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Effects of saline-alkaline stress on early growth strategy and colonization success of Flaveria bidentis ( L.) Kuntze (Asteraceae ) - a new exotic plant in Northern China

Chai M., Shi F., He K., Li R., Cao D., He Z.

Polish Journal of Ecology

2012

Vol. 60, nr 3

559-565

Flaveria bidentis, an annual grass native to South America, has invaded into many countries all over the world, including South Africa and Egypt in Africa, Britain and France in Europe, Japan in Asia, and Australia. In China, this plant species has been widely distributed in Hebei province since 2001 of its first discovery in Tianjin. In salinized soil of northern China, F. bidentis has formed mono dominant communities owing to its opportunistic characteristics. In this study, we investigated germination rate, germination energy, germination index and vigor index in response to different saline-alkaline stresses. Lengths of seedling, hypocotyl, and radicle were also examined. During germination process, germination rate, germination energy, germination index, and vigor index decreased due to higher salinity and alkalinity (pH). Hypocotyl elongation was stimulated at low salinity and alkalinity, but decreased with increasing salinity and alkalinity. The lengths of radicle and seedling were inhibited sharply with increasing salinity and alkalinity. These results suggest that a reciprocal enhancement between salt stress and alkaline stress was a characteristic feature during seed germination of F. bidentis. Ungerminated seeds resumed to germinate after transferred to distilled water, indicating that seeds remained viable during their exposure to saline-alkaline stresses. Stepwise regression analysis indicated that the effects of salinity, alkalinity (pH), and buffer capacity on seed germination and seedling growth were significantly different in magnitude. Salinity and alkalinity (pH) were the dominant factors in seed germination and seedling growth of F. bidentis respectively. Further, the results of this study suggest that F. bidentis has developed excellent adaptative strategy in its early stage of life cycle which partially explains its current invasion success in northern China.

Potential Jurassic/Cretaceous boundary in northeastern China

Sha J., Chen S., Cai H., Jiang B., Yao X., Pan Y., Wang J., Zhu Y., He Ch.

Volumina Jurassica

2006

Vol. 4, no. 1

269-270

On the basis of the geological ranges of the Buchia and dinoflagellate cyst assemblages and their global correlation, two distinct biostratigraphical boundaries (event horizons) can be distinguished in the continu ous deposits spanning the Jurassic/Cretaceous boundary in the Dong'anzhen Formation of Dong'an, Raohe County and the Dongrong Formation of boreholes SB86-11 and SB79-1 of Suibin, Suibin County of eastern Heilongjiang, northeasteren China (Fig. 1.). Level 1. The base of the Buchia fischeriana - Buchia unschensis assemblage is characterized by the occurrence of Buchia (e.g. B. unschensis) with inversoid ontogenetic growth of the right valve, and the absence of the underlying B. russiensis, one of the index species of the Buchia russiensis - Buchia fischeriana assemblage, with obliquoid ontogenetic growth of the right valve (Fig. 1, column 2b). The top of the dinoflagellate cyst Amphorula delicate assemblage underlies, but it is near this boundary (Fig. 1, column 2a). This level basically corresponds to the currently accepted Tethyan version of the Jurassic/Cretaceous boundary and the working base of the Cretaceous as recommended by the International Commission on Stratigraphy (www.stratigraphy.org) (Fig. 1, column 1), and approximately corresponds to the boundary between the Boreal Middle-Upper Volgian substages (Fig. 1, column 3). This is because the base of the Buchia unschensis Zone or the base of the Buchia fischeriana - Buchia unschensis assemblage nearly coincides with that of the Boreal Craspedites exoticus Subzone or Craspedites okensis ammonite Zone, which in turn correspond closely to the base of Tethyan Lower Berriasian Berriasella jacobi ammonite Zone (Fig. 1, column 1), which is the index ammonite zone of the Tethyan or the international chronostratigraphic base of Berriasian, and thus the base of the Cretaceous (Fig. 1, column 1). Level 2. The base of the Buchia volgensis - Buchia cf. subokensis - Buchia cf. okensis - Buchia unschensis assemblage, is characterized by those easy-to-recognize large-sized Buchia with inversoid ontogenetic growth of the right valve and even of the left valve, and absence of Buchia fischeriana (Fig. 1, column 2b). The base of the Oligosphaeridium pulcherrimum dinoflagellate cyst assemblage probably corresponds approximately to the base of this Buchia assemblage (Fig. 1, column 2a). This level is very near the Boreal version of the Jurassic/Cretaceous boundary, which corresponds approximately to the base of the Tethyan middle part of Middle Berriasian. This is because the bases of both Buchia volgensis and Buchia cf. okensis in the assemblage of Buchia volgensis - Buchia cf. subokensis - Buchia cf. okensis - Buchia unschensis are closely coincident with the base of the upper Lower Berriasian Boreal Hectoroceras kochi Zone (Fig. 1, columns 2b, 3), and the Tethyan upper Berriasella privasensis Subzone of the Tirnovella occitanica Zone of the middle part Middle Berriasian, approximately corresponds to the middle of the Boreal Lower Berriasian Substage (Fig. 1, columns 1, 3).