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Impact of extra nitrogen on ecological stoichiometry of Alpine grasslands on Tibetan Plateau: meta-analysis

100%

Zhang H. R., Sun W., Li S. W., Han F. S., Yu C. Q., Zhang X. Z., Wang J. S., He Y. T., Zhong Z. M.

Polish Journal of Ecology

2018

tom 66

nr 4

The general impact of extra nitrogen on ecological stoichiometry was examined in alpine grasslands on the Tibetan Plateau. Extra nitrogen increased the ratio of nitrogen to phosphorus (N:P ratio) in leaves and aboveground parts of plants by 43.4% and 32.7%, respectively. In contrast, extra nitrogen reduced the ratio of carbon to nitrogen (C:N ratio) in leaves by 30.6%. Extra nitrogen decreased soil C:N ratio by 9.1% in alpine meadows, but increased soil C:N ratio by 3.4% in alpine steppes. Extra urea had a stronger positive impact on aboveground vegetation N:P ratio than did extra ammonium nitrate. Extra urea rather than ammonium nitrate decreased aboveground vegetation C:N ratio and soil C:N ratio. The impact of extra nitrogen on aboveground vegetation N:P ratio was positively correlated with latitude, mean annual temperature and precipitation, nitrogen application rate and accumulated amount, but negatively correlated with elevation, duration and aboveground vegetation N:P ratio of the control plots. The impact of extra nitrogen on leaves N:P ratio was positively correlated with nitrogen application rate and accumulated amount. The impact of extra nitrogen on leaves C:N ratio was positively correlated with latitude, but negatively correlated with mean annual temperature and precipitation, nitrogen application rate, accumulated amount, duration and leaves C:N ratio of the control plots. Therefore, nitrogen enrichment caused by human activities will most likely alter element balance and alpine plants from nitrogen limitation to phosphorus limitation. This effect may weaken with time, and increase with climatic warming, increased precipitation and nitrogen input rate.

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Effects of selection for more vigorous seminal roots in two cross populations of oat [Avena sativa L.]

80%

Gorny A. G., Szolkowska A.

Journal of Applied Genetics

1996

tom 37

nr 4

Three steps of multi-stage selection for more vigorous seminal roots were done in two cross combinations of oat. The total length of roots (TRL) was measured in seedlings of the F₂, F₃ and F₄ generations grown in filter-paper rollers. On average, the finally selected F₅ (or F₆) progenies distinguished by 7-11% improved rooting ability than their midparents. Transgressive forms were selected only in one cross combination. Coefficients of realized heritability for TRL were low and ranged from 0.08 to 0.42 indicatinga relatively high proportion of non-additive gene effects in the variance of TRL. Tolerance of the F₆-progenies to water and nutrient limitations was evaluated in pot and field experiments. Correlated selection effects were dependent upon initial cross combination. Only progenies from one cross combination exhibited an improved drought tolerance at the 8-9 Feekes' stage. The both enhanced rooting and decreased S : R ratio of the F₆-progenies correlated with their improved tolerance to reduced P supply at the 4-leaf stage. However, no significant consistence occurred between indices of the tolerance to reduced nutrition at the vegetative growth and those at field maturity. Performed root selection identified more frequently high yielding genotypes with less stable grain yield. No progenies were obtained that outperform their parents under low-input conditions. It was emphasized that root selection should be accompanied by selection for integrated response components.

Ograniczanie wyników

1 Journal of Applied Genetics

1 Polish Journal of Ecology

1 Gorny A. G.

1 Han F. S.

1 He Y. T.

1 Li S. W.

1 Sun W.

1 Szolkowska A.

1 Wang J. S.

1 Yu C. Q.

1 Zhang H. R.

1 Zhang X. Z.

1 Zhong Z. M.

1 2018

1 1996

Wyniki wyszukiwania

Impact of extra nitrogen on ecological stoichiometry of Alpine grasslands on Tibetan Plateau: meta-analysis

Effects of selection for more vigorous seminal roots in two cross populations of oat [Avena sativa L.]