1 Palynological study of some Iranian Amaranthus taxa Seyed Mehdi Talebi*, Mitra Noori, Zeinab Nasiri Department of Biology, Faculty of Science, Arak University, Arak, Iran *Corresponding author, E-mail: seyedmehdi_talebi@yahoo.com Abstract Tere has been much discussion about infrageneric taxonomy of the genus Amaranthus. In the present study, in order to solve taxonomical problems and to aid identifcation of Iranian Amaranthus taxa, the palynological characteristics of seven taxa from two subgenera (Amaranthus and Albersia) were examined. Pollen grains were investigated with light microscopy and scanning electron microscopy using the prolonged acetolysis procedure. Twelve quantitative and qualitative characteristics were studied. Results showed that all of the studied taxa had poly pantoporate pollen and surface sculpturing was seen as scabrate, while its aggregation difered between samples. Statistical analysis showed that some quantitative morphological features were more valuable in identifcation of the studied taxa. Te studied taxa were separated from each other using multivariate analysis. Our data together with the results of previous investigations confrmed that the present infraspecifc classifcation of A. blitum requires change. It is advisable to return to the previous taxonomical status of the genus. Key words: Amaranthus, pollen characteristics, taxonomy. Abbreviations: PCA, principal coordinate analysis; PCO, principal coordinate ordination; UPMGA, unweighted paired group using average. Environmental and Experimental Biology (2016) 14: 1–7 Original Paper DOI: 10.22364/eeb.14.01 Introduction Approximately 60 Amaranthus L. species are native to the Americas, and an additional 25 species are present in the temperate and tropical regions of Africa, Asia, Australia, and Europe (Sauer 1967). Ofen collectively called “pigweeds,’’ at least 10 Amaranthus species are considered troublesome weeds in the North America (Horak et al. 1994; Wax 1995). Te cultivated taxa of the genus are utilized as food grains, leafy vegetables, and forage crops in diferent geographic areas of America, Asia and Europe (Stallknecht, Schulz- Schaefer 1993). Te genus Amaranthus naturally grows in Iran and is found in several regions of the country (Azadi 2013). Tere has been much discussion about its species number: Mobayen (1979) reported six species, Ghahreman (1980– 2002) more than seven species and Rechinger (1998) 11 species in Iran. Tese diferences were due to hybridization and domestication of some of the species. Identifcation of species of Amaranthus is necessary for an efective weed management (Mayo et al. 1998). Because of the large genetic and morphological diversity within the genus Amaranthus, species identifcation is difcult. Te presence of fowers is required to identify most species. In addition, interspecifc hybridization between Amaranthus species causes further difculties in identifcation, as these hybrids can exhibit characteristics of both parents (Horak et al. 1994). In modern systematics pollen morphology has been extremely useful in clarifying systematic relationships within plant taxa. Moreover, palynology of the species and subspecies can have taxonomic value as supporting evidence to morphological and phylogenetic traits. Also, studies on pollen grains morphology is considered as the basic necessity for palynology due to its fundamental value in the recognition and identifcation of grains found in various conditions (Arora, Modi 2008). Iwanami et al. (1988) considered that the morphology of the pollen grain is generally a conserved characteristic, which is an excellent means for identifcation of most species. Previous studies (Eliasson 1988; Costea 1998a; Costea 1998b; Costea et al. 2004) have confrmed that in Amaranthus taxa, fowers lack nectar glands and pollen grains are small (diameter 18 to 28 μm), usually with 30 to 45 pores uniformly distributed on their surface. In addition, they are tectate with granules and spinules. Te relationship between monoecious and dioecious Amaranthus as well as diferent ploidy level and interspecifc hybrids can be determined using pollen grain features. Pollen grains of dioecious species have a larger number of apertures on the visible surface. Te arrangement of pores creates high air turbulence, which minimizes the friction between the pollen grain and the air, therefore increasing the distance at which the pollen grain can be dispersed (Franssen et al. 2001). Roulston and Buchmann (2000) believed that Amaranthus pollens contain starch (up to 7. 5%), which protects them against desiccation. Studies showed that the genus Amaranthus is a Environmental and Experimental Biology ISSN 2255-9582