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Allelopathic effects of root
leachates of some obnoxious weeds on germination and seedling
vigour of wheat
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Research Note - Pankaj Oudhia
© 2001,2002,2003 Pankaj Oudhia - All Rights ReservedIntroduction
Wheat is one of the rabi crops of Chhattisgarh. Many weeds infest wheat field in the region (Oudhia, 1999a). These weeds compete with crops for moisture, light and nutrients and believed to reduce crop yields. In ancient Indian literatures it is mentioned that all weeds are not harmful (Oudhia, 1999b). Many studies conducted at the Department of Agronomy, IGAU, Raipur have revealed that all weeds present in crop fields are not harmful to crops (Oudhia, 1999c; Oudhia et al., 1999). These studies also revealed that many weeds are beneficial to crops and with the use of these weeds farmers can improve the crop performance. The negative (stimulatory) allelopathic effects of extracts and leachates of different weeds parts on germination and seedling vigour and final yield of agricultural crops have been reported (Oudhia and Tripathi, 1998a, b, 1999a; Oudhia et al., 1995). The identification of harmful and beneficial weeds can be done by studying its allelopathic effects on related crops. Parthenium hysterophours, Blumea lacera, Lantana camara, Calotropis gigantea, Datura stramonium and lpomoea carnea are common weeds of wheat fields in Chhattisgarh region. (Oudhia and Tripathi, 1999b). Due to non-availability of any information on allelopathic effects of these weeds on germination and seedling vigour of wheat, a pot culture experiment was carried out during February 2000.
Materials and Methods
Fresh samples of roots of selected weeds were collected at random at the vegetative stage in January 2000. To prepare the leachates, the roots were immersed in water for 24 hours in the ratio of 1:10 w/v (roots : water). After 24 hours, leachates were collected. The bioassay experiment was done in earthen pots filled with neutral clay loam soil. Wheat seeds were soaked in different leachates for 24 hours. As a control, wheat seeds were also soaked in distilled water for the same duration. After soaking, 25 seeds of wheat were sown in each pot. The experiment was laid out in randomized block design with four replications the experiment was repeated twice. Germination was recorded at 3, 5, 7, 9 and 11 DAS (Days After Sowing) and root and shoot lengths were noted a 11DAS.
Results and Discussion
The root leachates of different weeds produced significant allelopathic effects on germination and seedling vigour of wheat. At 3 DAS, Datura and lpomoea root leachates have hasten the germination and resulted in maximum germination (16.0%). At 5, 7, 9 and II DAS, Datura root leachate produced maximum germination as compared to rest of the treatments whereas at 5, 9 and 11 DAS, Blumea, Calotropis root leachates and control and at 7 DAS, Blumea, lpomoea root leachates and control produced comparable germination with maximum germination. At 5,7,9 and 11 DAS, Parthenium root leachate lowered the germination to the minimum (Table 1). In case of root elongation Blumea root leachate resulted in maximum elongation (9.1 cm) which was at par with elongation produced by all treatments except Parthenium and Lantana root leachates. Parthenium root leachate lowered the elongation to the minimum (4.9 cm). In case of shoot elongation, Blumea root leachate produced maximum elongation (13.1 cm) which was at par with elongation produced by Calotropis, Datura and lpomoea root leachates and control. Lowest elongation was noted under Lantana root leachates (5.2 cm).
In this study, Blumea leaf leachate was identified as potential leachate which can be utilized for promoting the seedling vigour of wheat without affecting its germination. These observations are in the with those observed in previous studies on different crops including wheat (Oudhia et al 1997; 1998a and b). Blumea lacera is a common bund and field weed of Chhattisgarh region. The present study indicated that presence of this weed in wheat field is beneficial for the crops. Also farmers can utilize this weeds, after uprooting it, to prepare extracts and leachates from different parts in order to use it for pre sowing soaking treatment of wheat seeds. Parthenium and Lantana root leachates are identified as most harmful leachates, as these leachates resulted in lower germination and seedling vigour. Harmful allelopathic effects of these weeds on germination and seedling vigour of many agricultural crops have been reported (Narwal, 1994; Oudhia 1999d). Many lethal allelochemicals viz parthenin, coronopillin, caffeic acid, p-coumaric acid, alkaloids and sesquiterpene lactones in Parthenium and protocatechuic acid, gentisic acid, p-hydroxy benzoic acid, vanillic acid, syringic acid, caffeic acid etc. In Lantana extracts and leachates have been reported (Narwal, 1994). The study suggested that early removal of these weeds from wheat field is essential in order to avoid the losses in terms of poor germination and seedling vigour. Calotropis, Datura and lpomoea root leachates are identified as relatively safe root leachates.
Acknowledgement
Author is thankful to SOPAM (Society for Parthenium Management) for providing laboratory facilities and also to Mr. Subodh Raile, Research Assistant, for his assistance during this work.
References
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Oudhia, P., Pandey, N. and Tripathi, R.S. (1999). Allelopathic effects of obnoxious weeds on germination and seedling vigour of hybrid rice. International Rice Research Notes. 24 (2): 36.[Originally published in Ecol. Env. & Cons. 7(1) : 2001; pp. (111-113)