The effects of acid rain and ozone on biomass and leaf area parameters of shortleaf pine (Pinus echinata Mill.)     

Shelburne VB  Reardon JC  Paynter VA 《Tree physiology》1993,12(2):163-172

Shortleaf pine (Pinus echinata Mill.) seedlings in 24 open-top chambers were exposed to combinations of ozone (carbon-filtered (control), ambient, 1.7 x ambient, and 2.5 x ambient) and acidic precipitation (pH 5.3, 4.3 and 3.3) for 16 months (1989 harvest) or 28 months (1990 harvest). Although the effects of acid rain were generally not significant, there was a trend toward increased aboveground biomass and leaf area in seedlings subjected to the low pH treatments. Because N concentrations in the soils generally increased with decreasing pH, we concluded that the effects of acid rain on aboveground biomass and leaf area were a consequence of an increasing concentration of soil N. In the 1989 harvest, seedlings in the 2.5 x ambient ozone treatment had significantly less biomass in all aboveground plant components and significantly less total leaf area than seedlings in the 1.7 x ambient ozone treatment. In the 1990 harvest, there were no significant effects of ozone on total aboveground biomass, although there was a trend toward reduced biomass in seedlings in the 2.5 x ambient ozone treatment. Both total leaf area and leaf biomass were significantly less in seedlings exposed to 2.5 x ambient ozone for 28 months than in both control seedlings and seedlings in the 1.7 x ambient ozone treatment. The greater, but not always significant, aboveground biomass and leaf area of seedlings in the 1.7 x ambient ozone treatment compared with control seedlings may be associated with the observed increase in soil nitrate concentration as a result of increased rates of leaf senescence and litterfall.  相似文献   

Dolphin echolocation     

Fullard JH 《Science (New York, N.Y.)》1993,260(5114):1672

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Creative misrenderings     

Gleason JB 《Science (New York, N.Y.)》1993,260(5114):1669-1670

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Animal rights and wrongs     

Herzog H 《Science (New York, N.Y.)》1993,262(5141):1906-1908

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Segregation and linkage analysis of DNA markers in microspore derived and F2 populations of oilseed rape (Brassica napus L.)     

P. K. Tanhuanpää  J. P. Vilkki  H. J. Vilkki 《Euphytica》1993,74(1-2):59-65

Summary The segregation of RFLP and RAPD markers was compared in two oilseed rape (Brassica napus L.) breeding populations from the cross Topas x R4, the latter being a low linolenic mutation line. A total progeny of 68 F₂ and 40 microspore derived plants were studied with 25 markers. The results indicated a significant excess of Topas alleles at five RAPD loci in the microspore derived population. This suggests that genomic regions which probably affect microspore culture ability do not have identical distribution in the two population types.  相似文献   

Galactic enthusiast     

Devorkin DH 《Science (New York, N.Y.)》1993,262(5142):2069

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Power from wind turbines     

Abelson PH 《Science (New York, N.Y.)》1993,261(5126):1255

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Theorists to the quantum mechanical wave: ;get real'     

Freedman DH 《Science (New York, N.Y.)》1993,259(5101):1542-1543

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Limitations of automobile insurance     

Horne RB 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(1):9

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Wanted: Disability benefits     

Meyers B 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(1):7

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