Weed suppressing ability of some monoterpenes

Abstract

Monoterpenes are the simple chemical constituents of volatile essential oils found in a number of aromatic plants. Being biologically active they provide the donor plants a number of characteristics. These are also known to play an important role in allelopathy as evidenced from the sparse vegetation around the donor plants. A study was under-taken to explore the effect of some monoterpenes viz. citronellol, citronellal and linalool for their inhibitory effect towards two weedy species viz. Echinochloa crus-galli and Bidens pilosa. Germination and growth of test weed species measured in terms of seedling length and dry weight were drastically reduced in response to the treatment of monoterpenes. Not only growth even the content of chlorophyll was also found to be less in the treated plants compared to control. These observations suggest that monoterpenes affect the photosynthetic machinery of the treated plants. Eight-week-old plants of E. crus-galli were completely killed with 2 ml spray treatment of 400 mM of citronellol. Monoterpenes also caused a rapid electrolyte leakage in the cotyledons of Cassia occidentalis thereby depicting a severe effect on the membrane integrity. The study, therefore, concludes that monoterpenes being chemically the simpler compounds can be utilized for the purpose of managing noxious weeds either directly as bioherbicides or indirectly by serving as template for the synthesis of new herbicides.