PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS IN TRIAZINE-RESISTANT BIOTYPES OF 4 AMARANTHUS SPECIES

A comparative study was made of the photosynthetic activity, growth an d productivity of triazine-resistant (R) and -susceptible (S) biotypes of A, albus, A. blitoides, A, hybridus and A. retroflexus collected f rom various areas in Spain. Fluorescence assay showed that herbicide t reatment totally inhibited electron transport in S plants but not in t heir R counterparts. Electron flow from QA to QB was lower in R plants , but no difference was observed for the electron flow rate through PS II + PSI nor for photosynthetic activity at different light intensitie s. Growth studies revealed that S biotypes were more vigorous than in R in A. hybridus and A. retroflexus; R and S were similar in A. albus, but S biotypes of A. blitoides showed greater growth at the first dev elopment stage (3-week-old plants), although R and S plants were not s ignificantly different at 5 and 6 weeks. No uniformity in productivity was observed across the 4 species.