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Notes: Glyphosate was applied at four rates under greenhouse conditions to Avena fatua L. plants at four stages of seed development. Application at anthesis completely prevented the formation of viable seeds. Application five days after anthesis (DAA) of the terminal floret of the panicle significantly reduced seed production at all herbi-cide rates used, and at 1.76 kg a.i. ha-1 no viable seeds were produced. When applied 10 DAA, only the highest rate of glyphosate resulted in substantial reduction in number of primary seeds, but seed viability suffered at all herbicide levels. Glyphosate applied 15 DAA still produced a significant decrease in primary and secondary seed production and biomass. Both the viability and the germination rate of seeds from treated plants were significantly affected. When the herbicide was applied to plants 5 DAA, no viable seeds were produced by plants surviving the highest rate, and all rates significantly reduced germination. Glyphosate applied 10 DAA significantly suppressed germination, with 1.76 kg a.i. ha-1 being the most effective rate. When applied to plants 15 DAA, only the highest rate of glyphosate significantly affected the overall germination of both primary and secondary seeds, but the normal imposition of dormancy was partially blocked in seeds from plants treated with 0.44 and 0.88 kg a.i. ha-1. These findings are relevant to chemical summerfallow and crop desiccation practices.

Notes: Greenhouse studies were conducted to determine the effect of both ester and amine formulations of MCPA on the phytotoxicity of imazamethabenz applied to wild oats (Avena fatua). The MCPA ester antagonized activity of the liquid concentrate (LC) formulation of imazamethabenz but not the suspension concentrate (SC) formulation of imazamethabenz when the combination was applied to wild oats at two-to three-leaf stage without tiller. The MCPA amine antagonized the efficacy of both formulations of imazamethabenz on wild oats at the two-to three-leaf stage. When the herbicides were applied at the three- to four-leaf stage with one or two tillers, the antagonism was found only with MCPA amine and imazamethabenz-LC. In general, antagonism is most likely to occur at an early stage of wild oats. MCPA amine was more antagonistic than MCPA ester on the phytotoxicity of imazamethabenz. Imazamethabenz-SC can be tank mixed with MCPA ester but should not be tank mixed with MCPA amine. Imazamethabenz-LC should not be tank mixed with either ester or amine of MCPA because of antagonism, especially when herbicides are applied at early stage. When MCPA was applied at intervals of from 2 to 24 h following applications of imazamethabenz-LC, there was no antagonistic effect of MCPA and the same level of phytotoxicity was produced as with imazamethabenz-LC alone. In the reverse sequence of MCPA followed by imazamethabenz-LC, the greatest antagonism of phytotoxicity of imazamethabenz-LC occurred when 2 h separated the two applications. This effect was lessened when the elapsed time increased. Effet du MCPA sur I'efficacitée de l'imazaméthabenz-méthyle sur la folle avoine (Avena fatua L.)Des études en serres ont étéé réalisées pour déterminer I'effet de formulations ester et amine du MCPA sur l'efficacité de l'imazaméthabenz contre la folle avoine (Avena fatua L.). Lorsque le mélange était appliqué sur des folles avoines au stade 2–3 feuilles sans talle, l'ester de MCPA était antagoniste de la formulation de l'imazaméthabenz en concentré liquide (LC) mais pas de la formulation en suspension concentrée (SC). Le MCPA amine était antagoniste des deux formulations d'imazaméthabenz. Quand les herbicides étaient appliqués au stade 3–4 feuiles avec 1–2 talles, l'antagonisme ne s'observait qu'avec le MCPA amine et l'imazaméthabenz- LC. En général, l'antagonisme se produisait surtout aux stades précoces de la folle avoine. Le MCPA amine était plus antagoniste de l'activité de l'imazaméthabenz que le MCPA ester. L'imazaméthabenz-SC peut étre mélangé au moment du traitement avec le MCPA ester mais pas avec le MCPA amine. L'imazaméthabenz- LC ne doit pas étre mélangé au moment du traitement avec le MCPA, qu'il soit sous forme ester ou amine, surtout quand les herbicides sont appliqués è un stade précoce. Quand le MCPA était appliquéè des intervalles de 2 è 24 h après l'imazaméthabenz-LC, il n'y avait pas d'antagonisme du MCPA. Si l'ordre des applications était inversé, l'antagonisme était le plus important lorsque 2 h les séparaient et il diminuait lorsque l'intervalle augmentail. Beinflussung der Phytotoxizität von Imazamethabenz-methyl auf Avena fatua L. durch MCPAIn Gewächshausversuchen setzte MCPA-Ester die Wirkurlg der Flüssig-Formulierung von Imazamethabenz-methyl auf Avena fatua L. im 2- bis 3-Blatt-Stadium herab, aber nicht die der Suspensions-Formulierung. MCPA-Amin war gegenüber beiden Formulierungen antagonistisch. Im 3- bis 4-Blatt-Stadium bei 1 bis 2 Bestockungstrieben trat die Wirkungsminderung durch MCPA-Amin nur bei der Flüssig- Formulierung ein. Also scheint der Wirkungsantagonismus in frühen Avena-fatua- Entwicklungsstadien und für MCPA-Amin am stärksten zu sein, so daé es von Tankmischungen mit der Suspensions-Formulierung ausgenommen werden sollte. Die Flüssig-Formulierung sollte weder mit MCPA-Amin noch -Ester gemischt werden. Bei Applikation von MCPA 2 bis 12 h nach Imazamethabenz-methyl in der Flüssig-Formulierung wurde die Wirkung nicht beeinträchtigt. Umgekehrt ergab sich bei Anwendung der Flüssig-Formulierung 2 h nach einer MCPA-Ausbringung der gröte Antagonismus, der sich mit längerem Abstand zwischen den Anwendungen verringerte.

Notes: Incubation in gibberellin A3 (GA3) or a 1 h immersion pretreatment with 800 mm sodium hypochlorite (NaOCl) both promoted 20% germination of freshly harvested dormant wild oat (Avena fatua L.) seeds that had been imbibed on water for 10 days. GA3 immediately following 1 h NaOCl immersion pretreatment induced maximum germination. Moist storage (MS) after NaOCl immersion pretreatment resulted in less germination on transference of the seeds to GA3, indicating that GA3 responsiveness was lost during MS. These seeds required a repeal NaOCl immersion plus a GA3 treatment to induce maximum germination. However, GA3 still gave maximum germination if the seeds were stored dry after initial NaOCl immersion. Seeds with water-induced dormancy responded similarly to freshly harvested dormant seeds when treated with NaOCl, MS, or GA3. Seeds afterripened a longer time had a reduced requirement for exogenous GA3 in the breaking of dormancy indicating that the depth of the GA3-dependent dormancy decreased with duration of after-ripening.Dormant dehulled seeds with a brief NaOCl pretreatment germinated about 30% on water but gave maximum germination when incubated on GA3, an effect that persisted even after 21 days of MS. This effect, coupled with the previous findings, suggested that the NaOCl treatment weakened membrane barriers of the seed coat through a scarification-like effect, similar to the effects of piercing and acid immersion, and thereby produced increased sensitivity to the presence of GA3. The loss of responsiveness to GA3 in NaOCl-treated seeds during MS may involve the restoration of integrity of the seed coverings, a process occurring only in the imbibed state, and, presumably, most rapidly in freshly harvested, intact seeds.

Notes: Summary Tubers of virus-free Norland, Kennebec, Norchip, Russett Burbank, Red Pontiac, Norgold and Early Ohio potato varieties with a common environmental history were freeze-dried, and the major phosphorus-containing fractions determined. The method devised gave very reproducible values for phospholipid, nucleotide phosphorus, phytic acid phosphorus, starch phosphorus and nucleic acid phosphorus. Very little varietal differences were found as long as environmental factors were constant. The greatest variation was in inorganic phosphorus levels. There were no obvious relationships between protein level and any of the phosphorus-containing fractions.

Notes: Summary Selection for high protein potatoes may be influenced by maturity level at harvest. as well as by genetic capacity. The phosphorus metabolism provided a clue as to physiological maturity. We determined the major phosphorus compounds present in tubers of named cultivars sampled at weekly intervals during the growing season. We also assessed the phosphorus compounds associated with mature tubers of twelve Phureja-Tuberosum hybrid lines varying widely in protein content, and in ploidy. High levels of organic phosphorus, nucleic acid phosphorus, and lipid phosphorus were characteristic of immature tubers. These values declined to a mid-season plateau that was maintained to harvest. Much greater variability in phosphorus balance was found in the hybrid clones analysed than in named cultivars. In some cases high protein levels were clearly associated with delayed maturity of hybrid lines. Other clones appeared to exhibit greater capacity for protein synthesis in the maturing tuber.

Notes: Abstract Foliar application of imazamethabenz at sublethal doses of 100 and 200 g a.i./ha to wild oat plants at the two-leaf stage without tillers greatly inhibited the growth of the main shoot but increased tillering. The near cessation of sheath and the main stem elongation indicated that the major effect of imazamethabenz on the main shoot was inhibition of intercalary growth. Low doses of imazameth-abenz treatment resulted in more leaves (including leaf primordia) in the main stem but did not affect mature first and second leaves. Sublethal doses of imazamethabenz only briefly inhibited tiller growth. A later increase in tillering in treated plants resulted from the stimulated resumed growth of tillers and the increased initiation of tiller buds. Such enhanced tillering mainly resulted from the release of apical dominance due to the inhibition or cessation of the main stem growth with imazamethabenz treatment. Both doses of imazamethabenz (100 and 200 g a.i./ha) significantly reduced the biomass of shoots and roots, but increased the ratio of roots/ shoots dry weight.

Notes: Abstract The absorption and translocation of fenoxaprop-ethyl and imazamethabenz-methyl were investigated in wild oat (Avena fatua L.) plants grown under different temperature and light intensity conditions by using 14C tracer techniques. The phytotoxicity of both herbicides, applied as individual droplets, was also determined under similar environments. The absorption of fenoxaprop-ethyl and imazamethabenz-methyl was increased by high temperature (30/20°C) and to a lesser extent by 70% shading; low temperature (10/5°C) had limited effect on the absorption. The basipetal translocation of fenoxaprop-ethyl was not affected by high temperature, and the increase in imazamethabenz-methyl translocation at high temperature was likely the result of the increased absorption. Low temperature decreased total translocation and translocation efficiency in both fenoxaprop-ethyl and imazamethabenz-methyl. Low light intensity tended to reduce the efficiency of basipetal translocation of both herbicides. Fenoxaprop-ethyl phytotoxicity was reduced by high temperature but not by low temperature. Temperature had little effect on imazamethabenz-methyl effectiveness. Under 70% shading, the phytotoxicity of both herbicides was enhanced.

Notes: Abstract Experiments were conducted in greenhouse, growth chamber, and laboratory conditions to determine the effect of ammonium sulfate [(NH4)2SO4] on the phytotoxicity, foliar uptake, and translocation of imazamethabenz on wild oat. Rates of (NH4)2SO4 up to 5% (w/v) applied with a greenhouse sprayer did not affect the phytotoxicity of the herbicide when the mix was applied at the one- to two-leaf stage. However, inclusion of 1 and 2% (NH4)2SO4 increased the phytotoxicity of the herbicide when the mix was sprayed at the two- to three-leaf, or the three- to four-leaf stage. At 10%, (NH4)2SO4 decreased the phytotoxicity of the sublethal dosage of the herbicide. When the herbicide was applied as individual drops to the growth chamber-grown plants, inclusion of (NH4)2SO4 at 1% did not affect phytotoxicity as measured by shoot growth. The presence of (NH4)2SO4 did not affect the amount of imazamethabenz retained by wild oat foliage, but it decreased [14C]imazamethabenz absorption, slightly antagonized acropetal translocation, and increased the basipetal translocation of [14C]imazamethabenz. It was concluded that application methods greatly modify the effect of (NH4)2SO4 on imazamethabenz phytotoxicity. Herbicide absorption and translocation as determined by one method do not necessarily represent the absorption and translocation patterns when different application methods are used. Absorption and translocation were not the factors that were responsible for the observed effect of (NH4)2SO4 on the herbicide phytotoxicity.

Notes: Abstract Skotodormant seeds of Lactuca sativa Grand Rapids imbibed in darkness for 10 days (10-day DS) germinated poorly upon terminal treatment with red light (R) or gibberellin A3 (GA3). Inorganic nitrogen salts in the imbibition solutions reduced seed skotodormancy. Ten-day DS seeds, imbibed in 25 mm salt solutions followed by terminal R, germinated 99% if imbibed in NH4NO3, 70% if imbibed in KNO3 or NH4Cl, and 55% if imbibed in NaNO3. Seeds imbibed in higher salt concentrations germinated fully upon terminal R treatment. Seeds imbibed in 25 mm NH4Cl or in 50 mm NH4NO3 germinated completely upon GA3 treatment. Osmotic effects of imbibition media accounted for only part of the effect, since seeds imbibed in 50 mm CaCl2 or NaCl germinated poorly following R or GA3 treatment. Seeds imbibed in 500 mm polyethylene glycol (PEG) 1000 or mannitol solutions for 10 days still exhibited skotodormancy. Treatments of R or GA3 did not stimulate germination in seeds imbibed in mannitol, but germination was complete if seeds were given 1-h acid immersion plus a water rinse before the terminal R or GA3 treatment. Seeds imbibed in 50–500 mm PEG during 10-day DS germinated significantly better in response to terminal R. Terminal GA3 significantly improved germination only in seeds imbibed at 500 mm PEG. Pfr appeared to function in mannitol-imbibed seed only after an acid treatment. Seed exposure to inorganic nitrogen salts during the 10-day DS maintained seed sensitivity to terminal R or GA3 treatment. The depth of seed skotodormancy was related to the availability of inorganic nitrogen and also involved the levels of Pfr or endogenous GA3.

Notes: Abstract. The element phosphorus made up 0.5% of the dry weight of dehulled Avena fatua caryopses 7 days after anthesis (DAA), half of it inorganic (Pi). Caryopses detached and pierced 7 DAA germinated in vitro with a rapid drop in Pi levels. By 15–20 DAA caryopsis dry weight had increased three- to fourfold, but phosphorus made up less than 0.04% of the dry weight of this enlarged caryopsis. Caryopses at this stage germinated readily without piercing if incubated in vitro. A further decrease in Pi accompanied by a marked increase in phytate phosphorus began about 15 DAA and continued during later seed maturation. By 20 DAA, when embryos were relatively mature and endosperm cell division had ceased, a decrease in caryopsis water content (as a percentage of dry weight) began, and seed dormancy became apparent. As starch and phytate reserves accumulated, Pi and water levels of the caryopsis diminished. Higher levels of endogenous Pi coincided with the anabolic events of initial seed formation and, to a lesser extent, with anabolic events of seed germination. Decreasing Pi levels coincided with accumulation of nutrient reserves, lowering of water content, and the initiation of dormancy. The data suggest that (1) enzymes associated with the formation and development of the embryo may be activated by the high Pi levels present during initial seed differentiation; (2) embryo quiescence and dormancy are facilitated by the drop of Pi levels which accompanies the accumulation of starch and phytate reserves; and (3) the increase in Pi which accompanies seed afterripening aids in the termination of dormancy and the resumption of germination.