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121.
Chlorophenoxyacetate weed-killers have been tested for the control of aquatic weeds in the canals of the Sudan Gezira. Using water in tanks, it was shown that 10 parts per million of sodium 2-methyl-4-chlorophenoxyacetate (Methoxone) or of sodium 2:4-dichlorophenoxyacetate (Fernoxone) would kill most of the angiospermous water-weeds found in the Gezira area.
Small-scale field experiments, using channels of known water capacity, have shown that not only leaves and stems but also seeds and underground rhizomes were killed in treated stagnant water, provided that the weed-killers were applied as dusts. The water remained toxic to crop plants for approximately 7 weeks after treatment.
In a large-scale experiment in 1950, treating normal irrigation canals, temporary weed clearance was attained, re-infestation was delayed, and one major canal, 4.5 km. long, remained weed-free 12 months after treatment. 相似文献
Small-scale field experiments, using channels of known water capacity, have shown that not only leaves and stems but also seeds and underground rhizomes were killed in treated stagnant water, provided that the weed-killers were applied as dusts. The water remained toxic to crop plants for approximately 7 weeks after treatment.
In a large-scale experiment in 1950, treating normal irrigation canals, temporary weed clearance was attained, re-infestation was delayed, and one major canal, 4.5 km. long, remained weed-free 12 months after treatment. 相似文献
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A note on the selection of data transformations 总被引:1,自引:0,他引:1
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The ontogeny of the proboscis in Nucclla lapillus was investigatedusing light and scanning electron microscopy. The proboscis develops by elongation of the body wall surroundingthe mouth, whilst the rhynchocoel is formed by imagination ofthe body wall surrounding the proboscis. Elongation of the snoutduring development of the proboscis results in the anteriormovement of the anterior oesophagus and part of the mid-oesophagus(the valve of Leiblein) which is drawn through the circum-oesophagealnerve ring. The acinous salivary glands and the radular sacalso come to lie anterior to the nerve ring. The mid-oesophagealgland of Leiblein and the glandular dorsal folds are not drawnthrough the nerve ring, and develop behind it. The anterioroesophagus elongates at a later stage of development to producethe oesophageal length required for extension of the adult proboscis.Modifications to this sequence of events, or changes in therate of growth of the various parts of the foregut, might accountfor the differences between the neogastropod and neotaenioglossanpleurembolic proboscis. The intraembolic proboscis found inthe Conoidea and the Pseudolivoidea may have been derived viaa modification of the developmental sequence which producesthe muricoidean pleurembolic proboscis. (Received 10 May 1996; accepted 15 August 1996) 相似文献
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The effects of different applied NO3 concentrations onextension growth and final length and area of leaves 14of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO3 in the range 0.10.5.0mol m3 caused decreased duration of growth but increasedgrowth rate and final length of leaves 24 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale, x Triticosecaleand Triticum aestivum. For all cereals, increased NO3resulted in increased area of leaves 14. Pasture grasseswere supplied either 0.5 or 50 mol m3 NO3. Increasedapplied NO3 (0.55.0 mol m3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 14 of Bromus wiltdenowii, leaves 24ofFestuca arundinaceae and leaves 3 and 4 of Lolium muitiflorum.In addition, length of leaves 3 and 4 of B. witidenowii increasedwith increased NO3. Increased NO3 resulted inincreased area of leaves 24 of Dactylis gtomerata andLolium perenne and leaves 3 and 4 of Phalaris aquaiica but hadno effect on extension growth of all three species. Avena sativa L, oat, Hordeum vulgare L, barley, Secale cereale L, rye, x Triticosecale Wittm, triticale, Triticum aestivum L, wheat, Bromus willdenowii Kunth, prairie grass, Dactylis gtomerata L, cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multijlorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate, leaf extension, leaf expansion 相似文献