[Effects of exogenous spermidine and arbuscular mycorrhizal fungi on plant growth of cucumber]. / äºšç²¾èƒºå’Œä¸›æžèŒæ ¹çœŸèŒå¯¹é»„ç“œç”Ÿé•¿çš„å½±å“.

Effects of spermidine (Spd) and arbuscular mycorrhizal fungi (AMF) on the growth and photosynthesis of cucumber (Cucumis sativus L., cv. Jinchun 2) seedlings, fruit yield and quality, microorganism and enzymatic activity in rhizosphere were investigated. The results showed that combined Spd and AMF addition significantly promoted the growth of cucumber seedlings, increased the root activity, fruit production and quality, enhanced nutrients absorption of seedlings. Net photosynthetic rate, actual photochemical efficiency, light quantum efficiency, carboxylation efficiency and light respiration rate of cucumber seedlings were increased by combined addition of Spd and AMF. The abundance of bacteria and actinomycetes in the rhizosphere of cucumber seedlings were increased, but that of fungi was decreased. The activities of enzymes, including sucrase, neutral phosphatase, catalase, and urease, were enhanced. These results suggested that the light utilization efficiency of cucumber seedlings was improved by combined addition of Spd and AMF. The growth substrate has been changed from a low-fertility type caused by fungi to a high-fertility one caused by bacteria. The decomposition and transformation of organic phosphorus and nitrogen in substrate were increased by combined addition of Spd and AMF, and thus could provide more N and P for the growth and development of cucumber, which further led to enhanced seedling growth, higher yield and quality of fruits. Moreover, Spd could increase the infection rate of AMF in cucumber roots, and together they had a synergistic effect on the growth of cucumber. Our results suggest that it is an effective method to enhance the infection rate of AMF by using Spd.

Cyanobacterial fossils from 252†Ma old microbialites and their environmental significance.

The end-Permian mass extinction was followed by the formation of an enigmatic rock layer with a distinctive macroscopic spotted or dendroid fabric. This deposit has been interpreted as microbial reef rock, digitate dendrolite, digital thrombolite, dendritic thrombolite, or bacterial deposits. Agreement has been reached in considering them as microbialites, but not in their formation. This study has revealed that the spotted and dendroid microbialites were composed of numerous fossil casts formed by the planktic cyanobacterium, Microcystis, a coccoid genus that at the present-day commonly forms blooms in modern lakes, rivers, and reservoirs. The abundance of the fossils and the diagenesis they experienced has determined the macroscopic fabric: where they abundant, the rock appears as dendroid, otherwise, it appears as spotted. The ancient Microcystis bloom might produce toxin to kill other metazoans, and be responsible for the oceanic anoxia that has puzzled so many researchers for so many years.

A sustainable landscape ecosystem design: a case study.

Landscape planning is clearly ecologically and socially relevant. Concern about sustainability between human and environment is now a driving paradigm for this professional. However, the explosion of the sustainable landscape in China is a very recent phenomenon. What is the sustainable landscape? How is this realized in practice? In this article, on the basis of the reviews of history and perplexities of Chinese landscape and nature analysis of sustainable landscape, the ecothinking model, an implemental tool for sustainable landscape, was developed, which applies ecothinking in vision, culture, conservation and development of site, and the process of public participation for a harmonious relationship between human and environment. And a case study of the south entrance of TongNiuling Scenic Area was carried out, in which the most optimum scenario was chosen from among three models according to the ecothinking model, to illustrate the construction of the ecothinking model and how to achieve a sustainable landscape.