that provide
benefits beyond normal health maintenance and nutrition. One important class of
such phytochemical is the carotenoids. Carotenoids are lipid-soluble pigments
found in all photosynthetic organisms. Among the naturally occurring plant
pigments, carotenoids are widely distributed, with a high degree of structural
diversity and large variation in biological functions. There are more than 600
carotenoids found in nature, with 40 dietary carotenoids regularly consumed by
human being (Kopsell, 2006). They may also be esters or complexes with protein,
during proteolytic digestion, carotenoids are released from associated proteins
and aggregate with other lipids. In humans, it has been reported that between 5
and 50% of carotenoids contained are absorbed by the body (Rao, 2007).
The treatment of ailments with medicinal
plants is an age long practice by which local herbalists have depended on as a
reliable means of healing or minimizing diseases infections. The use of gnetum
plants for treatments of microbial ailments is notable and has been reported
since antiquated occasions (Bari et al., 2010). Availability of gnetum
vegetables is limited in areas where this vegetable is cherished because of low
production, poor soil and high demand that greatly surpasses supply (Ndomou et
al., 2014). Indigenous gnetum vegetables have long been part of traditional
diets in communities worldwide, yet many of these crops are underutilized and
their nutritional composition not adequately determined (Keatinge, 2012).
In some developing countries this crucial problem is accentuated by limited
resources available for research work and lack of attention by indigenous
scientists (FAO, 2008). In most growing economy nations majorities of the rural
populace include wild products in their daily diets.
The
volume of exports of leafy vegetables has significantly increased in recent
year (Shiembo, 1997). Gnetum grows throughout the year. Its price increases
slightly when the drought period is dominant as a result of slow growth during
this period and scarcity of other vegetables. Gnetum species add value to the
diet of many people particularly in south eastern Nigeria where it is for the
most part devoured. Iweala et al.,
(2009), expressed that gnetum leaves are esteemed as delicious vegetables when
finely destroyed and fused into soup and stew or made into fixings or even
accepted crude as plate of mixed greens.
Majority
of Gnetum vegetables available in the market are collected from the wild
(Akachuku, 2015), however limited efforts are currently being made by farmers
to cultivate the important vegetable in homestead farms as a way of improving
the economic status of these farmers and also making the vegetable available
the entire year. Gnetum species survive well in soil rich in plant nutrients.
As a climber, it survives in a forest ecosystem where there are trees/shrubs
which it climbs for support and which also serve as shade. (Anthony et al.,
2014)
Gnetum plants are dioecious; the male produce
catkins of stamens and the female produce catkins of ovules barely protected by
an envelope. Presently, two species of Gnetum are mainly consumed in Nigeria.
These two species are Gnetum bulchozianum and Gnetum africanum.
The differences in morphological characteristics between the two species are as
follows: frond of Gnetum africanum are shorter and narrower, ovate in
shape with an acuminate apex, light green in colour while those of Gnetum
bulcholzianum are longer and greenish in colour with higher percentage of
chlorophyll and more fresh looking with a broader lanceolate shape, acuminate
apex and an acute leaf base (Ekanem, 1998). Both gnetum species have
significant value in many forest based communities and have a number of vernacular
and trade names (Bahuchet, 1990). Efik and Ibibio call it “Afang”, Ikom calls
it “Nkani”, while the Igbos call it “Ukazi” (Ekanem, 1998).
1.2 STATEMENT OF PROBLEM
It has been established that over exploitation or overharvesting
threatens over 150 plant species of which most are medicinal plants (Lange,
1998). Recent increase in sales of gnetum underscores the growing popularity of
the species. However, habitat loss, habitat degradation and over harvesting are
some of the factors that pose unprecedented threats to availability of gnetum
(Hamilton, 1997).
Poor conservation method is another reason why this leafy
vegetable is increasingly threatened. Information on morphological
characteristics, chemical composition, leaf biomass and growth requirements of
gnetum species are scanty. This study sets out to fill this gap, provide the
information from the study area.
1.3 AIM OF THE STUDY
The aim of this study was to determine the
growth characteristics and nutrient composition of gnetum species in natural
and plantation forests in Umudike, Nigeria
1.4 OBJECTIVES OF THE STUDY
The goals of this work were:
1. To
identify the effects of weeding regime on gnetum species in rubber plantation
and growth characteristics of the two gnetum species under the two ecosystems
(relic forest and rubber plantation).
2. To
determine the leaf biomass of both species in the two ecosystems.
3 To
ascertain the different levels of shade on growth and development of gnetum
species in both habitats.
4. To
determine the chemical composition of the two gnetum species under the natural
ecosystem (relic forest) and man-made ecosystem (Hevea brasciliensis
plantation).
5. To
determine the characteristics of soils from the relic forest and rubber
plantation and their effects on gnetum growth and development in the two
ecosystems.
1.4
JUSTIFICATION
Most
of the forest food species are harvested from the wild without their
corresponding domestication (Akachuku, 2005). Forest resources are being lost
to major land uses such as agriculture, commercial logging, livestock grazing,
construction and mining. At the same time human population growth, migration
boundary wars, over harvesting etc. are placing increasing stress on the
remaining natural resources (Akachuku, 2004). Gnetum is a wild leafy vegetable
used as food and food supplement in most African countries. In recent times,
the medicinal and nutritional values of gnetum species have been neglected
without due regard to its potentialities in offering tremendous health
benefits. Because of its various kinds of biological activity, it is regarded
as a medicinal plant with anti-carcinogenic and anti-inflammatory properties.
This work will provide more information on the physico-chemical, phytochemical
and as well as growth performance of these species under natural and man-made
ecosystems. Availability of gnetum vegetable is limited even in areas where
this vegetable is cherished such as in Nigeria because of low production, poor
soil characteristics and high demand that greatly surpass supply (Ndomou et
al., 2014). Even though gnetum vegetables have long been part
of the traditional diet of many communities in West Africa, literature on the
nutrient composition of the crop is scarce (Keatinge, 2012). Scarcity of
information on some indigenous vegetables for instance Gnetum africanum
and G. bulchozianum in growing economy nations is being attributed to
limited resources available for research work and lack of interest by
indigenous scientists of those countries (FAO, 2008)
At the
level of exploitation of gnetum species, if conscious effort is not made to
conserve the species, the plant may soon be facing extinction. One of the
steps that could be taken to avoid extinction of this important vegetable is to
encourage more farmers to develop and propagate the crop on a sustainable
basis.
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