ALBERT

Notes: The linear-chain approximation is used to calculate the spectrum of confined longitudinal-optical (LO) phonon frequencies in short-period strained-layer superlattices. The frequencies for confined LO-phonon modes are reported explicitly for the case of GaAs/GaP short-period strained-layer superlattices grown in the 〈001〉 direction. These results are compared with the few existing experimental measurements for such superlattices.

Notes: Classical Mendelian experiments were conducted to determine the genetics and inheritance of quinclorac and acetolactate synthase (ALS)-inhibitor resistance in a biotype of Galium spurium. Plants were screened with the formulated product of either quinclorac or the ALS-inhibitor, thifensulfuron, at the field dose of 125 or 6 g active ingredient (a.i.) ha−1 respectively. Segregation in the F2 generation indicated that quinclorac resistance was a single, recessive nuclear trait, based on a 1 : 3 segregation ratio [resistant : susceptible (R : S)]. Resistance to ALS inhibitors was due to a single, dominant nuclear trait, segregating in the F2 generation in a 3 : 1 ratio (R : S). The genetic models were confirmed by herbicide screens of F1 and backcrosses between the F1 and the S parent. F2 plants that survived quinclorac treatment set seed and the resulting F3 progeny were screened with either herbicide. Quinclorac-treated F3 plants segregated in a 1 : 0 ratio (R : S), hence F2 progenitors were homozygous for quinclorac resistance. In contrast, F3 progeny segregated into three ratios: 1 : 0, 3 : 1 and 0 : 1 (R : S) in response to ALS-inhibitor treatment. This segregation pattern indicates that their F2 parents were either homozygous or heterozygous for ALS-inhibitor resistance. Therefore, there were clearly two distinct resistance mechanisms encoded by two genes that were not tightly linked as demonstrated by segregation patterns of the F3.

Notes: The dose-response, foliar uptake, translocation and metabolism of the methylheptyl ester (MHE) of fluroxypyr were examined in lambs-quarters (Chenopodium album L.), wild buckwheat (Polygonum convolvulus L.), Canada thistle (Cirsium arvense L. Scop.) and field bindweed (Convolvulus arvensis L.). Under controlled environment growth room conditions, E50 values, determined from shoot dry weights of the susceptible species, wild buckwheat (16 g ha−1) and field bindweed (40 g ha−1), were markedly different than those of the tolerant species, lambsquarters (331 g ha−1) and Canada thistle (〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:00431737:WRE333:ges" location="ges.gif"/〉800 g ha−1). Regardless of species, more than 80% of applied [14C]fluroxypyr-MHE was absorbed by foliar surfaces 120 h after treatment. Translocation of radioactivity out of the treated leaves of susceptible species was significantly greater than that of tolerant species. For example, 120 h after treatment with [14C]-fluroxypyr-MHE, the proportion of applied radioactivity translocated in tolerant Canada thistle and lambsquarters was 15 and 10%, respectively, whereas in susceptible wild buckwheat and field bindweed it was 41 and 40% of applied radioactivity, respectively. High-performance liquid chromatography (HPLC) of plant extracts indicated four distinct chroma-tographic peaks common to all four species. More fluroxypyr was recovered in the susceptible species (70%) than in the tolerant species (30%), 120 h after application. Selectivity differences between the tolerant and susceptible species may be the result of enhanced metabolic transformation of the herbicide to more polar, non-phytotoxic compounds with limited mobility within the tolerant species. Les bases de la sélectivité du fluroxypyr La courbe dose effet, la pénétration foliaire, la migration et le métabolisme de Tester méthyle-heptyle (MHE) du fluroxypyr ont étéétudiés chez le chénopode blanc (Chenopodium album L.), la renouée faux-liseron (Polygonum con-vulvulus L.), le chardon des champs (Cirsium arvense L. Scop.) et le liseron des champs (Convolvulus arvensis L.). En conditions de crois-sance contrôlées, les valeurs ED50, déterminées à partir du poids de matière sèche des parties aériennes étaient nettement différentes chez les plantes sensibles et chez les plantes résistan-tes:renouée faux-liseron, 16 g ha−1; liseron des champs, 40 g ha−1; chénopode blanc, 331 g ha−1; chardon des champs, 〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:00431737:WRE333:ges" location="ges.gif"/〉800 g ha−1. Quelle que soit 1'espèce, plus de 80% du [14C]fluroxypyr-MHE pénétrait dans les feuilles en 120 h. La migration de la radioactivité hors des feuilles traitérs était significativement plus importante chez les plantes sensibles que chez les plantes tolérantes. Par exemple, 120 h après le traite-ment avec du [14C]fluroxypyr-MHE, la proportion de radioactivité appliquée qui avait migré dans le chardon des champs et le chénopode, tolérants, était respectivement 15 et 10%, alors que chez la renouée faux-liseron et le liseron des champs, sensibles, elle était respectivement 41 et 40%. Des analyses par HPLC des extraits de plantes montraient quatre pics chro-matographiques distincts dans chacune des quatre espèces. Davantage de fluroxypyr était retrouvé 120 h après 1'application chez les plantes sensibles que chez les plantes résistantes (70% contre 30%). Les différences de sensibilité entre espèces pourraient être dues chez les plantes tolérantes à un métabolisme plus important de l'herbicide en composés plus polaires, non phytotoxiques et peu mobiles. Grundlagen für die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, Translokation und Metabolismus des Methylheptyl-Esters (MHE) von Fluroxypyr wurden bei Weißem Gänsefuß (Chenopodium album L.), Gemeinem Windenknöterich (Polygonum convolvulus L.), Acker-Kratzdistel (Cirsium arvense (L.) Scop.) und Gemeiner Ackerwinde (Convolvulus arvensis L.) untersucht. Unter den kontrollierten Umweltbedingungen eines Phytotrons wurden anhand des Trockengewichts die ED50-Werte bestimmt, die bei den empfindlichen Arten Polygonum convolvulus mit 16 g ha−1 und Convolvulus arvensis mit 40 g ha−1 sich deutlich von denen der toleranten Arten Chenopodium album mit 331 g ha−1 und Cirsium arvense mit 〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:00431737:WRE333:ges" location="ges.gif"/〉800 g ha−1 unterschieden. Unabhängig von der Art waren mehr als 80 % der Aufwandmenge von [14C]-Fluroxypyr-MHE durch die Blattoberflächen 120 h nach der Behandlung aufgenommen. Die Translokation der Radioaktivität aus den behandelten Blättern war bei den empfindlichen Arten signifikant größer als bei den toleranten. Z. B. waren 120 h nach der Behandlung bei den toleranten Arten Cirsium arvense und Chenopodium album 15 bzw. 10 % der Radioaktivität transloziert, während es bei den empfindlichen Arten Polygonum convolvulus und Convolvulus arvensis 41 bzw. 40 % waren. Bei allen 4 Arten ergab eine HPLC-Untersuchung der Pflanzenextrakte 4 distinkte Peaks. Bei den empfindlichen Arten wurde 120 h nach der Anwendung mit 70 % mehr Fluroxypyr wiedergefunden als bei den toleranten (30 %). Die Selektivitätsunterschiede zwischen den toleranten und empfindlichen Arten könnten auf einen beschleunigten Metabolismus des Herbizids zu stärker polaren, nichphytotoxischen Stoffen mit eingeschränkter Mobilität bei den toleranten Arten zurückgeführt werden.

Notes: The patterns of absorption and translocation of 14C clopyralid commercially formulated as the acid, monoethanolamine salt, potassium salt, 2-ethylhexyl ester and 1 -decyl ester were compared in Cirsium arvense and Polygonum convolvulus grown under three environmental regimes. Plants were grown under a 35% or 65% RH regime in silica sand maintained at 33% w/w moisture or under a water stress regime at 65% RH. Approxi mately 26,39,86,93 and 100% of the applied 14C-activity from the 2-ethylhexyl ester, acid, monoethanolamine salt, 1-decyl ester and potas sium salt, respectively, were recovered 72 h after application to glass cover slips placed in the growth room. However, loss of applied 14C-activity after application of the five formulations to both plant species was significant only for the 2-ethylhexyl ester. Regardless of environmental regime, the acid was the most readily absorbed formulation. In contrast to the acid, the salts and esters were less readily absorbed. When the data were expressed as a percentage of absorbed radioactivity, there was no significant difference in translocation when the acid, monoethanolamine salt and potassium salt were compared. However, significantly smaller quantities of the absorbed 2-ethylhexyl and 1-decyl ester were exported from the treated leaf. These results indicate that once absorbed, the esters do not readily partition out of the cuticle, whereas the acid and two salts move into the symplast for subsequent translocation. When the results of the three environmental regimes were compared, the absorption of the monoethanolamine and potas sium salts were greatly reduced under low humi dity or water stress, whereas the acid and esters were not affected.

Notes: In controlled environmental studies, a marked difference was observed between the growth pattern of tomato and eastern black nightshade plants that received doses of 2,4-D ranging from 28 to 952 g a.e. ha−1. The highest dose of 2,4-D reduced the dry weight of eastern black nightshade and tomato by approximately 15 and 50%, respectively, when compared with controls. Although the height of both species was reduced by all doses of 2,4-D, eastern black nightshade plants produced secondary shoots, which compensated for any potential loss in dry weight that otherwise may have occurred. Tomato plants did not produce secondary shoots. After application of 14C-2,4-D to tomato and eastern black nightshade, the pattern of 14C absorption and translocation was similar in both plant species. However, there was significantly more radioactivity recovered in tomato (72%) than in eastern black nightshade (52%) plants, 72 h after treatment. Assay radioactivity in the nutrient solution of hydroponically grown plants indicated that 7·0 and 27·9% of the applied radioactivity was exuded from the roots of tomato and eastern black nightshade, respectively, within 72 h after treatment. Assay of plant extracts by thin layer chromatography revealed that the amount of radioactivity that remained as unaltered 2,4-D was 73 and 49% in tomato and eastern black nightshade, respectively, 72 h after treatment. Thus the greater tolerance of eastern black nightshade appeared to be due to greater rates of 2,4-D metabolism and/or greater rates of herbicide elimination by root exudation.

Notes: Laboratory experiments were conducted to determine the effects of soil moisture, simulated rainfall and time of day of spray application on the efficacy of glufosinate-ammonium in barley (Hordeum vulgare L. cv. ‘Samson’) and green foxtail (Setaria viridis (L.) Beauv.) plants. Environmental variables examined were three soil moisture levels (18% moisture, 50% moisture and saturated), three intensities of simulated rainfall following spray application [drizzle (4 mm), moderate (9 mm) and heavy (22 mm)] and two times of spray application (begin ning and end of a 16-h photoperiod). The efficacy of 100 g ha−1 glufosinate-ammonium on barley was greatest at 18% soil moisture when measured by both ammonia and dry weight accumulation in the shoots. At the same dose green foxtail showed less ammonia accumula tion at 18% soil moisture than under other soil moisture levels, but showed no significant differences in dry weight accumulation 14 days after treatment (DAT). Simulated rainfall shortly after spraying reduced the efficacy of glufosinate-ammonium on both species. At the field dose of 800 g ha−1, a rain-free period of 1–8 h was necessary for barley, while a period of less than 20 min was necessary for green foxtail to obtain herbicidal activity comparable with that of treated plants which received no rain. Based on dry weight accumulation, barley plants were equally sensitive and green foxtail plants were significantly more susceptible when glufosinate-ammonium was applied at the end compared to the beginning of the photoperiod. Both species accumulated significantly more ammonia in the shoots during the initial 24 h following application if sprayed at the end of the photoperiod. Of the environmental factors examined in this study, rainfall after spray application caused the greatest reduction of glufosinate-ammonium efficacy. Influence de I'humiditt du sol, de la pluie artificielle et de I'époque d'application sur I'effi cacité du glufosinate-ammonium Des essais de laboratoire ont été conduits pour déterminer les effets de Phumidité du sol, de la pluie et de I'époque d'application sur 1'efficacité de glufosinate-ammonium sur 1'orge (Hordeum vulgare L. c.v. ‘Samson’) et la sétaire (Setaria viridis (L.) Beauv.). Les variables environne mentales examinées étaient 3 taux d'humidité du sol (18%, 50% et saturation), 3 intensités de pluie artificielle suivant ('application (faible—4 mm; modéré 9 mm; et forte 22 mm) et 2 époques d'application (début et fin d'une photopériode de 16 h). L'efficacite de 100 g ha−1 de glufosinate-ammonium sur orge était maximale a 18% d'humidité du sol, mesurée à la fois par I'accumulation d'azote et de matiére séche dans les tiges. A la même dose, la sétaire exprime une moins grande accumulation d'azote à 18% d'humidité du sol qu'aux autres taux d'humidité mais ne montre pas de différences dans I'accumulation de matière sèche 14 jours après le traitement (JAT). Une pluie artificielle suivant de près la pulvérisation réduit 1'eficacité du glufosinate-ammonium sur les deux espèces. A la dose d'utilisation de 800 g ha−1, une période sans pluie de 1 à 8 heures est nécessaire pour l'orge, tandis que moins de 20 minutes sont nécessaires pour le sétaire pour obtenir une activité herbicide comparable à celle observée avec des plantes traitées sans pluie. En se fondant sur l'accumulation de matière sèche, les plantes d'orge étaient également sensibles, et les sétaires étaient significativement plus sensibles quand le glufosinate-ammonium était appliquéà la fin plutêt qu'au début de la photopériode. Les 2 espèces accumulent significativement plus d'azote dans les tiges pendant les 24 premières heures suivant l'application quand elle a lieu en fin de photopériode. Des facteurs environnementaux examinés dans cette étude, la pluie après la pulvérisation cause la plus grande réduction d'efficacité glufosinate-ammonium. Einfluβ von Bodenfeuchte, simuliertem Niederschlag und Applikationszeitpunkt auf die Wirksamkeit von Glufosinat-ammonium In Laborversuchen wurde der Einfluß von Bodenfeuchte, simuliertem Niederschlag und Applikationszeitpunkt auf die Wirksamkeit von Glufosinat-ammonium auf die Gersten-Sorte ‘Samson’ (Hordeum vulgäre L.) und Grüne Borstenhirse (Setaria viridis (L.) Beauv.) untersucht. Als Umweltvariablen wurden 3 Bodenfeuchtegrade (18%, 50% und gesättigt), 3 Niederschlagsintensitäten [Niesei (4 mm), mäßig (9 mm) und stark (22 mm)] nach der Behandlung und 2 Applikationszeitpunkte (Beginn und Ende einer 16-h-Photoperiode) eingesetzt. Die Wirkung von 100 g ha−1 Glufosinat-ammonium auf die Gerste war bei 18% Bodenfeuchte sowohl hinsichtlich des Ammoniumgehalts als auch der Trockenmasse des Sprosses am größten. Bei derselben Dosis hatte die Grüne Borstenhirse einen geringeren Ammoniumgehalt bei 18% Bodenfeuchte als bei anderen Feuchtegraden, zeigte jedoch 14 Tage nach der Behandlung keine signifikanten Unterschiede in der Trockenmasse. Niederschlag kurz nach der Behandlung verminderte die Wirksamkeit bei beiden Arten. Bei der Felddosis von 800 g ha−1 war eine niederschlagsfreie Periode von 8 Stunden notwendig, bei der Grünen Borstenhirse jedoch weniger als 20 Minuten, um dieselbe Wirkung zu erreichen wie bei Pflanzen, die ohne Regen geblieben waren. Hinsichtlich der Trockenmassebildung waren Gerstenpflanzen gleich empfindlich und Borstenhirsenpflanzen signifikant empfindlicher, wenn Glufosinat-ammonium am Ende statt am Beginn der Photoperiode appliziert wurde. Beide Arten hatten in den Sprossen während der ersten 24 Stunden nach der Behandlung am Ende der Photoperiode einen signifikant höheren Ammoniumgehalt. Von den hieruntersuchten Umweltfaktoren reduzierte der Niederschlag nach der Behandlung die Wirkung von Glufosinat-ammonium am meisten.

Notes: Experiments were conducted to examine the up take, translocation and metabolism by S. vulgaris of two distinctly different herbicides: 2,4-D, a phenoxyalkanoic acid with growth regulator activity to which this species exhibits complete tolerance, and chlorsulfuron, a sul-fonylurea to which S. vulgaris is highly sensitive. Despite their structural dissimilarities 2,4-D and chlorsulfuron was readily absorbed by S. vulgaris with 65 and 69%, respectively, of the applied dosage being absorbed within 72 hours after treatment. Approximately 35% of the 2,4-D and 10% of the chlorsulfuron label was translocated out of the treated leaf after 72 hours. Neither herbicide accumulated in the terminal bud. Seventy-two hours after treatment 63% of the recovered 14C remained as unaltered 2,4-D in S. vulgaris, while in tomato, a 2,4-D sensitive species, 65% of the recovered 14C remained as intact herbicide. In S. vulgaris approximately 86% of the radioactivity remained as intact chlorsulfuron 72 hours after treatment compared to 12% in the tolerant wheat. The tolerance of S. vulgaris to 2,4-D could not be accounted for by limited absorption, translocation nor metabolic degradation of the herbicide. The sensitivity of S. vulgaris to chlorsulfuron would appear to be related to the inability of this species to metabolize the herbicide molecule.