Differences in manganese efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.) as related to root‐shoot relations and manganese influx

Manganese efficiency is a term used to describe the ability of plants to obtain higher relative yields at low Mn supply compared to other species. To evaluate Mn efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.), a greenhouse pot experiment was conducted using Mn deficient Typic Ustochrept loamy sand soil, treated with 0, 50, and 100 mg Mn (kg soil)^–1. In the no‐Mn treatment, wheat had produced only 30 % of its maximum dry matter yield (DMY) with a shoot concentration of 10.8 mg Mn (kg DM)^–1 after 51 days of growth, while raya had produced 65 % of its maximum DMY with 13.0 mg Mn (kg DM)^–1. Taking relative shoot yield as a measure of Mn efficiency, raya was more efficient than wheat. Both crops produced the maximum DMY with 50 mg Mn (kg soil)^–1. Even though raya had a lower root length : DMY ratio and a higher shoot growth rate, it acquired higher Mn concentrations in the shoot than wheat under similar soil conditions, because of a 2.5 times higher Mn influx. Model calculations were used to calculate the difference of Mn solution concentration (ΔC_L) between the bulk soil (C_Li) and the root surface (C_L0) that is needed to drive the flux by diffusion equal to the measured influx. The results showed that ΔC_L was smaller than C_Li, which indicates that chemical mobilization of Mn was not needed to explain the observed Mn uptake even for raya. According to these calculations, the higher Mn influx of raya was caused by more efficient uptake kinetics, allowing for a 4.5 times higher Mn influx at the same Mn concentration at the root surface.     

不同农艺措施处理对烟草根际微生态的影响

为探究烟株根际微生态环境与青枯病发生的关系,在烟草青枯病发生典型的植烟区采用常规地膜覆盖、稻草覆盖、地膜覆盖并开深沟3种农艺措施处理,研究不同农艺措施处理对土壤根际微生物、土壤养分及烟株病害发生情况的影响。结果表明,与常规地膜覆盖相比,稻草覆盖和开深沟两种农艺措施均可促进植物根际的物质代谢,使土壤根际的微生物数量显著增加。同时也可提高烟株对土壤养分的利用率,为植物提供更多的营养物质,使植株处于良好的生长状态。其青枯病发病率分别比常规地膜覆盖处理降低了27.22、16.11个百分点,病情指数分别降低了18.27、9.32。     

Effect of soil drying on mucilage exudation and its water repellency: a new method to collect mucilage

Despite the importance of mucilage for soil–plant relations, little is known about the effect of soil drying on mucilage exudation. We introduce a method to collect mucilage from maize growing in wet and dry soils. Mucilage was collected from brace roots. The amount of mucilage exuded did not change with soil water content and transpiration rate. Mucilage exuded in dry soils had a higher degree of hydrophobicity, suggesting that the wetting properties of mucilage change in response to soil drying.     

木霉菌制剂对甜瓜根际微生态的影响

[目的]为了研究根际微生态。[方法]采取土壤分离培养分析了施用木霉菌制剂后甜瓜根际土壤中真菌、细菌、放线菌等在甜瓜生长不同时期的数量变化。[结果]接种木霉菌制剂后,甜瓜根际不同生长时期的真菌、细菌、放线菌数量明显增多。[结论]施用木霉菌制剂,能提高土壤中有益微生物的活性,提高甜瓜的抗病性。     

固氮、解磷复合菌剂对小麦根际土壤细菌群落的影响

为研究固氮芽孢杆菌、固氮巨大芽孢杆菌、解磷假单胞菌、巴西固氮螺菌组成的复合菌剂对小麦根际土壤细菌群落多样性的影响,通过构建16SrRNA克隆文库及采用核糖体DNA扩增片段酶切分析(ARDRA)的方法,以文库库容值(C)、Rarefaction曲线(R)对克隆文库进行评价。系统发育分析表明,对照及菌剂处理样品均检测到酸杆菌门、变形菌门、浮霉菌门、厚壁菌门、拟杆菌门、疣微菌门、放线菌门和芽单胞菌门8个细菌类群,并且优势菌群均为变形菌门和酸杆菌门。接种菌剂后小麦根际土壤检出了绿弯菌门、蓝藻门、产水菌门和硝化螺旋菌门,而梭杆菌门未被检出。假单胞菌属由1.59%增加至21.28%。芽孢杆菌属由未检出增至3.05%。两样品中均未检出固氮螺菌属。多样性分析表明,接种菌剂后,小麦根际土壤细菌多样性指数和丰富度指数均提高。因此,接种菌剂对小麦根际土壤细菌类群的组成及所占比例有较大影响。     

鄂尔多斯沙地油蒿根际土壤微生物数量的季节动态

对油蒿根际土壤微生物数量的季节动态、垂直分布及影响微生物分布的环境因子进行了研究。结果表明:(1)微生物总数、细菌数量的季节动态为:春季>夏季>秋季>冬季,放线菌数量的季节分布为秋冬季多于春和夏季,真菌数量的季节动态为夏季达到最高值,其他季节变化不显著。(2)微生物数量的垂直分布总体上表现为随土层加深而逐渐减少,表层土壤(0-10cm)微生物数量是下面3层(10-40cm)的1.05-9.79倍。(3)土壤微生物根际效应明显,且细菌>真菌>放线菌,R/S值介于1.16-3.76之间。微生物根际效应的季节变化为春、夏季高于秋和冬季。(4)微生物分布与水热等环境因子密切相关,细菌数量与水热组合条件共同作用有关,真菌受温度影响较大,放线菌对土壤水分含量变化较敏感。     

根际促生细菌混合接种对甜樱桃/东北山樱根际微生物区系及根系呼吸的影响

为探讨有益微生物对甜樱桃根系的接种效应,试验采用灌根的方法,研究了从野生东北山樱根际分离筛选出的4株促生细菌,混合接种对甜樱桃/东北山樱根际微生物区系及根系呼吸代谢途径的影响.结果表明:接种促生菌液改变了甜樱桃根际细菌、放线菌及真菌的数量比例,使根际细菌数量显著增加.接种2次,根际细菌增加幅度最大,为对照的3.4倍;接种促生菌液提高了根系活力,接种2次效果最显著,为对照的2.4倍,达到200.4μg/(g·h);接种促生菌液对根系呼吸的基础生化途径与末端氧化电子传递途径运行比例无明显影响,但整体上提高了根系呼吸速率.     

生姜根际姜瘟病拮抗菌的筛选及鉴定

从生姜根际土样分离获得了65个细菌分离物和42个放线菌分离物,通过离体拮抗试验,筛选出对姜瘟病有良好拮抗效果的细菌一株,放线菌两株,编号分别为H16-8、WF1和JW02-6。通过形态学观察、生理生化测定以及16S rDNA序列分析,初步确定:H16-8为短短芽孢杆菌(Brevibacillus brevis),WF1为弗雷德氏链霉菌(Streptomyces fradiae),JW02-6为劳伦链霉菌(Streptomyces laurentii)。H16-8、WF1和JW02-6的16S rDNA序列的GenBank登录号分别为:EU812754,FJ972686和FJ972687。     

Al~(3+)胁迫对茶树根际青霉菌丝生长及酶活性的影响

[目的]研究外源添加Al3+对来自茶园土壤一种青霉生长及酶活性的影响。[方法]采用液体摇瓶培养,测定霉菌菌丝干重、发酵液胞外蛋白含量及胞外相关酶的活性。[结果]添加0～100mg/LAl3+对青霉生长有刺激作用,过氧化氢酶活性呈下降趋势,葡萄糖氧化酶活性变化与菌丝干重变化呈正相关。在0～200mg/LAl3+胁迫下,发酵液胞外蛋白含量、纤维素酶活性呈上升趋势。[结论]在不同浓度Al3+作用下,表现为不同程度的刺激或抑制作用。     

秦岭太白山区鹿蹄草根际与非根际土壤养分及酶活性研究

【目的】分析秦岭太白山区不同林分下鹿蹄草的根际和非根际土壤养分和酶活性状况,探索其空间变异规律,为野生鹿蹄草资源的保护提供依据。【方法】采用野外调查和室内分析的方法,对秦岭北坡太白山区4种林分下鹿蹄草根际与非根际土壤养分及酶活性差异及其相互间的关系进行研究。【结果】在鹿蹄草根际和非根际间,土壤有机质、全氮、有效氮、速效磷、速效钾均呈现出明显的根际聚集现象,根际平均富集率分别达34.64%,58.29%,126.94%,114.02%,96.38%,土壤全钾含量基本保持不变。土壤酶也表现出根际活性较强的特性,根际土壤脲酶、转化酶、过氧化氢酶、酸性磷酸酶活性比非根际土壤分别高出32.04%,22.40%,30.57%,8.17%。在鹿蹄草根际土壤中,有机质、速效钾含量与脲酶、转化酶、过氧化氢酶、酸性磷酸酶活性均呈极显著正相关,有效氮、速效磷含量与脲酶呈极显著正相关;而在非根际土壤中,有机质与转化酶、脲酶呈极显著正相关,速效磷含量与 4种酶活性均呈显著正相关。【结论】秦岭北坡太白山区鹿蹄草根际和非根际土壤养分与酶活性密切相关,各土壤酶活性之间也存在不同程度的相关性,较好地反映了鹿蹄草生境的土壤肥力状况。因此,土壤酶活性可以作为评价该区域土壤肥力的指标之一。