EFFECT OF FLUROXYPYR AND FENOXAPROP-P-ETHYL ON SOYBEAN AND MAIZE ROOT TIPS TISSUE CULTURE

Abstract

This study was conducted using tissue culture as a model system to evaluate the effect of the herbicides; Fluroxypyr (F) [4-amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid], Fenoxaprop-p-ethyl (Fp) [(R)-2-{4-(6-chlorobenzoxazol-2-yloxy) phenoxy} propionic acid] and their combinations on growth, development and some biochemical changes of soybean (Glycine max) and maize (Zea mays) root tips. The herbicide concentrations were 10 and 100 µM of both F and Fp for post-emergence control of weeds. F control broadleaf weeds and Fp is used for grasses. Normal root tip growth was inhibited by 10 and 100 µM F in both plants, resulting in shortening and swelling accompanied by callus growth. Fp at 10 and 100 µM inhibited main root growth in Fp sensitive maize. The addition of Fp with F in the medium suppressed callus and swelling formation by F in maize whereas it did not reverse the morphogenic changes induced by F in soybean. F increased fresh and dry weights of maize roots but the reverse was true with soybean roots. Fp at 10 and 100 µM alone and their combinations with F reduced fresh and dry weights of both plants (except 10 µM F + 10 µM Fp in soybean). Individual treatments of F and Fp reduced total soluble carbohydrates in maize (except 10 µM Fp); a marked reduction in soybean roots was also obtained by F. F at 10 and 100 µM reduced indole content in soybean. Opposite trend occurred in both plants by Fp at 100 µM. All combinations of F and Fp increased indoles in maize as well as in soybean (except 100 µM F + 10 µM Fp). Fp at 100 µM markedly increased phenols in soybean. Generally, combination treatments increased phenols in both plants. Combined applications of F and Fp (at 10 and 100 µM each) increased free amino acids and proline in maize. Their effects on soybean were variable. Therefore, plants treated with herbicides undergo state of stress as reflected by biochemical analyses even though this effect could not be realized by plant morphology. Tissue culture demonstrated reciprocal antagonism between auxin and anti-auxin herbicides as shown by biochemical and / or morphogenic changes.