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.     

Comparison of the adsorption of maize root mucilage and polygalacturonic acid on montmorillonite homoionic to divalent lead and cadmium

Summary Root mucilage material (RM) was isolated from maize plants grown in the field, and its affinity to montmorillonite (M) homoionic to Pb²⁺ and Cd²⁺ was compared with that of a commercial polygalacturonic acid (PGA). Adsorption isotherms of the commercial and natural materials on the two clay systems were compared in unbuffered systems at pH 3 and pH 6. Adsorption of PGA occurred only at pH 3, and was higher on M-Pb than on M-Cd. In contrast, the adsorption of RM was higher on M-Cd than on M-Pb. Total amounts of RM adsorbed at pH 3 were about 3 times lower on M-Cd and 20 times lower on M-Pb than the respective amounts of PGA adsorbed at the same pH. Polygalacturonic acid had a high content of relatively well dissociated (pKa = 3.5) carboxylic groups, and adsorbed on the clay surface at pH values lower than its pKa. At pH 6, the dissociation of the acid groups favoured its solubility, and the metal cations were then probably displaced by ion exchange. The lower affinity of RM to the clay materials was related to its average molecular weight, which was lower than that of PGA, and to its water solubility, which was higher than that of PGA. The low pH dependence of the adsorption of RM was related to its lower carboxylic acidity and higher content in hydroxyl and amino groups.     

一串红种子黏液对其基本性状及萌发的影响

【目的】研究种子黏液对一串红种子基本性状和萌发的影响,为一串红种苗生产提供支持。【方法】以一串红‘奥运圣火’有黏液和无黏液种子为材料,研究了黏液对种子基本物理性状、吸水和失水特性、粘土能力、萌发特性和植株主要观赏性状的影响。【结果】吸水后,一串红有黏液种子的平均长度、宽度、厚度和质量均显著增大,而无黏液种子仅平均长度和宽度显著增大。黏液可以增强一串红种子的粘土能力,粘土后有黏液干种子的平均质量是无黏液干种子的9.3倍。与无黏液种子相比,黏液可以促进一串红种子吸收大量水分,减缓种子水分散失。黏液种子在吸水100min时可以达到饱和状态,吸收的水分是自身质量的6.81倍,在室温条件下经过36h脱水才能达到质量恒定;无黏液种子在吸水60min时可达到饱和状态,吸收的水分是自身质量的0.59倍,经3h脱水即可达到质量恒定。一串红有黏液种子发芽势、发芽率、发芽指数、活力指数、根长、苗长均显著高于无黏液种子,发芽持续时间显著短于无黏液种子。种子黏液对一串红主要观赏性状无显著影响。【结论】黏液对一串红种子萌发特性有明显影响,有利于一串红种子的萌发和成苗。     

黏质物脱除工艺优化及其提高亚麻籽提油率的效果

为了提高水酶法提取亚麻籽油的提油率,该文探究了亚麻籽表面黏质物的存在对水酶法提取亚麻籽油提油率的影响,并对热水浸提法脱除亚麻籽黏质物的工艺进行优化。结果表明,水酶法提取亚麻籽油的提油率随亚麻籽表面黏质物的减少而升高,未脱黏亚麻籽的提油率为69.20%±1.51%,渣相含油量为26.00%±1.24%。经100 ℃浸提脱黏后,黏质物的脱除率为94.69%±1.94%,此时亚麻籽的提油率可达84.26%±0.63%,渣相含油量降低至10.45%±0.89%。对热水浸提脱除黏质物的工艺（浸提温度、浸提时间、体系pH值、料水比以及浸提次数）进行了单因素优化,发现在浸提温度85 ℃、pH值3、料水比1:7 g/mL、浸提2次,每次浸提60 min的条件下,黏质物的脱除效果最好,脱除率为97.88%±0.69%,脱黏后亚麻籽的提油率可达84.47%±0.53%,亚麻籽油和蛋白质的损失率分别为0.70%±0.16%和10.78%±0.41%,且浸提脱黏过程对水酶法提取亚麻籽油的品质（酸值和过氧化值）无显著影响。此外,浸提脱黏过程还可有效去除亚麻籽中的抗营养因子生氰糖苷,使生氰糖苷的含量由浸提前的（242.6±0.8）mg/kg显著降低到浸提后的（7.1±0.6）mg/kg。该研究提供了一种简单高效的热水浸提脱黏工艺,显著提高了后续水酶法提取亚麻籽油的提油率,同时也有利于亚麻籽多糖的回收和亚麻籽粕的进一步利用,为亚麻籽资源的综合利用提供有益参考。     

玉米根鞘改变土壤粒径及养分有效性

Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field experiments.The results showed that there was a significant size decrease of soil particles in the rhizosheath.Meanwhile,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of maize.The contents of Fe and Mn were also differentially altered in the rhizosheath.Rhizosheath development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental period.The formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient availability.The subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.     

Effects of Dietary Fibre Concentrates on growth performance and digestive enzyme activities of jundiá (Rhamdia quelen)

This study was conducted to investigate the prebiotic effect of different Dietary Fibre Concentrates (DFC) (Mucilage =MG; Pectin = PN or β‐glucan + mannan = βg + M) on growth and somatic parameters, body composition and digestive enzyme activities of jundiá (Rhamdia quelen). After acclimation, fish (7.16 ± 0.06 g) were allocated into 24 tanks (30 fish per tank) and triplicate groups were fed with Control diet (0 g kg^?1 of DFC); diet supplemented with 5 g kg^?1 commercial prebiotic (CP) or diets supplemented with 5 or 10 g kg^?1 diet of MG; PN or βg + M. At the end of the trial (8 weeks), growth was significantly (P < 0.05) higher in fish fed diets supplemented with DFCs and did not differ from animals supplemented with CP. The animals that were fed Control diet presented a body protein content higher compared to those supplemented with diets containing pectin or β‐glucan + mannan (P < 0.05). However, fish fed diets added with β‐glucan + mannan yielded a higher level of protein deposited in the whole body. The activity of digestive enzymes was lower in the group supplemented with Pectin. Results indicate that supplementation with DFCs in the diet had positive effects on the performance of jundiá and are prebiotic potential candidate.     

太门哲罗鱼消化系统形态学和组织学的研究

采用解剖和显微技术对哲罗鱼(Hucho taimen)消化系统形态学和组织学进行研究.结果显示:哲罗鱼口咽腔内除分布有味蕾和粘液细胞外,还着生有丰富的齿结构;食道粗而短,内壁有9～15个舌状粘膜褶皱,在粘膜层扁平上皮细胞间分布有大量的粘液细胞和少量梭型细胞;胃呈V型在粘膜层形成丰富胃小凹,柱状上皮下有发达的胃腺;肠分前...     

铝、硼对豌豆原位根边缘细胞粘胶层厚度的影响

在缺硼和施硼红砂土上种植并收获豌豆种子后,采用雾培法培养豌豆根及根边缘细胞,并于5 h、16 h、24 h、44 h在雾培液中加入500 μmol/L AlCl3(pH 4.5),培养至48 h后,测量豌豆根边缘细胞粘胶层相对面积,探讨硼和铝对豌豆原位根边缘细胞粘胶层变化的影响.结果显示:正常条件下豌豆原位根边缘细胞粘胶层相对面积随时间延长无变化;与pH 6.5的对照相比,酸性条件下(pH 4.5)豌豆根边缘细胞粘胶层相对面积显著变小,且随处理时间延长减小幅度越来越大.与相同pH溶液(pH 4.5)相比,加铝处理边缘细胞粘胶层相对面积显著大于不加铝处理;而与pH 6.5的对照相比,加铝处理后粘胶层相对面积却显著减小.硼对边缘细胞粘胶层无明显影响.结果表明:酸性条件引起原位边缘细胞粘胶层变薄,在酸性条件下加铝处理又引起粘胶层增厚;而硼对边缘细胞粘胶层无明显影响.     

Gel formation mechanism and gel properties controlled by Ca2+ in chia seed mucilage and model substances

Polygalacturonic acid (PGA) is considered as a model substance for mucilage to study mucilage–soil interactions, assuming that the gel formation mechanism of mucilage is comparable to the one of PGA. However, some studies question the accepted hypothesis, which states that, like for PGA, this mechanism relies on cross‐links between uronic acid and calcium for mucilage. The aim of this study was therefore to understand the influence of the abundance and degree of esterification of uronic acids and the influence of calcium on the gel formation mechanism in mucilage as compared to model substances. The mucilage used was from chia seeds, as it is easily available in great quantity and has gel properties shared by root mucilage. Results reported here demonstrate that, while the gel formation mechanism of PGA relied on specific cross‐links with calcium and led to heterogeneous gels, low‐methoxy pectin (LMP) formed homogeneous calcium gels also characterized by nonspecific ionic interactions with calcium. On the contrary, despite similar uronic acid content to LMP, chia seed mucilage was mostly governed by weak electrostatic interactions between entangled polymer chains, which conferred the gel poor water retention. Addition of calcium reduced repulsion and molecular expansion, resulting in a reduction of the water content in chia seed mucilage. Finally, the discrepancies between PGA, LMP and chia seed mucilage discredit the use of PGA as model for chia seed mucilage. Comparison with root mucilage is still needed. This study offers the keys for further mechanistic understanding on the influence of mucilage on soil properties.