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To study how phosphate fertilizer regulates the photosynthetic of summer soybeans in low light environment, this study used Qihuang 34 as the test variety, two light treatments[ambient sunlight (L1) during the whole growth period and 40% shade (L2) from 40 days after sowing to 24 days after flowering] with two phosphate fertilizer treatments including non-phosphate fertilizer application (P0), conventional phosphate fertilizer application (P1) in each light treatment was set up to measure the gas exchange, chlorophyll a fluorescence differences of photosynthetic performance as well as the yield and its components in Qihuang 34. The results showed that phosphorus significantly increased chlorophyll content, photosynthetic rate, and grain yield in shading treatment. The yield of soybean was significantly reduced after shading treatment, which was 29.9%, but compared with L2P0, L2P1 treatment yield increased by 36.7%, which was significantly higher than the 27.1% under L1 treatment. The photosynthetic rate under saturated light (Asat) under L2 treatment decreased by 31.5% and 15.6% in R1 and R3 periods, respectively, and average increased by 27.4% and 45% after phosphorus application under two light condition. Furthermore, photosynthetic measurements demonstrated a more significant increase in the maximum efficiency of CO2 fixation, maximum rates of RUBP-carboxylation (Vcmax) in phosphorous treatment under shading conditions. Moreover, further analysis of OJIP curves revealed that phosphate fertilizer significantly improved the electron transfer and light energy absorption performance of the PSII reaction center in shading. The above results demonstrate that phosphate fertilizer contributes to light energy utilization efficiency, increase the low light utilization efficiency by improving PSII performance, promote RUBP regeneration, ensure the source of carboxylates substrates, and coordinate the balance of the photochemical reaction and the Calvin cycle, then alleviate the reduction of photosynthetic efficiency under shading, increase the rate of dry matter accumulation, and greatly increase yield.

Somatic embryogenesis (SE) plays a vital role in genetic transformation and massive propagation of important agronomical and economical crops. Here, we conducted a systematic assessment of the morphological, cytochemical, and cytogenetical characteristics of six culture strains with various embryogenic/regenerative potential during SE process in cotton. Results indicated that the six cell culture strains had stable ploidy levels, and did not reveal any relationship between the cytogenetic state and their morphogenetic potential. Moreover, the six culture strains were compared via double staining with Evans blue and Acetocarmine to efficiently distinguish embryogenic and non-embryogenic cells and determine the embryogenic nature of the calli. In addition, the kind of auxins added in medium affected not only growth property, color, size of cell clumps but also ploidy level and regeneration ability. By combining analysis of morphological, cytochemical, and cytogenetical characteristics of the cell cultures, we are able to obtain and maintain homogeneous cell population with high morphogenic and regeneration ability and establish efficient somatic embryogenesis and regeneration system from short-term cell cultures in upland cotton, which highlight the application of biotechnological approaches in crop breeding, and above all, to better understand totipotency of cells in higher plants.

To improve light environment, photosynthetic capacity, and thus the yield of maize, the effects of directional planting on light distribution in canopy and photosynthetic characteristics of ear leaves, as well as the performance of PSII that closely related with photosynthetic characteristics and reflected by the rapid chlorophyll fluorescence kinetic curves were examined in Zhengdan 958 maize variety. The results showed that the orientation of leaves remarkably affected photosynthetically active radiation (PAR) interception of ear leaves, with PAR interception of ear leaves in southward treatment being 271.8% higher than that under northward treatment. The orientation of leaves affec-ted photosynthetic light use efficiency of ear leaves under high and low light conditions. The southward treatment increased net photosynthetic rate (P为改善玉米群体内光环境,进一步提高玉米单株光合能力以获得高产,本研究以郑单958为试验材料,通过设置种子定向入土方式,研究了定向有序种植条件下群体内光分布特征,以及单株玉米穗位叶花后光合性能,并借助快速叶绿素荧光动力学曲线分析了与叶片光合性能有密切联系的光系统II(PSII)的性能特征.结果表明: 叶片不同朝向显著改变夏玉米群体内穗位叶处光合有效辐射截获量,朝南处理(S)平均比朝北处理(N)高271.8%.不同朝向的叶片对高光与弱光的利用能力差异显著,朝南处理饱和光强下净光合速率(

SUMMARYThe relationship between climate, crop growth and crop yield is complicated. This study aimed to determine the ratio of CO2–C emission to grain yield, the field treatments were initiated in 2003, but the measurements for this analysis were collected during the summer maize-growing seasons of 2011 and 2012 in the North China Plain. The experiment showed that conventional tillage with straw application significantly increased grain yield and the ratio of CO2–C emission to grain yield of summer maize. The mean soil CO2–C emission rate with no tillage was significantly lower than that when conventional tillage was used; however, straw application significantly increased the soil CO2–C emission rate, irrespective of whether tillage was performed or not. This was mainly because straw application changed the soil total porosity and organic carbon content. In conclusion, the results of this study support the hypothesis that the ratio of CO2–C emission to grain yield in the North China Plain can be increased by straw application, whereas no tillage decreases this ratio.

Managements of organic matter and irrigation after anthesis will increase the capacities of water conservation and supply in maize field, with consequences on photosynthetic performance and yield under water-saving condition. We analyzed the gas exchange parameters and the performance of the photosystem 2 of ear leaves, and yield of maize cultivars Zhengdan 958, under three modes of ditch-buried organic matter (no straw returned: M有机物沟埋还田与花后灌水配合对增加玉米田保水供水能力,提高玉米花后光合性能、实现节水增产有重要意义.本试验以郑单958为供试材料,设置有机物沟埋还田和花后灌水量两个因素,有机物沟埋还田包括不还田(M

A 2-year field experiment was conducted to study the effects of CaCN2 combined with cucumber straw retention on soil microbial biomass carbon (SMBC) , soil microbial biomass nitrogen (SMBN) and soil enzyme activities under cucumber continuous cropping system. Four treatments were used in this study as follows: CK (null CaCN2), CaCN2-90 (1350 kg CaCN2 . hm-2) CaCN2-60 (900 kg CaCN2 . hm-2), CaCN2-30 (450 kg CaCN2 . hm-2). The results indicated that, compared with the other treatments, CaCN2-90 treatment significantly decreased SMBC in 0-10 cm soil layer at seedling stage, but increased SMBC in 0-20 cm soil layer after early-fruit stage. Compared with CK, CaCN2 increased SMBC in 0-20 cm soil layer at late-fruit stage, and increased SMBN in 0-10 cm soil layer at mid- and late-fruit stages, however there was no significant trend among CaCN2 treatments in the first year (2012), while in the second year (2013) SMBN increased with the increasing CaCN2 amount after mid-fruit stage. CaCN2 increased straw decaying and nutrients releasing, and also increased soil organic matter. Furthermore, the CaCN2-90 could accelerate straw decomposition. Compared with CK, CaCN2 effectively increased soil urease, catalase and polyphenol oxidase activity. The soil urease activity increased while the polyphenol oxidase activity decreased with the increase of CaCN2, and CaCN2-60 could significantly improve catalase activity. Soil organic matter, urease activity and catalase activity had significant positive correlations with SMBC and SMBN. However, polyphenol oxidase activity was negatively correlated to SMBC and SMBN. Our findings indicated that CaCN2 application at 900 kg . hm-2 combined with cucumber straw retention could effectively improve soil environment, alleviating the soil obstacles under the cucumber continuous cropping system.

Methane oxidation in aerated soils is a significant sink for atmospheric methane (CH4). Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about CH4 turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of CH4 consumption in saline soils, CH4 fluxes were measured in intact cores of the slightly (ECe = 3.2 mS cm−1), moderately (ECe = 7.1 mS cm−1) and extremely (ECe = 50.7 mS cm−1 and 112.6 mS cm−1) saline soils from the Yellow River Delta, China. CH4 uptake of cores from the slightly saline soil ranged from 14 to 24 μg CH4–C m−2 h−1, comparable to those in the non-saline forest soils with similar texture. CH4 uptake of cores from the moderately saline soil was only about 6% of that in the slightly saline soil. CH4 uptake was too low to be measurable in the extremely saline soil. Compared with the non-saline soil, CH4 uptake in the saline soils was much less sensitive to salt, suggesting the higher salt-tolerance of CH4 oxidizers in the saline soil. The result also indicated an underestimate in CH4 uptake for the naturally-occurring saline soils by adding salt to non-saline soils. These results should be useful to study the global CH4 budget and to explore the physiological and ecological characteristics of methanotrophic bacteria in the salt-affected soils.

To explore the effects of different tillage methods and straw recycling on soil respiration and microbial activity in summer maize field during the winter wheat and summer maize double cropping system, substrate induced respiration method and CO2 release method were used to determine soil microbial biomass carbon, microbial activity, soil respiration, and microbial respiratory quotient. The experiment included 3 tillage methods during the winter wheat growing season, i.e., no-tillage, subsoiling and conventional tillage. Each tillage method was companied with 2 straw management patterns, i.e., straw recycling and no straw. The results indicated that the conservation tillage methods and straw recycling mainly affected 0-10 cm soil layer. Straw recycling could significantly improve the microbial biomass carbon and microbial activity, while decrease microbial respiratory quotient. Straw recycling could improve the soil respiration at both seedling stage and anthesis, however, it could reduce the soil respiration at filling stage, wax ripeness, and harvest stage. Under the same straw application, compared with conventional tillage, the soil respiration and microbial respiratory quotient in both subsoiling and no-tillage were reduced, while the microbial biomass carbon and microbial activity were increased. During the summer maize growing season, soil microbial biomass carbon and microbial activity were increased in straw returning with conservation tillage, while the respiratory quotient was reduced. In 0-10 cm soil layer, compared with conventional tillage, straw recycling with subsoiling and no-tillage significantly increased soil microbial biomass carbon by 95.8% and 74.3%, and increased soil microbial activity by 97.1% and 74.2%, respectively.

By using static chamber-TGC method, an in situ observation was conducted in a 10-year conservation tillage winter wheat field to study the effects of different maize straw-returning modes on the soil respiration. The soil respiration had a significant positive correlation with the stubble height of maize straw, and two peaks were observed in wheat growth period. Under no tillage and no straw-returning, the soil respiration was 72.5% of that under no tillage with all straw-returning, and the soil respiration under conventional tillage and no straw- returning was 76.5% of that under conventional tillage with all straw-returning. The soil respiration was significantly positively correlated with the soil temperature and soil organic carbon at 20 cm depth, but no significant correlation with the soil organic carbon at 40 cm depth. A correlation was also observed between the soil respiration and soil moisture. The diurnal soil respiration in the treatments of all straw-returning presented a single-peak curve, with the peak at 18:00. There was a similar variation trend of soil temperature and soil respiration at the depth of 20 cm. Among the treatments of different straw-returning amounts, straw-returning with the stubble of 1 m height could reduce the soil respiration significantly, being a reasonable straw-returning mode.

Taking a long-term (since 2004) straw-returning winter wheat field as the object, an investigation was made in the wheat growth seasons of 2008-2009 and 2009-2010 to study the effects of different tillage methods (rotary tillage, harrow tillage, no-tillage, subsoil tillage, and conventional tillage) and weed management on the soil water and organic carbon contents. No matter retaining or removing weeds, the weed density under subsoil tillage and no-tillage was much higher than that under rotary tillage, harrow tillage, and conventional tillage. From the jointing to the milking stage of winter wheat, retaining definite amounts of weeds, no matter which tillage method was adopted, could significantly increase the 0-20 cm soil water content, suggesting the soil water conservation effect of retaining weeds. Retaining weeds only increased the soil organic carbon content in 0-20 cm layer at jointing stage. At heading and milking stages, the soil organic carbon contents in 0-20, 20-40, and 40-60 cm layers were lower under weed retaining than under weed removal. Under the conditions of weed removal, the grain yield under subsoil tillage increased significantly, compared with that under the other four tillage methods. Under the conditions of weed retaining, the grain yield was the highest under rotary tillage, and the lowest under conventional tillage.

A two growth seasons experiment was conducted to study the effects of different tillage methods, straw-returning, and their interaction on the dynamic change of organic carbon content in 0-20 cm soil layer during the whole growth period of winter wheat. An obvious change was observed in the soil organic carbon content. Treatments with straw-returning had higher soil organic carbon content than treatments with no straw-returning, and conservation tillage induced higher soil organic carbon content than conventional tillage. In all treatments except conventional tillage, the organic carbon content in 0-10 cm soil layer was higher than that in 10-20 cm soil layer. In treatments with straw-returning, the organic carbon content in 0-10 cm soil layer decreased in order of deep soiling (PS)rotary tillage (PR)no tillage (PZ)normal ploughing (PH)conventional tillage (PC), while that in 10-20 cm soil layer was PCPSPRPHPZ, suggesting that conservation tillage could improve the organic carbon content in 0-10 cm soil layer. Multi factor variance analysis showed that tillage method, straw-returning, and their interaction had significant effects on the organic carbon content in 0-20 cm soil layer at various growth stages of winter wheat.

In order to understand the relationships between CH4 fluxes and its affecting factors in a wheat field with conservation tillage, the CH4 fluxes in two wheat fields, one with conservation tillage and the another with conventional tillage, were measured in situ by static chamber-GC method, with soil temperature and soil moisture and inorganic nitrogen contents determined at the same time. The results showed that these two fields had an obvious and similar seasonal variation pattern of CH4 fluxes, but the average and seasonal CH4 absorption fluxes differed significantly. In the growth period of wheat, the fields were the sink of CH4, and the CH4 absorption fluxes was in the order of conventional tillage with no straw returning (CN)conventional tillage with straw returning (CS)subsoiling with straw returning (PS)harrowing with straw returning (HS)rotary tillage with straw returning (RS)no tillage with straw covered (NS). Comparing with conventional tillage, conservation tillage reduced the CH4 absorption fluxes. In conservation tillage, the CH4 absorption fluxes was positively correlated with soil temperature but negatively correlated with soil moisture content; while in conventional tillage, the CH4 absorption fluxes had no significant correlations with the two factors. In all treatments, there was a significant negative correlation between CH4 absorption fluxes and soil NH4+ -N content.

A field experiment was conducted to study the effects of maize-peanut intercropping on the economic yield of the two crops and the light response of their functional leaves' photosynthesis. The results showed that maize-peanut intercropping had an obvious yield advantage, with the total economic yield being 2,896 kg hm(-2) in 2004 and 2,894 kg hm(-2) in 2005, and enhanced the land utilization rate by 14%-17%. For maize's functional leaves, the intercropping enhanced their light saturation point, compensation point, and photosynthetic rate under strong light; while for peanut's functional leaves, it reduced their light saturation point and compensation point but enhanced the apparent quantum yield of photosynthesis and photosynthetic rate under weak light, indicating that maize-peanut intercropping enhanced the utilization efficiency of strong light by maize and that of weak light by peanut, making this intercropping system present an obvious yield advantage.