21 Journal of Environmental Biology January 2012 Phytotoxic effect of 2-benzoxazolinone (BOA) against some vegetable crops Author Details Mukta Chum Department of Botany, Panjab University, Chandigarh - 160014, India Daizy R. Batish Department of Botany, Panjab University, Chandigarh - 160014, India (Corresponding author) e-mail: daizybatish@yahoo.com Harminder Pal Singh Department of Environment Studies, Panjab University, Chandigarh - 160014, India Ravinder Kumar Kohli Department of Botany, Panjab University, Chandigarh - 160014, India © 2012 Triveni Enterprises Vikas Nagar, Lucknow, INDIA editor@jeb.co.in Full paper available on: www.jeb.co.in J. Environ. Biol. 33, 21-25 (2012) ISSN: 0254- 8704 CODEN: JEBIDP Abstract Benzoxazolin-2(3H)-one (BOA) is a well known allelochemical that is being explored for its herbicidal activity. However, not much is known about its effect on crop plants. The present study investigated the effect of BOA on germination and early growth of four vegetable crops viz. Pisum sativum L., Raphanus sativus L., Brassica oleracea L. var. botrytis and Brassica oleracea L. var. capitata. At 1000 µM, germination of P. sativum, R. sativus and B. oleracea var. botrytis was reduced by more than 50%, whereas that of B. oleracea var. capitata was completely suppressed. Further, BOA reduced the root and shoot length of the test plants by ~ 40-82% and ~55-85% , respectively. In general, the effect was more pronounced on the root (~82% in B. oleracea var. botrytis) than on the shoot growth (~73% B. oleracea var. botrytis). 2- Benzoxazolinone significantly enhanced the contents of proteins (by 6-28%) and carbohydrates (by 61- 189%) in B. oleracea var. capitata and decreased the activities of related enzymes like proteases (by 13- 36%), α-amylases (19-60% ) and β-amylase (25-70%). The observed decline in the activities of hydrolytic enzymes amylases suggest that BOA interferes with the vital metabolic processes in the germinating seedlings leading to growth reduction. The study reveals that BOA interferes with the germination and early seedling growth of vegetable crops and induces biochemical alterations. Key words 2-Benzoxazolinone, Germination, Phytotoxicity, Seedling growth, Vegetable crops Publication Data Paper received: 05 March 2010 Revised received: 30 June 2010 Re-revised received: 30 March 2011 Accepted: 23 April 2011 Introduction Allelopathy is a process involving secondary plant metabolites that negatively influence the growth and development of other plants (Rice, 1984). Chemicals that bring about the phenomenon of allelopathy are known as allelochemicals and are involved in practically every aspect of plant growth acting from stimulants to suppressants (Singh et al., 2001). In modern sustainable agricultural system, the use of these allelochemicals is being encouraged to utilise this untapped resource for weed control thereby reducing the concerns of ecological, environmental and health problems associated with synthetic pesticides (Singh et al., 2003). Natural plant products with biological activity are the ideal leads for new chemical structures useful in the development of molecules with potential utilization in agronomy. Unlike traditionally thought of, crops are now known to possess greater potential in managing pests and weeds in a number of ways owing to their allelopathic nature. As many as 35 crops with allelopathic tendencies have been enlisted (Batish et al., 2001) and can be utilized for sustainable weed management. Allelopathic property of cover, smother and green manure crops grown in rotation has proved as a strategy worth exploiting for weed management (Singh et al., 2001; Batish et al., 2002). Further, the residues of allelopathic crops like rye, sunflower, wheat and barley also bear a great potential in suppressing weeds (Batish et al., 2001; Singh et al., 2003). Wheat (Triticum aestivum L.) is a major cereal crop of Northern India and exhibits allelopathic tendency that has been