Finite dose diffusion studies: III. Effects of temperature, humidity and deposit manipulation on NAA penetration through isolated tomato fruit cuticles

Effects of temperature, humidity, rewetting and removal of deposits on penetration of NAA [2-(1-naphthyl)acetic acid] through isolated tomato (Lycopersicon esculentum Mill) fruit cuticles were studied using a finite dose diffusion system. In this system, an aqueous 5-microliter droplet (0.1 mM NAA in 20 mM citric acid buffer) is applied to the outer surface of a cuticle, which is mounted in a glass diffusion half-cell. The cell wall surface is in contact with a receiver solution (20 mM citrate). Penetration is monitored by repeated sampling of the receiver solution. Droplets appeared dry on visual inspection within 1 h of application, but significant NAA penetration continued after droplet drying. Maximum rates of NAA penetration increased exponentially as temperature was increased (from 5 degrees to 35 degrees C), the energy of activation averaging 153 (+/- 11.6)kJ mol-1. At 35 degrees C, penetration reached a plateau within 10 h of application (at 91.1 (+/- 1.0)% of dose applied) while at 5 degrees C penetration after 800 h reached only 30.2 (+/- 7.5)%. Increasing relative humidity from 20 to 80% increased maximum rates [from 1.0 (+/- 0.21) to 2.7 (+/- 0.80)% h-1] and penetration at 120 h after application [from 36.8 (+/- 2.1) to 64.3 (+/- 3.7)%]. Rewetting deposits at 120, 240 and 360 h after application resulted in increased NAA penetration. However, amounts and rates of NAA penetration progressively decreased with each subsequent rewetting. Removal of deposits by cellulose acetate stripping at various times after droplet application resulted in a rapid decrease in NAA penetration. NAA penetration following deposit removal was always less than 6.1% of the amount of NAA applied and averaged 0.5 (+/- 0.2)% when deposits were removed immediately after droplet drying.     

农药对靶喷撒技术研究初报

通过稻，麦，棉，茶，黄瓜，油菜等作物上一系列农药喷撒试验和生产性示范表明，采用对靶喷撒技术和相应的喷撒手段，可显著提高农药在有效靶区的沉积率，农药用量可％－５０％，喷雾用水量可降低９５％以上。农药对靶喷撒技术是根据病菌或害虫在作物上的分布，作物的田间群体结构以及农药雾滴在株冠中的行为的综合研究所提出的化学防治法的一项基本原理和基本技术。     

锥栗罐藏的研究

对锥栗罐头制作中所产生的沉淀、褐变进行了研究。试验结果表明,通过栗仁表面果胶的钙化,可以抑制因栗仁表层淀粉的脱落而使汤汁沉淀的现象;通过杀菌温度和时间的控制,可以防止酶促褐变引起的栗仁变色现象。     

Finite dose diffusion studies: I. Characterizing cuticular penetration in a model system using NAA and isolated tomato fruit cuticles

A finite dose diffusion system was employed to study cuticular penetration of 2‐(1‐naphthyl) [1−¹⁴C]acetic acid (NAA) from simulated spray droplets through enzymatically isolated tomato fruit cuticles (Lycopersicon esculentum Mill cv Pik Red). Isolated cuticles were mounted on diffusion half‐cells with the cell wall surfaces facing a 20 mM citric acid receiver solution (pH 3.2, volume 2.9 ml, prepared with deionized water). A 5‐µl donor droplet containing NAA at 100 µM in 20 mM citric acid buffer (pH 3.2) was applied to the outer surface. Penetration was monitored by repeated sampling of the receiver solution. NAA penetration was characterized by (1) an initial lag phase of about 2.3 h, (2) a phase of nearly constant maximum rate of penetration averaging 6.3% of applied NAA h⁻¹ (equivalent to 0.032 nmol h⁻¹) and (3) a plateau phase approaching an asymptote at 81.2% of applied NAA (equivalent to 0.406 nmol) at 120 h. Within 1 h after application droplets appeared dry on visual inspection. Immediately after droplet drying, 7.0% of the applied NAA was sorbed to the cuticle, but only 0.5% penetrated into the receiver solution, indicating that penetration occurred almost exclusively from the apparently dry deposit. At 120 h, 5.2% of the NAA applied was associated with the deposit and 4.3% with the cuticle. The distribution of maximum rates of penetration was log‐normal, but penetration at 120 h followed a normal distribution. Cuticle thickness (estimated 5–25 µm) had no significant effect on NAA penetration. Maximum rates of penetration through pepper fruit and citrus and ficus leaf cuticles were 4.9‐, 2.6‐ and 0.1‐times that through tomato fruit cuticles. At 120 h, penetration averaged 85.5, 79.5 and 34.7% for pepper, citrus and ficus cuticles, respectively. Extracting epicuticular and embedded waxes increased NAA penetration rates through tomato fruit cuticle more than three‐fold, but had little effect on penetration at 120 h (71.0 vs 87.7% for cuticular vs dewaxed cuticular membranes). The maximum penetration rate and total penetration were found to be useful parameters in describing the penetration time‐course. © 2000 Society of Chemical Industry     

Behaviour of famoxadone deposits on grape leaves

Famoxadone is a new fungicide developed for the control of crop diseases, including grape downy mildew (Plasmopara viticola). The majority (>90%) of the spray deposit from a famoxadone 500 g kg⁻¹ water‐dispersible granule formation on a grape leaf were found on the leaf surface or associated with epicuticular waxes. A significant fraction of this deposit could not be removed by a water wash, suggesting strong binding to the waxes. Nearly 100% of the spray deposit was still recovered after 12 days of exposure to a dry environment, confirming the good residual properties of the substance. Thirty per cent of the applied active ingredient was lost after exposure to a wet environment, probably via hydrolysis or wash‐off. Studies with radiolabelled famoxadone formulated as a suspension concentrate indicated that redistribution occurred both in dry conditions, via diffusion in the cuticular waxes, and in wet conditions via dissolution in water followed by re‐deposition. No systemic movement of famoxadone was observed within the treated plant. Grape plants treated with famoxadone alone or in mixture with cymoxanil and subjected to up to 50 mm of artificial rain remained well protected against downy mildew infections. Good rain‐fastness was observed even 2 h after fungicide application. Despite low water solubility, famoxadone spray residues on grape leaves were reactivated in surface water sufficiently quickly to prevent infection by P viticola. © 2000 Society of Chemical Industry     

风送式喷雾机风筒结构对飘移性能的影响

为改善风送式喷雾机的飘移性能,为原有喷雾机的出风口设计安装一个锥形导风筒和一个同轴柱形导风筒.试验结果表明:锥形导风筒可以约束气流的运动轨迹,提高气流在水平方向的速度,有效约束雾体、减小能量损失;同轴柱形导风筒可以使风筒出口的气流速度成梯度分布,速度外高内低的气流可约束雾滴的运动轨迹,减小雾滴飘移,使沉积率提高30.6%.     

渭河流域全新世古洪水滞流沉积物地球化学特征

对渭河流域野外实地详细调查,在渭河中游发现了具有典型古洪水滞流沉积物(SWD)的全新世黄土-古土壤沉积剖面。根据地层学对比和OSL测年,确定渭河流域在3200-2800aB.P.发生了特大古洪水事件。对沉积物地球化学特征分析表明,SWD为典型的古洪水滞流沉积物,各化学元素和氧化物的变异系数大,元素数据分布较为分散;Fe2O3、Al2O3、Ba、Cr、Cu、V、Rb含量高于S0和L0,SiO2、Zr含量低于S0和L0;化学元素粒度效应表明,SWD粒径小、粘粒强,是在滞流环境的水动力条件下沉积而成;通过气候指标Rb/Sr和Ba/Sr分析,认为古洪水滞流沉积物(SWD)记录的3200-2800aB.P.的特大古洪水事件,是在全新世大暖期结束之际,因夏季风减弱、气候系统不稳定、降水变率较大所导致的。     

连续降雨条件下工程堆积体产流产沙对砾石含量的响应

[目的] 探究连续降雨条件下不同砾石含量对陕北沙壤土上方有来水工程堆积体坡面产流产沙的影响,为生产建设项目水土流失治理提供数据支撑和理论参考。 [方法] 通过室内模拟降雨试验,研究不同砾石含量(0,10%,20%,30%,40%)工程堆积体坡面土壤水动力学特性及产流产沙特征。 [结果] ①降雨强度相同,随砾石含量增加,工程堆积体坡面初始产流时间表现为递减趋势,减幅为27.22%～64.62%,35.09%～71.70%,47.37%～78.77%,51.75%～82.31%。次降雨径流率表现为“迅速增加—稳定波动”的变化趋势,平均径流率随砾石含量、降雨时间的增加显著增大;但产流峰值随砾石含量增加而降低,且出现时间逐渐提前。 ②试验各场次雷诺数的变化范围介于74.13～165.05,均小于500,水流属于层流;弗劳德数的变化范围集中在2.14～3.71,表现为急流。水流剪切力、水流功率和单位水流功率随降雨场次的增加而显著增加。 ③0%～40%砾石含量工程堆积体坡面侵蚀速率介于0.45～6.73,0.13～4.09,0.25～1.26,0.14～0.96,0.13～0.88 g/(m²·min),各砾石含量堆积体减沙幅度分别为36.06%,49.05%,55.23%和56.62%,其中砾石高覆盖度(40%)的沙壤土工程堆积体坡面土壤侵蚀强度较小。 [结论] 砾石覆盖在沙壤土工程堆积体坡面的水土流失过程中可显著降低土壤侵蚀速率,从而实现拦蓄水土,保持较高的减沙效益。     

Deposition Effects of Electrostatic and NonElectrostatic Aerial Spray

In this study,we compared the aerial electrostatic spray with non-electrostatic spray by helicopter R44 and fixed-wing aircraft Y5B equipped with an own-made aerial electrostatic spraying system.The results showed that the spray deposits on targets and leaves of tree crowns were notable enhanced comparing with the non-electrostatic and conventional aerial spray.The spray deposits were fine,uniform and the densities were 1.0-1.75 times higher than the non-electrostatic spray.Deposit rate of the electrostatic spray on the backs of leaves by helicopter R44 was 2.15 times of the non-electrostatic, and 3.31 times of the conventional aerial spray.The deposit rate of the electrostatic spray on the backs of leaves by the Y5B was 2.38 times of the non-electrostatic,and 3.44 times of the conventional aerial spray.     

山西吉县黄土区切沟分类的研究

该文对黄土区土壤侵蚀最为严重的切沟进行研究 .通过实地调查及建立观测设施 ,分析得出黄土区沟道的泥沙主要来自切沟 ,采用聚类分析方法对切沟进行分类 ,切沟内塌积土的数量是分类的主要依据之一 ,也是沟道治理进行造林的关键 .