Kayode, J, SPJTS.1.(2), ISSN

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1 ALLELOPATHIC POTENTIALS OF RICE HUSKS AND MAIZE ROOT RESIDUES ON THE GERMINATION AND INITIAL GROWTH OFOKRA (ABELMOSCHUSESCULUNTUS L. ) Ayeni, M.J 1, Kayode, J 2* Salimon,O.E. Department of Plant Science, Ekiti State University, Ado Ekiti, Nigeria. Abstract This experiment was designed to determine the allelopathic effects of powdered extracts fromresidues of rice husk and maize roots on the germination and the initial growth of okra (Abelmoschus esculentus L).The extracts of both crop residues (powders), inhibited the growth parameters examined in this crop, the degree of inhibition increased with increase in the concentration of the extracts, thus suggesting that the effects of the extracts (residues) were concentration dependent. However, sstatistical analysis (P 0.05) revealed that there were no significant differences in the % germination, speed of germination, number of leaves at harvest, dry root weight (biomass) and the relative growth rate of the extracts-treated seeds when compared to the control experiment while statistical differences abound in other growth parameters such as leaf area at 50g extract concentration, and shoot dry weight at 40 and 50g extract concentrations in the maize root powdered extract treated seeds and 50g extract concentration in the rice husk extract-treated seeds. Keywords: Allelopathy, Allelochemicals, Crop residues,, Rice husks, Abelmoshus esculentus INTRODUCTION Allelochemicals are present in plant parts such as leaves, stem,root, fruit, seed, rhizomes and grains 1 where they are released to the environment through the process of leaching, volatilization, root exudation and decomposition of plant residues 2 which are capable of suppressing the growth of other plants. When plants are exposed to allelochemicals, their growth and development are affected through inhibition of seed germination or decrease in seedling growth. The readily visible allelopathic effects include inhibited or retarded germination rate 3, seeds darkening and swelling, reduced root or radicle and shoot or coleoptile extension 4,5 swelling or necrosis of root tips, curling of the root axis, discolouration, lack of root hairs, reduced dry weight accumulation, and lowered reproductive capacity 6. These gross morphological effects may be secondary manifestations of primary events, caused by a variety of more specific effects acting at the cellular or molecular level in the receiver plants 7. These could include decrease in cell turgor 8, photosynthesis rate, transpiration, enzymes activity, metabolic energy for respiration and developmental activity 9. Delay or cessation of the storage compounds transmission can reduce respiration substrates and metabolic energy in the allelochemical exposed seeds which decrease germination and seedling growth. Allelochemicals also have osmotic effects by reducing water absorbing rate leading to delay in seed germination in cell elongation 8. In Nigeria, previous researchers revealed the interference of weeds on agricultural crops. These include the works of Kayode 10, 11 on effects of Calotropis procera and Aspillia africana on Zea mays, Tijani- Eniola 12 on effects of Siam weed on tomatoes. Similarly, the allelopathic effects of trees on crops were demonstrated by Oyun 13 on the extracts of G. sepium on Zea mays and Bora et. al. 14 on leaf extracts of Acacia auriculiformis on the germination of some agricultural crops. 90

2 There is however, a gross dearth of study on the allelopathic effects of crop residues in Nigeria. Recently Kayode and Ayeni 15,16, Ayeni and Kayode 17 reported the allelopathic effects of some crop residues on some agricultural crops. This study being reported here aimed at examining the effects of residues of rice husk and maize roots on okra an important vegetative crop in Nigeria. Materials and Methods A greenhouse experiment was conducted in the Department of Plant Science, Ekiti State University, Ado Ekiti, Nigeria, between July and September Top soil to the depth of 10cm depth was evacuated from regenerated vegetation on the university campus. The soil was autoclaved at C for one hour to destroy the existence of unwanted and buried seeds in the soil. Rice husk were obtained from a rice mill at Ode Ekiti in Gbonyin Local Government area of Ekiti State which is about 52km from Ekiti State University Campus while maize roots were harvested from a farm within the University Campus and were air- dried for three weeks after which they were chopped into pieces with knife, pounded with pestle and mortar and later blended into powdery forms. Portions of 10g, 20g, 30g, 40g and 50g each of the powdered extracts were measured out from the rice husks and maize roots residues (powder) and were mixed thoroughly with 500g of sterilized soil in planting pots. Each treatment was replicated five times in Completely Randomized Block Design. Five okra seeds obtained from a local market in Ado Ekiti, Nigeria, were planted in each of the planting pots after proper seed selection and testing had been made and was moistened daily with equal amount of distilled water at 7.00GMT. The seed were considered germinated upon plumule emergence and they were counted for seven days until no further emergence was observed. The speed of germination known as coefficient of velocity (COV) was calculated according to Kayode 18 as: COV = A 1 + A 2 + A 3.. A n T n x 100 Where: A 1 T 1 + A 2 T 2 + A 3 T 3 + AnT n 1 A = number of seedling that emerge at a particular day T = number of days involved. At three weeks after planting, the okra plants were thinned to one plant per pot leaving the most vigorous and healthier plant and the weekly height measurements were recorded for eight weeks. At the end of the eighth week, growth parameters such as number of leaves at harvest, length of leaves (length and breadth) were recorded to obtain the leaf area according to Kayode and Otoide 19 as: A = L X B X 0.75 Where: A = Area of the leaf, L= Length of the leaf, B= Breath of the leaf and 0.75= a constant The plant heights obtained were used to determine the relative growth rate (RGR) according to Kayode and Tedela 20 as: RGR = Ln H 2 Ln H 1 T 2 - T 1 Where: H 2 = final height of the plant, H 1 = initial height of the plant, T 2 = Final time and T 1 = initial time 91

3 The plants were carefully uprooted and washed thoroughly before it was later separated into roots and shoots. The fresh weights of the roots and shoots were determined using Electronic Top Loading Digital Balance; G& G model JJ 300Y.China.They were properly tagged and air-dries in the laboratory of the Department of Plant Science, Ekiti State University for three weeks to obtain the dry weights. The means from the parameters were subjected to one -way analysis of variance (ANOVA, P 0.05) using a computer software SPSS 2009 version 15. RESULTS AND DISCUSSION The effects of rice husk and maize roots residues (powder) on the germination percentage of okra seeds were shown in Table 1. The results revealed that both residues caused considerable reductions in the germination of okra seeds. The % germination decreased with increase in the concentration of the powder extracts showing that the effects were concentration dependent. Results from rice husk extracts-treated seeds revealed that while the % germination was 96% in the control experiment, % germination in 10g, 20g, 30, 40g, and 50g powdered extract concentrations were 92%, 92%, 92%, 76% and 64% respectively. Also in the maize root treated seeds, % germination was 96% in the control, those of 10, 20, 30, 40 and 50g powdered extract concentrations were 92%, 84%, 80%, 80% and 68% respectively. Statistical analyses (ANOVA, P 0.05) revealed that there were no significant differences in the % germination of okra seeds in both treatments when the results obtained from the treated seeds were compared to the control experiment. The effects of rice husk and maize roots residues (powder) on the speed of germination of okra were shown in Table 2.The results also showed that the speed of germination reduced with increase in the concentration of the extracts. Results from okra seeds treated with rice husk showed that while the speed of germination in the control was 19.66, those of 10, 20, 30, 40 and 50g extract concentrations were 19.57, 19.15, 18 79, and 18, 26 respectively. In maize root powdered extract-treated seeds, the speed of germination in the control was 19.07, those of 10, 20, 30, 40 and 50g concentrations were 18.95, 18.95, 18.89, and respectively. Statistical analyses (ANOVA, P 0.05) revealed there were no significant differences in the speed of germination when the results obtained from the treated seeds were compared with those of the control experiment. The effects of rice husk and maize roots residues on the number of leaves at harvest were shown in Table 3. The results revealed that the number of leaves at harvest were reduced in the two extract treated seeds, but the reduction was more pronounced in maize roots powdered extract-treated seeds. The number of leaves decreased with increase in the concentration of the extracts. For example, the rice husk treated seeds showed that the mean number of leaves in the control experiment was 7.00 which decreased to 4.60 in 50 g concentrations. Likewise maize roots treated seeds had mean value of 6.60 in the control which reduced to 2.60 in 50g concentration. The effects of the two powdered extracts on the leaf area (cm 2 ) of okra were shown in Table 4. The leaf area of okra treated with maize roots powdered extract had cm 2 in the control which decreased to 81.57cm 2 in 50g extract concentration. Similar results were obtained in okra seeds treated with rice husks, the control experiment had cm 2 which decreased to cm 2 in 50g concentration. Statistical differences were observed in the leaf areas of okra seeds treated with both rice husk and maize roots at 50g concentrations when compared the control experiments. Other treatments showed no significant difference to the control experiments in both extract treated seeds. 92

4 The effects of the extracts on the dry root and shoot weights (g) of okra were shown in Table5. The dry root and shoot weights decreased with increase in the concentration of the extracts. The dry root weight of rice husk in the control was 0.32g in the control experiment, those of 10, 20, 30, 40 and 50g were 0.32, 0.24, 0.18, 0.16 and 0.16g respectively. The dry shoot weight in the control was 1.74 in the control which decreased to 0.64g in 50g concentration. For maize root treated seeds, the dry root weight of okra in the control was 0.44g in the control experiment which decreased to 0.30g in 50g concentration. The dry shoot weight of maize root treated seeds was 1.92g in the control which decreased to 0.66g in 50g concentration. Statistical analysis revealed that no significant differences were observed in the dry root weights of both rice husk and maize root treated seeds when compared to the control experiments. For the dry shoot weights, statistical analysis revealed that significant differences were observed in 40 and 50g concentrations of maize root powdered extract-treated seeds when compared to the control experiment while other treatments showed no significant difference. For rice husk treated seed, only 50g concentration showed significant difference to the control experiment. The effects of the two crop residues on the relative growth rate (RGR) of okra were shown in Table 6. The results revealed that both treatments have inhibitory effects on the RGR of okra. The rate of inhibition increased with increase in the concentration of the extracts. In rice husk treated seeds, the relative growth rate of okra seed in the control was 0.35g. Those of 10, 20, 30, 40 and 50g were 0.31, 0, 27, 0.26, 0.24 and 0.24g respectively. Similarly in maize roots treated, the RGR of okra in the control was 0.19, those of 10, 20, 30, 40 and 50g were 0.18, 0, 18, 0.16, 0.15 and 0.13g respectively. Statistical analysis (P 0.05) revealed that there were no significant differences in the relative growth rates of both maize root and rice husks treated seeds when compared to the control experiments. The present findings was in accordance with the study of Bora et. al. 14 who also observed the inhibitory effects of leaf extracts of Accacia auriculiformis on the germination of some agricultural crops and contended further that the effect was proportional to the concentration of the extracts. Similarly, Stephen 21 noted the allelopathic potentials of some plant species that completely inhibited the germination of downy broom seeds. Seyyed et. al. 22 also asserted that aqueous extracts of rice hull had inhibitory effects on the dry weight of Silybum marianum and Echincchloa crus-galli. Also Monical et. al. 23 reported that aqueous extracts of Ascarum europaeum L. inhibited the germination and growth of Lycopersicum esculentum. CONCLUSIONS Previous researchers such as Chuo and Lin 24 reported that rice husks contained phytochemicals such as P-hydroxyl benzoic acid, syringic acid, vallinic, ferrullic, acetic-o-hydroxyl phenyl acetic, propionic and butyric acids. Also Olofsodotter et. al. 25 and Geally et. al. 26 reported that allelopathic chemicals such as ferulic acids are abundant in rice straw. Similarly, An et al. 27 and Alberto et al. 28 reported that maize root allelopathy contained 2, 4- dihydroxy-7-methoxy-2h-1, 4- benzoxazin-3(4h) one (DIMBOA). All these allelochemicals might be responsible for the inhibitory effects shown on the growth of okra in this study. 93

5 REFERENCES 1. Ahmad S, Arfan M, Khan AL, Ullah R, Hussain J, Muhammad Z, Khan R, Khan N, Watanabe N. Allelopathy of Teucriumroyleanum Wall. Ex. Benth. Pakistan J. Med. Plants. Res. 2011; 5(5): Ben HM, Hebit G, Kremer RJ, Quassama O. Allelopathic effects of barley extracts on germination and seedlings growth of bread and durum wheat. Agrono. 2001; 21: Williamson GB, Richardson DR, Fischer NH. Allelopathic mechanism in fire-prone communities. In: S.J.H. Rizvi and V. Rizvi (Eds.). Allelopathy: Basic and Applied Aspects, London: Chapman and Hall; p Turk MA, Tawaha AM. Allelopathic effects of black mustard(brassica nigra L.) on the germination of wild oats (Avena fatula L).Crop Protection 2003; 22 (4): Bhatt BP, Todoria NP. Studies on the allelopathic effects of some agro forestry tree crops of Garhwal Himalaya. Agroforestry System 1990; 12: Ayeni AO, Lordbanjou DT, Majek BA. Tithonia diversifolia (Mexican sunflower) in South Western Nigeria: Occurrence and growth habit. Weed Res. 1997; 37(6): Rice EL. Allelopathy, New York, London: Academic Press, El- Khawas SA, Shehala MM. The allelopathic potentials of Acacia niticola and Eucalyptus prostrate on monocot (Zea mays L.) and dicot (PhaseolusvulgarisL.) plants. Biotechnology. 2005; 4(1): Bond W, Turner R. The biology and non-chemical control of common amaranth (Amaranthus retroflexus L.). Coventry: HDRA, Bryton Organic Garden, Kayode J.: Allelopathic effect of aqueous extracts of Calotropis procera on the germination and the seedling growth of maize. Pakistan Journal of Scientific and Industrial Research 2004(a); 47(1): Kayode J. Allelopathic effects of aqueous extracts of Aspillia africana on radicle and plumule growth of Zea mays. Journal of Physical and Biological Science 2004b; 2: Tijani-Eniola HA, Fawusi OA. Allelopathic activities of crude methanol extracts of Siam weed and wild poinsettia on seed germination and seedling growth of tomato. Nigerian Journal of Weed Science 1989; 2: Oyun MB. Allelopathic potentials of Gliricidia sepium and Acacaia auriculiformis on the germination and seedling vigour of maize (Zea mays L.). American Journal of Agricultural and Biological Science 2006; 1(3): Bora I P, Singh J, Borthakur R, Bora E. Allelopathic effect of leaf extracts of Acacia auriculiformis on seed germination of some agricultural crops. Ann. For. 1999; 7: Kayode J, Ayeni, JM. Allelopathic Effects of some Crop Residues on the Germination and Growth of Cowpea (VignaungiculataL. Walp.). Ethnobotanical Leaflets 2009; 13: Kayode J, Ayeni M.J. Allelopathic Potentials of Aqueous Extracts from Maize ((Zea mays) Roots and Pigeon pea (Cajanus cajan L.) Leaves on the Growth and Germination of Soybeans (Glycine max.l.merril.). Bulletin of Pure and Applied Science 2010; 29B (No. 2): Ayeni MJ, Kayode J. Allelopathic Potential of Some Crop Residues on the Germination and Growth of Soybean (Glycine max L.) Merrill. Journal of Agricultural Science and Technology B. 2012; 2(10): Kayode J. The seed bank of Euphorbia heterophylla along a successional gradient following slash and burn agriculture. Journal of Physical and Biological Sciences 2000; 1(1):

6 19. Kayode J, Otoide JE. Leaf cuticle variation in Amaranthusspinosus as indicators of environmental pollution.. Pakistan Journal of Scientific and Industrial Research 2007; 50 (5): Kayode J, Tedela PO. Effects of irrigation frequency on growth and nodulation of Leucaena leucocephala. Pakistan Journal of Forestry 2005; 554(1): Stephen M. Allelopathic potentials of various plant species on DownyBrome: Implication for weed control in wheat production. Agron. J. 2007; 99: Seyyed MS, Haniyeh K, Fatemeh N, Maryam K. Allelopathic effect of aquatic hull extract of rice (OryzasativaL.) on growth of Silybummarianum and Echincchloa crus- galli. African Journal of Agricultural Research.2010; 5(16): Monica M, Anea P, Lucia M, Zorica V, Georgeta M. Allelopathic potentials of Ascarum europaeum toward Lycopersicum esculentum.analeleuniversitatii din Oradea- Fascicula Biologie Tom.2011 XVIII: Chuo CH, Lin HJ. Auto intoxication mechanism of Oryza sativa L.: Phytotoxic effects of decomposing rice residues in soil. J. Chem. Ecol. 1979; 2: Olofsodotter M, Nawarez D, Moody K. Allelopathic potential in rice (Orza sativa L.) germplasm. Ann. Appl. Biol.1995; 127: Geally DR, Mattice JD, Moldenhauer KA, Dilday RH. Allelopathy in rice as a weed control strategy. International Weed Science Congress 2000; 3: An M, Johnson IR, Lovett JV. Mathematical modelling of allelopathy: II. The dynamics of allelochemicals from living plants in the Environment. Ecological Modelling. 2003; 161: Alberto OB, Marcias FA, Molinillo JMG. Variation in Endogenous and Exogenous of Allelochemical 2, 4- dihydroxy-7-metoxy-1, 4-benzoxazin-3, (4H) - one (DIMBOA) in Root Architecture of maize (Zea mays), Table 1. Allelopathic effects of maize root and rice husk on the germination % of seeds of okra Treatments Rice husk (g) a 92.00a 96.00a 92.00a a 84.00a a 76.00a 64.00a 80.00a 80.00a 68.00a Means followed by the same letter within column are not significantly different at P Table 2. Allelopathic effects of maize root and rice husk on the speed of germination of Okra. Treatments Rice husk (g) a 19.07a a 18.95a a 18.95a ab 18.89a ab 18.66a a 15.17a Means followed by the same letter within column are not significantly different at P (0.05) 95

7 Table 3. Allelopathic effects of maize root and rice husk on the number of leaves of okra Treatments (g) Rice husk a 6.60a a 6.60a a 5.40a a 5.00ab a 4.60b a 2.60c Means followed by the same letter within column are not significantly different at P Table 4. Allelopathic effects of maize root and rice husk on the leaf area (cm 2 )of okra. Treatments Rice husk ( g ) a a ab ab ab ab ab ab ab 99.72ab b 81.57b Means followed by the same letter within column are not significantly different at P Table 5. Allelopathic effects of crop residues on the Dry Root and Shoot weights of okra. Treatments (g) Rice husk R S R S a 1.74a 0.44a 1.92a a 1.64ab 0.44a 1.36ab a 1.24ab 0.40a 1.18b a 1.00ab 0.40a 1.00b a 0.68b 0.32a 0.84b a 0.64b 0.30a 0.66b Means followed by the same letter within column are not significantly different at P

8 Table 6. Allelopathic effects of maize root and rice husk on the Relative Growth Rate (RGR) of okra. Treatments Rice husk ( g) a 0.19a a 0.18ab a 0.18ab a 0.16ab a 0.15ab a 0.13ab Means followed by the same letter within column are not significantly different at P