Control of stem nematode, Ditylenchus dipsaci, in onions, by granular nematicides applied to the soil

Aldicarb at 1.4–5.6 kg a.i. ha^-l or oxamyl at 1.3–5.2 kg a.i. ha^-1 applied over the seed furrows during sowing prevented much of the damage resulting from stem nematode attack in spring-sown onions. Rotting of bulbs in store due to stem nematode infestation was sometimes lessened by these treatments. Neither sowing onion seeds on soil ridges, nor applying aldicarb in two equal doses, one over the seed furrows during sowing, the other over the plants mid-season, controlled the nematode better or increased onion yields more than a single equivalent dose over the seed furrows. Applied as two doses in this way, aldicarb was sometimes more effective against the nematode in summer-sown onions than was an equivalent amount applied over the seed furrows during sowing. Only 2.5 kg or less aldicarb ha^-1 can be applied to onions without leaving unacceptable residues (>0.15 μg g^-1) in the harvested bulbs.     

Regulation of Pregerminative Rates of Respiration in Seeds of Various Weed Species by Potassium Nitrate

The effects of potassium nitrate (KNO₃) on germination and O₂uptake in seeds of various weed species were compared and contrastedwith water controls. When KNO₃ promoted germination, rates ofO₃ uptake were increased, when it was inhibitory, rates weredecreased, and when it had no effect there were no appreciabledifferences between the rates of O₂ uptake of KNO₃-and water-imbibedseeds. These effects were clearly the result of early metabolicevents for differences in O₂ uptake were detectable soon afterthe seeds were placed in the liquid media and for some considerabletime prior to germination (i.e. the protrusion of the radicle).The results are discussed in relation to a published hypothesisof other workers concerning the mechanism of seed dormancy breakage. Key words: Potassium nitrate, respiration, seeds     

The Effects of Temperature on Vegetative and Early Reproductive Growth of a Cold-Tolerant and a Cold-Sensitive Line of Phaseolus vulgaris L. 2. Nodular Uricase, Allantoinase, Xylem transport of N and Assimilation in Shoot Tissues

The activities of nodular uricase and allantoinase, the compositionof bleeding sap N, estimated rates of xylary N translocationand ureide assimilation in shoot tissues were compared in acold-tolerant (194) and sensitive (Seafarer, SF) line of nodulatedPhaseolus vulgaris grown under three different temperature regimes.Uricase activity increased with increasing growth temperatureand was generally greater in nodules of 194 than in SF at anyparticularly temperature. Extractable allantoinase activity,on the other hand, was highest in nodules from plants grownat the coolest temperature (15/10 C day/night) and there waslittle or no difference in activity between the lines. There was little difference in sap composition between linesor amongst temperature treatments. Ureides contributed between80–91 percent of the total sap N in both lines grown at25/15 or 20/15 C with a slightly lower per cent (65–84)when grown at 15/10 C. Estimated rates of N translocation werehigher in 194 than SF at the coolest growth temperature. Increasesin rates of N translocation between successive harvests of eitherline were often correlated with increases in total N accumulationand also an accumulation of ureides in stems plus petioles butnot leaves. Generally leaves assimilated all of the ureidesinto other compounds at all growth temperatures. Nodules andshoots of either line did not accumulate ureides at 15/10 C.194 Accumulated greater amounts of ureides in stems and petiolesthan SF when grown at the two warmer temperatures. The resultsare discussed in relation to the ability of 194 to fix greateramounts of N than SF at suboptimal growth temperatures. Phaseolus vulgaris, common bean, uricase, allantoinase, sap composition, ureide assimilation, low temperature stress     

Photoregulation of Phytochrome Synthesis in Germinating Embryos of Avena sativa L.

Hilton, J. R. and Thomas, B. 1987. Photoregulation of phytochromesynthesis in germinating embryos of Avena sativa L.—J.exp. Bot. 38: 1704–1712. The effect of light on the accumulation of phytochrome in germinatingAvena embryos was determined. A quantitative ELISA using monoclonalantibody AFRC MAC 56 was used to measure specifically type 1(or dark) phytochrome. A pulse of red light given after 14 himbibition but prior to the onset of type 1 phytochrome synthesis,strongly inhibited subsequent type 1 phytochrome accumulation.This effect of red light at 14 h was reversible by far-red lightindicating the involvement of phytochrome. Red light also inhibitedphytochrome synthesis after 18 h and 24 h imbibition but after24 h, far-red light did not reverse the effect. The effect ofred light treatment at 18 h was reversed by giving a pulse offar-red light at any time up to 30 h. Seed germination was notinfluenced by light under the conditions of these experiments.It is proposed that type 2 (or light) phytochrome may be responsiblefor photoregulation of type 1 phytochrome synthesis in germinatingAvena embryos. Key words: Photoregulation, phytochrome, seed.