  alternanthera is a genus of flowering plants in the amaranth family, amaranthaceae. it is a widespread genus with most species occurring in the tropical americas,sÃ¡nchez-del pino, i., et al. (2012). molecular phylogenetics of alternanthera (gomphrenoideae, amaranthaceae): resolving a complex taxonomic history caused by different interpretations of morphological characters in a lineage with c4 and c3âc4 intermediate species. botanical journal of the linnean society 169(3), 493-517.alternanthera. flora of north america. and others in asia, africa, and australia. plants of the genus may be known generally as joyweeds.alternanthera. integrated taxonomic information system (itis). several species are notorious noxious weeds.tanveer, a., et al. (2013). a review on genus alternanthera weeds implications. pak. j. weed sci. res 19(1), 53-58. ==description== these are annual or perennial herbs or subshrubs. while some of the better-known species are aquatic plants, most are terrestrial. they take many forms, from prostrate to erect to floating. the leaves are oppositely arranged. the inflorescence is a spike or a rounded head occurring in the leaf axils or the ends of branches. the flowers have 5 tepals. there are 3 to 5 stamens which are fused into a rim at the bases, and 5 pseudostaminodes, appendages between the stamens that are not true staminodes. the fruit is a utricle containing one seed. ==biology== the photosynthetic pathways vary in this genus. some alternanthera species undergo c3 carbon fixation, and others have the c4 pathway. certain other species have an intermediate c3-c4 pathway.chinthapalli, b., et al. (2001). phosphoenolpyruvate carboxylase purified from leaves of c3, c4, and c3-c4 intermediate species of alternanthera: properties at limiting and saturating bicarbonate. photosynthetica 38(3), 415-19. ==ecology== many species have been reported as 
Alternanthera