Leaf K/Na ratio predicts salinity induced yield loss in irrigated rice

Salinity is a major constraint to irrigated rice production, particularly in semi-arid and arid climates. Irrigated rice is a well suited crop to controlling and even decreasing soil salinity, but rice is a salt-susceptible crop and yield losses due to salinity can be substantial. The objective of this study was to develop a highly predictive screening tool for the vegetative growth stage of rice to estimate salinity-induced yield losses. Twenty-one rice genotypes were grown over seven seasons in a field trials in Ndiaye, Senegal, between 1991 and 1995 and were subjected to irrigation with moderately saline water (3.5 mS cm^-1, electrical conductivity) or irrigation with fresh water. Potassium/sodium ratios of the youngest three leaves (K/Na_Leaves) were determined by flame photometry at the late vegetative stage. Grain yield was determined at maturity. All cultivars showed strong log-linear correlations between K/Na_Leaves and grain yield, but intercept and slope of those correlations differed between seasons for a given genotype and between genotypes. The K/Na_Leaves under salinity was related to grain yield under salinity relative to freshwater controls. There was a highly significant correlation (p < 0.001) between K/Na_Leaves and salinity-induced grain yield reduction: the most susceptible cultivars had lowest K/Na_Leaves and the strongest yield reductions. Although there were major differences in the effects of salinity on crops in both the hot dry season (HDS) and the wet season, the correlation was equally significant across cropping seasons. The earliest possible time to establish the relationship between K/Na_Leaves under salinity and grain yield reduction due to salinity was investigated in an additional trial in the HDS 1998. About 60 days after sowing, salinity-induced yield loss could be predicted through K/Na_Leaves with a high degree of confidence (p < 0.01). A screening system for salinity resistance of rice, particularly in arid and semi-arid climates, is proposed based on the correlation between K/Na_Leaves under salinity and salinity-induced yield losses. This revised version was published online in July 2006 with corrections to the Cover Date.     

复合酶制剂对樱桃谷肉仔鸭小肠黏膜的形态及DNA、RNA含量的影响

试验选用180只体重为(59.46±0.09)g的1日龄樱桃谷肉仔鸭,随机分为4组,每组3个重复(栏),每栏15只鸭,分别饲喂玉米-豆粕型、稻谷-玉米-豆粕型和稻谷-玉米-豆粕型日粮 500 mg/kg或1000 mg/kg复合酶制剂日粮.在试验的第7和14天,每重复选取体重相近的5只肉仔鸭进行屠宰,在十二指肠远端、空肠中端和回肠中端分别截取5 cm和10 cm的两段相邻肠段,观测了小肠绒毛高度、隐窝深度、绒毛宽度,并测定了黏膜DNA和RNA含量.结果表明,在1～14 d肉仔鸭稻谷型日粮中添加复合酶制剂可使十二指肠的绒毛高度显著增加,而对小肠黏膜DNA和RNA的含量无显著性影响;在8～14 d,添加1000 mg/kg复合酶制剂可显著增加空肠和回肠的绒毛高度.     

A Study of the Vertical Vibration of the 4200 Thick Plate Rolling Mills

In this paper,the mill stand and the rolled piece were studied as a system. Based on the disoreted masses and the deformation of bending curve of the roller and roll housing, according to Rayleigh method,the equivalent mass and and the equivalent stiffness of the mode were solved,and set up a multiple degree of freedom vibration dynamic model. And also did theoretical analysis and calculation with an exapmle of the 4200 thick plate rolling mills.     

民商合一体制下的商法地位

20世纪以来,随着市场经济的发展,出现了"私法公法化"的现象。商法的边界出现了模糊化的趋势,经济法发展起来,商法的地位进一步受到挑战。但在民商合一体制下,商法仍是一个相对独立的法律部门,它既区别于民法又区别于经济法。     

甘肃省主要耕作土壤对施入钾的吸收能力研究

研究了甘肃省主要耕作上壤对施入钾吸收的数量和比例。结果表明,经过一次干湿交替后,在施钾0～1600mg／kg范围内,随着施钾数量的增加,土壤中速效钾含量、施入钾被土壤吸收量呈直线上升,吸钾率也逐渐增加。随着干湿交替次数的增加,吸钾量及吸钾率随之增加。对施入钾的吸收率与土壤速效钾含量成负相关。     

论天气系统下云的观测

在地面气象观测工作中,云的观测是一项最基本的观测要素,它既是现在天气的重要判定依据,也是未来天气预测的重要指标,所以做好云的观测是观测工作的重中之重.地面气象观测中只有把云和与它相对应的天气系统联系起来,借助天气形势的分析判断,把地面气象观测和天气系统的分析判断有机结合起来,用天气学的原理和方法来指导我们的地面气象观测.     

榆叶白鹃梅的人工栽培及园林应用

榆叶白鹃梅(Exochorda serratifolia S.Moore)树姿优美,耐旱、耐寒,且较耐修剪,萌蘖性强,较耐瘠薄,野生分布在辽宁、河北省及朝鲜,生长于山坡、河边及灌木丛中,人工栽培种植后,适宜与其他乔木、花灌木及花卉等多种景观植物配置,能取得良好的观赏效果。     

试论鄱阳湖湿地资源可持续发展的制度创新

以可持续发展战略为指导 ,站在市场经济的角度 ,运用西方经济学和新制度经济学的原理 ,分析指出鄱阳湖湿地资源保护与合理开发利用的经济本质是实现湿地资源的有效配置 ,并从理论上探讨了产生鄱阳湖湿地问题的制度根源———市场和政府配置湿地资源手段失灵 ,提出了解决鄱阳湖湿地问题必须进行制度创新的切入点 ,即构建绿色经济制度。     

涉身语言认知理论与英语教学初探

涉身语言认知思想是认知语言学上的一种创新。针对传统认知语言学"语言内在论"和"天赋论"等理论的局限性,以拉可夫和约翰逊为代表的涉身语言认知思想,从身体维度对语言认知机制给予了新的解读。这种以"大脑、身体和环境"共同参与的语言的认知模式对当前我国的英语教学和改革具有重要的理论指导意义,能够为解决当前高校英语教学和改革中出现的新问题给予方法论的指导。     

新形势下高等职业教育实践教学形式的改进研究

本文对21世纪新形势下如何改进高等职业教育的实践教学形式进行了一些探讨,对提高高等职业教育实践教学效果、培养高素质的应用型人才有一定的借鉴作用。