The Effect Of Moringa Oleifera Leaf Extract On The Growth And Yield Of Pepper (Capsicum Annum)

Project and Seminar Material for Soil Science

The Effect Of Moringa Oleifera Leaf Extract On The Growth And Yield Of Pepper (Capsicum Annum)


Abstract


This study was carried out during the two summer seasons of 2014 and 2015 on pepper (Capsicum annuum L.) cv. California Wonder. The goals of this investigation were enhancing either the speed of pepper seeds germination or its percentage, produce healthy seedlings, vigour growth and improve fruit yield and its quality by using moringa leaf extract (MLE). The concentrations used of MLE extract were 2% – 4% – 6% in addition to 0% (tap water) as control. The moringa extract was added through two methods i.e., seed soaking treatment for 3 and 6 hours before planting the nursery and as plant foliar spray either on the seedlings during nursery stage or after transplanting in the open field . The obtained results indicated that moringa leaf extract at 4% concentration as seed soaking for 6 hours stimulated germination percentage, rate, index as well as coefficient of germination velocity. Moreover, the same concentration (4%) of MLE as a foliar spray on pepper seedlings in the nursery was sufficient to support all seedlings parameters expressed as height, fresh and dray weight, number of leaves and leaf area. Moreover, the maximum plant growth parameters as well as superior early and total fruit yield were obtained from the same treatment. Furthermore, MLE at concentration of 4% increased average fruit weight, length and diameter as well as fruit chemical contents such as carbohydrate, ascorbic acid and both of K and Ca elements. For that it can recommend that soaking pepper seeds in moringa leaf extract solution at concentrate of 4% for 6h for enhancing the germination percentage and seedling characteristics as well as spraying the seedling and pepper plants with 4% MLE solution to obtain superior fruit yield with best quality.

Key words: Pepper, moringa leaf extract, seed germination, seedlings vigor, plant growth, fruit yield and its quality.


Chapter One


Introduction

1.1 Background of the Study

Agriculture is facing the dual challenges of increasing crop production and climate change. Rising temperature, drought, salinity, floods, desertification and weather extreme are adversely affecting agriculture especially in developing world (IPCC, 2007). Most of the predicted population growth to 2030 will be in developing countries (Population Reference Bureau, 2011) and more than half of the work force engaged in agriculture in the third world countries is prone to more damage by climate change. Thus, there is need to improve crop productivity under changed climate, abiotic stresses and to meet the needs of increasing world populations.

Of various abiotic stresses, high temperature, salt stress and drought alone or in combination are major threats to crop productivity. Rising temperatures may lead to altered geographical distribution and growing season of agricultural crops by allowing the threshold temperature for the start of the season and earlier crop maturity (Porter, 2005). An extreme temperature shortens the growing period and adversely effects all phases of growth such as tillering, flowering and grain filling in late sown wheat. The early senescence of leaves results in too low photosynthetic rate to contribute in fixing carbon to rest of the plant (Hensel et al., 1993; Sharma-Natu et al., 2006) leading to poor quantity and quality of the harvest (Hussain et al., 2008). A series of morphological, physiological, biochemical and molecular changes may reduce expression of full yield potential of crop plants under these climatic stress conditions (Wang et al., 2001).

The decreased soil water potential causes much reduction in leaf expansion as compared to root expansion rate under drought or salinity (Kaminek et al., 1997). The water scarcity disturbs plant metabolic activities by upsetting the membrane structure, altered mineral uptake (Pospíšilová et al., 2000), reduction in the chlorophyll contents, relative water contents and membrane stability index (Tas and Tas, 2007). The limited availability of water not only reduces number of grains per spike but also decreases the grain weight in wheat (Li et al., 2000) and quality like low proteins (Garg et al., 2004).

The increased accumulation of Na+ and Cl- under saline conditions leads to the reduced growth of vascular plants (Munns, 2002). Salt stress causes less germination and poor seedlings establishment in most of the crops such as wheat (Afzal et al., 2006b), maize, barley (El-Tayeb, 2005), sugar beet (Ghoulam et al., 2001), sunflower (Ashraf and Tufail, 1995), canola (Athar et al., 2009), cotton and rice (Sattar et al., 2010). Reduction in growth and yield under salinity is mainly due to salt-induced osmotic stress and specific ion toxities (Munns and Tester, 2008). The depressed level of natural osmoprotectants and endogenous hormones are observed in several plants growing in saline soils (Debez et al., 2001).

The combined effect of extreme temperature, drought and salinity includes osmotic damages (Xiong et al., 2002), oxidative stress like increased generation of reactive oxygen species (ROS) (Mittler, 2002, Gill and Tuteja, 2010) and protein denaturation (Zhu, 2002). Biomolecules such as proteins, DNA and lipids are badly injured by reactive oxygen species (ROS) resulting in denaturation, mutation and peroxidation (Quiles and Lopez, 2004). The peroxidation of membrane lipids of plasmalemma and other cellular organelles (Candan and Tarhan, 2003) leads to cell death as a consequence of ROS toxicity.

It has been identified that plants develop many adaptations to cope with stress conditions i.e. osmotic adjustment, compartmentalization of compatible solutes, alterations in nutrients ratios specially K+/Na+, evapotranspiration modifications by reducing leaf size, changes in photosynthetic pigments, stimulation of plant hormones and better antioxidant scavengers (Sairam and Tyagi, 2004). The breeding programmes to develop crop plants with aforementioned traits are laborious and time consuming (Javid et al., 2011). The alternative approaches are management practices including exogenous application of various antioxidants, mineral elements and plant growth regulators (PGRs). The antioxidants increase the scavenging capacity against ROS (Mano, 2002). The antioxidants involved in detoxification of ROS exist in all plants under stress and are categorized as enzymatic such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), glutathione reductase (GR) and monodehydroascorbate reductase (MDAR) and non- enzymatic i.e. total phenolics (TPC) and ascorbic acid (AA) (Foyer, 2002). The degree to which the amount and activities of antioxidant enzymes increase under abiotic stress is extremely variable among several plant species and even between two cultivars of the same species (Chaitanya et al., 2002). The level of response depends on the species, the development and the metabolic state of the plant, as well as the duration and intensity of the stress.

Many plants produce significant amount of antioxidants to prevent the oxidative stress caused by photons and oxygen, they represent a potential source of compounds with antioxidant activity such as ascorbic acid, total phenols, and vitamins in addition to mineral elements K+, Ca2+ and PGRs.

Ascorbic acid is an important antioxidant, which reacts not only with H2O2 but also with O2, OH and lipid hydroperoxidases. In addition to the well established ascorbic acid in animals against a wide range of ailments and diseases it has been implicated in several types of biological activities in plants such as an enzyme co-factor, as an antioxidant and as a donor/ acceptor in electron transport at the plasma membrane or in the chloroplasts, all of which are related to oxidative stress resistance (Conklin, 2001). In chloroplasts ascorbate peroxidase uses ascorbic acid thereby minimizes the risk of escape and reaction of ROS with each other near PSI (Foyer and Noctor, 2000). Ascorbate also protects or regenerates oxidized carotenoids or tocopherol (Imai et al., 1999).

Plant phenolic compounds are also known for their function as antioxidants due to their free radical-scavenging capabilities (Wattenberg et al. 1980; Barclay et al. 1990; Fauconneau et al. 1997).

In addition to antioxidants plants also contain a wide range of vitamins that are essential not only for human metabolism but also for plants, because of their redox chemistry and role as cofactors, some of them also have strong antioxidant potential. The antioxidant vitamins that have been the focus of most attention in plants are carotenoids (pro-vitamin A), ascorbate (vitamin C) and tocochromanols (vitamin E, including both tocopherol and tocotrienols) (Demmig-Adams and Adams, 2002; DellaPenna and Pogson, 2006; Linster and Clarke, 2008; Foyer and Noctor, 2009: Cazzonelli and Pogson, 2010; Falk and Munne´-Bosch 2010; Me`ne-Saffrane´ and DellaPenna, 2010).

To combat abiotic stresses and enhance crop yields, application of mineral nutrients is widely used. Among mineral nutrients calcium is a very important not only for cell wall and membrane stabilisation, but has also been found to be involved in the regulation of specific plant responses to environmental stresses (Braam et al., 1996). Cramer et al. (1988) depicted that Ca2+ has alleviating effect on Na+-induced root growth inhibition. Similarly, shortening of root growth zones was prevented by Ca2+ under saline condition (Bernstein et al., 1993). Perera et al. (1995) reported that Ca2+ increased the stomatal conductance and restores the photosynthesis. Transport of water in the root and leaf growing zones was affected with Na+/Ca2+ ratio (Cramer, 2002). Tyerman et al. (1997) showed that salinity changed the ionic content and transport within the plants. They concluded that calcium has many regulatory functions over membrane characteristics and ionic transport in glycophytes and halophytes. For example, increasing the external Ca2+ concentration decreased the transport of Na+, thereby reducing Na+ influx in root cells. The cross talk between Ca2+ and ROS has been studied during defense and growth responses and stomatal closure (Foreman et al., 2003; Hu et al., 2007; Mori and Schroeder, 2004). Other studies also implicated Ca2+ function both upstream and downstream of ROS production (Jiang and Zhang, 2003; Hu et al., 2007).

Potassium (K) is the most abundant cation in higher plants. K+ has been the target of some researchers mainly because it is essential for enzyme activation, protein synthesis and photosynthesis (Marschner, 1995; Silva, 2004), and it mediates osmoregulation during cell expansion, stomatal movements, tropisms, phloem solute transport and the maintenance of cation: anion balance in the cytosol as well as in the vacuole. K+ supply from soil can be rate limiting for agricultural production under conditions of osmotic and ionic stress.

Proper exogenous application of PGRs along with certain nutrients, antioxidants, organic and inorganic chemicals has been used to promote plant growth and development for inducing abiotic and biotic stress tolerance that results in higher economic return (Ashraf and Foolad, 2007; Farooq et al., 2009). Exogenous use of cytokinins improves the crop growth and yield under normal or stressful environments in a number of crop species (Zahir et al., 2001). Cytokinin retards the leaf senescence and increased the photosynthetic pigments (Galuszka et al., 2001). In a field trial with the application of a commercial cytokinin containing product, cytogen, increase in yields of corn (26.3%), rice (45.8%), pepper (24.4%), cucumber (62.9%) and cantaloupe (36.8%) has been reported (Mayeux et al., 1983). Priming with cytokinins like kinetin or benzyl amino purine (BAP) induces physiological adaptation in wheat by hormonal balance under stress conditions (Iqbal and Ashraf, 2006). BAP delayed the ROS- induced senescence of wheat leaves owing to increased activities of catalase and ascorbate peroxidase in addition to preventing chlorophyll degradation under oxidative stress (Zavaleta et al., 2007). Under drought less reduction in total soluble protein, chlorophyll and carotenoids contents were observed by exogenous application of cytokinin like products such as thidiazuran, BAP, Kartolin 4 and Kartolin 2 (Chernyad’ev and Monakhova, 2003).

Ashraf and Foolad (2005; 2007) suggested that exogenous application of these compounds as seed priming or foliar spray enhanced endogenous level and abiotic stress tolerance. These biologically active substances can modulate plant responses to stress factors. But continuous use of synthetic chemicals and use of commercially available plant hormones as osmoprotectants and stimulators of antioxidants to quench ROS is usually not cost effective and environmentally friendly. Alternatively, toxicological effects of synthetic antioxidants and consumer preference for natural products have resulted in increased interest in the application of natural antioxidants (Castenmiller et al., 2002; Kaur and Kapoor, 2001; Koleva et al., 2002; Pizzale et al., 2002). The search for safe and effective naturally occurring antioxidants is now focused on edible plants, especially spices and herbs (Nakatani, 1997). A large number of plants have been screened as a viable source of natural antioxidants including tocopherols, vitamin C, carotenoids and phenolic compounds which are responsible for maintenance of health and protection from coronary heart diseases and cancer (Castenmiller et al., 2002; Kaur and Kapoor, 2001). Such as seaweed extract which is a natural products possess cytokinin and auxin like properties and can stimulate endogenous cytokinin activities of plants (Crouch et al., 1990). Another example is humic acid, which has auxin-like activity, not only enhances plant growth and nutrient uptake but also improves stress resistance (Zhang and Ervin, 2004). Among different natural sources used to extract PGRs and antioxidants moringa (Moringa oleifera) is gaining a lot of attention these days (Foidle et al., 2001).

Moringa is one of the 13 species of genus Moringa and family Moringnance. It is well known vegetable in Africa, Arabia, India, Southeast Asia, America and Pakistan (Sengupta and Gupta, 1970). Its roots, fruits, leaves and flowers been used as vegetables (Siddhuraju and Becker, 2003). Moringa leaves are potential source of vitamin A and C, iron, calcium, riboflavin, beta-carotene and phenolic acid (Nambiar et al., 2005). Its leaves and oil are a powerful natural antioxidant (Njoku and Adikwu, 1997). Siddhuraju and Becker (2003) observed antioxidant properties in the solvent extract of moringa leaves. On the basis of their results they reported that, moringa leaves are a potential source of natural antioxidants.

According to Arabshahi et al. (2007) the extracts from drumstick and carrot had a higher antioxidant activity (83% and 80%) than α-tocopherol (72%). Jongrungruangchok et al. (2010) compared the composition and mineral contents of moringa leaf obtained from different regions of Thailand and reported 19.1-28.8, 2.1-2.5, 16.3- 3.9 and 8.5-13.5 percent of protein, fat, fiber and moisture. The potassium, calcium and iron contents were in range of 1504.2 – 2054.0, 1510.4 – 2951.1 and 20.3 – 37.6 mg / 100 g dry weight basis. Moreover, moringa leaf extract (MLE) is enriched with zeatin, a purine adenine derivative of plant hormone group cytokinin (Barciszweski et al., 2000) known for stay green and stress tolerance capabilities.

Pepper (Capsicum annuum L.) is considering an important fruit vegetable crop belong to family Solanaceae which remembered since more than 6000 years ago (Perry et al., 2007). It is the second most important vegetable in the world after tomato for internal consumption and for export. Pepper fruit is rich in vitamins A and C and contain appreciable quantities of proteins and minerals Temu and Temu (2005) and Olaniyi and Ojetayo (2010). Pepper seed germination is considered a critical step in the development cycle of the plant, germination rate and seedling growth in pepper plants are very low comparing with the other vegetable seedlings. (Korkmaz and Korkmaz, 2009).

Different pre- treatments have been investigated to improving rate of pepper seeds germination and seedling growth, some of these treatments are chemical and others are natural product such as moringa leaf extracts (Wien, 1997). Moringa oleifera are belonges to family Moringaceae which it is consider the most widly tropical trees. (Foidl et al., 2001 and Shahzad et al., 2013). The moringa leaf extract (MLE) is consider as a natural plant growth regulator where, it is a source of zeatin which it is natural derivative of cytokinin, proteins, vitamins E, phenolics, ascorbates, essential amino acid and several mineral elements, making to putting it as a potential natural growth stimulant, as mentiond by Emongor (2012), Rady et al. (2013), Howladar (2014) and Rady et al. (2015). Other reports have been showed that moringa extract play as a plant hormone which enhances seed germination, growth and yield of crops.

MLE foliar spray improved crop performance, resulting from its role on vigorous plant growth, maintained optimum tissue water status, improved membranes stability, enhanced antioxidant content, as mentioned by Anwar and Bhanger (2003), Nagar et al. (2006) Yasmeen et al. (2012), Yasmeen etal. (2013) and Rehman et al. (2014). Many investigators reported that the effective concentrations of MLE were differing according to plants type. However, Phiri and Mbewe (2010) revealed that moringa leaf extract at concentration of (1:10) was forced beans to germinate early and increased duration to first germination by100%, also increased germination percentage of cowpea while the same concentration lead to reduction in groundnut germination seed. They added also that, this reduction may be attributed to that MLE contain an inhibitory substance for groundnut seed germination. Moreover, Basra (2011) illustrated that MLE at concentration of (1:30) was the most effective concentration for causing higher emergence rate and better early seedling growth of spring maize. Furthermore, the rate of cowpea seed germination was decreased with the increase concentration of MLE as reported by Moktar et al. (2012). Also, Muhammad (2015) reported that moringa leaf extract at 5% was encouraged cowpea rate germination and final germination percentage followed by concentration of 2%. Culver et al. (2012) found that moringa extract significantly increased tomato average fruit weight and plant height as well as yield and its components. Muhammad et al. (2013) found that tomato plant height, plant dry weight and fruit yield were significantly affected with aqueous moringa extract.

Also, Bashir et al. (2014) revealed that moringa leaf extract significantly increased the average plant height, leaves number, number of branches and yield of tomato plant. Oluwagbenga and Odeghe (2015) mentioned that sweet bell pepper plant height; number of leaves, fruit weight and yield were significantly influenced by the application of moringa leaf extract. Aluko (2016) reported that the highest values of pepper plant growth and yield parameters were obtained with MLE foliar application at concentration of (1:20).


1.2 Statement of the Problem

It is evident from earlier mentioned reports that MLE possess antioxidants in considerable amounts but very little published literature is available that explains MLE regulated metabolic/physiological processes of wheat and other crops subjected to abiotic stress.

In view of all these reports, it is hypothesized that leaf extract from moringa, having a number of plant growth promoters, mineral nutrients and vitamins in a naturally balanced composition, may be beneficial for plant growth and development. This study was conducted to evaluate whether the adverse effects of stress on wheat plants could be mitigated by exogenous application of osmoprotectants i.e. K+, H2O2, synthetic cytokinin benzyl amino purine (BAP) and MLE especially focusing the plant antioxidant enzyme system. The objectives of study were the optimization of MLE dose as natural plant growth enhancer in comparison to synthetic ones in different crops under normal and abiotic stresses.


1.3 Research Objectives

The aim of this investigation was to

  1. Enhancing germination percentage of pepper seeds and reducing the period of seed germination
  2. Obtaining vigour seedlings
  3. Improving fruit yield characterized with the best quality by using natural extract of moringa oleifera leaves as seed soaking or foliar spray.

1.4 Research Questions

  1. What are the effects of enhanced germination percentage of pepper seeds on period of seed germination?
  2. How can improved fruit yield characterized with the best quality be obtained using natural extract of moringa oleifera leaves?

1.5 Research Hypothesis

  1. There is no effect of enhanced germination percentage of pepper seeds on period of seed germination.
  2. There is no improved fruit yield characterized with the best quality be obtained using natural extract of moringa oleifera leaves

1.6 Significance of the Study

Following the potential increase in the use of Moringa extracts as growth enhancer for plants and recent publicising of the nutritional and medicinal benefits of the plant, there is therefore the need to identify and characterise effect of moringa oleifera leaf extract and compost on the growth and yield of pepper and investigate the presence or absence of harmful chemicals in the crop.


1.7 Limitations of the Study

This study was limited to the usage of moringa oleifera leaf extract and compost on the growth and yield of pepper.


Chapter Five


Conclusion and Recommendations

5.1 Conclusion

As a general from this study, it can said that, spraying pepper plants with moringa leaf extract at concentration of 4% was the superior treatment to obtain the maximum values of vegetative growth, fresh fruit yield and its components as well as chemical constituents in the fresh fruits, i.e. K, Ca and carbohydrates as well as vitamin C content (%). Moreover it can by using moringa leaf extract at concentration of 4% for 6h duration as seed soaking treatment, it stimulate the rapid of germination furthermore enhances germination percentage and also as foliar application on seedlings stage where produce strong and healthy seedlings as well as in plant development phase.


5.2 Recommendation

The simple method of extraction and exogenous application were used, so that it can be easily adopted by community, however, more refinements like extraction methods and blending of MLE with other natural and synthetic compounds, of theses techniques be required in future research.


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