植物响应低硫胁迫的分子生物学机制研究进展

[目的]硫是植物生长发育所必需的营养元素之一.硫不仅参与半胱氨酸和蛋白质等初生代谢产物的合成,还参与硫代葡萄糖苷、植保素、植物螯合肽、维生素、辅酶A等次生代谢物质的合成.因此,适量的硫供给可促进植物生长发育,提高作物的产量和品质,增强植物耐受生物和非生物胁迫的能力.[主要进展]植物主要通过根系从土壤吸收硫酸盐,硫酸盐在...     

洛惠渠灌区水土化学特性分析

为了深入了解洛惠渠灌区土壤盐碱化程度,分别测试了2004年实地采集的63个土壤样品和71个地下水样品,测定项目分别为土壤含盐量、碱化度、阴阳离子含量和地下水化学成分,并分析了该灌区土壤盐碱化现状以及地下水水质状况.结果表明,洛惠渠灌区土壤盐碱化较明显,盐渍化土壤分成盐土和碱土两类,主体成分为钠(钾)、钙的硫酸盐和碳酸盐;而地下水化学类型基本属于氯化钠-硫化钠型.通过计算其钠吸附比和镁系数可以推知该灌区地下水大部分对灌溉作物有不利影响,并且对土壤有进一步碱化的威胁.因此,有效控制该灌区地下水位是治理土壤盐碱化的重要措施,还要考虑不同区域土壤易溶盐含量,作物耐盐碱性等因素.应当综合工程、生物、化学等方法来改良利用盐碱土地,方能起到事半功倍的治理效果.     

广西亚热带岩溶地区石灰性土壤钾素特征研究

试验研究广西亚热带岩溶地区石灰性土壤K素特征结果表明,该区农田生态系统中棕色石灰土速效钾含量和速效钾可释放量能较好地反映土壤对当季作物的供K能力;当土壤速效钾含量降至30~32mg/kg时,作物难以吸收土壤中的K素,严重限制作物生长;土壤主要养分限制因子为土壤缺K,且P、S、B、Zn不足;棕色石灰土缓效钾含量和缓效钾可释放量不能正确反映土壤对当季作物的供K能力,但能较正确反映土壤的持续供K能力。施K有利于维持土壤K素平衡,通过增施K肥获得作物高产可行。     

植物镁素营养诊断及镁肥施用

本文对近些年来有关植物镁素营养诊断及镁肥施用问题作了综述.主要内容包括:缺镁时植物的外部形态表现及内部结构变化、植物镁素化学分析诊断和生物化学方法诊断以及镁肥施用技术和国内镁肥使用状况.     

湖北潮土区不同轮作制度下土壤养分平衡状况与评价

通过连续5年定点调查和取样分析,研究了湖北省2个潮土区域农田土壤养分平衡状况,并用允许养分平衡盈亏率进行了评价.结果表明:①在几种主要轮作制中,所有作物的K肥施用量及施用比例均明显比N肥低,但几乎所有作物的K素吸收量均明显高于N素吸收量,早、晚稻吸收P、K的比例明显高于其它作物.②不同轮作制中土壤养分平衡状况表现为N素有不同程度的盈余、P素基本平衡、K素总是亏缺的,且水田K素亏缺量明显高于早地.在此基础上,作者提出"减N稳P增K"和以一个轮作周期为单位进行统筹施肥的养分平衡调控措施,以实现作物生产的高产稳产和土壤养分平衡的良性循环.     

滇池流域磷矿山区优势植物叶片与土壤养分生态化学计量特征

为了研究滇池流域磷矿山区不同生活型优势植物叶片和土壤的养分含量及其计量比特征,选取流域内磷矿退化山区内4种常见优势植物(马桑、云南松、蔗茅和紫茎泽兰)作为研究对象,分析植物叶片及土壤的C、N、P含量。结果表明:云南松影响下的土壤有机质、全氮、碱解氮和有效磷含量最高,分别为22.42 g/kg、1.85 g/kg、140.78 mg/kg、1 048.89 mg/kg,全磷含量最低,为2.51 g/kg;云南松叶片C含量为492.86 g/kg,显著高于其他植物,而N、P含量分别为11.22和2.78 g/kg,显著低于其他植物;土壤N含量与叶片C含量显著正相关,而与叶片N︰P比显著负相关。研究结果表明:磷矿山地土壤C、N养分是限制植物生长的主要限制因子;在土壤C、N养分相对匮乏的立地条件下,云南松和蔗茅叶片能够固定更多的C,而马桑叶片能够固定较多的N。因此,结合不同生活型植物的属性特征及该区域内群落的演替特征,建议磷矿山区废弃地的生态恢复可以构建蔗茅和马桑为主的植物群落,随后种植云南松形成针叶林以增加土壤C含量,并在恢复后期种植固N阔叶树种形成针阔混交林,以达到全面改善土壤养分、保持水土并控制土壤P素流失的目的。     

干湿度梯度及植物生活型对土壤氮磷空间特征的影响

通过对我国土壤氮磷含量及化学计量比值的分布特征研究,探讨了湿度梯度与植物生活型对土壤氮磷空间分布的影响。研究结果表明:中国陆地系统自然土壤氮、磷含量及氮磷比分别在0.02~8.78 g/kg,0.05~1.73 g/kg和0.06~9.85范围内变化,地形和气候因素对其空间变异性的影响均较为显著。干湿度梯度分带对土壤氮含量和氮磷比值的影响较磷含量更为明显,氮含量与氮磷比呈现出明显的梯度变化特征,表现出湿润区半湿润区干旱区半干旱区的规律,而磷含量变化不显著。在不同生活型植被土壤中,森林土壤氮磷的变化规律较灌木和草本土壤更为复杂;其植物磷平均含量低于全国平均值,说明森林生态系统植物受磷元素的限制作用与其较低的土壤磷含量供给有关。土壤氮磷含量和氮磷比与年均降水量和年均温度的相关性及逐步回归分析表明,土壤氮磷及其化学计量的变异性主要是受降水的影响。     

天津小站稻种植区土壤质量综合评价

为了解天津小站稻种植区土壤养分水平与肥力状况,本次调查分析了稻田土壤pH、盐分、有机质、速效量和全量氮磷钾、铜锰硫等中微量元素共24项指标,通过主成分分析法对土壤质量进行综合评价.结果表明:研究区土壤pH介于7.80～8.95,平均盐分含量为1.6 g/kg,有机质、全氮与碱解氮含量属于中下水平,钾素含量丰富而磷素缺乏...     

甘肃沿黄灌区马铃薯/大豆套作效应分析

应用土地当量比、产量当量、产值当量等不同量化指标,对甘肃沿黄灌区马铃薯套作大豆产出效果进行分析,通过测定薯豆套作复合群体光合参数、土壤养分、微生物数量及作物品质及调查间套作系统中杂草生长状况等,研究马铃薯间套作大豆的生理效应及微生态效益。结果表明, 马铃薯套作大豆的模式(薯/豆)显著提高了日照利用率、≥10 ℃温度利用率、绿色期降水利用率及地面覆盖期利用率,可提高土地复种指数及土地利用率,具有良好的产出效果,单位面积产量间作当量比、产值间作当量比分别为1.53和1.49。由于马铃薯对氮素和钾素吸收量大,而大豆对磷素比较敏感,马铃薯/大豆套作模式具有很强的养分吸收互补特性,可显著提高作物对养分资源的高效利用,降低化肥施用量。马铃薯/大豆连续套作可提高土壤有机质含量、促进土壤微生物活性和酶活性,有效改善土壤微生物结构,在一定程度上缓解了马铃薯连作障碍;还能降低马铃薯淀粉含量,极显著降低还原糖的含量,提高商品薯率、维生素C和蛋白质含量。马铃薯套作大豆栽培模式实现了土地、劳动力、土壤养分和水热资源在时间和空间上的集约化利用,具有提高土地产出量及可持续利用性的优势,同时能适应机械化作业,显著提高生产效率,适宜在西北沿黄灌区大面积示范推广。     

植物镁素营养诊断及镁肥施用

本文对近些年来有关镁素营养诊断及镁肥施用问题作了综述。主要内容包括：缺镁时植物的外部形态表现及内部结构变化、植物镁素化学分析诊断和生物化学方法诊断以及镁肥施用技术和国内镁肥使用状况。     

Fate of nitrogen and sulphur as affected by the rhizosphere of oilseed rape and barley

Abstract

Within plants, sulphur (S), and nitrogen (N) equilibrium is a requisite for their normal development. Pot experiments with oilseed rape and barley fertilized at different N to S ratios were carried out under glasshouse conditions by using the “rhizobag”; technique. The objective was to compare the induced‐influence of rhizosphere and non‐rhizosphere soil on N and S nutrition of the studied plants. Thus, SO₄ ²‐S, NC₃ ^‐‐N and NH₄ ⁺‐N concentrations, and total N and S taken up by the plants were examined. Barley increased the pH of rhizosphere soil whereas no real change of pH was observed with oilseed rape. Both plants took up all the NO₃ ^‐ present in the soil solution, but rapeseed took up greater quantities of NH₄ ⁺‐N and SO₄ ^2‐ ‐S than barley. Moreover, the ratio values of N to S of the aerial parts of the rapeseed were significantly and positively correlated to those of soil available‐N to ‐S ratios while this correlation was significant but negative with barley. This indicated a clear‐cut different influence between the two rhizospheres which oppositely induce the N and S nutrition of the two plant species.     

An automated turbidimetric method for total sulfur in plant tissue and sulfate sulfur in soils

Abstract

An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO₄ on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0–35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO⁼ ₄‐S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO₄ assays are not practical.     

Determination of total sulfur in soil and plant samples using sodium bicarbonate/silver oxide,dry ashing and ion chromatography

Abstract

The determination of total sulfur (S) in soils and plant tissue samples can be accomplished using a combination of sodium bicarbonate/silver oxide, dry ashing and ion chromatography(IC). The proposed method offers high precision and acceptable accuracy for samples with more than 0.02% S. At the same time this procedure makes use of standard analytical equipment used in other phases of soil, water and plant tissue analysis. Soil sample sizes larger than 0.1g or high total S or barite (BaSO₄) may not have acceptable S recoveries due to incomplete S oxidation or dissolution of BaSO₄. In order to optimize recoveries of total S in these special soil samples, varying (decreasing) sample sizes is required.     

Determination of optimum nutrient element ratios in plant tissue

A new approach for determining optimum nutrient element ratios in plant tissue is presented. Essential steps in the procedure involve: a) measuring patterns of response to pairs of nutrient elements in factorial fertilizer trials, b) modeling the yield response surface using a bivariate, Mitscherlich‐related response function, c) defining balanced nutrition in terms of the parameters of the response surface, d) identifying combinations of P and S fertilizer resulting in balanced nutrition, and e) determining from plant chemical analysis the ratio of nutrients in plant tissue in nutritionally balanced combinations. The approach is illustrated by data from a phosphorus (P) by sulfur (S) factorial field fertilizer trial on a mown mixed white clover (Trifolium repens cv Grasslands Huia) and ryegrass (Lolium perenne L cv Grasslands Nui) sward. Different parameters of yield [total dry matter production, clover dry matter production, clover nitrogen (N) uptake] required different ratios of S:P in fertilizer and consequently in plant tissue for nutritional balance. Also, plant tissue S:P ratios for balanced nutrition declined as the level of nutrition increased. Economic optimum S:P fertilizer ratios were higher than those ratios required for nutrient element balance due to the lower cost and higher effectiveness per kilogram of fertilizer S compared with fertilizer P. Ratios of S and P to N in clover tissue were useful indicators of the adequacy of S and P for clover which was dependent on N₂ fixation for its N supply. It is suggested that a nutrient element index system showing both relative and absolute nutrient element status might be built around N as an internal standard for legumes dependent on N₂ fixation and possibly also for non‐legumes.     

Evaluation of some soil and plant analysis procedures as predictors of the need for sulfur for corn production

Abstract

The objective of this study was to evaluate the usefulness of measures of mineralized sulfur (S), soil sulfate‐sulfur (SO₄‐S), concentration of S in plant tissue, and the N: S ratio in plant tissue as predictors of the need for S in a fertilizer program for corn (Zea mays L.). Data to evaluate the use of plant analysis for S as a predictor were obtained from ten sites where various rates of N and S were applied to corn. Regression analysis was used to relate the S concentration in the ear leaf tissue as well as the N: S ratio in the same tissue to relative yield when the rate of applied N was held constant at a rate of 168 kg/ha. These measures of S in plant tissue were not significantly related to relative yield at sites where there was no response to fertilizer S as well as sites where added S increased yield.

Data from the same sites were used to assess the ability of soil tests to predict the need for fertilizer S. A measurement of extractable SO₄‐S in the surface soil (0–15 cm) was not reliable for predicting the need for S for corn grown on soils with a silt loam texture.

Static incubation techniques were used to evaluate the amount of S mineralized from soil collected from seven sites. The amount of SO₄‐S measured after four and twelve weeks of incubation was curvilinearly related (p <.05) to yield increase from a S fertilizer. Net mineralized S was less than 2.1 and 3.7 ppm SO₄‐S after four and twelve weeks of incubation, respectively, for soils taken from sites where response to fertilizer S was obtained. Data collected in this study indicate that a measure of mineralized S could improve the ability to predict S needs for corn production on soils with a silt loam texture and a low organic matter content.     

Uptake and remobilization of selenium in Brassica napus L. plants supplied with selenate or selenium‐enriched plant residues

Selenium (Se) biofortification via crops is one of the best strategies to elevate the daily Se intake in areas where soil Se levels are low. However, Se fertilizer recovery (SeFR) is low and most of the Se taken up accumulates in non‐harvested plant parts and returns to the soil with plant residues. A pot experiment with soil was undertaken to study the efficiency of inorganic Se (Na₂SeO₄) and Se‐enriched plant residues for biofortification, as well as to identify the bottlenecks in Se utilization by Brassica napus L. The soil was fertilized with Na₂SeO₄ (0 and 7 µg Se kg^?1) or with Se in stem or leaf residues (0 and 7 µg Se kg^?1). A treatment with autoclaved soil was included (0 and 7 µg kg^?1 as Na₂SeO₄) to unravel the impact of microbial activity on Se uptake. The Se‐enriched plant residues produced a lower Se uptake efficiency (SeUPE) and SeFR than did inorganic Se, and soil autoclaving enhanced Se accumulation in the plants. The time required for decomposition seems to preclude crop residues as an alternative source of Se. Furthermore, B. napus had a limited capacity to accumulate Se in seeds. The study shows that the bottlenecks in Se biofortification appear to be its low bioavailability in soil and poor loading from the silique walls to seeds. Thus, improved Se translocation to seeds would be a useful breeding goal in B. napus to increase SeFR.     

Use of labeled sulphur‐35 for tracing sulphur transfers in developing pods of field‐grown oilseed rape

Abstract

This study was conducted to better understand the dynamics of sulphur (S) transfer between pod walls and seeds of field‐grown oilseed rape by using sulphur (³⁵S) as an investigative tool. Labeling experiments with ³⁵S were carried out to determine the effects of nitrogen (N) and sulphur fertilization on these transfer mechanisms. Sixty‐four plants from field trials fertilized with 200 kg N ha^‐1 in the forms of ammonium nitrate (AN) or urea (U), with or without 75 kg S ha^‐1 in the forms of ammonium thiosulphate and MgSO₄ were sampled. At 30, 43, 56, and 77 days after flowering (DAF), terminal racemes were cut and labeled with ³⁵S‐SO₄ ^2‐. After labeling, pods and seeds were separated into 3 groups according to their position on stem, and measurements of ³⁵S levels were performed accordingly. This short‐term labeling experiment showed that the pod walls retained from 39 to 61% of labeled ³⁵S, according to the different treatments, whereas seeds accumulated from only 1 to 16% of applied ³⁵S. On average, when S was added, a sharp decrease of ³⁵S in seeds from 2.6 to 1.7%, 9.0 to 5.4%, and 14.8 to 7.7% was observed at 30, 43, and 56 DAF, while progressively the percentage values in pod walls increased from 49.6 to 50.5%, 43.1 to 52.2%, and 41.7 to 63.5%, respectively. The increase of ³⁵S in pod walls was found to be tied to the glucosinolate concentration of seeds. By artificially increasing the ratio values of external N‐NO₃ ^‐ to S‐SO₄ ^2‐, these results demonstrated that the transfer of ³⁵S to seeds was more affected by the higher level of N‐NO₃ ^‐ in plant tissues than S‐SO₄ ^2‐ levels. The N/S ratio value above which the transfer of S was disrupted was around 6.     

Influence of sulfur on growth and nutrient composition of soft red winter wheat

Sulfur (S) deficiencies in soft red winter wheat (Triticum aestivum L.) result in reduced yields and inferior grain quality. Diagnosis of S deficiency has been unreliable since soil testing does not accurately measure available soil S, and tissue S concentration varies with plant age. In order to establish more reliable guidelines for determining S deficiency in winter wheat we used nutrient solution culture to provide uniform conditions for determining the effect of tissue S content on dry matter accumulation and nutrient uptake. The critical level of S for 90% of maximum growth in winter wheat seedlings (Feekes scale 1 with 5 leaves) was calculated at 1.4 g kg^‐1 using a modified Mitscherlich model. Root growth was less sensitive to low S levels than top growth which may reduce the effect of S deficiency in the field. Concentrations of N, Mg, Fe, and Cu in the plant tissue increased with increased S concentration. An N/S ratio of greater than 22 was associated with reduced growth. Our results suggest that if care is taken in standardizing the plant age when sampling early diagnosis of S deficiency could be based on total S analysis.     

Soil chemical and microbial effects of simulated acid rain on clover and soft chess

Effects of simulated acid rain, comprised of HNO₃ and H₂SO₄ in the mole ratio of 3:1, at pH 5.6, 4.5, 4.0 and 3.0, were tested on the grass, soft chess (Bromus mollis L.) and on clover (Trifolium subterraneum L. var. Woogenellup) in a sandy soil of granodiorite parent material. Soft chess was grown in unfertilized soil, whereas clover was grown in both unfertilized soil and soil fertilized with NH₄NO₃ and CaSO₄·2H₂O at the rates of 224 kg ha^?1 N and 78 kg ha^?1 S. Two acid-spray irrigation periods of 31 and 26 weeks duration, each delivering 400 mm and separated by a dry period of 23 weeks, simulated typical rainfall of northern California rangeland. Plants were harvested after each of the two spray periods. There were very few deleterious effects of acid rain on plant growth or soil and microbial processes. No significant (p<0.05) effects were shown by soil microbial biomass, CO₂ production, nodules per unit weight of clover root, acetylene reduction, denitrification and nitrification potentials, or for soft chess plant weights, and N and P uptake. Mineralizable-N was unaffected also, except in one case. However, pH of soil to 10 mm depths was significantly lower in the pH 3.0 treatment after the first spray period, with a corresponding decrease in exchangeable soil Ca; these effects became significant at greater soil depth only after the second spray period. There were significant effects of acid treatments shown by clover, some of which may be advantageous. Treatments of intermediate acidity generally provided added N and S, which acted as fertilizers, and compensated for possible decreases in plant productivity attributable to acidity per se. There was also evidence of decreased P uptake in unfertilized soil at pH 3. In conclusion, effects of simulated acid rain were minimal, and in some cases were advantageous because of the added N and S having a fertilizer effect on plant nutrition and growth.     

Earthworms as seedling predators: Importance of seeds and seedlings for earthworm nutrition

Anecic earthworms have been shown to collect, concentrate and bury seeds in their burrows. Moreover, recent studies suggest that earthworms function as granivores and seedling herbivores thereby directly impacting plant community assembly. However, this has not been proven unequivocally. Further, it remains unclear if earthworms benefit from seed ingestion, i.e., if they assimilate seed carbon. We set up a series of three laboratory experiments in order to test the following hypotheses: (1) anecic earthworms (Lumbricus terrestris L.) not only ingest seeds but also seedlings, (2) ingestion of seedlings is lower than that of seeds due to a ‘size refuge’ of seedlings (i.e., they are too big to be swallowed), and (3) seeds and seedlings contribute to earthworm nutrition. L. terrestris readily consumed legume seedlings in the radicle stage, whereas legume seeds and seedlings in the cotyledon stage, and grass seeds and seedlings in the radicle and cotyledon stage were ingested in similar but lower amounts. Importantly, ingestion of seedlings, in contrast to seeds, was lethal for all plant species. Moreover, earthworm weight change varied with the functional identity and vitality of seeds and natural ¹⁵N signatures in earthworm body tissue underlined the importance of seedlings for earthworm nutrition. The results indicate that the anecic earthworm L. terrestris indeed functions as a granivore and seedling herbivore. The selectivity in seedling ingestion points at the potential of direct earthworm effects on plant community assembly. Further, seeds and seedlings most likely contribute significantly to earthworm nutrition potentially explaining the collection and concentration of seeds by L. terrestris in its middens and burrows; however, the present results call for experiments under more natural conditions.