[Effects of nutrient and water addition on soil inorganic phosphorus fractions in an old-field grassland]. / å »åˆ†å’Œæ°´æ·»åŠ å¯¹å¼ƒè€•è‰åœ°åœŸå£¤æ— æœºç£·ç»„åˆ†çš„å½±å“.

Reasonable nutrient and water management is effective ways to improve productivity and biodiversity of degraded grasslands. However, little is known about the effects of nutrient and water addition on soil inorganic phosphorus (P) fractions in old-field grasslands. Based on a field experiment with nutrient addition (N: 10 g·m-2·a-1, P: 10 g·m-2·a -1) and water addition (180 mm water irrigated during plant growing season) in Duolun County, Inner Mongolia in 2005, we examined the changes of inorganic P fractions and Olsen-P contents in the topsoil (0-10 cm). Results showed that 11-year P addition significantly increased total inorganic P (TIP) content, and that exogenous P was mostly transformed into calcium phosphate (Ca-P: 62.6%-69.2%), and then into aluminium phosphate (Al-P: 19.9%-25.1%), ferric phosphate (Fe-P) and occluded P (O-P). Phosphorus incorporated with nitrogen (N) addition significantly increased Fe-P and Al-P contents by declining soil pH and activating Fe3+ and Al3+ in soil. Water addition alone significantly increased Fe-P, Al-P, and decalcium phosphate (Ca10-P) fractions, and the contents of Fe-P, Al-P, octacalcium phosphate (Ca8-P), and Ca10-P were greater in P incorporated with water treatment than in P addition alone. There was no difference of each inorganic P fraction between P incorporated with N and water treatment and P incorporated with N treatment. Phosphorus and P incorporated with N additions significantly increased soil Olsen-P content, while water addition significantly decreased soil Olsen-P content under P addition alone and P incorporated with N treatment. In the calcareous soils, calcium superphosphate addition could enhance soil inorganic P pool through increasing Ca-P fraction.

[Changes of persistent soil seed bank along a precipitation gradient in forest-steppe ecotone]. / æ£®æž—è‰åŽŸè¿‡æ¸¡å¸¦æŒä¹ åœŸå£¤ç§å­åº“æ²¿é™æ°´æ¢¯åº¦çš„æ ¼å±€.

This study aimed to examine the responses of persistent soil seed bank to future precipitation reduction of global climate change in the forest-steppe ecotone of Hulunbuir. Samples of soil seed bank were collected from 0-10 cm soil layer along a precipitation gradient. We examined the density, species composition, diversity of seed bank and their relationship with vegetation. Structural equation model was used to explore the direct impact of annual precipitation on soil seed bank and the indirect impact through vegetation, soil nitrogen, soil phosphorus, and soil pH. The results showed that seed bank density and species richness were negatively correlated with annual precipitation. The species diversity of soil seed banks in grasslands was higher than that in forests. The similarity between soil seed bank and vegetation was generally low. The results of structural equation model showed that the effects of annual precipitation on seed bank density and species richness were negative, with the standard path coefficients of -0.051 and -0.122, respectively. The direct effect of annual precipitation on seed bank density and species richness were positive. Precipitation had indirect and positive effect on seed bank density and species richness through soil nitrogen, a significantly indirect negative effect on seed bank species richness through soil pH and soil available phosphorus, and a significantly indirect negative effect on seed bank density through soil pH. The reduction of precipitation under furture climate change might alter the hedging strategies of plants. The persistent soil seed bank in the forest-steppeecotone had a potential buffering effect against future precipitation reduction.

[Changes of non-structural carbohydrates and nitrogen contents of needles and twigs in Pinus sylvestris var. mongolica plantations along an aridity gradient]. / 沿干旱梯度樟子松人工林针叶和枝条非结构性碳水化合物及氮含量的变化.

With six Pinus sylvestris var. mongolica plantations (Huinan, Xifeng, Fujia, Zhanggutai, Naiman and Wulanaodu) along an aridity gradient in the Horqin sandy land, we examined the changes in non-structural carbohydrates (NSCs) and nitrogen (N) contents of current and one-year-old needles and twigs, to explore the carbon supply and demand status as well as the nutrient accumulation strategies of P. sylvestris var. mongolica under drought. The results showed that the contents of NSCs and soluble sugars in needles and twigs of P. sylvestris var. mongolica plantations significantly decreased with increasing aridity. From the most humid site (Huinan) to the most aridity site (Wulanaodu), the soluble sugar contents in current and one-year old needles of P. sylvestris var. mongolica decreased from 12.8% and 12.5% to 9.0% and 9.5%, respectively. The soluble sugar contents in current-year old twigs decreased from 15.6% to 9.2%. With increasing aridity, the starch contents in needles and twigs remained relatively stable, soluble sugars/starch ratio in current and one-year old needles decreased, the N contents in current and one-year old twigs significantly increased. The P. sylvestris var. mongolica plantations in the Horqin sandy land consumed soluble sugar storage under drought, resulting in a risk of mortality from 'carbon starvation'. P. sylvestris var. mongolica tended to maintain stable starch storage and accumulate N in twigs to cope with long-term drought stress.

Glucose deprivation induces chemoresistance in colorectal cancer cells by increasing ATF4 expression.

AIM: To investigate the role of activating transcription factor 4 (ATF4) in glucose deprivation (GD) induced colorectal cancer (CRC) drug resistance and the mechanism involved. METHODS: Chemosensitivity and apoptosis were measured under the GD condition. Inhibition of ATF4 using short hairpin RNA in CRC cells under the GD condition and in ATF4-overexpressing CRC cells was performed to identify the role of ATF4 in the GD induced chemoresistance. Quantitative real-time RT-PCR and Western blot were used to detect the mRNA and protein expression of drug resistance gene 1 (MDR1), respectively. RESULTS: GD protected CRC cells from drug-induced apoptosis (oxaliplatin and 5-fluorouracil) and induced the expression of ATF4, a key gene of the unfolded protein response. Depletion of ATF4 in CRC cells under the GD condition can induce apoptosis and drug re-sensitization. Similarly, inhibition of ATF4 in the ATF4-overexpressing CRC cells reintroduced therapeutic sensitivity and apoptosis. In addition, increased MDR1 expression was observed in GD-treated CRC cells. CONCLUSION: These data indicate that GD promotes chemoresistance in CRC cells through up-regulating ATF4 expression.