African Journal of Plant Science Vol. 3 (4), pp. 064-073, April 2009 Available online at http://www.academicjournals.org/AJPS ISSN 1996-0824 © 2009 Academic Journals Full Length Research Paper Investigation of morphophysiological variation in field bindweed (Convolvulus arvensis L.) populations of Karaj, Varamin, and Damavand in Iran A. Mehrafarin 1 , F. Meighani 2 , M. A. Baghestani 2 , M. J. Mirhadi 1 and M. R. Labbafi 2 * 1 Department of Weed Science, Faculty of Agriculture, Science and Research Campus, Islamic Azad University, Tehran, Iran. 2 Weed Research Department, Iranian Plant Protection Research Institute, P. O. Box, 19395-1454, Tehran, Iran. Accepted 19 March, 2009 Diversity in field bindweed (Convolvulus arvensis L.) populations collected from Karaj, Varamin, and Damavad during 2006 (for seed collection) to 2007 (for seed germination and plant growth in green- house) at the Weed Research Department, Iranian Plant Protection Research Institute for identification of morphophysiological variation using multivariate analysis methods. The most important variables were shoot dry weight, leaf dry weight, and leaf area, respectively. Results showed 11, 15 and 16 biotypes in Karaj, Varamin, and Damavand populations, respectively. Varamin was clustered near to Damavand, but both these populations had significant differences with Karaj population. Key words: Biodiversity, ecotype, biotype, principal component analysis, cluster analysis, field bindweed, Convolvulus arvensis. INTRODUCTION Field bindweed (Convolvulus arvensis) is one of the 10 noxious weeds in the world and 54 countries reported that it is found as a weed in 32 different crops (Swan, 1980; Holm et al., 1991). This is considered as one of the problematic weeds in Iran (Shimi and Termeh, 2004) and found in a wide range of habitats (Weaver and Riley, 1982). This species have a broad geographical range, often include either ecotypes or biotypes (Klingaman and Oliver, 1996). It is self-incompatible species which may play an important role in maintaining the high degree of phenotypic variation (Westood, and Weller, 1997). Numerous examples of intraspecific variation in growth and morphology of weed species have been reported (Degennaro and Weller, 1984). Morphological parame- ters are generally used as a tool for investigation of diver- sity and genetic relatedness (Hubner et al., 1998). Seve- ral morphologically distinct biotypes of field bindweed have been identified and more than one biotype often exists in the same infested area. The morphological variability in the species is thought responsible for diff- erential response of field bindweed to herbicides (Duncan and Weller, 1987). Variation in morphology and herbicide *Corresponding author. E-mail: mohammad1700@yahoo.com. susceptibility of field bindweed has been observed by various researchers (Degennaro and Weller, 1984). The objective of this investigation is to determine the differences in morphophysiological characteristics of field bindweed biotypes or ecotypes in these regions. MATERIALS AND METHODS Seed of field bindweed (C. arvensis L.) were collected from Karaj, Varamin, and Damavand in Tehran province in September 2006. In March 2007, after seed scarification with sulfuric acid 97%, these were planted in plastic pots having mixtures of sterilized clay, sand, manure and perlite in a ratio of 1:5:5:0.5, respectively. The plants were maintained in a greenhouse for 22 wks under day/night temp- eratures of 30/18 ± 4ºC and 500 μmol.m -2 .s -1 with supplemental lighting (incandescent and fluorescent) to provide a 14 h day length with 45% relative humidity. Plants were irrigated weekly, and as needed with a nutrient solution containing 200 ppm N, 100 ppm P, and 100 ppm K (Samadani and Minbashi, 2004). Morphophysiological characteristics studied At the end of flowering (154 days after sowing), 60 plants were randomly collected from each population and observations were recorded on traits like. shoot number, shoot fresh weight, shoot dry weight, shoot water content, stem dry weight, leaf dry weight, root dry weight, whole plant dry weight, whole plant biomass, collar (crown) diameter, leaf number, leaf area, chlorophyll concentration,