Summary. The influence of the four herbicides 2,6‐dichlorobenzonitrile (dichlobenil), isopropyl‐N‐(3‐chlorophenyl)carbamate (chlorpropham), 2‐chloro‐N‐isopropylacetani‐lide (propachlor) and 2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)acetanilide (alachlor) on GA induction of a‐amylase in the barley endosperm test was studied. Amylase induction by GA was inhibited by all four herbicides, dichlobenil and chlorpropham being more active in this respect. In all cases, inhibition increased with the addition of increasing concentrations of herbicide. Addition of the herbicides to the reaction mixture showed that none of them directly affected the enzyme—starch reaction. Inhibition de V induction par l'acide gibbirellique de activité de α‐amylase dans l’endosperne de I'orge, sous faction de certains herbicides Résumé. Les auteurs ont étudié l'influence de 4 herbicides, le 2,6‐dichlorobenzonitrile (dichlobénil), le. N‐(3‐chlorophényle) carbamate d'isopropyle (chlorpropham), la 2‐chloro‐N‐iso‐propylacétanilide (propachlore) et la 2‐chloro‐2′,6′‐diéthyl‐N‐(méthoxy‐méthyle) acétanilide (alachlore), sur l'induction par l'acide gibbérellique de l'α‐amylase dans l'endosperme de I'orge. L'induction de l'amylase par l'acide gibbérellique fut inhibée par les quatre herbicides, le dichlobénil et le chlorpropham se montrant les plus actifs à cet égard. Dans tous les cas, l'inhibition s'accrut avec I'addition de concentrations croissantes d'herbicide. L'addition des herbicides au mélange en réaction montra qu'aucun d'entre eux n'affectait directement la réaction enzymatique de l'amidon. Die Hemmung der gibberellininduzierten α‐Amylaseaktimtdt in Gerstenendosperm durch gewisse Herbizide Zusammenfassung. Der Einfluss der vier Herbizide 2,6‐Dichlorbenzonitril (Dichlobenil), Isopropyl‐N‐(3‐chlorphenyl)‐carbamat (Chlorpropham), 2‐Chlor‐N‐isopropylace‐tanilid (Propachlor) und2‐Chlor‐2′,6′‐diäthyl‐N‐(methoxymethyl)‐acetanilid (Alachlor) auf die gibberellininduzierte α‐Amylasebildung in Gerstenendosperm wurde untersucht. Die Induktion von α‐Amylase durch Gibberellinsäure wurde von alien vier Herbiziden ge‐hemmt. Am wirksamsten waren hierbei Dichlobenil und Ghlorpropham. In alien Fällen wurde die Hemmwirkung durch ansteigende Herbizidkonzentrationen verstärkt. Die Zugabe der Herbizide zu dem Reaktionsgemisch zeigte, dass keines von ihnen die Reaktion zwischen Enzym und Stärke direkt beeinflusste.

BAS-145-138 considerably muted the herbicidal effect of the sulfonylurea herbicides on corn. Decreases of 54 and 52% in shoot fresh and dry weight caused by 10 μM chlorsulfuron were countered almost completely by 1.5 mM BAS-145-138 with only a 10% loss in fresh weight and a 3% loss in dry weight. Similar strong antidotal influence by BAS-145-138 on chlorimuron was observed. BAS-145-138 partially protected corn against sulfometuron. Shoot fresh weight of corn treated with 0.2 μM sulfometuron was inhibited 88%, whereas adding 0.5 or 1.5 mM BAS-145-138 reduced inhibition to 52 and 24%, respectively.

This study demonstrates that corn can be partially safened by BAS-145138 against sulfonyl­urea and imidazolinone herbicides. The corn seeds were impregnated with BAS-145138 by soaking the seeds for 6 h in solutions of the safener. BAS-145138 had no effect on corn growth. However, corn shoot and root growth in length, fresh weight, and dry weight was partially protected by BAS-145138 from the phytotoxic effects of the sulfonylurea herbicides thiametu­ron and CGA -136872. Similar protection was given to corn against the phytotoxic activity of the imidazolinone herbicides imazapyr, imazaquin, and imazethapyr. This study suggests that corn could be safened with BAS-145138 against the phytotoxic effects of residual amounts of sulfonylurea and imidazolinone herbicides found in rotations take place.

Chlorophyll content of wheat (Triticum aestivum L. ‘Mericopa’) and corn (Zea mays L. ‘Merit’) treated with the herbicide fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)-phenyl]-4(1H)-pyridinone} and grown under high light intensity (10.8 klux), was markedly reduced. Corn and wheat germinated from seeds treated with 10 uM fluridone and grown for 6 days were almost completely bleached. Under low light intensity (108 lux) the influence of fluridone on chlorophyll production was greatly reduced. Under very low light intensity (21.5 lux) this influence was almost completely lost. The effect of light on the activity of fluridone suggests that the inhibition of carotenoid production may represent the mode of action of this herbicide. This study shows that the carotenoid content of wheat or corn drops dramatically when these plants are treated with fluridone.

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