Behaviour of Herbicides in Dicotyledonous Roots Transformed by Agrobacterium rhizogenes: II. TRANSPORT TO REGENERATED SHOOTS

Mugnier, J. 1988. Behaviour of herbicides in dicotyledonousroots transformed by Agrobacterium rhizogenes. II. Transportto regenerated shoots.—J. exp. Bot. 39: 1057–1064. Regenerated plants from roots of Anagallis arvensis transformedby Agrobacterium rhizogenes were propagated in Petri disheson Murashige and Skoog's medium. The roots were exposed to differentherbicides. We report here the relationship between root uptakeand translocation of the herbicides acting upon the shoots.The results show that regenerated Anagallis arvensis plantspropagated in Petri dishes reflected the situation in normalplants in their responses to symplastic herbicides (aminotriazole,glyphosate, 2,4-D) which have strong bleaching or wilting effects.Sucrose seemed to be the critical driving force by which symplasticherbicides were transported from the root towards the shoot.The results applied to a limited range of environmental conditionssince the transport and performance of apoplastic herbicides(S-triazines, triazinones, substituted ureas) was apparentlylimited by the sucrose and moisture conditions in the Petridish. The mode of transport, in phloem versus xylem, of herbicidewithin a transformed root is discussed. Key words: Agrobacterium rhizogenes, herbicides, root organ culture     

Behaviour of Herbicides in Dicotyledonous Roots Transformed by Agrobacterium rhizogenes: I. SELECTIVITY

Mugnier, J. 1988. Behaviour of herbicides in dicotyledonousroots transformed by Agrobacterium rhizogenes. I. Selectivity.—J.exp. Bot. 39: 1045–1056. The effect of various herbicides on the growth of dicotyledonousroots transformed by the root-inducing transferred DNA of Agrobacteriumrhizogenes was studied. When a compound affected the growthof different root species differentially, the difference mightbe attributed to root uptake and metabolism of the herbicide.In general, metabolism of the herbicide led to inactivation(clopyralid, linuron, phenmedipham), but in certain instances,the change resulted in activation (quizalofop-ethyl). Visibleeffects on the root morphology were observed: dinitroanilinesand certain carbamates led to remarkable swelling of the roottips; norflurazon and diflufenican were effective bleachingagents in greening root cultures in Murashige and Skoog medium,whereas the presence of sucrose in the medium antagonized theeffect of triazine herbicides. Growth inhibition by sulphonylureascan be antagonized by addition of valine and leucine; asulaminhibition was antagonized by addition of folic acid but glyphosateinhibition was not significantly reversed by aromatic aminoacids. Bipyridinium and diphenyl ether herbicides, with certainexceptions, have rapid and devastating phytotoxic effects onroot growth. The phytotoxic effects of the herbicides on transformedroot growth is discussed with particular reference to theirmode of action in intact plants. Key words: Arobacterium rhizogenes, herbicides, root organ cultures