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Notes: Primisulfuron-resistant (AR and MR) and -susceptible (AS and MS) Bromus tectorum biotypes were collected from a Poa pratensis field at Athena, Oregon, and in research plots at Madras, Oregon. Studies were conducted to characterize the resistance of the B. tectorum biotypes. Whole plant bioassay and acetolactate synthase (ALS) enzyme assay revealed that the AR biotype was highly resistant to the sulfonylurea (SU) herbicides, primisulfuron and sulfosulfuron and to a sulfonylaminocarbonyltriazolinone (SCT) herbicide, propoxycarbazone-sodium. However, the AR biotype was not resistant to imazamox, an imidazolinone (IMI) herbicide. Results of the whole plant bioassay studies showed that the MR biotype was moderately resistant to all ALS inhibitors tested. However, there were no differences in ALS sensitivities between the MR and MS biotypes. The nucleotide and amino acid sequence analysis of the als gene demonstrated a single-point mutation from C to T, conferring the exchange of the amino acid proline to serine at position 197 in the AR biotype. However, this mutation was not found in the MR biotype. Results of this research indicate that: the resistance of the AR biotype to SU and SCT herbicides is based on an altered target site due to a single-point mutation; resistance in the MR biotype is not due to a target site mutation.

Notes: Maximum arrowleaf sida (Sida rhombifolia L.) germination occurred at 35°C, whereas prickly sida (Sida spinosa L.) germinated to the same extent at 35 or 40°C. Arrowleaf sida germinated better than prickly sida at 20 and 25°C, but did not germinate at 40°C. Less than 50% of seed from both species were viable at 45°C after 21 days of exposure. Both species exhibited more than 75% germination at a range of pH from 5.0 to 8.0. Arrowleaf sida germinated to a greater extent than prickly sida from 0 to —800 kPa, and an osmotic stress of —200 kPa reduced prickly sida germination, whereas —400 kPa was necessary to reduce arrowleaf sida germination. Prickly sida emergence was optimal at a planting depth of 0.5 cm, and declined rapidly at deeper planting depths. However, arrowleaf sida emergence was equivalent at planting depths of 0.5–2.0 cm, with declining emergence below 2.0 cm. Neither species emerged from depths exceeding 5.0 cm. Light did not influence the germination of arrowleaf sida or prickly sida.Sida rhombifolia et Sida spinosa: germination et leveeLe maximum du germination pour Sida rhombifolia L. a été atteint à 35°C tandis que Sida spinosa L. a germé de facon équivalente à 35 ou 40°C. S. rhombifolia a mieux germé que S. spinosaà 20 et 25°C, mais n'a pas germéà 40°C. Moins de 20% de graines des deux espèces étaient encore viables à 45°C après 21 jours dèxposition. Les deux especes ont germéà plus de 75% dans des niveaux de pH allant de 5 à 8. S. rhombifolia a mieux germe que S. spinosa de 0 à 800 kPa, et un stress osmotique de —200 kPa a réduit la germination de S. spinosa, tandis que —400 kPa ont été nécessaires pour réquire la germination de S. rhombifolia. La levée de S. spinosaétait optimale à une profondeur de semis de 0,5 cm, et décroissait rapidement à des profondeurs plus élevées. Cependant la levée de S. rhombifoliaétait équivalente pour des profondeurs de 0,5 à 2 cm, avec une baisse à partir de 2 cm. Aucune des deux espèces n'a levéà des profondeurs supérieurs à 5 cm. La lumière n'a pas d'influence sur la germination des 2 espèces. Keimung und Auflaufen der Sidafaserpflanze (Sida rhombifolia L.) und der Stacheligen Samtmalve (Sida spinosa L.)Die stärkste Keimung lag bei der Sidafaserpflanze (Sida rhombifolia L.) bei 35 °C vor, während Samen der Stacheligen Samtmalve (Sida spinosa L.) bei 35 oder 40 °C gleich gut keimten. Samen der Sidafaserpflanze keimten bei 20 und 25 °C besser als die der Stacheligen Samtmalve, keimten jedoch nicht bei 40 °C. Nach Lagerung bei 45 °C für 21 Tage waren die Samen beider Arten zu 〈 20% keimfähig. Bei pH-Werten zwischen 5 und 8 keimten beide Arten zu 〉75%. Bei osmotischen Drücken zwischen 0 und —800 kPa keimte die Sidafaserpflanze besser als die Stachelige Samtmalve, deren Keimung ab —200 kPa gehemmt wurde, wahrend bei der Sidafaserpflanze —400 kPa erforderlich waren, die Keimung zu verringern. Samen der Stacheligen Samtmalve keimten am besten in 0,5 cm Tiefe, in gröβerer Ablagetiefe schnell schlechter. Bei der Sidafaserpflanze jedoch waren Aussaattiefen zwischen 0,5 und 2,0 cm gleich gut, erst bei Tiefen unter 2 cm ging der Auflauf zurück. Aus Tiefen unter 5 cm keimte keine der beiden Arten. Durch Licht wurde die Keimung der beiden Sida Arten nicht beeinflußt.

Notes: An accession of Camelina microcarpa suspected to be resistant to sulfonylurea herbicides was identified in Oregon in 1998 field experiments. Greenhouse research confirmed that the putative resistant biotype was resistant to chlorsulfuron and metsulfuron on a whole plant level. Compared with the resistant (R) biotype, the susceptible (S) biotype was 1000 and 10 000-fold more sensitive to metsulfuron and chlorsulfuron respectively. The R biotype was also resistant to other sulfonylurea, sulfonylaminocarbonyl-triazolinone, imidazolinone and triazolopyrimidine herbicides. An in vivo enzyme assay indicated that acetolactate synthase (ALS) from the R plants required 111 times more chlorsulfuron to inhibit activity by 50% compared with the amount required to have a similar effect on ALS from S plants. Analysis of the nucleotide and amino acid sequences demonstrated that a single-point mutation from G to T in the als1 gene conferred the change from the amino acid tryptophan to leucine at position 572 in the resistant biotype. This research confirmed that ALS inhibitor resistance in an Oregon accession of C. microcarpa is based on an altered target site conferred by a single-point mutation.

Notes: Abstract Polyadenylated-RNA (Poly(A)+RNA) levels have been studied during the germination of wheat embryos of high viability but differing vigour. In high-vigour embryos imbibed at 20°C the level of poly(A)+RNA falls dramatically over the first hour of imbibition, then remains constant up to 3 h of imbibition before increasing rapidly to a level similar to that found in the quiescent state by 7 h of imbibition. Median-vigour embryos imbibed at 20°C show similar changes in poly(A)+RNA content but the initial decrease and subsequent increase in poly(A)+RNA levels are less marked. On imbibition at 10°C, the poly(A)+RNA content in high-vigour embryos decreases to a lesser extent during the first hour than at 20°C and the level increases more slowly over the next 6 h than during the same time period at 20°C. The level of poly(A)+RNA in medianvigour embryos remains constant over the first 4 h of germination and then falls to a level of about half that found in quiescent high-vigour embryos. Polyacrylamide gel electrophoresis of total-RNA samples shows that the polyadenylic acid (poly(A)) sequences occur in RNA species ranging in size from 35-7S. Polyacrylamide gel electrophoresis of isolated poly(A) sequences demonstrates the presence of two size classes of poly(A) in quiescent embryos, but at 20°C a more heterodisperse pattern appears by 2 h of imbibition. At 10°C, two size classes of poly(A) persist throughout the period studied in both high- and median-vigour embryos, although in median-vigour embryos the ratio of larger: smaller poly(A)-tail sizes decreases more rapidly than in high-vigour embryos.