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THE EFFECT OF DIFFERENT LIGHT INTENSITIES ON THE GERMINATION AND EARLY GROWTH OF CHRYSOPHYLLUM ALBIDUM SEEDLINGS

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Non-Timber Forest Products (NTFPs) are used by billions of people around the world for different purposes. They have immense economic, nutritional, cultural, and social importance, especially to rural dwellers that depend on them (Okafor, 1991; Shiembo et al., 1996; Adisa, 2002). Thus, they add to the peoples' livelihood security, especially the rural dwellers, who tend to share a sort of cultural connection and significance with their forests and the NTFPs from them. Although there is a growing understanding of the importance of NTFPs amongst international and national governments, its importance has not been fully introduced within government frameworks and rural development measures. In Nigeria, NTFPs have always served as life support for many rural dwellers, especially those who live in and around the forests. However, the importance of NTFPs was only brought to limelight within the past few decades (Byers et al., 2001; Sunderland et al., 2004). They are therefore, a major part of livelihood earning in Nigeria, in both the rural and urban sectors – implying that NTFPs have the potentials to play a major role in alleviating the livelihood challenges of the country's rural poor which constitutes a little above half of its population.

Traditionally, tropical forests have provided Non-Timber Forest Products (NTFPs) such as fruits, vegetables, medicines, etc to rural people for centuries. There are indigenous tree species everywhere in the tropics that produce locally important fruits and other Non-Timber Forest Products that have potential to be domesticated to provide food, social-cultural, medicinal, economic, and livelihood benefits to subsistence farmers (Leakey and Simons 1998). As rural households become more integrated into formal market, the proportion of the contribution of non-timber tree products (NTFP) to household income increases (Ruiz-Perez et al. 2004). A few indigenous fruits trees products have large market potential in Nigeria. Households use indigenous fruits to diversify their income and the benefits from selling indigenous fruits come at a critical time when income is generally low, and provides nutrition and food when agricultural labor demands are high (Mithofer, 2005).

Local plantings, product development, and market expansion are the first steps in domesticating indigenous fruit trees in their fields, homesteads, and communal lands (Maghembe et al. 1998, Leakey et al. 2004), adapting them to their needs and environmental conditions by deliberately or inadvertently selecting for certain characteristics. Domestication involves accelerated and human-induced evolution to bring species into wider cultivation through a farmer-driven and market-led process (ICRAF 1997). However, without an expanded or new market, the incentives to domesticate indigenous fruit trees are not sufficient (Simons and Leakey, 1998; Akinnifesi et al. 2006). Improvements in tree yield and earlier fruiting of indigenous fruit tree create incentives for farmers to cultivate indigenous fruits and, that household vulnerability to hunger and poverty can be reduced (Mithofer and Waibel 2003; Mithofer et al., 2006).

Chrysophyllum is a genus of about 70-80 species of tropical trees, growing to a height of 10-20 m. The genus is native to tropical regions throughout the world, with the greatest number of species found in North and South America. One species, Chrysophyllum oliviforme, extends from North to Southern Florida. Chrysophyllum albidum is one of the most popular species within the Chrysophyllum genus. Chrysophyllum albidum (also known as African star apple) belongs to the family of Sapotaceae (Keay, 1989). It is primarily a forest tree species and their natural occurrences have been reported in Nigeria, Cote d'Ivoire, Cameroon, Uganda, Kenya, Sierra Leone, Central African Republic, Democratic Republic of Congo, etc (Bada, 1997; Boateng and Yeboah, 2008; Onyekwelu and Stimm, 2011).

Chrysophyllum albidum is among forest tree species that provide NTFPs of immense domestic importance to rural and urban dwellers in West Africa, with great export potentials (Nwoboshi, 2000). The fruit pulp is widely consumed and thus plays an important role in food security. Apart from serving as a delicacy and an alternative source of food during the "hungry season" (i.e., November to April, when farm crops are planted), it also provides an alternative source of income and rural employment through the collection and sale of the fruits. Chrysophyllum albidum has been noted to be of great nutritional, social, and medicinal importance (Okigbo, 1978; Okafor, 1979). Reports have shown that the economic importance of C. albidum has increased in recent years due to awareness of its nutritional and medicinal value (Afem, 2000).

However, the immense economic importance, the increasing demand as well as the price for the fruit, etc has led to intense exploitation pressure on the tree species, which has resulted in its stocks diminishing at an alarming rate. Consequently, C. albidum, along with other important fruit tree species like Irvingia gabonensis and Treculia africana has been classified as a highly endangered or threatened tree species (Sarumi et al., 1996; FORMECU, 1999). For sustainable provision of the fruits, domestication of this species is inevitable. According to Finkeldey and Hattemer (2007) the three important elements of domestication are inventory, selection and change of the reproduction system. The study evaluates the effect of different light intensities on the germination of the C. albidum seeds as well as the early growth of its seedlings under different light intensities.

Light influences the growth of plant seedlings. While some plant species survive under low light intensity, other plant species survive under high light intensity. The importance of light to plant is significant because it goes a long way to affect the physiological processes such as stomata action, germination, chlorophyll formation, and transpiration (Nwoboshi, 1982). Therefore, this study focuses on the effect of various light intensities on germination of C. albidum seeds as well as on the early growth of its seedlings under greenhouse environment. It is expected that this will contribute to our understanding of the ecological mechanism of plant growth and their distributions (Anjana, 2010) as well as understand the effect of light on seed germination and early growth performance of tree seedlings.

1.2 Statement of the problem

Despite the importance of C. albidum, and other forest food tree species, they have been greatly neglected, especially with respect to their regeneration and domestication. The yield of the current crop of trees is decreasing due to old age and the fact that they have been harvested for decades. Thus, if the current practice of allowing C. albidum, to grow in the wild (i.e. naturally) and without deliberate silvicultural interventions is allowed to continue, the probability of obtaining their much valued products on a sustained basis will be very low. Due to lack of care, a lot of the trees of the species have died or are in the process of doing so. In Nigeria, C. albidum is classified among the endangered tree species (FORMECU, 1999), with a high possibility of going into extinction in the near future except something is done to conserve them or increase their population. Artificial regeneration and subsequent improvement of the species (domestication) appear to be a very viable option of saving the species from extinction and ensuring that its products are supplied on a sustained basis. Consequently, this study proposes to investigate the seed germination and early growth of C. albidum seedlings under different light intensities under controlled environment (screen house) in the nursery as a first and necessary step towards the domestication of the species. It is hoped that this will lead to a good understanding of the silviculture of the species.

1.3 Objective of the study

The general objective of this study is to examine the effect of different light intensity on seed germination and early growth rate of Chrysophyllum albidum seedlings.

The specific objectives are to;

Investigate the germination potentials of C. albidum seeds under different light intensities in a controlled environment (screen houses), open nursery conditions (control I), and under forest canopy (control II)

Raise and monitor the survival, and early growth characteristics of the seedlings of C. albidum under three different light intensities, open nursery conditions (control I) as well as under forest canopy (control II).

1.4 Justification

Nigeria's tropical rainforest and derived savanna ecosystems serve as habitat for C. albidum because of their favorable ecological condition that readily support the growth of the species. However, there is a need for further domestication because of an increase in the demand trend of its product and the fact that the current tree crops are old and over-exploited. The success of any initiative to obtain good fruits is no doubt an important step towards the domestication of C. albidum that would provide good fruits and seeds (Okafor, 1991).

Although some investigations have been carried out on C. albidum fruit and seeds (Okafor, 1991; Adebisi, 1997; Bada, 1997; Onyekwelu and Akindele, 2002; Onyekwelu and Fayose, 2007), no documented study on the silviculture of the species in the nursery, especially the germination of the seeds and early growth rate of the seedlings under different light intensities exist. Nursery investigation of the growth characteristics of the species should be the next step in the effort to domesticate the species, which is the focus of this project work. This study will investigate seed germination and early growth characteristics of the Chrysophyllum albidum seedlings under different light intensities in the nursery.

1.5 Scope of the study

This research work was carried out at the nursery site of the Department of Forestry and Wood Technology, Federal University of Technology Akure, Nigeria. Chrysophyllum albidum seeds were sown in poly pots filled with forest topsoils. The seedlings were raised inside three different screen houses of varying light intensities (40%, 60%, and 100%), under forest canopy (control I) as well as open nursery condition (control II). The seeds were collected from mother trees of the species in the tropical rainforest of Nigeria. Seed germination as well as the early growth rate of the seedlings were monitored for twelve weeks.