[Photosynthetic characteristics of Leymus chinensis and Medicago sativa in artificial grassland]. / ç¾Šè‰å’Œç´«èŠ±è‹œè“¿äººå·¥è‰åœ°å ‰åˆç‰¹æ€§.

To explore the effect of monoculture and mixture sowing artificial grassland on the photosynthetic characteristics of Leymus chinensis and Medicago sativa, we determined the diurnal variation of photosynthetic properties of L. chinensis and M. sativa under different treatments. The results showed that the diurnal changes of net photosynthetic rate, blade temperature and transpiration rate of L. chinensis and M. sativa showed 'unimodal type' in monoculture, the stomatal conductance of M. sativa showed 'unimodal type', and the stomatal conductance and water use efficiency of L. chinensis showed 'bimodal type'. Under the mixed sowing treatment, the diurnal changes of net photosynthetic rate, blade temperature and transpiration rate of L. chinensis and M. sativa showed 'unimodal type', the stomatal conductance and water use efficiency of L. chinensis showed 'unimodal type', and the stomatal conductance of M. sativa showed 'bimodal type'. The peak photosynthetic rate of L. chinensis under mixture was signi-ficantly higher than that under monoculture, being 17.72 and 13.65 µmol CO2·m-2·s-1, respectively. Under monoculture and mixture sowing treatments, the chlorophyll content of L. chinensis was higher than that of M. sativa, nitrogen content of the leaves of L. chinensis was lower than that of M. sativa, and the nitrogen content in the leaves of mixture sowing L. chinensis was significantly higher than that of monoculture sowing L. chinensis, which were 27.60 and 22.55 g·kg-1, respectively. Net photosynthetic rates of L. chinensis and M. sativa were significantly positively correlated with stomatal conductance and transpiration rate, and significantly negatively correlated with intercellular CO2 concentration under different planting methods. Net photosynthetic rate of M. sativa was significantly positively correlated with blade temperature and water use efficiency. In summary, mixed sowing was beneficial to enhance nitrogen content of L. chinensis. Our results provided a theoretical basis for the response of the photosynthetic characteristics of forage to planting mode of artificial grassland.

Trade-off relationship and internal mechanism of plant leaf size and number in Hulunbuir grassland, China.

The trade-off between leaf size and number is the basis for plant growth strategies. It is of great significance to study the underlying mechanism of leaf size and number trade-offs for well understanding plant growth strategies. In this study, leaf size was expressed by the dry mass of single leaf, while leafing intensity was expressed by the number of leaves per unit stem volume. We used standardized major axis regression analysis method to examine the trade-off relationship between leaf size and number in Hulunbuir grassland. There was a significant negative isometric-growth trade-off between leaf size and number in Chenqicuogang (typical steppe) and Chenqibayi (meadow steppe). There was a significant negative allometric-growth trade-off between leaf size and number in Xeltala (meadow steppe). The underlying mechanism of the relationship between leaf size and number depended on the leaf and stem biomass allocation mechanism and the changes of the stem tissue density.

Genistein attenuates brain damage induced by transient cerebral ischemia through up-regulation of Nrf2 expression in ovariectomized rats.

OBJECTIVE: Postmenopausal women possess higher incidence of stroke and worse prognosis. Although estrogen replacement therapy has obvious neuroprotective effects against stroke, it is always accompanied with several adverse effects and undesired outcomes. Genistein, a natural phytoestrogen, has been indicated to be a potential neuroprotective alternative for postmenopausal women against stroke. However, the role and mechanism of genistein's neuroprotective effects against stroke in ovariectomized rats have rarely been explored. METHODS: In this study, ovariectomized rats were treated with genistein (10 mg/kg) or vehicle daily for two weeks before they received middle cerebral artery occlusion (MCAO) and reperfusion. After 72 hours of reperfusion, the neurological function was evaluated by Garcia test, infarct volume was detected by 2,3,5-triphenyltetrazolium chloride staining, and neuronal damage was detected by Nissl staining. In addition, ROS production and the expression of Nrf2, NQO1 and cleaved-Caspase3 in the ischemic penumbra were detected. RESULTS: The results showed that genistein treatment significantly improved the neurological outcome, reduced infarct volume, increased Nrf2 and NQO1 expression, and reduced ROS production and cleaved-Caspase3 expression in ovariectomized rats. DISCUSSION: Our findings indicated that treatment with genistein could alleviated oxidative stress injury induced by cerebral ischemia in ovariectomized rats via promoting Nrf2 and NQO1 expression, which provide a new molecular mechanism for the neuroprotective effects of genistein against stroke in postmenopausal women.

[Response of plant leaf traits to grazing intensity in Stipa krylovii steppe.] / å ‹æ°é’ˆèŒ è‰åŽŸæ¤ç‰©å¶ç‰‡æ€§çŠ¶å¯¹æ”¾ç‰§å¼ºåº¦çš„å“åº”.

Grazing disturbance is one of the ways to influence plant traits, and plant leaf traits actually reflect the adaptability of plants to the environment. In this study, taking Stipa krylovii steppe under different grazing intensities in Hulunbuir as research area, the relationships of leaf traits and the variation of plant traits among plant life-form functional groups was investigated. Results showed that plant traits with different life-forms had no significant difference in S. krylovii steppe. However, the relationships between plant traits were strongly correlated. The leaf phosphorus content (LPC) and the ratio of nitrogen and phosphorus (N/P) in the heavy grazing treatment had significant difference from those in the moderate grazing and the light grazing treatments. For different life-form functional groups, grazing disturbance had significant effect on LPC and N/P in the perennial forbs, indicating the perennial forbs were sensitive to grazing, and the plant nutrient utilization strategy was changed by heavy grazing. It was suggested that reasonable grazing could improve the nutrient traits of plants and restrain the degradation in S. krylovii steppe.

[Salinization-alkalization of Leymus chinensis grassland in Songnen Plain of Northeast China].

Field survey and site study were conducted to approach the process and causes of salinization-alkalization of Leymus chinensis grassland in Songnen Plain, and to examine the hypothesis of soil disturbance-bareness. In the grassland, surface soil (0-30 cm) had a lower salt content, while deeper soil (> 30 cm) was in adverse. Thereby, the grassland was defined as soil-salted grassland. There was an increasing salt content in surface soil. This process was called as soil salinization-alkalization, and the grassland under the salinization:alkalization was named as alkali-salinized grassland. The leading reason for the surface soil salinization-alkalization was that the surface soil originally with low salt content was disturbed and lost away, subsurface soil rich in salt emerged as new surface soil, and the salt in deeper soil layers accumulated in the new surface soil and other soil layers. Secondary halophyte communities formed on the surface-soil-disturbed new bare land, but the communities had no succession sequence. The degradation process of the grassland was soil degradation first, followed by vegetation degradation, halophyte invasion, and successive evolution from nearly primitive condition.

[The study on the UV and fluorescence properties of PAMAM dendrimers].

From 0.5 to 5.0 generation PAMAM dendrimers were synthesized with ethylenediamine core by Michael addition reaction and aminolysis reaction two repeated steps. The structure of dendrimers were confirmed by FTIR 1H NMR 13C NMR MS and all of these measurements showed that they were successfully synthesized. Furthermore, The authors studied the UV and fluorescence properties of different generation dendrimers. Because of diffenent terminal groups, it was found that the whole generation and half generation show different ultraviolet absorption peaks and the intensity of ultraviolet absorption is closely related to the molecular skeleton. There is no traditional fluorescence emission groups, but PAMAM dendrimers show the peculiar phenomenon. In this paper we detailedly studied the factors which affect PAMAM dendrimers fluorescence properties.