ABSTRACT
The effects of auxins and cytokinins at different concentrations rations on the growth and yield parameters of three genotypes of cassava were investigated. Randomized complete block design (RCBD) was used with three replications and genotypes consisted of TME 419, CR 41-10 and UMUCASS 36. The treatments used were auxins (α- naphthalene acetic acid at 0, 0.01 and 0.02mm ) and cytokinins (6-benzyladenine at 0, 0.02 and 0.05mm). The growth regulators were medially applied to the cutting and allowed to dry for 30minutes before planting. Data collected was subjected to analysis of variance using GenSTAT statistical tool. The result of the experiment showed that the plant growth regulators has significant increase for tuberization of cassava plant but showed no significant effect on the growth parameters at 3month after planting. The result revealed that increase in the concentration of auxins have positive effect on the yield parameter but cytokinin showed negative effect with increase in the concentration. Treatments with 0.02mM auxins induced the greatest increase in root weight, biomass and root number of M. esculenta, thereby suggesting that auxins at 0.02mM concentration could thus be used to enhance tuberization of cassava plant.
TABLE OF CONTENTS
Title page - - - - - - - - - - i
Certification - - - - - - - - - - ii
Declaration - - - - - - - - - - iii
Dedication - - - - - - - - - - iv
Acknowledgements - - - - - - - - - v
Table of contents - - - - - - - - - vi
List of Tables - - - - - - - - - viii
List of Figures - - - - - - - - - ix
Abstract - - - - - - - - - - x
CHAPTER ONE:
INTRODUCTION - - - - - - 1
1.1 Justification of Study - - - - - - - 4
1.2 Objectives of the study - - - - - - - 4
CHAPTER TWO:
LITERATURE REVIEW - - - - - 5
2.1 Botanical Description of Cassava - - - - - - 5
2.2 Evolution, Domestication and Distribution
of Cassava - - - 7
2.3 Ecology
and Agronomy of Cassava - - - - - - 9
2.4 Botanical
characteristics of cassava - - - - - - 11
2.5 Role
in the modern economy - - - - - - - 12
2.6 Cassava production in Nigeria - - - - - - 13
2.7 Cassava Uses - - - - - - - - - 14
2.8 Growth
Responses - - - - - - - - 15
2.8.1 Auxins - - - - - - - - - 15
2.8.2 Cytokinins - - - - - - - - - 17
CHAPTER THREE:
MATERIALS AND METHODS - - - - 18
3.1 Experimental
site, Climate and Soil composition - - - - 18
3.2 Plant
Growth Regulators Experiment - - - - - 18
3.2.1 Experimental design and Intercultural
operations - - - - 18
3.2.2 Planting materials and the treatment - - - - - - 18
3.3 Data collection - - - - - - - - 21
3.4 Data analysis - - - - - - - - - 23
CHAPTER FOUR: RESULTS - - - - - - - 24
CHAPTER FIVE:
DISCUSSION AND CONCLUSION - - - - 29
5.1 Discussion - - - - - - - - 29
5.1.1 The Effect of NAA and BA Concentration on
growth parameters - 29
5.1.2 Effects of auxin and cytokinin on
tuberization of cassava - - 29
5.2 Conclusion - - - - - - - - - 31
References - - - - - - - - - 32
Appendice - - - - - - - - 39
LIST OF TABLES
Table 4.1: Effect
of Auxins and cytokinins concentrations on the growth
parameters of different cassava genotypes at 3month after planting - 25
Table 4.2: Effect
of Auxins and cytokinins concentrations on the yield
parameters of different cassava genotypes at 3month after planting - 26
LIST OF FIGURES
Figure
2.1: Chemical structure of auxins - - - - - - 16
Figure
2.2: Chemical structure of
cytokinnin - - - - - 17
Figure 4.1: Effects of
different concentration of auxins and cytokinins on
Harvest index of three cassava genotypes. - - - - 27
LIST OF PLATES
Plate 3.1: Picture showing (A) Cassava cuttings soaked in plant growth
regulator (Auxins/cytokinins) (B) Hand weighing scale used to obtain total
weight of the plant (C) Sensitive weighing balance (D) cassava roots being
weighed on sensitive weighing balance - - - - - - - - 22
Plate 3.2: Picture showing the layout of the experimental field
containing the three cassava genotypes. - - - - - - - - - 28
Plate
3.3: Picture showing how the total weight of the cassava plant was taken with
the help of hand weighing balance. - - - - - - - 28
Plate 4.1: Pictures showing the tuberization of the three cassava
genotypes as affected by the treatments. - - - - - - - - - 26
CHAPTER ONE
1.0 INTRODUCTION
Cassava (Manihot esculenta Crantz) is a woody perennial
shrub grown for its starchy tuberous roots. Cassava belongs to the
Euphorbiaceae which also contains other commercially important plants like
castor bean (Ricinus communis L.) and rubber (Havea brazilienesis L.). The genus Manihot
comprises 98 species and all the species studied so far have a chromosome
number of 2n=36 (Rogers, 1963; Rogers and Appan, 1973; Nassar 1978; Hersey,
1983; Bai et al., 1993). The plants
contain lacitifers and produce latex, and M.
glazioviiis used as a minor source of
rubber (Cock, 1985). Cassava is native to tropical South America, and is one of
the oldest cultivated crops (Jennings, 1976) with possibly two centers of
origin. Since cassava does not exist in the wild states and its wild
progenitors are not known, the regions of its domestication are disputed
(Renvoize, 1972; Rogers and Appan, 1973; Rogers and Flemming, 1973; Nassar,
1978). From Latin America cassava was introduced to Africa in the 16th
century and today it is cultivated worldwide in more than 80 countries between
300 South and 300 North of the equator.
Cassava (Manihot esculenta Crantz) is cultivated mainly
in the tropical and sub-tropical regions of the world, over a wide range of
environmental and soil conditions. It is very tolerant of drought and heat
stress and produces well on marginal soil. It is an important dietary staple in
many countries, within the tropical regions of the world (Perez and Villamayor,
1984), where it provides food for more than 800 million people (FAO, 2007). As
a subsistence crop, cassava is the third most important carbohydrate food
source in the tropics after rice and maize, providing more than 60% of the
daily calorific needs of the populations in tropical Africa and Central America
(Nartey, 1978).
According to Alexandratos (1995), cassava plays an important role in
alleviating food problems, because it thrives and produces stable yields under
conditions in which other crops fail. Cassava is a versatile crop and can be
processed into a wide range of products such as starch, flour, tapioca,
beverages and cassava is also gaining prominence as an important crop for
emerging biofuel industry and, as corroborated by Ziska et al. (2009) is a potential carbohydrate source for ethanol production.
A well planned strategy for the development and utilization of cassava
and cassava products can provide incentives for farmers, crop vendors and food
processors to increase their incomes. It can also provide food security for
households producing and consuming cassava and cassava products (Plucknett et al., 1998).
Traditionally, cassava has been grown by farmers throughout the Bahama
Islands and has been of particular importance to small farmers of the central
and southeastern islands, where it is still cultivated. It is a crop that is
generally grown on marginal lands with a minimum of agricultural inputs
(Hillocks et al., 2002). Once
established, the cassava crop is given little attention, but still is able to
tolerate weed competition, as well as insect, pest and disease. The potential
exists for improving the productivity of cassava through better agronomic
practices, superior varieties and pest and disease management.
Cassava varieties are generally distinguished from each other by their
morphologically characteristics which include leaf, stem and tuber colour, leaf
shape and number of storage roots per plant. The plant produces all year round
and can be harvested over an extended period of time. Although it is easily
propagated by stem cuttings, the lack of quality planting material is a major
constraint to the development of available cassava production system.
Growth regulators play a key role for developing a specific mode of
growth in the cultured cells or tissues, which may be due to accumulation of
specific biochemical contents in them. The single or combination of different
hormones in the medium causes maintenance of specific and balanced inorganic
and organic contents in the growing tissue. This leads the cells or tissues to
develop either into shoots/or roots or even death (Ikram-ul-Haq and Dahot,
2007).
Cytokinins such as benzyl aminopurine (BAP) and
kinetin are known to reduce the apical meristem domi- nance and induce both
axiliary and adventitious shoot formation from meristematic explants in banana
(Mok and Mok, 2001). However, the
application of higher BAP concentrations inhibits elongation of adventitious
meristems and the conversion into complete plants (Choi, et al.,
2010).
Auxins are a class of plant hormones (or plant growth substances) with
some morphogen-like characteristics. Auxins have a cardinal role in
co-ordination of many growth and behavioural processes in the plant’s life
cycle and are essential for plant body development. Auxins and their role in
plant growth were first described by the Dutch scientist Fritis Warmolt Went.
Kenneth V. Thimann isolated this phytohormone and determined its chemical
structure as Indole-3 Acetic Acid (IAA).
Auxins are toxic to plants in large concentrations. They are most toxic
to dicots and less so to monocots. Because of this property, synthetic auxins,
herbicides including 2, 4 – D and 2, 4, 5 – T have been developed and used for
weed control.
However, synthetic auxins especially 1 – naphthalene acetic acid (NAA)
and indole – 3 – butyric acid (IBA) are also commonly applied to stimulate root
growth when taking cuttings of plants or for different agricultural purposes
such as the prevention of fruit drop in orchards.
Auxin promotes cell growth and elongation process by altering the plant wall
plasticity, making it easier for the plant to grow upwards. Auxins also
influence root formation.
Rooting and sprouting behavior of stem has been studied in relation to
auxin application. Pretreatment with indole-3-butyric acid (IBA) and
1-naphthalene acetic acid (NAA) increased both the rooting and sprouting.
Sprouting of buds on the cuttings preceded rooting. (Michael p.2012)
1.1 JUSTIFICATION
OF STUDY
In the study of the relationship between hormone structure and plant response,
some limitations are involved. For example, the stage of plant development,
timing of chemical treatment application, the environment, the responses that
should be measured, and finally differences in phenotype and genotype are all
factors that have to be considered and these variables certainly make the plant
regulator research and development more complex.
Nevertheless, along with progress in many branches of agriculture, the
research with growth regulators has been fruitful and undoubtedly there is an
integrated. Interdependent role for growth regulators in the cassava tuberization
has not been understudied comprehensively with the used of auxins and
cytokinins thus this study was undertaken.
1.2 OBJECTIVES OF THE STUDY
1. To
determine the rate of cassava growth in auxin mediated sprouting of cassava
cuttings and sprouting of cassava without auxin mediation.
2. To
determine the rate of cassava growth in cytokinnin mediated sprouting of
cassava cuttings and sprouting of cassava without cytokinin mediation.
3. To
determine the effect of different concentrations of auxins and cytokinins on
tuberization of cassava roots.
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