Ultrastructural and cytochemical investigations of pathogen development and host reactions in susceptible and partially-resistant carrot roots infected by Pythium violae, the major causal agent for cavity spot

Two carrot genotypes, cultivar Nanco and line 24, susceptible and partially- resistant respectively to cavity spot, were compared ultrastructurally and cytochemically 24 h, 48 h and 72 h after root inoculation with a virulent Pythium violae isolate. The extent of pathogen ingress and the response of the host differed markedly with the two genotypes. In cv Nanco, growth of fungal hyphae was predominantly intracellular and was accompanied by pronounced damage; by 48 h after inoculation, pericycle and the first cell layers of the phloem parenchyma were invaded, resulting in host wall dissolution and cytoplasm aggregation. The growth of P. violae in line 24 was limited to the pericycle, even up to 72 h after inoculation; fungal colonization was accompanied by retraction of cytoplasm and in the appearance of granular or fibrillar material in the host cell lumen. Some affected host cells were filled with structureless osmophilic material. In cultivar Nanco, invading fungal hyphae were unaffected; by contrast in line 24, the cytoplasm of invading hyphae, particularly those inside the cell host, was disorganised and structureless. Infection and host response in the two cultivars were studied with two specific labels: Aplysia gonad lectin (AGL), a polygalacturonic acid-binding lectin, and an exoglucanase complexed to colloidal gold were used to locate pectin and cellulosic -(1,4)-glucans respectively in infected tissues. The decrease of cytochemical labeling beyong fungal penetration showed clearly hydrolysis of pectin and cellulose in cell walls of the cv Nanco. By contrast, the cell wall of line 24 remained largely intact, although, unlabeled amorphous and electron-dense material was observed inside the wall. Fibrillar or electron dense material commonly observed in infected tissue of line 24 apparently did not contain pectic or cellulosic substances. Moreover, material observed in host cells or fungal hyphae was also free of labeling. The origin and the chemical composition of these compounds as well as their possible role in the defence mechanisms of carrot against P. violae are discussed.     

桔皮中提取果胶的优化工艺

通过正交实验设计,利用方差分析,确定了提取果胶的最佳方案为按干桔皮与质量分数０．５％的ＨＣｌ的质量比１：９投料,在９０℃下保温浸提０．５ｈ。     

山楂果胶提取工艺的研究

为研究山楂果胶有效提取工艺方法,以干燥的山楂果粉为原料,采用传统的酸法(直接加热法)和微波辐射法提取果胶,通过单因素试验和正交试验确定果胶提取的最佳工艺参数。结果表明:山楂果胶提取的最佳工艺为微波辐射提取,功率700W,料液比为1∶30,提取液pH 2.0,提取时间为120s,果胶提取率为5.7%。与传统的酸法直接加热提取相比,微波提取果胶提取率增加了1.0%,提取时间也缩短为传统酸法提取的1/40倍。     

南瓜果胶提取方法及果胶得率与理化特性相关性研究

对南瓜提取果胶前的预处理及3种不同提取方法的效果进行比较,并通过单因素试验对其螯合剂＋超声波＋蛋白酶提取果胶的最佳条件进行了初步研究,并对南瓜果肉、果皮中果胶提取得率与其南瓜理化特性的相关性进行了分析。结果表明：添加2.0 g/L EDTA 0.1%,蛋白酶0.7%,料液比1∶20,温度50℃,pH值4.5,超声提取40 min为最佳提取工艺。南瓜果肉果胶提取得率与水分呈显著负相关（r=-0.615,P〈0.05）,果胶得率与总纤维素呈极显著正相关（r=0.660,P〈0.01）。南瓜果皮果胶提取与果皮水份呈显著负相关（r=-0.641,P〈0.05）,与果皮固形物呈显著正相关（r=-0.638,P〈0.05）。     

不同时期苹果渣对苹果果胶制备的影响

研究了不同时期的苹果渣内果胶含量、果胶提取率及其它的指标的变化。比较了人工干燥和自然干燥两种方式对果胶的影响,并测定了果胶在保存了一段时间后胶凝度的变化情况。结果表明,苹果渣果胶含量从8月到11月保持高水平,以后下降,9月份达到最大值。果胶提取率与果胶含量变化相一致,以9月份为最高。且人工干燥比自然干燥条件果胶提取率高。果胶在存放一段时间后胶凝度会有不同程度的下降。     

AAS法间接测定植物果胶含量的研究

利用果胶在碱性条件下水解成果胶酸,再以ＣａＣｌ２生成果胶酸钙沉淀。利用原子吸收光谱法（ＡＡＳ法）测定果胶酸钙中Ｃａ的含量,乘以换算系数１２．０７２,从间接测定果胶含量,并与经典重量法比较,结果较理想。ＡＡＳ法与重量法测定结果比值为９４．４％～９６．０％,同时因ＡＡＳ法是以Ｃａ的含量换算其果胶含量,大而避免经典重量法因存在少量蛋白质、草酸,而产生的干扰（使结果偏高）,ＡＡＳ法检出限可达μｇ／ｇ级低含     

甜菜粕在动物生产中的饲用价值和研究进展

甜菜粕是甜菜制糖的副产物,由甜菜渣制粒而成。甜菜粕产量大,作为非粮饲料原料利用潜力巨大。甜菜粕营养丰富、适口性好、果胶含量较高,可在动物生产中用作能量饲料。文章综述甜菜粕的营养价值和在动物生产中的应用研究进展,为甜菜粕进一步的应用和研究提供参考。     

火龙果果皮中提取果胶的工艺研究

通过单因素与正交试验,研究料液比、萃取pH值、萃取温度、萃取时间对火龙果果皮中果胶提取量的影响。结果表明,从火龙果果皮中提取果胶的最佳工艺条件为：料液比1∶8,萃取液pH2.0,萃取温度100℃,萃取时间120min。火龙果果皮中果胶提取量达1.48%。