Effect of Lime and Flooding on Phosphorus Availability and Rice Growth on Two Acidic Lowland Soils

Abstract

Loss of soil‐water saturation may impair growth of rainfed lowland rice by restricting nutrient uptake, including the uptake of added phosphorus (P). For acidic soils, reappearance of soluble aluminum (Al) following loss of soil‐water saturation may also restrict P uptake. The aim of this study was to determine whether liming, flooding, and P additions could ameliorate the effects of loss of soil‐water saturation on P uptake and growth of rice. In the first pot experiment, two acid lowland soils from Cambodia [Kandic Plinthaqult (black clay soil) and Plinthustalf (sandy soil)] were treated with P (45 mg P kg^?1 soil) either before or after flooding for 4 weeks to investigate the effect of flooding on effectiveness of P fertilizer for rice growth. After 4 weeks, soils were air dried and crushed and then wet to field capacity and upland rice was grown in them for an additional 6 weeks. Addition of P fertilizer before rather than after flooding depressed the growth of the subsequently planted upland rice. During flooding, there was an increase in both acetate‐extractable Fe and the phosphate sorption capacity of soils, and a close relationship between them (r²=0.96–0.98). When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed, indicating that flooding decreased availability of fertilizer P. A second pot experiment was conducted with three levels of lime as CaCO₃ [to establish pH (CaCl₂) in the oxidized soils at 4, 5, and 6] and four levels of P (0, 13, 26, and 52 mg P kg^?1 soil) added to the same two acid lowland rice soils under flooded and nonflooded conditions. Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming after 6 weeks' growth, but the addition of P increased rice dry matter substantially in both soils. In nonflooded soils, when P was not applied, shoot dry matter was depressed by up to one‐half of that in plants grown under continuously flooded conditions. Under the nonflooded conditions, rice dry matter and leaf P increased with the addition of P, but less so than in flooded soils. Leaf P concentrations and shoot dry matter responded strongly to the addition of lime. The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake. The current experiments show that the loss of soil‐water saturation may be associated with the inhibition of P absorption by excess soluble Al. By contrast, flooding decreased exchangeable Al to levels below the threshold for toxicity in rice. In addition, the decreased P availability with loss of soil‐water saturation may have been associated with a greater phosphate sorption capacity of the soils during flooding and after reoxidation due to occlusion of P within ferric oxyhydroxides formed.     

铬天青S－溴化十六烷基三甲铵－乙醇高灵敏分光光度法测定植物和土壤水中铝

本文探讨了铝与铬天青Ｓ的最佳显色反应条件。当ｐＨ为６．５，在溴化十六烷基三甲铵（ＣＴＭＡＢ）和乙醇的存在下，铝与铬天青Ｓ形成绿色配合物，最大吸收峰位于６３５ｕｍ，表观摩尔吸光系数为１．６５×１０５Ｌ／ｍｏｌ·ｃｍ，铝含量在０～０．２４μｇ／ｍＬ范围内符合比耳定律。在本实验条件下，该方法具有良好的选择性，应用于植物和土壤水中铝的测定，结果满意。     

Proton toxicity interferes with the screening of common bean (Phaseolus vulgaris L.) genotypes for aluminium resistance in nutrient solution

Common bean (Phaseolus vulgaris L.) proved to be very sensitive of low pH (4.3), with large genotypic differences in proton sensitivity. Therefore, proton toxicity did not allow the screening of common bean genotypes for aluminium (Al) resistance using the established protocol for maize (0.5 mM CaCl₂, 8 μM H₃BO₃, pH 4.3). Increasing the pH to 4.5, the Ca²⁺ concentration to 5 mM, and addition of 0.5 mM KCl fully prevented proton toxicity in 28 tested genotypes and allowed to identify differences in Al resistance using the inhibition of root elongation by 20 μM Al supply for 36 h as parameter of Al injury. As in maize, Al treatment induced callose formation in root apices of common bean. Aluminium‐induced callose formation well reflected the effect of Ca supply on Al sensitivity as revealed by root‐growth inhibition. Aluminum‐induced callose formation in root apices of 28 bean genotypes differing in Al resistance after 36 h Al treatment was positively correlated to Al‐induced inhibition of root elongation and Al contents in the root apices. However, the relationship was less close than previously reported for maize. Also, after 12 h Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes, indicating a different mode of the expression of Al toxicity and regulation of Al resistance in common bean than in maize.     

铝中毒对蛋鸡白细胞和红细胞免疫功能的影响

采用连续腹腔注射相同体积不同浓度梯度的三氯化铝，建立不同程度的鸡亚慢性铝中毒型，检测铝中毒雏鸡外周血白细胞数(WBC)、淋巴细胞总数、ANAE+T数及红细胞C3b受体花环率和红细胞免疫复合物花环率。结果表明，铝中毒雏鸡外周血白细胞数、淋巴细胞总数、ANAE+T数及红细胞C3b受体花环率均明显低于健康对照组雏鸡，而红细胞免疫复合物花环率明显高于健康对照组雏鸡。上述结果说明, 铝中毒对雏鸡细胞免疫和非特异性免疫功能有明显的抑制作用。     

Response of Sorghum to Abiotic Stresses: A Review

Sorghum [(Sorghum bicolor L.) Moench] is a highly productive crop plant, which can be used for alternative energy resource, human food, livestock feed or industrial purposes. The biomass of sorghum can be utilized as solid fuel via thermochemical routes or as a carbohydrate substrate via fermentation processes. The plant has a great adaptation potential to drought, high salinity and high temperature, which are important characteristics of genotypes growing in extreme environments. However, the climate change in the 21st century may bring about new challenges in the cultivated areas. In this review, we summarize the most recent literature about the responses of sorghum to the most important abiotic stresses: nutrient deficiency, aluminium stress, drought, high salinity, waterlogging or temperature stress the plants have to cope with during cultivation. The advanced molecular and system biological tools provide new opportunities for breeders to select stress‐tolerant and high‐yielding cultivars.     

LY12合金冷拉棒性能的研究

对淬火前的热挤压棒用不同的冷拉拔量进行拉拔，结果表明；冷拉拔量对棒材的组织和性能有不同的影响．当变形量达到10％时，经淬火后的棒材其组织是均匀的细晶组织．     

磷化锌药签配方及工艺改良研究

通过对6组助剂组合吸潮速度的测定，筛选出磷化锌药签最佳助荆组合，以KT50为指标筛选出最佳的药签配方，并在选择调制剂的基础上实现了药签生产的一步法工艺。     

Swimming performance,whole body ions,and gill Al accumulation during acclimation to sublethal aluminium in juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (2–5 g) were chronically exposed (for 22 days) to acidified softwater (Ca²⁺ = 25 Eq/l, pH 5.2) in the presence or absence sublethal Al (30 g/l). Al-exposed fish (5.2/Al group) suffered 20% whole body Na⁺ and Cl^– losses and a 30% reduction in the maximum sustainable swimming speed (U_crit) over the initial 7 days. These disturbances were approximately 2 fold greater than those observed in the fish exposed to low pH alone (5.2/0 group). However, whole body ion levels were completely restored in the 5.2/Al fish by day 22, whereas they merely stabilized at a new reduced level in the 5.2/0 group. Increased resistance to acutely lethal Al (200 g/l at pH 5.2) was observed from day 17 onwards in the 5.2/Al fish. Despite this acclimation and recovery of whole body ions, U_crit remained significantly lower than in the 5.2/0 group throughout. Growth on a restricted diet of 1% body wt. /day was normal in the 5.2/0 group compared with controls maintained in pH 6.5 softwater, whereas 5.2/Al fish suffered a 50% reduction in growth rate on the same diet. The 5.2/Al fish accumulated large amounts of Al on the gills, reaching an initial peak after 4 days, followed by a decline at 7 days, and a secondary rise thereafter. Therefore acclimation and recovery of whole body ionic status was not associated with a reduction in the gill Al burden. Some of the metabolic costs of acclimation to Al, namely a continued impairment of swimming speed and growth, are discussed in light of the physiological and structural changes reported to occur at the gills.     

壳寡糖及其复合聚合氯化铝絮凝微藻富集的研究

［目的］ 为了找到可以加速微藻富集的合适絮凝剂。［方法］ 制备了壳聚糖的降解产物壳寡糖,用于绿色巴夫藻（Pavlovaviridis Tseng, Chen et Zhang）和小球藻（Chloreiia spp.） 絮凝富集。［结果］ 终浓度为30 mg/L以上的壳寡糖溶液对2种藻类具有显著的促沉降效应。当壳寡糖与6 mg/L聚合氯化铝混合使用时,壳寡糖/聚合氯化铝促沉降效应明显提高。［结论］ 壳寡糖可以用于微藻大规模生产的采收。