Effect of Secondary Salinization on Photosynthesis in Fodder Oat (Avena sativa L.) Genotypes

The effect of secondary salinization on photosynthesis was studied in fodder oat genotypes Kent, JHO-829, JHO-881, UPO-94 and OS-6 at the flower initiation stage. With an increase in the electrical conductivity (EC) of irrigation water, the net photosynthesis rate (P_N) and the transpiration rate (E) of all the genotypes decreased. The intercellular CO₂ concentration (Ci) increased in all genotypes at 10 dS m^−1. Stomatal resistance (R_s) had a strong negative correlation with PN and E. The increase in Ci together with the increase in the R_s shows that at higher EC non-stomatal factors also start contributing to the limitation of photosynthesis. This study suggests that secondary salinization effects are strongly under stomatal control at lower saline water irrigation levels, but at higher levels non-stomatal factors may come into play.     

Chemical stress can increase crop yield

Low dose chemical stress has been shown to increase plant vegetative growth, though not all chemicals induce the response. Glyphosate is the most widely used herbicide by volume and treated area. At low doses, it can increase growth in a variety of species. Here we show that a glyphosate-induced growth increase can be transformed into an increase in crop yield, if applied at the right time. Glyphosate, in the dose range of 2.5–20 g a.e. ha⁻¹, corresponding to less than 1% of the rate normally used for weed control in the field, increased grain yield of barley by 12–15% when applied at the time of grain filling. Straw yield and the quality of the grains in terms of nitrogen and starch content were not affected by the treatment. The physiological mechanism behind this counter intuitive increase in growth is still unknown, as are possible adverse effects. It is, however, evident that understanding the physiological processes behind chemically induced growth increases in plants holds the promise of improving food yield.     

小鼠卵母细胞的电激活

采用宁波新科CRY 3 细胞融合仪及其配备的镀银电融合槽(电极宽度为0. 5mm)对影响小鼠卵母细胞电激活效率的诸多因素,如直流脉冲的强度(1. 0 kV/cm、1. 5kV/cm、2.0 kV/cm、2.5 kV/cm)、脉冲宽度(40μs、80 μs、100 μs、150 μs)和脉冲次数(1次、2次、3次)进行了比较研究,结果表明,卵母细胞激活率随电场强度的增加而升高,场强为2.0 kV/cm时,获得了较高的卵母细胞激活率和卵裂率(74.47%,77.14%),场强继续增加,卵母细胞的激活率和卵裂率反而开始下降。场强为2.0 kV/cm,脉宽为80μs时,卵母细胞的激活率最高(77.78%)。多次连续脉冲(3次,每次间隔10 min)处理卵子,可明显升高卵母细胞的激活率和囊胚发育率(89.58%,20.59%)。     

高酸海棠苗木抗寒性生理指标的分析

为了研究高酸海棠栽种适宜区域,用高酸海棠新品种‘冰心1 号’、‘红勋1 号’与现有品种‘新苹1号’进行抗寒性比较,以枝条作为试验材料进行低温处理,并根据外渗电导法、脯氨酸及丙二醛(MDA)含量的变化,研究了各样品的抗寒性能。通过试验测定结果可判定3 个样本的相对电导率大小依次为‘新苹1 号’＞‘红勋1 号’＞‘冰心1 号’,脯氨酸含量由高到低的顺序依次为‘冰心1 号’＞‘红勋1 号’＞‘新苹1 号’,MDA含量大小的总体趋势依次为‘红勋1 号’＞‘新苹1 号’＞‘冰心1 号’。总体而言,‘冰心1号’的抗寒性最强,3 个品种的抗寒顺序依次为‘冰心1 号’＞‘红勋1 号’＞‘新苹1 号’。其中‘冰心1 号’与‘红勋1号’都具有较强的耐寒能力,适宜栽种于新疆天山以北及其他寒冷区域。     

The influence of nitrogen and phosphorous status on glyphosate hormesis in Lemna minor and Hordeum vulgare

The herbicide glyphosate has been shown to stimulate growth and photosynthetic capacity of barley and other plant species. The growth increase, however, only takes place under certain, yet undefined, growth conditions. We hypothesise that glyphosate growth stimulation only takes place, when growth is nutrient limited. Nutrient limitation was induced in this study by limiting nitrogen and phosphorous availability. The experiments were performed on hydroponically grown lesser duckweed and barley and on barley in the field. Hydroponic duckweed and barley grown under a range of N- and P-availabilities displayed glyphosate induced growth increases in plants which were slightly stressed by N-deficiency, but not in response to P-deficiency in the case of barley. The growth increase found for P-deficient duckweed was hypothesised to be caused by glyphosate derived P, acting as a nutrient source. No growth increase was found in the 2012 field experiment, which was in contrast to earlier year’s findings. Our hypothesis that nutrient limitation makes plants susceptible to glyphosate induced growth was only confirmed for nitrogen but not for phosphorous and not under field conditions in 2012. Mechanisms related to high C:N ratios might be of importance, as this trait varies depending on N- and P-availability during plant growth.     

电动旋耕培土机的田间性能试验研究

针对目前大多中耕培土作业机械依靠燃油作为动力源严重污染环境且作业成本高等问题,通过替换动力源的方式,设计了电动旋耕培土机。试验结果表明:作业耕深稳定性、培土高度合格率、培土角度合格率及碎土率等作业性能指标均能达到国家相关标准规定,同时其经济性优于同功率燃油机械。     

基于电特性的新疆骏枣含水率的试验研究

为探究新疆地区红枣含水率的检测方法,运用TH2828S型LCR测量仪对红枣电特性与含水率的变化进行测定,分析了红枣含水率不同频率下电特性变化,并建立红枣含水率电特性参数模型。以整颗红枣为试验对象,在电源电压1V及纵向压力(0.1kg)下测试了低频段(200~1 000Hz)红枣含水率电特性参数变化规律。试验结果表明:在含水率55.85%以下,红枣含水率与复阻抗Z呈负相关,通过电特性参数可以实现红枣含水率检测。     

高职电工技术教学模式改革的探索

高职院校现已将电工技术这门课程为基础专业课程。掌握好这门课程的基础知识和实践技能,对于高职学生以后进一步学习和以后的发展,将起到非常重要的作用。因此根据当前电工技术这门课程发现比较普遍和严重的问题,结合现实的课程教学内容,笔者将从课程的内容和教学方法、以及教学实践这几方面考虑做出比较符合现在需求的研究和探索。     

中职机电专业理实一体化教学模式探究

笔者阐述了中职机电专业实施“理实一体化”教学的背景和必要性,进而解析了“理实一体化”教学的内涵和作用,针对性提出了中职机电专业进行“理实一体化”教学的策略,以期推动中职机电专业教学的改革。     

Herbicides and plant hormesis

Herbicide hormesis is commonly observed at subtoxic doses of herbicides and other phytotoxins. The occurrence and magnitude of this phenomenon are influenced by plant growth stage and physiological status, environmental factors, the endpoint measured and the timing between treatment and endpoint measurement. The mechanism in some cases of herbicide hormesis appears to be related to the target site of the herbicide, whereas in other examples hormesis may be by overcompensation to moderate stress induced by the herbicides or a response to disturbed homeostasis. Theoretically, herbicide hormesis could be used in crop production, but this has been practical only in the case of the use of herbicides as sugar cane ‘ripeners’ to enhance sucrose accumulation. The many factors that can influence the occurrence, the magnitude and the dose range of hormetic increases in yield for most crops make it too unpredictable and risky as a production practice with the currently available knowledge. Herbicide hormesis can cause undesired effects in situations in which weeds are unintentionally exposed to hormetic doses (e.g. in adjacent fields, when shielded by crop vegetation). Some weeds that have evolved herbicide resistance may have hormetic responses to recommended herbicide application rates. Little is known about such effects under field conditions. A more complete understanding of herbicide hormesis is needed to exploit its potential benefits and to minimize its potential harmful effects in crop production. © 2014 Society of Chemical Industry