1.1 Introduction
Ultraviolet light is extremely important for plant growth. In safe doses, it helps plants and crops produce essential plant oils which not only enhance the flavour and smell of fruit but also helps the plants protect themselves from excessive ultraviolet exposure; acting as their own natural sun block. This natural protection ensures that the internal processes of the plant are protected and ensures optimal growing conditions. Ultraviolet is radiation on both the visible and non-visible spectrum, the shorter the wavelength, the less visible and harmful it can be. There are three different kinds of ultraviolet radiation based on wavelength. UV-A radiation (from 315 to 420 nm) - Barely visible to the human eye, UV-A has the longest wavelength, is the least harmful to the human eye and is the most efficient.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
The amount of ozone in the stratosphere over middle latitudes in the northern hemisphere has declined since 1978 (Stolarski et al. 1992). Assuming full compliance with the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer and its 1992 amendments, it is predicted that ozone depletion at northern mid-latitudes will peak at the turn of the century and be 12–13% less in winter}spring and 6–7% less in summer}autumn relative to 1960 (Madronich et al. 1994). Stratospheric ozone will return to pre-depletion concentrations by the end of the 21st century (Madronich et al. 1994). However, continued implementation of the Montreal Protocol remains uncertain (Greene 1995; Jordan 1995) and factors other than the concentration of ozone depleting substances may place the ozone layer at risk. Other factors remaining constant, ozone reductions are accompanied by predictable increases in surface ultraviolet B radiation (UV-B, 280–315 nm). In recent springs, episodic ozone losses have been associated with significant increasesing round-levelUV-Binanumber of European countries, including the United Kingdom (UK) (DoE 1996).
Many experiments have shown that plants can be damaged or otherwise affected by UV-B radiation (Tevini 1993). However, 80% of the studies of plant responses to UV-B published up to 1994 were conducted in controlled environment (CE) chambers or glasshouses (Caldwell & Flint 1994). In these experiments, plants usually received daily integrated doses of photo synthetically active radiation (PAR: 400–700 nm) and UV-A (315–400 nm) much less than summer sunlight: conditions which tend to exaggerate plant responses to UV-B (Caldwell & Flint 1994; Teramura & Sullivan 1994; Fiscus & Booker 1995). In field experiments, ambient solar UV-B was either reduced using wavelength-selective filters or supplemented by radiation from UV-B-emitting lamps. When artificial UV-B sources were used, incident solar UV-B was supplemented either by a fixed dose-rate (‘squarewave’) addition or a variable (‘modulated’) addition that was a constant proportion of the ambient dose (or of the dose incident on a control plot).
A typical square-wave system provides supplementary UV-B radiation at one or two fixed dose-rates for a certain number of hours centred on solar noon. It takes no account of variation in cloud cover and provides an addition based on the modelled consequences of ozone depletion under clear sky conditions. Squarewave systems thus tend to provide UV-B additions greater than those expected from any realistic prediction of future ozone losses, and so are likely to over-estimate the effects of stratospheric ozone loss on crop production. Fiscus & Booker (1995) pointed out that a proper understanding of crop responses could only be obtained from field experiments that simulate the consequences of likely ozone loss and, in particular, from those using ‘modulated’ lamp systems, which provide a more realistic increased UVB environment. Unfortunately, modulated systems are technically more complex and expensive than square-wave systems and have not been widely used (Caldwell & Flint 1994).
Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Effect of Ultraviolet Light on Plant Development and Fruit Production.
1.3 Statement of Problems
Irrespective of UV-B delivery system, most agricultural UV-B field experiments have been performed under conditions unlike those in the UK. An exception is the study of four cultivars of pea (Pisum sativum L.) in which increases in UV-B equivalent to a 15% ozone depletion reduced yield by an average of c. 10% (Mepsted et al. 1996). However, the experiment of Mepsted et al. (1996) was limited to one season and results may have been influenced by particular conditions during that season, for example late sowing, the unusually dry conditions and pathogen attack. The present study aimed to extend the observations of Mepsted et al. (1996) to a second year and to consider barley (Hordeum vulgare L.), a crop of greater economic significance in the UK (cultivated areas in 1994: pea 124000 ha, barley 1106000 ha; FAO 1996).
1.4 Aim and Objectives of Study
The aim of the study is to investigate the Effect of Ultraviolet Light on Plant Development and Fruit Production. In achieving this aim, the following specific objectives were laid out as follows:
- To present an assessment and statistical power of the experiments on plant development.
- To estimate the interaction species and different levels of UV-B radiation.
- To assess the effect of UV-B radiation on some morphological and physiological traits of plant development.
- To evaluate the effects on plant growth, yield pigment composition or chlorophyll fluorescence variables.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- Is there any significant effect on growth, pigment composition or chlorophyll fluorescence variables?
- What do you understand by statistical power of the experiments on plant development?
1.6 Research Hypothesis
In order to pursue the objective of this study, the following generalized statements have been designed to guide and aids in obtaining the result for the experiment to be conducted. For this work, the null hypothesis will be represented with H0 while the alternative hypothesis will be represented with hypothesis H1.
- H0: There is no significant effect on plant growth, yield, pigment composition or chlorophyll fluorescence variables.
- H1: There is a significant effect on plant growth, yield, pigment composition or chlorophyll fluorescence variables.
1.7 Significance of Study
This study will be of great importance to the society as well as the nation at large because of its scientific, social, economic, and technological value particularly the agriculture. This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.8 Scope of Study
The study focuses on the Effect of Ultraviolet Light on Plant Development and Fruit Production in Nigeria.
1.9 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet).
