Response of photosynthesis,growth,and acorn mass of pedunculate oak to diff erent levels of nitrogen in wet and dry growing seasons

The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought stress.According to the results,moderate drought stress significantly reduced net photo synthetic rate,stem diameter increment and height growth increment,while acorn mass was not affected.Suboptimal nitrogen nutrition significantly reduced the net photo synthetic rate and stem diameter increment only in the wet year,acorn mass in both wet and dry years,while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either year.The results indicate that optimal nitrogen levels can stimulate photo synthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought stress.Moreover,the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition,while for acorn development,it is the more dominant stressor.

基于MapGuide的校园信息系统开发研究

互联网信息技术与地理信息技术相结合的WebGIS技术已成为GIS发展的主流趋势之一,该文阐述了该主流技术的特点和相关技术,又以MapGuide软件作为主要支持技术,以SQL Sever 2000作为数据库管理工具,以校园信息数据为例,设计并实现了校园信息系统。实现了地图浏览、地图查询、要素编辑、三维实景浏览、数据信息的编辑等功能,为用户浏览校园信息提供了方便快捷的方式,亦可以在网页中浏览、方便管理地图信息。

Does nitrogen fertilization impact nonstructural carbohydrate storage in evergreen Podocarpus macrophyllus saplings?

Nonstructural carbon(NSC),which represents the relationship between the carbon source and carbon sink,is an important factor that reflects the functions and performance of a tree.However,little is known regarding the timeseries responses of NSC storage in evergreen species to different nitrogen(N)fertilization regimes.This study,which was based on a pot experiment,examined the response of the NSC(soluble sugars and starch storage to different N addition intensities[light N addition(LN):6.5 g N m^(-2)a^(-1);moderate N addition(MN):13.0 g N m^(-2)a^(-1);and heavy N addition(HN):26.0 g N m^(-2)a^(-1))]in saplings of the evergreen species Podocarpus macrophyllus.Our results showed that the net photosynthetic rate(P_(n))under MN was significantly higher than that under LN,but was comparable to that under HN.Moreover,saplings subject to MN had a significant higher leaf biomass than that to LN and HN.These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN.The NSCs reserve under MN was considerable with that under LN,which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group.However,saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments.The leaf N concentrations were found in the increasing sequence of LN<MN<HN,whilst the leaf chlorophyll concentration under HN was obviously lower than that under MN.The growth rate under MN was higher than that under LN and HN.We concluded that the NSCs allocation between con-sumption and reserve in P.macrophyllus saplings depended on soil N availability,and an excessive N addition to soil favors the storage rather than the consumption of NSCs by plants.

Study on Effect of Pesticides on Rice Leaf Photosynthate Export Rate with Tracer Kinetics

Impacts of three pesticides, triazophos, jingganmycin and bisultap, on the export rate of pho-tosynthate of rice leaf were studied with 14C for rice varieties, spraying time and application rate. Dynamics data of photosynthate of labeled rice functional leaves of different treatments were recorded with living plant nutrient detection instrument with multi-probes through tracer method of radioactive nuclide. Compartment analysis model and mathematical equations were constructed using principle and method of kinetics analysis, calculating constant (K) of export rate. The result showed that the export rate of photosynthate of labeled leaf reduced after pesticide treatments. The reduction of the export rate was positively related with the pesticide application rates and mainly attributed to decrease of photosynthetic rate.

Quantification of drought tolerance in Ethiopian common bean varieties

Understanding the level of drought tolerance of the varieties available in each country is of paramount importance for breeding common bean for drought adaptation. The goal of this study was to evaluate 25 common bean genotypes of which 24 were released/recommended varieties for production by farmers and one was a drought tolerant check. The genotypes were planted at two sites in Ethiopia, Hawasssa and Amaro, using variable sowing dates, one that was early to avoid drought and one that was late to expose the crop to drought. The experiments were repeated over two years in Hawassa and one year in Amaro. This resulted in treatments with high and low total seasonal rainfall and six environments for analysis. The impact of drought stress on the trait expression of the varieties was not uniform across traits assessed and varieties tested. The effect of drought on photosynthate translocation and partitioning traits was much greater than on yield component traits in the varieties studied. This indicating less breeding efforts has been made in improving the varieties ability to mobilize photosynthate to the developing grain as compared to the yield component traits. Drought tolerant varieties like Hawassa Dume maintained better photosynthate translocation and partitioning than the drought sensitive varieties like Brown Speckled bean. Hawassa Dume also showed better yield stability and performed well under both drought stress and nonstress conditions. Our results indicate the relevance of high levels of photosynthate translocation and partitioning as an effective selection objective for improving drought tolerance in common bean. The information generated on the drought tolerance of the available varieties should help in the design of a breeding strategy that incorporates adaptation traits with commercial characteristics preferred by common bean farmers for varieties to be grown in diverse environments.

Genotypic variance in 13C-photosynthate partitioning and within-plant boll distribution in cotton

Background:Photosynthate partitioning and within-plant boll distribution play an important role in yield formation of cotton;however,if and how they interact to mediate yield remains unclear.The objective of this study was to investigate the genotypic variance in photosynthate partitioning and within-plant boll distribution,with a focus on their interactions with regard to yield and yield components.A field experiment was conducted in the Yellow River region in China in 2017 and 2018 using a randomized complete block design with three replicates.Photosynthate partitioning of three commercial cultivars(DP 99 B,Lumianyan 21 and Jimian 169),varying in yield potential,to different organs(including bolls)at early flowering,peak flowering,and peak boll-setting stages,as well as withinplant boll distribution at harvest,and their effects on yield formation were examined.Results:Lint yield of Jimian 169 was the highest,followed by Lumianyan 21 and DP 99 B.Similar differences were observed in the number of inner bolls and boll weight among the three cultivars.J169 partitioned significantly more photosynthate to the fruit and fiber than Lumianyan 21 and DP 99 B and allocated over 80%of assimilates to the inner bolls.Additionally,Lumianyan 21 allocated a higher proportion of photosynthate to bolls and fiber,with12.5%–17.6%more assimilates observed in the inner bolls,than DP 99 B.Conclusions:Genotypic variance in lint yield can be attributed to differences in the number of inner bolls and boll weight,which are affected by photosynthate partitioning.Therefore,the partitioning of photosynthate to fiber and inner bolls can be used as an important reference for cotton breeding and cultivation.

Systemic Signaling and Local Sensing of Phosphate in Common Bean： Cross-Talk between Photosynthate and MicroRNA399

Shoot-to-root communication is crucial for plant acclimation to phosphorus （P）-deficiency. Both sugars and miRNAs have been implicated as potential signal molecules transported through phloem from shoot to root for the reg- ulation of gene expression and Pi uptake in the root. By studying the expression patterns of both a serine/threonine phos- phatase gene （PvHAD1） and microRNA399 （miR399） in common bean （Phaseolus vulgaris L.）, we provide evidence for the interaction between light, phloem transport, and miR399 in the systemic regulation of gene expression under P-deficiency. Especially, miR399 expression in both the shoot and the root requires photosynthetic carbon assimilation during the onset of P-deficiency. In contrast to systemic signaling, local sensing was the primary causal factor for rapid down-regulation of PvHAD1 by Pi prior to the reduction of miR399 level in P-deficient roots. Furthermore, this initial response to Pi in P-de- ficient root was also mimicked by the Pi analog, phosphonate （Phi）. Our current findings suggest that plants have developed a highly coordinated dual regulatory pathway, namely long-distance signaling of P-deficiency from shoot to root versus local sensing of Pi in the root.

Effects of Elevated CO_2 on Growth, Carbon Assimilation, Photosynthate Accumulation and Related Enzymes in Rice Leaves during Sink-Source Transition

To study the effects of growing rice （Oryza sativa L.） leaves under the treatment of the short-term elevated CO2 during the period of sink-source transition, several physiological processes such as dynamic changes in photosynthesis, photosynthate accumulation, enzyme activities （sucrose phosphate synthase （SPS）, and sucrose synthase （SS））, and their specific gene （spsl and RSusl） expressions in both mature and developing leaf were measured. Rice seedlings with fully expanded sixth leaf （marked as the source leaf, L6） were kept in elevated （700 μmol/mol） and ambient （350 mol/L） CO2 until the 7th leaf （marked as the sink leaf, L7） fully expanded. The results demonstrated that elevated CO2 significantly increased the rate of leaf elongation and biomass accumulation of L7 during the treatment without affecting the growth of L6. However, in both developing and mature leaves, net photosynthetic assimilation rate （A）, all kinds of photosynthate contents such as starch, sucrose and hexose, activities of SPS and SS and transcript levels of spsl and RSusl were significantly increased under elevated CO2 condition. Results suggested that the elevated CO2 had facilitated photosynthate assimilation, and increased photosynthate supplies from the source leaf to the sink leaf, which accelerated the growth and sink-source transition in new developing sink leaves. The mechanisms of SPS regulation by the elevated CO2 was also discussed.

Split nitrogen fertilizer application improved grain yield in winter wheat (Triticum aestivum L.) via modulating antioxidant capacity and ^(13)C photosynthate mobilization under water-saving irrigation conditions

A water-saving cultivation technique of supplementary irrigation based on soil moisture levels has been adopted for winter wheat production in the Huang-Huai-Hai Plain of China,due to the enhanced water-use efficiency.However,appropriate split nitrogen management may further improve crop growth and grain yield.Here,we conducted a 2-year field experiment to determine if split nitrogen management might improve wheat productivity by enhancing ^(13)C photosynthate mobilization and the antioxidant defense system under water-saving conditions.Split nitrogen management involved a constant total nitrogen rate(240 kg ha^(−1))split in four different proportions between sowing and jointing stage,i.e.,10:0(N1),7:3(N2),5:5(N3),and 3:7(N4).The N3 treatment significantly enhanced“soil-plant analysis development”values,superoxide dismutase antioxidant activity,soluble protein content,sucrose content,and sucrose phosphate synthetase activity,although it reduced the accumulation of malondialdehyde(MDA).The N3 treatment ultimately increased the amount of dry matter assimilation after anthesis significantly.In addition,the ^(13)C isotope tracer experiment revealed that the N3 treatment promoted the assimilation of carbohydrates after anthesis and their partitioning to the developing grains.Compared to the unequal ratio treatments(N1,N2,and N4),the equal ratio treatment(N3)increased grain yield by 5.70–16.72%via increasing 1000-grain weight and number of grains per spike in both growing seasons.Therefore,we recommend the use of a 5:5 basal-topdressing split nitrogen fertilizer application under water-saving irrigation conditions to promote antioxidant enzyme activity and the remobilization of photosynthate after anthesis for improving wheat grain yield.

Effect of terminal locations of pods on biomass production and ^(13)C partitioning in a fasciated stem soybean Shakujo

This study addresses the hypothesis that stagnation of soybean yield on the farm can be improved by selection of a physiological trait favoring carbon assimilate partitioning to terminally placed pods versus genotypes having axillary pods at close plant spacing.13C was fed to source-sink units comprising a leaf,axillary/terminal pods,and petioles at upper and lower positions of the stem axis in two soybean cultivars,namely Shakujo and Enrei,at different densities of populations.The cultivars differ significantly in architecture,Shakujo bearing a few hundreds of pods in close succession to one another in a terminally placed raceme,in contrast to Enrei having axillary racemes.Pod yield per plant was higher in Enrei than in Shakujo at low density,but Shakujo out-yielded Enrei at close spacing.Population density decreased yield per plant and altered the pattern of assimilate partitioning significantly within the plants for both varieties.At high density more assimilates moved to the upper parts at the cost of the lower parts.The terminally placed pods of Shakujo were advantaged to receive assimilates under density stress.No benefit was accrued to pod filling of Enrei,however,under this condition.