Floristic composition and biological spectrum of weeds in agro-climatic zone of Nalbari district, Assam, India

Abstract

Present paper deals with the study of floristic composition and biological spectrum of the agro-climatic zone of Nalbari district of Assam. Field observation encompasses a total of 217 weed species from both angiosperms and pteridophytes belonging to 150 genera under 60 families. Asteraceae, being the largest family possesses 19 genera and 22 species. Out of the total species, 183 species (84.33 %) showed the annual life span as against 34 species (15.67 %) showing the perennial life span. One hundred thirty eight species (63.59 %) were recorded to be propagated by seeds/spores; 66 species (30.41 %) were found to opt for both seeds and vegetative propagules and only 13 species (5.99 %) were listed to be propagated exclusively by vegetative propagules. The phytoclimate of the agro-climatic zone can be regarded as thero-cryptophytic since major percentage of the species falls under the life forms Therophytes and Cryptophytes which has been assessed after comparison with the normal world spectrum as proposed by Raunkiaer.