ABSTRACT
African
walnut (Plukenetia conophorum Muell Arg) is a member of the family
Euphorbiaceae. It is cultivated principally for the nuts which are eaten raw or
served as snacks after roasting or boiling. P. conophorum serves many
nutritional and medicinal purposes as well as good source of rural income.
Despite the potentials of this plant, its existence is threatened by
deforestation, urbanization and similar activities. The present study was
designed in an attempt to salvage this useful plant from extinction and provide
basis for its conservation. Four accessions of P. Conophorum were
collected from Abia, Anambra, Enugu and Rivers states, southeastern Nigeria.
The objectives of the research were to evaluate the effects of three manure
rates on juvenile growth stage of the accessions; determine the amino acid
profile of the kernels and investigate possible bio-diversity among the
accessions with respect to the seed physical traits and proximate components.
Four specific experiments were conducted to achieve the set objectives. Seed
physical traits (edible portion, pulp weight, seed volume, seed weight, pulp
(kernel) weight, seed circumference and seed coat thickness) were measured.
Standard laboratory procedures were employed in determining the proximate
composition (moisture content, ash, fat, crude protein, fibre and
carbohydrates) and amino acids profile of raw and boiled kernels. A pot
experiment was set up to evaluate the seedling emergence and growth responses
to three level of pig manure applications (0, 5. and 10t/ha). Data were
collected on days to seedling emergence, emergence percentage, vine length,
vine base girth, number of leaves per plant, number of branches, root volume
and dry matter yield and partitioning to the leaves, stem and roots. All the
data were subjected to Analyses of Variance (ANOVA) following the procedures
outlined for completely randomized design (CRD). Significant treatment means
were separated with the aid of F-LSD at 5% probability level. All statistical
analysis were done using Genstat 7.1 version 2003 software. Results indicated
that all the seed physical traits showed significant (P < 0.05) variation
across the four locations (states). Seeds from Enugu (74.08%) had the highest
edible proportion followed by Abia (70.68%) and Rivers (66.65%). Anambra
accession had the highest seed and pulp weight followed by Abia, Enugu and
Rivers, respectively. Seed coat thickness was higher in accessions from Abia
and Rivers States compared to others. The nutritional quality assessment
revealed that ash, fat and moisture varied significantly (P<0.05) among the
different accessions while carbohydrates, fibre and protein contents of the
seeds did not differ across the locations. The moisture and fibre contents
showed significant (P< 0.05) differences in the boiled and fresh seeds. Fibre
content was higher in the boiled seeds, whereas the fresh seeds had higher
moisture content.
The
ash, carbohydrate, fat and protein contents were not influenced by processing.
All the proximate contents of the seeds across locations did not differ in
their response to interaction of location and processing. Location showed no
significant effect on iso-leucine, leucine, phenylamine and tryptophane
contents of the seeds. Seeds collected from Rivers, Enugu and Anambra States
gave significantly (P< 0.05) higher histidine than those from Abia. Abia
accession has the highest lysine content compared with those from other
locations. Enugu and Rivers accessions gave significantly (P< 0.05) higher
methionine than those from Anambra and Abia State. Enugu and Abia accessions
recorded higher threonine content than Anambra and Rivers accession. The effect
of processing on essential amino acids showed that the histidine, isoleucine,
leucine, lysine, methionine, phenylamine, valine and threonine contents of the
seeds were not influenced by processing. Except for tryptophane, all the other
essential amino acids were found to be higher in the fresh seeds. The effect of
location on non-essential amino acids showed that alanine, arginine,
asparagine, glutamine and glutamic acid were significantly influenced by
location while aspartic acid, glycine, proline, serine, trimethlisine and
tyrosine did not vary among the locations. Seeds collected from Abia State gave
significantly higher alanine and arginine contents than those from other locations.
Asparagine content was significantly (P < 0.05) higher in seeds from Rivers
and Abia than those from Anambra and Enugu. Glutamine acid content of seeds
from Enugu and Anambra was higher than those from Abia and Rivers. The effect
of processing on the non-essential amino acid components showed that glutamine,
glutamic acid and trimethlisine contents of the seeds varied significantly (P
<0.05) with processing. Glutamic acid and trimethlisine contents were higher
in the fresh seeds whereas glutamine was higher in the boiled seeds. Alanine,
arginine, asparagine, aspartic acid, glycine, proline, serine and tyrosine did
not differ in their response to processing. Field growth performance evaluation
indicated that plant height, stem girth, number of branches and vine length
were all significantly (P < 0.05) improved with increasing manure rate. The
10 tonnes manure rate partitioned the greatest portion of the biomass to the
shoot in all the accessions.
TABLE OF CONTENTS
Title page
Table of contents
List of tables
List of figures
Abstract
INTRODUCTION
LITERATURE REVIEW
MATERIALS AND METHODS
Materials
Methods
Statistical Analysis
RESULTS
Discussion
Conclusion and recommendation
REFERENCES
INTRODUCTION
African Walnut (Plukenetia conophorum Muell Arg) is a member of the family Euphorbiaceae. It has been described as a semi-wild plant found naturally in the wild (Okigbo, 1977), or may be extensively encountered in rural dwelling and in farmlands where they are protected. Walnut (P. conophorum) is of African origin (Nwosu, 1979); hence “African” mostly attached to its common name. It is cultivated principally for the fruits (nuts) which is edible and are eaten alone or served as snacks with kola nut when boiled. Egharevba et al., 2005 also reported that the fruit is known in other African countries like Gabon, Sierra Leone, Cameroon, Madagascar and Central African Republic, where it provides income to the rural people consequently improving their economy and nutrition.
P. conophorum is a twining vine, and rarely sprawling herb, found in tropical wet andseasonally dry forest regions (Gillespie, 1993). The seeds are available in June-September when other fruits are scarce, throughout the southern states of Nigeria (Egharevba et al., 2005). As documented by Irvine (1990), the plant which is a perennial is also a climber requiring support of woody sticks to climb, grow and survive. The plant starts flowering between eighteen to twenty four months after planting. The importance of P. conophorum as an indigenous fruit climber is enormous as it is a multi-purpose crop. In most homes in southeastern Nigeria the fruits provide income to rural people, thereby improving their economy. The roots, leaves and seeds are said to have medicinal values (Johansen, 1950). The high nutrient potentials of the nut has been reported in literatures (Oke and Funsho, 1975; Ogunsua and Adebona, 1983). The plant also provides a microclimate within the forest as its branches spread on the canopy cover of forest trees (Egharevba et al., 2005).
The fruits are oil-bearing yielding 48-60% of light golden coloured oil which is similar to linseed oil. The oil is composed of 64% linolenic acid, 15% palmitic acid and stearic acids, 11% oleic acid and 10% linoleic acid. The oil is also known as conophor oil, and is useful in paint or varnish industry. It is edible and could be used in food preparations (Burkill, 1984). There is also a report that the cake left after extraction of the oil contains 45% protein, and has local uses for food and is obviously a good source of protein. It can be fed to livestock (Burkill, 1984).
Plukenetia conophorum is one of the non-wood forest products, which are essentially part of the forest products. According to Osemeobo and Ujo (1999), these non-wood forest products provide a safety net for most rural dwellers in many third world countries including Nigeria,
Increases in production and availability of African walnut just like other semi-wild indigenous species, can only be possible when suitable production practices are exploited coupled with enough biochemical and biophysical knowledge. At present, there is paucity of information on the regeneration and perpetuation of this very important plant. The walnut is still in the wild. There is no evidence of efforts to fully domesticate this useful plant. The high rate of forest destruction affects their habitat. The plant could face possible extinction in the very near future. To salvage this useful plant from extinction and provide basis for its conservation, the present study was undertaken. With increased recent interest in the exploitation, conservation and domestication of less common forest products, it is important to examine the African walnut in order to ascertain its full usefulness. The objectives of this research are:
1) Evaluation of the effects of three manure rates on early growth stages of four accessions of African walnut;
2) Determination of the amino acid profile of kernels from four different accessions; and
3) Investigation of possible bio-diversity among accessions collected from different locations (states) of southeastern Nigeria, with respect to the seed physical traits and proximate components......
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