Extraction of water‐soluble organic matter from mineral horizons of forest soils

Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H₂O, 0.01 M CaCl₂, and 0.5 M K₂SO₄. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K₂SO₄ extracted the largest amounts of WSOC (up to 126 mg C kg^–1) followed by H₂O followed by CaCl₂. The H₂O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol^–1 cm^–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K₂SO₄ bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.     

中国沙棘和俄罗斯沙棘叶片在不同土壤水分条件下脯氨酸、可溶性糖及内源激素含量的变化

通过对中国沙棘(Hippophaerhamnoidessinensis)和俄罗斯沙棘(Hippophaerhamnoides)在野外不同生境和田间不同干旱胁迫条件下叶片脯氨酸、可溶性糖及内源激素含量的变化进行研究后发现:坡上土壤水分含量显著低于沟底的土壤水分含量,坡上中国沙棘叶片中的脯氨酸、可溶性糖含量比沟底明显增加,雌株的增加幅度大于雄株。在田间不同的干旱胁迫条件下,沙棘叶片内脯氨酸含量随着干旱胁迫程度和干旱胁迫时间的延长而增加,脯氨酸积累能力为中国沙棘>俄罗斯沙棘,雌、雄株之间的差异为雌株>雄株。沙棘叶片内可溶性糖含量随着干旱胁迫程度和干旱胁迫时间的延长而持续增加,沙棘叶片可溶性糖的积累能力因雌雄株和品种不同而出现一定差异,表现为俄罗斯沙棘>中国沙棘,雌株>雄株。随着土壤含水量的降低,沙棘叶片中的ABA显著增加,IAA和ZR的含量明显降低,GA的含量在胁迫初期升高,之后逐渐下降;中国沙棘叶片内源激素的变化幅度小于俄罗斯沙棘,雌株的变化幅度小于雄株。综合沙棘叶片中脯氨酸、可溶性糖、内源激素的变化,在干旱的适应性方面,中国沙棘和沙棘雌株更具有优势。     

几种化学药物混合物熏气催熟杧果的综合效应

为解决果后熟过程中存在的黄熟程度不均匀、易感炭疽病和蒂腐病等问题,进行几种化学药物的混合物所产生气体催熟果的试验。结果表明:最佳的处理(处理Ⅱ),果黄熟仅需4 d,防炭疽病效果可达93%,防蒂腐病效果可达100%,可溶性固形物含量提高1%以上,轻耗仅为自然后熟的17.38%,果皮色泽鲜艳,果肉硬,风味佳,外观整洁,商品率高。该处理方法简单易行。     

水培条件下CO2与NH+4/NO-3配比对番茄幼苗生育的影响

升高CO₂浓度能够促进作物的光合作用，提高作物的生物量和产量，但关于CO₂与NH⁺₄/NO^-₃比及其交互作用对作物影响的研究较少，为探索番茄幼苗生长发育对CO₂浓度升高的响应是否对NH⁺₄/NO^-₃配比有较强的依赖关系，本试验在营养液栽培条件下，以番茄(Lycopersicun esculentum Mill)为试材，研究正常大气CO₂浓度(360 μL/L)和倍增CO₂浓度(720 μL/L)与不同NH⁺₄/NO^-₃配比的交互作用对番茄幼苗生长的影响。结果表明：CO₂浓度升高提高了低NH⁺₄/NO^-₃比例处理中番茄叶片的光合速率和水分利用率，提高幅度随NH⁺₄/NO^-₃比例的降低而增强，光合速率增强最大达55%。在同一CO₂浓度处理下净光合速率与水分利用率均随NH⁺₄/NO^-₃比例的增加而显著降低。这说明CO₂浓度升高对番茄幼苗生长发育的促进作用随NH⁺₄/NO^-₃比例的降低而提高，但并没有减弱全NH⁺₄-N处理中番茄幼苗的受毒害作用。综上所述，CO₂浓度升高能提高植物生产的节水能力和水分生产力；水培条件下，NO^-₃-N是最适合番茄幼苗生长发育的氮源，其它NH⁺₄/NO^-₃比例对番茄幼苗的生长发育有一定的抑制作用，仅以NH⁺₄-N作氮源则番茄幼苗很难生长。     

甘蔗节间蛋白质含量与生长发育关系的研究

选用8个不同基因型的甘蔗，即粤糖86-368、新台糖16号、农林8号、拔地拉、割手密和从甘蔗杂交后代F1中选出的3株种茎的无性系(单株)。在甘蔗伸长初期，测定其 2节间至 8节间的长度、茎径，同时取 3、 5、 8节间，测定其可溶性蛋白质、细胞壁离子型结合蛋白质、细胞壁共价型结合蛋白质及可溶性总糖的含量。结果表明：从 2节间到 8节间，不同基因型的节间长度的变化极为相似，除割手密外，其它基因型甘蔗的节间长度都在 6节达到最长；但其茎径在 6节间以后仍保持稍微的增粗。从 3节间到 5、 8节间，所有基因型的三类蛋白质含量都逐渐下降，而可溶性总糖含量都逐渐提高。其中，三个节间较粗的基因型即拔地拉、粤糖86—368和无性系3号，其三类蛋白质含量相对较高，而可溶性总糖含量相对较低。     

速溶乌龙茶工艺研究

速溶茶具有重量轻、体积小、速溶的特点。本实验采用最廉价的茶叶,通过温度、时间、茶水比对浸提的影响,得到最佳浸提条件;添加β-环状糊精,可以更好的保留茶的香味以及提高茶叶有效成分的提取率。     

绣球菌水溶多糖的提取及其抑菌效果

[目的]从绣球菌中提取水溶多糖,研究其抑菌的效果,为绣球菌的开发利用提供试验依据。[方法]采用水煮醇沉法获得绣球菌水溶粗多糖,并采用三氯乙酸法对其进行脱蛋白后,通过滤纸片法和平板打洞法研究水溶粗多糖与脱蛋白后多糖的抑菌效果。[结果]水溶粗多糖含量与得率分别为28.5%、3.0%;脱蛋白后糖含量与得率分别为48.9%、2.2%。绣球菌水溶多糖与去蛋白多糖对大肠杆菌抑菌效果明显,滤纸片法去蛋白多糖最小抑菌浓度低于1.6 mg/ml;平板打洞法去蛋白多糖最小抑菌浓度低于25 mg/ml,对酿酒酵母、根霉菌、黑曲霉具有抑菌效果;去蛋白水溶多糖抑菌效果较水溶粗多糖好。[结论]绣球菌水溶多糖对不同菌具有不同的抑菌效果。     

干湿交替灌溉改善稻田根际氧环境进而促进氮素转化和水稻氮素吸收

[目的]阐明不同水氮管理模式下水稻根际内外氧环境变化特征及其对土壤碳氮转化和水稻氮吸收利用的影响,以期从稻田"根际氧环境"调控角度揭示适宜水氮耦合促进水稻生长和提高氮素利用效率的内在机制.[方法]在长期定位试验基础上,采用根箱模拟培养以及Unisense微电极系统和15N同位素示踪相结合的研究方法,以常规粳稻日本晴和常...     

Effect of Soil Temperature on the Carbohydrate Status in the Potato Plant (S. tuberosum L.)

Seed tubers of the variety Ostara were raised in growth chambers of 16°C air temperature continuously. The vessels were placed in a water bath of automatic temperature regulation so that soil temperatures of 16°C and 28°C could be maintained. Four weeks after emergence the plants were treated with ¹⁴CO₂ and 24 hours later the plants were harvested. Three more treatments and time harvests followed in two weeks intervals. C-14 activity was determined in soluble carbohydrates, in insoluble carbohydrates, and in non extractable residues respectively of the various plant parts in order to obtain information about the translocation of assimilates in the plant.
While the plants at 28°C soil temperature reduced the soluble sugar levels to 50% up to 70 days after emergence, the plants at 16° brought it down to 33% much faster. — The C-14 activity in insoluble carbohydrates amounted to only 50 % in the plants at 28°C while at 16°C it was more than 2/3 (Tables 1 and 2). — The C-14 activity in non extractable residues is much less at 28°C than at 16°C (Tables 3 and 4). — The starch weight reaches only 30% of the value obtained at lower temperature 70 days after emergence (Table 5). — At the higher temperature starch is also increasingly transferred to the tubers but to a much lesser extent and not from the stems and stolons (Table 6).
Possible causes, particularly the role of phytohormones, and consequences are discussed.     

Influence of Water Stress on the Chemical Composition of Seeds of Two Lupins (Lupinus albus and Lupinus mutabilis)

We have performed chemical proximate analysis and determined the carbohydrate profile of mature seeds of Lupinus albus, cv. Rio Maior and Lupinus mutabilis, cv. Potosi plants, either well watered (ww) or subjected to a water-stress period (imposed from the 15th to 35th day after anthesis). Protein content from lupin seeds was 450 and 320 g kg⁻¹ of seed on dry weight basis, for ww plants, respectively, of L. albus and L. mutabilis. Water stress did not affect protein content. The oil content of ww plants was about 120 g kg⁻¹ of seed dry weight for L. albus and 180 g kg⁻¹ of seed dry weight for L. mutabilis. Water stress reduced those values of half. The sugar content was about 90 g kg⁻¹ for L. albus and 50 g kg⁻¹ of seed dry weight for L. mutabilis, in ww plants. Water stress led to an increase in sugar content to 200 and 130 g kg⁻¹ of seed dry weight, respectively, for L. albus and L. mutabilis. The α-galactosides amounted to 70 % of the total sugars (raffinose being 30 % and stachyose, 40 %) and sucrose was about 20 % of the total sugars. Water stress increased total carbohydrates and increased the sucrose/α-galactoside ratio, although reducing raffinose content and increasing sucrose content.