INFLUENCE OF DIFFERENT LIGHT INTENSITIES ON THE GERMINATION AND EARLY GROWTH OF Treculia Africana
ABSTRACT
This study was carried out to investigate the effect of different light intensities on the germination and early growth of Treculia Africana under different light intensities (100%, 60%, and 40% light intensities) as well as under forest canopy (control I), open nursery condition (control II). The experiment was carried out at the tree nursery site of the Department of Forestry and Wood Technology, Federal University of Technology, Akure, and lasted for eighteen weeks. T. Africana fruits were collected from the Forestry Research Institute of Nigeria, Jericho hills, Ibadan. Both germination and early growth characteristics (total height, collar diameter, number of leaves, and biomass production) of the seedlings were monitored. A higher value of plant height was recorded under 40% and 60% light intensities while seedlings grown under higher light intensities (open nursery condition and 100% light intensity) showed higher values in both collar diameter and the number of leaves. The results also indicated that T. Africana seedlings Planted under a high light environment (open nursery condition and 100% light intensity) had more biomass accumulated than those recorded under a low light environment (40% and 60% light intensities). Faster growth in stem height may be achieved by subjecting T. Africana seedlings to a low light environment but will result in the spindle and fragile stem, due to their low collar diameter. Collar diameter, number of leaves, and biomass accumulation will be higher for T. Africana seedlings under higher light intensities (open nursery condition and 100% light intensity), with the shorter but more stable and less fragile stem. As a result of this, it has come to light that better T. Africana would be produced under a high light environment. Domestication and cultivation of T. Africana will be enhanced using information from this study.
TABLE OF CONTENTS PAGE
ABSTRACT ii
CERTIFICATION iii
iv
DEDICATION
ACKNOWLEDGEMENT v
TABLE OF CONTENTS vi
LIST OF TABLES viii
LIST OF FIGURES ix
LIST OF PLATES x
CHAPTER ONE 1
1.0 INTRODUCTION 1
1.1 General 1
1.2 Statement of Problem 5
1.3 Objectives 6
1.4 Justification 6
1.5 Scope of Study 7
CHAPTER TWO 8
2.0 LITERATURE REVIEW 8
2.1 Description of Treculia Africana 8
2.2 Ecology and distribution 8
2.2.1 Habitat and Distribution 8
2.3 Propagation and management 9
2.3.1 Propagation by Seeds 10
2.3.2 Stem Cuttings 11
2.3.3 Coppicing 11
2.4 Functional uses 12
2.4.1 Products 12
2.4.2 Services 14
2.5 Conservation of forest genetic resources 14
2.6 Opportunities for commercial development of edible forest species 15
2.7 seed germination and tree growth 16
2.7.1 Requirements For Seed Germination 18
2.8 Factors Affecting Survival and Early Growth of Seedlings 21
2.9 Effects Light Intensities on Seed Germination and Early Growth of Seedlings 21
CHAPTER THREE 23
3.0 METHODOLOGY 23
3.1 Experimental site 23
3.2 Fruit collection 23
3.3 Seed extraction/Processing 24
3.4 Experimental Procedure 25
3.5 Biomass Estimation 27
3.6 Experimental Design 29
3.7 Statistical Analysis 30
CHAPTER FOUR 31
4.0 RESULT AND DISCUSSION 31
4.1 Results 31
4.1.1 Germination Rate 31
4.1.2 Seedlings growth characteristics 33
4.1.2.1 Mean Height 33
4.1.2.2 Mean Colar Diameter 35
4.1.2.3 Mean Number of leaves 37
4.1.5 Biomass Estimation 39
4.1.5.1 Leaf Biomass 39
4.1.5.2 Stem Biomass 42
4.1.5.3 Root Dry Weight 43
4.2 Discussion 45
CHAPTER FIVE 48
5.0 CONCLUSION AND RECOMMENDATION 48
5.1 Conclusion 48
5.2 Recommendation 48
REFERENCES 50
APPENDICES 59
CHAPTER ONE
1.0 INTRODUCTION
1.1 GENERAL
Non-timber forest products (NTFPs) are wild plant and animal products harvested from forests,
such as wild fruits, vegetables, nuts, edible roots, honey, palm leaves, medicinal plants, poisons
and bush meat. They are all non-timber resources that are extractable from forests, which have
economic, cultural and social values and are utilisable in households (FAO, 1990). NTFPs add to
peoples’ livelihood security, especially the rural dwellers who depend on them. Non-timber
forest products (NTFP) are also considered as any commodity obtained from the forest that does
not necessitate harvesting trees. It includes game animals, fur-bearers, nuts and seeds, berries,
mushrooms, oils, foliage, medicinal plants, peat, fuelwood, forage, etc (Emery et al, 2001).
Millions of people – especially those living in rural areas in developing countries – collect these
products daily, and many regard selling them as a means of earning a living (Tinde van Andel,
2006).
Non-timber forest products (NTFPs) were long considered as minor forest resources. Economic
studies of forest management generally ignored the subsistence these resources provide local
populations. Only recently has NTFPs attracted the attention of researchers, particularly those
concerned with tropical forests (Lescuyer, 1996). These studies have confirmed that the forest
ecosystem generates other resources which also have economic values apart from the well know
timber that are popularly harvested (Karsenty and Maîtres, 1995).
For centuries, humans around the world have relied on products derived from forest species for
their survival and well-being. NTFPs harvesting and utilisation remains widespread throughout
the world. People from diverse income levels, age groups, and cultural backgrounds harvest
NTFPs for household subsistence, maintaining cultural and family traditions, obtaining spiritual
fulfilment, maintaining physical and emotional well-being, scientific learning, and earning
income. NTFPs serve as raw materials for industries ranging from large-scale floral greens
suppliers and pharmaceutical companies to micro-enterprises centered around basket-making,
woodcarving, medicinal plant harvesting and processing, and a variety of other activities.
Estimating the contribution of NTFPs to national or regional economies is difficult due to the
lack of broad-based systems for tracking the combined value of the hundreds of products that
make up the various NTFP industries.
In tropical forests, NTFPs can be an important source of income that can supplement farming or
other activities. A value analysis of Amazonian rainforest in Peru found that exploitation of
NTFPs could actually yield higher net revenues per hectare than timber harvest of the same area,
while still conserving vital ecological services. Their economic, cultural, and ecological value
when considered in aggregate makes managing for NTFPs an important component of
sustainable forest management and the conservation of biological and cultural diversity (Encarta,
2011).
Treculiaafricana (African breadfruit, African boxwood or Wild jackfruit) belongs to the mono
specific genus TreculiaDecne. Ex Trec which is one of the fifteen genera of plants belonging to
the tribeArtocarpeae in the Mulberry family (Moraceae) (Keay, 1989). This species is largely
13
cultivated within the rainforest belt of West, Central and East Africa (Keay, 1989). It is an
evergreen forest fruit tree species (Onyekwelu and Stimm, 2008). The plant produces large,
usually round and compound fruits covered with rough pointed outgrowths (Keay, 1989;
Onyekwelu and Stimm, 2008).
Treculiaafricanahas very large simple and alternate leaves. The leaves, which are about 30
(max. 50) x 14 (max 20) cm in dimension, are dark green in colour. The leaves are smooth above
with tough, paler below with some hiars on the 10-18 pairs of clear veins with a pointed tip
(Rohwer, 1993; Orwa et al 2009). Treculiaafricana has compound, rounded, very large fruits,
on the trunk or main branches, containing many orange seeds, about 1 cm, buried in spongy pulp
of the fruit. The outer surface is covered with rough pointed outgrowths. The fruit attains 40 cm
in diameter and weighs 8-14 kg (Orwa et al 2009).
Based on detailed field observations, 3 varieties have been recognized, which are: T. africana
var. africana, T. africana var. inversa and T. africana var. Mollis (Chris Chinaka, 1998). Their
taxonomic differences are based mainly on the size of the fruit head (infructence) and the
hairiness of branchlets and leaves. There is a striking variation in the number of fruit heads
produced by trees belonging to T. african var. africana (with large fruit heads) and T. African
var.inversa (with small fruit heads). The former is clearly superior in the weight of seeds
produced while the latter produces more fruit and also produces twice as many branches
(Nwokolo, 1987; Omobuwajo et al., 1999; Orwa et al 2009).
Treculiaafricanaand other forest food plants like Pentachlethramacrophylla (oil bean seed),
Dacryodesedulis are of high nutritional value which needs to be introduced or added to our food
materials consumed (Edet et al., 1985; Nwokolo, 1987). The importance attached to them is due
to the fact that many of them are usually available at strategic period of the year when annual
crops that are difficult to store are unavailable or scarce (Okafor, 1978).
Despite the socio-economic importance of Treculiaafricana to a very large population of the
people of southern Nigeria, it is still a protected crop and a semi domesticated species. Increase
in human population and agricultural practices have put pressure on the forest thereby depleting
some genetic resources, Treculiaafricana being a good example. To prevent total loss or
extinction of important forest food tree species, especially those that are endangered, they must
be cultivated more intensely (Baiyeri, 2003; Ugwunze, 2003).
While seed germination and plant growth are regulated internally, they are greatly influenced by
external conditions such as the intensity and duration of light and temperature. Aside from its
effect through photosynthesis, light influences the growth of individual organs or of the entire
plant in less direct ways. The most striking effect can be seen between a plant grown in normal
light and the same kind of plant grown in partial darkness or total darkness. The plant grown in
the partial dark or total dark will have a tall and spindling stem. The leaves fail to expand, and
both leaves and stem, lacking chlorophyll, are pale yellow. Such a plant is said to be etiolated
(Dennis Holley, 2009)
Both the intensity and duration (length) of light may have different and characteristic effects
upon plant growth and development. It has been found that the length of the daylight period may
have a striking effect upon vegetative growth and reproductive activities of plants. The reaction
of plants in relation to the length of the day is called photoperiodism(Dennis Holley, 2009)
This study is carried out to investigate how Treculiaafricanaseeds and seedlings respond to
various light intensities and to also monitor the early growth characteristics and habits of the
seedlings of the species under three different light intensities using three screen houses, which
are compared with the performance of seeds and seedlings of the species sown and planted under
open nursery condition as well as under forest canopy.
1.2 STATEMENT OF PROBLEM
Despite the economic, nutritional, cultural and social importance of Treculiaafricana, especially to
rural dwellers that depend on them, ithas been greatly neglected, especially with respect to their
regeneration. The yield of current crop of trees is decreasing due to old age and the fact that it has
been harvested for decades. Thus, if the current practice of allowing T. africana to grow in the wild
is allowed to continue without deliberate silvicultural interventions, the probability of obtaining its
valued products on a sustained basis will be very low. Due to lack of care and old age, a lot of the trees of the species have died or are in the process of doing so, thus the species is classified among
the endangered tree species in Nigeria (FORMECU, 1999), with a high possibility of going into
extinction in the near future except something is done to increase its population. Allowing the
species to go into extinction will endanger the livelihood of millions of rural dwellers in Nigeria and
reduce the rich biological diversity of the ecosystem. Artificial regeneration and subsequent
improvement (domestication) appears to be a very viable option of saving the species from
extinction and ensuring that its products are supplied on sustained basis. The need to rapidly
domesticate tropical forest food tree species has been stressed and is now one of the three pillars
of the International Centre for Agroforestry Research (ICRAF) program (Leakey and Simons,
1998).
Seed germination and early growth of forest seedlings is affected by some factors such as light
intensity, air, temperature, water, soil condition, etc. Except these factors or their combinations are
provided at the right time and in good quantity, seed germination and growth of seedlings may be
adversely affected. Till date, research work on the effect of light intensity of the germination of T.
africana seeds and the early growth of its seedlings is scanty, which is the focus of this study.
1.3 OBJECTIVES
The general objective of this study is to investigate the effect of different light intensities on seed
germination and early growth rate of Treculiaafricanaseedlings.
The specific objectives are:
a.To investigate the germination potential of Treculiaafricana seeds under different
light intensities.
b.To assess the influence of light intensity on survival and early growth performance
of Treculiaafricanaseedlings.
1.4 JUSTIFICATION
Research on domestication of forest food tree species is still at a preliminary stage. Specifically,
efforts on domestication of T. africana only covers seed storage and germination, vegetative
propagation, germplasm collection, priority setting exercise, integration into agroforestry,
economic and nutritional importance, selection of multiple traits for potential cultivars, (Okafor,
1991; Leakey and Simons, 1998; Enibe, 2003; Leakey et al., 2003; Kumar and Nair, 2004;
Onyekwelu and Fayose, 2007; Onyekwelu and Stimm, 2008). Till date no known work on the
effect of different light intensities on seed germination and early growth rate of T. africana
seedlings has been carried out, though it has been established that light intensity affects seed
dormancy breakage, seed germination, early growth performance, etc of seedlings. This
underscores the need for a study that will investigate the effect of various light intensities on the
germination and early growth rate of T. africanaseedlings, which is the focus of this study. It is
believed that this will aid the selection of the most appropriate light intensity that will facilitate
the highest and regular seed germination as well as the fastest growth rate. In this study, nursery
experiment with the seeds of T. africana will then be conducted to investigate the germination
and early growth characteristics of the seedlings of the species under three different light
intensities using three screen houses.
1.5 SCOPE OF STUDY
The research work was carried out at the nursery site of the Department of Forestry and Wood
Technology, Federal University of Technology Akure, Nigeria. Treculiaafricana fruit was
obtained from Forestry Research Institute of Nigeria from which the seeds were extracted. Four
hundred (400) seeds of Treculiaafricanaweres sown in each of the three screen houses which
allows 40%, 60% and 100% light intensities. Also, 400 seeds were sown in open nursery
condition (i.e. outside the screen house) as well as under forest canopy, which served as controls
1 & 2, respectively. Seed germination as well as early growth characteristics of the seedlings,
such as survival, collar diameter, height, root length, number of leaves and biomass. were
monitored for Eighteen weeks.
.