Comparative analysis of the anatomy of two populations of red-root amaranth (Amaranthus retroflexus L.)

The anatomy of stems and leaves of two populations of the weed species Amaranthus retroflexus L. (red-root amaranth) (pop. AMARE1 having green stems covered in sparse hairs and pop. AMARE2 with green but notably dense stem hairs) was analysed in order better to understand the uptake and translocation of herbicides that could be indicative of the species' evolving resistance to herbicides. Samples of the two populations (AMARE1 and AMARE2) were collected from arable land of the Institute of Maize Research at Zemun Polje in 2006. Sampling was performed at the stage of full vegetative growth of plants. Permanent microscoping preparations were made to measure and analyze elements of the anatomy of stems (stem epidermis, cortex, collenchyma, central cylinder and diameter) and leaves (leaf epidermis upper surface and underside, mesophyll, leaf thickness and bundle sheath thickness). Both analysed populations of A. retroflexus, morphologically characterized by different density of stem hairiness, were found to have a typical structure of herbaceous dicots. The stem had three distinctive zones: epidermis, cortex and central cylinder. Amaranth leaves have dorsoventral structure, i.e. their upper surface and underside can be differentiated. The results indicated high and very high significance of differences found in stem anatomy between the two analysed populations, while leaf anatomy was not found to display significant differences other than in mesophyll thickness.