[Effects of drought stress and recovery on photosynthesis and physiological characteristics of Hibiscus hamabo]. / å¹²æ—±èƒè¿«åŠå¤æ°´å¯¹æµ·æ»¨æœ¨æ§¿å ‰åˆä½œç”¨å’Œç”Ÿç†ç‰¹æ€§çš„å½±å“.

A greenhouse experiment was conducted to examine the photosynthetic and physiological responses of two-year-old cuttings of Hibiscus hamabo to the drought stress (20 days) and subsequent rewatering (21 days). The results showed that after 20-day drought, all individuals were survived in spite of the 5.9% soil water content. Drought stress drastically reduced net photosynthetic rate of H. hamabo, with the highest value only being 1.1 µmol·m-2·s-1. Drought stress declined the maximum photochemical efficiency to 84.3% compared with the control plants. Under drought stress, H. hamabo could stabilize cell osmotic potential and eliminate the drought-caused lipid peroxidation by coordinating the accumulation of soluble protein and antioxidant enzymes. After rewatering for seven days, net photosynthetic rate of treated H. hamabo recovered to 57.3% of that under control treatment. Meanwhile, the activities of superoxide dismutase and catalase decreased with the decline of malondialdehyde content. After rewatering for 21 days, no significant differences in the activities of antioxidant enzymes, soluble protein and relative water were found between the treated and control treatment. At harvest, the total biomass of treated H. hamabo decreased, while the root-shoot ratio remarkably increased when compared with control plants. In short, our results indicated strong drought tolerance of H. hamabo, which could play important roles in landscape improvement and greening in coastal areas.

Index system and method for the evaluation of highway ecological landscape quality: A case study of Nantong City, Jiangsu Province, China.

The construction of highway ecological landscape is an important part of highway entity and an iconic feature of scenic countryside and ecological garden city, which plays an important role in the process of achieving social and economic sustainable development. The efficient index system and method is a basic measurement for the assessment of the interior quality and its associated outer environment. By taking five arterial highways (G15, G228, G204, S334 and S335) in the territory of Nantong City, Jiangsu Province as the case, an evaluation system containing quantitative and qualitative indices was developed to deal with the ecological landscape quality. The system composed of 12 evaluation indices which were divided into three categories including ornamental value, ecological efficiency, and safety design. Based on the survey and calculation of the raw data, the variable matrix was established and analyzed with principal component (PC) analysis. The results showed that the equation of highway greening ecological evaluation score was H=0.694×PC1+0.191×PC2+0.115×PC3, and scores of 5 highways ranked in the ordination of G204 > G15 > S334 > G228 > S335. The results would provide methods and references for efficient evaluation of highway landscape.

[Response in cuttings of Taxodium hybrid 'Zhongshanshan' and their parents to drought and re-hydration.] / ä¸­å±±æ‰åŠå ¶çˆ¶æ¯æœ¬å¹¼è‹—å¯¹å¹²æ—±èƒè¿«å’Œå¤æ°´çš„å“åº”.

In this study, three different strains of Taxodium hybrid 'Zhongshanshan' varieties [T. hybrid 302 (T. distichum♀×T. mucronatum♂), T. hybrid 407 (T. mucronatum♀×T. distichum♂), T. hybrid 118 (T. hybrid 302 ♀×T. macronatum ♂)] and their parents, T. distichum and T. mucronatum, were applied to investigate the response of photosynthetic characteristics, antioxidant enzyme systems and morphological characteristics to drought stress and recovery. The results indicated that as drought days were prolonged, all plants' net photosynthetic rate (Pn) decreased, while proline accumulated. Meanwhile, the antioxidases functioned to eliminate malonaldehyde toxicity. On the 8th day, the decrease of Pn of T. distichum was the biggest, T. hybrid 118 plants showed the highest water use efficiency and the smallest MDA content, while T. macronatum plants increased the activity of superoxide dismutase and content of proline. After rewatering for 2 days, all these parameters showed signs of recovery, and the T. hybrid 118 plants showed the fastest recovery rate since their Pn and proline content had recovered for 74.4% and 60.2%, respectively. Then after recovered for 9 days, all tested parameters had almost restored to equivalent levels of CK plants. The total biomass of T. hybrid 118 plants was not affected, while the ratio of root to shoot was significantly (P<0.05) increased. The drought-resistance capacity ranged as T. macronatum>T. hybrid 118>T. hybrid 407>T. hybrid 302>T. distichum plants. In conclusion, the backcross generation T. hybrid 118 plants largely inherited the drought resistance of T. mucronatum, and the result would be instrumental in breeding and popularization of drought-resistant hybrid varieties.

[Diversity of carbon source metabolism of microbial community in farmland soils in an arsenic mining area].

By using Biolog technique, this paper studied the diversity of carbon source metabolism of microbial community in three farmland soils with different levels of arsenic (As) in an As mining area, and the relationships between the diversity of the carbon source metabolism and the main soil chemical properties. The total N (TN), total P (TP), total K (TK), organic matter (OM), total Cu, and total Zn contents in the three soils were in the order of medium level As > high level As > low level As. The average well color development (AWCD), Shannon index (H'), Simpson index (D), and McIntosh index (U) of soil microbes were significantly higher in the soils with medium and high levels As than in the soil with low level As. The principal component analysis and the fingerprints of the physiological carbon metabolism of the microbial community in the three soils demonstrated that the microbes in the soils with medium and high levels As had a significantly higher (P<0. 05) utilization rate in carbohydrates and amino acids than the microbes in the soil with low level As. The correlation analysis showed that the AWCD, H', D, and U were significantly positively correlated with the contents of soil TN, TP, OM, total As, total Cu, total Pb, and total Zn (P<0.05), and the canonical correspondence analysis revealed that soil TP, OM, total Pb, total Zn, TN, and pH rather than soil total As were the main soil chemical properties affecting the carbon source metabolism of soil microbial community. It was considered that soil nutrients could be the main factors affecting the community structure and functions of soil microbes in long-term contaminated soils.