ABSTRACT
The effect of the aqueous leaf extract of Moringa oleifera on the germination and seedling growth of groundnut and cowpea was investigated. Five treatment levels having different concentration of extracts (undiluted, 1:1, 1:2.5, 1.50) and control were used. Both laboratory and field (pot) experiment were conducted in completely randomized design (CRD) with three replications. The control treatment was only distilled water. The result showed that the rate of germination of groundnut decreased with the increase in aqueous extract concentration. The extract stimulated the growth of groundnut at all treatment levels but has no significant effect on its dry weight. The study revealed that aqueous leaf extract of Moringa oleifera inhibited the germination of cowpea and as the concentration of extract increases, it decreases the height and dry weight of the seedlings. This study therefore suggests that allelochemicals released from the leaf part of Moringa oleifera inhibited the germination of groundnut and cowpea while it stimulated the height of groundnut but has no significant effect on its dry weight. It was also observed that the aqueous leaf extract of M. oleifera inhibited the height and dry weight of cowpea. This result therefore suggests that allelochemicals may contribute to the allelopathic effect caused by moringa leaves.
TABLE OF CONTENT
Title i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Content vi
List of Tables ix
List of Plates x
Abstract xi
CHAPTER
ONE
1.1 Introduction 1
1.2 Botany of Plants 8
1.3 Justification 10
1.4 Aim and Objectives 10
CHAPTER
TWO
2.0 Literature review 11
2.1
Inhibition Role of Aqueous Plant Extract
on the Germination and Seedling
Growth of Plant 12
2.2
Stimulatory
Role of Aqueous Plant Extract on the Germination and Seedling
Growth of Plants. 16
CHAPTER THREE
3.0
Materials
and Methods 20
3.1
Plant
Materials 20
3.2 Preparations
of Aqueous Extracts 20
3.3 Seed
Germination Test (%) 21
3.4 Seedling Growth Test 22
3.4.1 Plant Height (cm) 22
3.4.2
Dry Weight (G) 22
3.5 Experimental
Design and Statistical Procedure 22
CHAPTER
FOUR
4.1 Result 23
4.1.1. Height Growth (cm) 23
4.1.2. Seed Germination (%) 25
CHAPTER
FIVE
5.1 Discussion
28
5.1.1 Effect of the Aqueous Leaf Extract of
Moringa Oleifera on the Germination
Of Groundnut and Cowpea Seed 28
5.1.2 Effect of Aqueous Leaf Extract of Moringa
Oleifera on the Seedling Growth of
Groundnut (Arachis Hypogea)
and Cowpea (Vigna Unguiculata). 29
5.2 Conclusion 30
5.3 Recommendation 31
References
LIST
OF TABLE
Table 1: Effect
of aqueous leaf extract of Moringa oleifera on the seedling height and dry
weight of
groundnut (Arachis hypogea) 23
Table 2: Effect
of aqueous leaf extract of Moringa oleifera on the seedling height and
dry
weight of
cowpea (Vigna unguiculata) 24
Table 3: Effect
of aqueous leaf extract of Moringa oleifera on the percentage
germination of
groundnut and cowpea. 25
LIST OF PLATES
Plate1: Groundnut seeds
growing in the petri dish 26
Plate 2: Cowpea seeds
growing in the petri dish 26
Plate 3: Groundnut
seedlings growing in pots in the screen house 27
Plate 4: Cowpea
seedlings growing in pots in the screen 27
CHAPTER
ONE
1.1 INTRODUCTION
Plants are reservoir of different types of natural
occurring bio-organic compounds having a wide range of biological activities.
Different parts of plants and their extracts have been used for various
purposes since long time ago due to their chemical properties, availability,
and simple use without side effects (Asadujjaman et al., 2004). All these
compounds usually are called secondary plant products or waste products of the
main metabolic pathways in plants (Turk et
al., 2003; Yokotani et al., 2003; Iqbal et al., 2006).
Certain
plant extracts are found to have cytotoxic effects and occurs as a result of a
single chemical produced by the organism or plant which is harmful to another
but beneficial to a third organism or plant (Whittaker and Fenny, 1971; Rice,
1979; Sai and Rizvi, 1992). Allelopathy is one of the most controversial of
ecological interactions (Williamson, 1990).
Bioherbicides represent solution to
heavy use of synthetic herbicides which causes serious threats to the
environment, consumers and increases costs of crop production (Asghari and
Tewari, 2007). Moreover, continuous use of herbicides for weeds control causes
herbicide resistant (Naseem et al., 2009). Many authors report employ
plants extracts for controlling weeds with variable success (Hussain et al.,
2007; Iqbal et al., 2009; Naseem et al., 2009).
Apart
weeds, all plant parts of the weed including leaf, stem, root, and fruit
depending upon plant species have allelopathic potential (Alam and Islam, 2002;
Tinnin and Muller, 2006).
These
plants have the ability to directly or indirectly stimulate or inhibit the
germination, growth, flowering and fruiting
of other plants by releasing chemical compounds known as allelochemicals into
the environment (Rice et al., 2003).
The production of the allelochemicals is widely influenced by genetics as well
as environmental factors at different growth stages (Yu et al., 2003). This phenomenon is common for many plant species and
can be observed at any level of biological organization (Gawronska, 2003; Chon et al., 2003; Gholami et al., 2011; Al-Rabiah, 2012).
Allelopathy
phenomenon has been long observed in natural ecosystem in the pre-historic time
(Willis, 2004) and before agriculture. Allelopathy was detected in the agro
ecosystem through observations on what was termed as a “soil sickness” or from
the harmful effect of certain plant species on others (mainly crops), and thus
was exclusively related to negative chemical interactions among plant species.
For over 2,000 years, allelopathy has been reported in the literature with
respect to plant interference (Westa and Duke 2003) and the concepts related to
allelopathy may go back to 600 B.C. (Willis, 1999) and innate plant and was
first reported more than 2000 years ago (Formgaard, 2006). Also, early observations
of weed and crop allelopathy were made by none other than Theophrastus,
"the father of botany", who in 300 B.C. wrote in his botanical works about
how chickpea "exhausted" the soil and destroyed weeds. Cato the Elder
(234–140 B.C.), the famous Roman politician and writer, was a farmer in his
youth. In his book, he wrote about how chick pea and barley "scorch
up" corn land. He also mentioned that walnut trees were toxic to other plants
(Zeng et al., 2008).
Although
this form of plant–plant interference had been known for quite some time, it
was only recently (1937) that the Austrian plant physiologist, Hans Molisch,
gave it a formal name, allelopathy (Molischs, 1937) and as a consequence, he is
currently recognized as the father of allelopathy and understood by certain
researchers that referred to both harmful and beneficial chemical interactions
between plants in nature, although the lateral translation of the Greek term
root words “Allelo” means mutual and
“pathy” means suffering and by this,
allelopathy should refer to negative chemical effects. Allelochemicals involved
were best defined by Whittaker and Feeny (Whittaker, 1971) as chemicals by
which organisms of one species affect the growth, health, behavior or
population biology of organisms of another species (excluding substances used
only as food by the second species). This definition, however, was revised
later by (Rice, 1974) who defined it as any direct or indirect harmful interaction
between plants (including microorganisms) through chemicals released into the
environment after which one of the species is harmed. In 1994, the
International Allelopathy Society (IAS) has concluded that allelopathy term should
include both stimulatory and inhibitory chemical effects after allelochemicals
received in the environment in either modified forms or not.
Allelopathy particularly of crops, if properly
understood, coped and applied can play a significant role (Chou, 1999). It is
intensely recognized that the natural plant products being decomposable are
environmentally safe and can be reliant on to improve the crop production in a
sustainable allelopathic interaction in development and growth (El-Khatib et al; 2004). Example includes: protein, hormone and chlorophyll
synthesis, cell division, cell wall structure, membrane permeability and
function and active transmission of especially enzymes, anther and spore
germination, organelle synthesis, photosynthesis, respiration, leg-hemoglobin
biosynthesis, activity of nitrogen fixation bacteria and mycorhizal fungi, crop
water uptake rate are liable to disturbances by allelochemicals (De Neergard et al., 2000).
Allelopathy is therefore an
interference mechanism in which live or dead plant materials release chemical
substances, which inhibit or stimulate the associated plant growth (Haper, 1998;
May and Ash 1990). Once these allelochemicals get
dissolved in the soil they may come into contact with other element of
different physical, chemical, biological and physiochemical properties which
may influence activity of allelochemicals and therefore either amplify or
reduce their impact on recipient plants (Inderjit, 1996).
Allelochemicals
are believed to be a joint action of several secondary metabolites including
phenolic compounds (Dalton, 1999), flavonoids (Berhow and Voughn, 1999),
juglone (quinone) (Jose and Gillespie, 1998), terpenoids (Langenheim, 1994).
Many researchers have found that the inhibitory substances involved in
allelopathy are terpenoids and phenolic (Alexa et al., 2004; Chaves and Escudero, 2006; Khanh, et al., 2007). Phenolics are broad variety
of compounds with a wide array of allelechemical activities and most important
in allelopathy. Phenolic compounds are water soluble and leach from leaves,
stem and roots into the soil solution (Katase, 1993; Zhu and mallik, 1994).
The extent of the allelopathic effects resulting from
allelochemicals concentration in soil may be affected by other factors such as
soil pH, organic matter content, nutrient and moisture content and
microorganisms (Blum 1995).
Bhadoria
(2011) produced an extended list of readily visible effects of allelochemicals
on the growth and development of other plants. These effects include inhibition
or retardation of germination rate; darkening and swollen of seeds; reduction
of root and shoot length; swelling or necrosis of root tips; curling of the
root axis; discoloration, lack of root hairs; increased number of seminal
roots; reduced dry weight accumulation; and lowered reproductive capacity. Examples of plant species that exhibit
allelopathy include many trees (sugar maple, eucalyptus, and oak), shrubs,
(sumac, rhododendron, and elderberry), agricultural crops (tobacco and rice),
and various grasses and ferns (Brown, 2006).
Each releases its own type of allelochemicals. In contrast to
herbicides, allelochemicals are generally weak phytotoxins that exert their
effects at low, but constant or increasing concentrations over long periods.
Allelopathy
can affect all ecological factors, e.g. growth, plant canopy succession,
survival, extension and crop production (Fergusen et al., 2003).
Allelopathic
plants also interfere with nearby plants by dispersing chemicals into the soil
that may inhibit neighboring plant growth, nutrient uptake or germination
(Abhilasha et al., 2008) typical allelopathic inhibitory effects result
from the action of groups of allelochemicals that collectively interfere in
various physiological processes altering the growth patterns of plants (Kil
& Shim, 2006). That action of allelochemicals can affect the respiration,
photosynthesis, enzyme activity, water relations, stomatal opening, hormone
levels, mineral availability, cell division and elongation, structure and
permeability of cell membranes and walls (Chou, 1999; Reigose et al., 1999),
through these actions, allelopathic substances may play a role in shaping plant
community structure in semi-arid and arid lands (Jefferson and Pennacchio,
2003).
The allelopathic effects are selective,
depending upon the concentrations and residue type, either inhibitory or
stimulatory to the growth of companion or subsequent crops or weeds (Mushtaq et
al., 2003; Cheema et al., 2004; Javaid et al., 2007). Many
scientists related to the field of allelopathy are continuously working on it
to explore it more and more (Macias, 2002).
In
agricultural practice, allelopathy is exploited for weed control (Kohli et al., 1998). These
chemicals products mainly affect plants at seed emergence and seedling levels
(Alam and Islam, 2002; Hussain et al., 2007). Root exudation, leaching by dews and rains and volatilization
or decaying plant tissue from allelopathic plant results in the release of
compounds into the environment which could either affect positively or
negatively the growth of other species. (Stamp and Nancy, 2003). In
volatilization, the toxic chemicals are released in the form of a gas from the
leaves and then are absorbed by another plant, causing it to die. In leaching,
the chemicals that are stored in the plant’s leaves seep into the soil, either
by the littering and decomposition of the leaves, or via runoff rain, fog, or
dew that comes into contact with the leaves. In exudation, the chemicals are
released into the soil through the plant’s roots. It has been documented that allelopathy may play an
important role on plant-plant interference by those chemical compounds (Inderjit
and Dakshini, 1992). A number of weed and crop species have been reported to possess
allelopathic effect on the growth of other plant species (Rice, 1984).
Chemicals with inducing and inhibiting activity are present in many plants and
in many organs, including leaves, flowers, fruits and buds. (Inderjit, 1996; Ashrafi
et
al., 2007). Plant
species that are particularly aggressive in their interactions with other
species may be allelopathic. Allelopathy has been invoked frequently to explain
the success of invasive species. For example, spotted knapweed (Centaurea stoebe L., formerly Centaurea maculosa L.) often eliminates
most native plant species where it invades (DiTomaso, 2000). Allelopathy has
been implicated as a component of its interference (Ridenour and Callaway
2001), although the identity of the allelochemical(s) involved remains unclear
(Duke et al., 2009). The ‘‘novel
weapons hypothesis’’ suggests that invasive plant species are more likely to be
allelopathic to native vegetation because native vegetation has not evolved
resistance to unique allelochemicals produced by the invader that are not found
in the flora of the invaded area (Inderjit et
al., 2006).
Sparse
or no vegetation patterning around a particular species can indicate that it is
allelopathic. An example of this is the long-observed difficulty in growing most
plant species around black walnut (Juglans
nigra L.) which led to the discovery of the allelochemical juglone (Davis,
1928). The discovery of the phytotoxic effects of the phytochemical triketones
was apparently due to the observation of vegetation patterning around the red
bottlebrush plant (Callistemon citrinus
(Curtis) Skeels) (Knudsen et al.
2000).
However,
other factors, such as competition for water in a dry environment, can be
involved in vegetation patterning around species that are highly competitive
for water. Mineral depletion by a species might also be detrimental to other
species that are in close proximity.
Poor
growth of a crop after other species or the same species has grown on that
field is often attributed to buildup of allelochemicals in the soil. This
occurs, but is sometimes hard to prove, as there may also be an accumulation of
plant pathogens in the soil, soil nutrient depletion, or other effects on the
soil unrelated to allelochemicals, especially if the same crop is grown year after
year. Knowledge that a
plant species produces one or more potent cytotoxins
can be a clue obtained from the phytochemical literature that the species might
produce an allelochemical. For example, the fact that all species of Sorghum so
far tested produce sorgoleone, a phytotoxic compound implicated in allelopathy
of Sorghum spp. (Dayan et al., 2010),
would suggest that any species of Sorghum might be allelopathic because of
sorgoleone production.
Allelopathy plays an important role
in agricultural ecosystems and in a large scale, in the plant covers among the
crop-crop, crop-weed and tree-crop covers. It also plays an important role in
weed and weed interaction (Wilson and Rice, 1996), weed-crop interaction
(Cotton and Einhelig, 1999). These interactions are detrimental and
occasionally, are useful and gave attention to allelopathy in natural and
agricultural ecosystems.
Finally, competition can influence allelopathy
and vice versa, often making separation of the two processes can be extremely challenging.
Thus, an absolute proof of the involvement of a particular compound in
allelopathy is very difficult in cases of weak phytotoxins.
A
potential complication is that the plant making the putative allelochemical
(the donor plant) may only make sufficient amounts of allelochemicals for an
allelopathic effect when in the presence of a targeted plant species (receiving
plants). This is similar to the case of induction of phytoalexin production in
the presence of plant pathogens. Few studies have looked for enhanced
production of putative allelochemicals by competing plant species or extracts
from such species.
Allelopathic
potentiality under field conditions can be utilized in different ways. For
example, surface mulch (Cheema and
Khaliq, 2000), incorporation into the soil (Sati et al., 2004), aqueous
extracts (Iqbal and Cheema, 2007a),
rotation (Narwal, 2000), smothering
(Singh et al., 2003) or mix cropping/intercropping (Iqbal and Cheema, 2007b). Today, allelopathy is recognized as appropriate
potential technology to control weeds using chemicals released from decomposed
plant parts of various species (Naseem et al., 2009).
1.2 BOTANY OF PLANT
Genus Moringa
is the only genus in family Moringaceae and comprises 13 species from Africa,
Madagascar, Western Asia and the Indian subcontinent (Verdcourt, 1985). The tree is large and tall (up to 40m) with a
rounded canopy or foliage with leathery leaves and big fleshy edible drupes as
fruit (Neon, 1984). Moringa is fast-growing, drought
resistance tree, native to the southern foothills of the Himalayas in northern
India, and widely cultivated in tropical and subtropical areas where its young
seed pods and leaves are used as vegetables. It has been reported to provide human,
livestock and crop nutritional benefits (Fuglie, 2001). The
tree loses its leaves from December to January, though during droughts it may
also lose its leaves at other times of the year (HDRA, 2002). It can also be used
for water purification and hand washing, and is sometimes used in herbal
medicine. (Leone et al., 2015).
Moringa oleifera has been reported to serve immense benefits
as food, Vitamins and in folk medicine. M. oleifera contains a complete
food as it contains all the essential Amino acids required for healthy living (Vanisha et al., 2003). It possesses all the
vitamins needed to keep the body healthy (Subadra and Vanisha, 2003). Leaf
extracts can be used against bacterial or fungal skin complaints (Vanisha et al., 2003). Flower juice of M.
olifera can also be used to improve the quality and flow of mother’s milk
when breast feeding (Fahey, 2005). Moringa oleifera tagged the “tree
of life” is a miraculous plant that is nutritious and beneficial to human
health. The ancient traditional medicine of India called “Ayurveda” says the leaves
of the Moringa prevent 300 diseases (Alford, 2010). Modern science is
confirming that these leaves could help prevent untold suffering and death caused
by malnutrition and related diseases (Alford, 2010). Nearly, all parts of moringa
are edible and can be used as super food, oil fiber, medicine or purification
of water. It is one of the world’s most useful plants and nutritious crops.
(Asian vegetable research and development center, 2003).
In
addition to the numerous reported uses of M. oleifera, its allelopathic
effects had been studied and reported (Fuglie, 2000; Phiri and Mbewe, 2009;
Phiri, 2010).
Arachis hypogea (groundnut or peanut) is an annual herbaceous
leguminous plant, belonging to the botanical family of Fabaceae like other
legumes, groundnut harbor symbiotic nitrogen-fixing bacteria in their root
noodles (Rolloff et al., 2009). Like
other legumes, their leaves are nyctinastic, that is, they have “sleep”
movements, closing at night. The specific name hypogea mean “under the earth”,
because peanut pods develop underground, a feature known as geocarpy. It is a
crop of global importance and widely grown in the tropics and subtropics being
important to both smallholder and large commercial producers. It is classified
as both a grain legume and because of its high oil content an oil crop.
Vigna unguiculata (cowpea) is one
of the most widely adapted, versatile and nutritious of all the cultivated
grain legume, they are mainly grown in warm climates since they require warm
soil temperatures for good establishment (Kellher,1994)
Cowpea is a
native of Africa, with West Africa (Nigeria) being a major center of diversity (Ng
and Padulosi, 1994). It is one of several species of the widely cultivated
genus Vigna four subspecies
are recognized of which three are cultivated and they includes: Vigna textilis, Vigna pubescens and Vigna sinensis. It also has the useful ability to fix atmospheric
nitrogen through its root noodles.
1.3 JUSTIFICATION
This research
work is aimed at investigating the allelopathic effect of aqueous leaf extract
of Moringa oleifera on the
germination and seedling growth of Arachis hypogea (groundnut) and
Vigna
unguiculata (cowpea). This
is as a result of the need to search and develop alternative sources of plant
nutrient by promoting plant extracts as possible supplement or substitute to
inorganic fertilizer.
1.4 AIMS AND OBJECTIVES
This research is
aimed at determining the effects of aqueous leaf extract of Moringa oleifera on:
·
The germination of
groundnut (Arachis hypogea) and cowpea (Vigna unguiculata).
·
Seedling growth
of groundnut (Arachis hypogea) and cowpea (Vigna unguiculata).
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