Phloem transport of xenobiotics in Ricinus communis var. Gibsonii

Whole plants of Ricinus communis var. Gibsonii were used to study the mobility of some xenobiotics in the phloem. Solutions of ¹⁴C- or ³⁵S-labelled test compounds were introduced directly into the hollow petiole of a leaf that was exporting assimilates. Translocation was monitored by collecting phloem exudate from an incision in the stem bark beneath the treated leaf. Using [³H]sucrose as an internal standard, qualitative and quantitative results were obtained for a variety of model compounds, including herbicides, fungicides and a nematicide.     

Phloem translocation of strong acids—glyphosate,substituted phosphonic and sulfonic acids—in Ricinus communis L

The mobility in phloem of several substituted phosphonic acids and a sulfonic acid was studied in the castor bean plant, Ricinus communis L. For a series of¹⁴C-labelled phosphonate mono-esters applied to the petioles of mature leaves, phloem transport was modest, becoming poor over longer distances in the plant. Substituted phenylphosphonic acids were more efficiently moved in phloem; uptake from the petiole and subsequent redistribution were slow, but these dibasic compounds were very stable in plants and substantial amounts reached the roots after 72 to 120 h. Glyphosate was very efficiently transported to phloem sinks even within 24 h, with high concentrations in phloem sap. Toluene-4-sulfonic acid moved predominantly in the xylem to the mature leaves and its phloem transport was poor. Transport patterns are considered in relation to the physico-chemical properties of the compounds. Ion trapping appears to play little part in the phloem transport of these strong acids, though the good accumulation and transport in phloem of the complex molecule glyphosate cannot at present be explained.     

Relationships between lipophilicity and root uptake and translocation of non-ionised chemicals by barley

The uptake by roots from solution, and subsequent translocation to shoots in barley, of two series of non-ionised chemicals, O-methylcarbamoyloximes and substituted phenylureas, were measured, Uptake of the chemicals by roots was greater the more lipophilic the chemical, and fell to a lower limiting value for polar chemicals. Translocation to the shoots was a passive process, and was most efficient for compounds of intermediate polarity. Both processes had reached equilibrium within 24h of treatment. The reported behaviour of many pesticides in various plant species agrees with the derived relationships, but the detailed mechanisms of these processes are unknown.     

Phloem transport in Ricinus

Recently, Ricinus has been used extensively to investigate the mechanism of phloem transport. This work is reviewed. In many respects, both anatomically and physiologically, Ricinus seems to approach the ideal for work on phloem physiology. Its anatomy is typical of many plants so that valid comparisons can probably be drawn with other species. However, the actual measurement of the proportion of sieve tubes is difficult. Exudation from the wounded phloem can be controlled by a variety of treatments. It seems to represent the true phloem transport stream, and from all observations to date seems to fulfill the requirements of the pressure flow theory. The actual velocity of the mass flow of sap by displacement has been shown to be very considerable, as might be expected on the pressure flow theory, and to become polarised towards a wound from each side in roughly equal proportions. There seem to be considerable concentration gradients in the stem, as indicated by refractometry in the direction one would expect on the basis of pressure flow. Attention has been drawn to the mechanism by which exudation is prevented by the plant. Ricinus seems ideal material for investigations into the sealing mechanisms which can curtail or permit exudation on wounding. Probably, when these systems are understood we can solve the ultimate problem of the condition of intact sieve plate pores.     

Uptake and translocation of non-ionised pesticides in the emergent aquatic plant parrot feather Myriophyllum aquaticum

The uptake of four (14)C-labelled non-ionised compounds, the methyl carbamoyloxime insecticide/nematicide oxamyl and three model phenylureas, from solution by rooted stems of the aquatic plant parrot feather [Myriophyllum aquaticum (Vell.) Verdc], together with translocation to the emergent shoots, was measured over periods of 24 and 48 h. Uptake into the submerged tissues of roots and stem base could be ascribed to two processes: movement into the aqueous phase of cells and then partitioning onto the plant solids. This latter process was related to lipophilicity (as measured by the l-octanol/water partition coefficient, K(ow)) and gave rise to high uptake rates of the most lipophilic compounds. Translocation to shoots was passive and was optimal at log K(ow) approximately 1.8, at which the efficiency of translocation of compound was about 40% of that of water. This optimum log K(ow) was identical to that observed previously in barley, although the translocation efficiency was somewhat less in parrot feather. Solvation parameters were applied to model uptake and translocation of a set of ten compounds by barley with the particular objective of understanding why translocation efficiency is lower at log K(ow) > 1.8.     

Relationships between lipophilicity and the distribution of non-ionised chemicals in barley shoots following uptake by the roots

Determinations were made of the distribution of two series of non-ionised chemicals, ^O-methylcarbamoyloximes and substituted phenylureas, in barley shoots, following uptake by the roots from solution. The concentrations in basal and central shoot sections became constant after 24 to 48 h for all but the most lipophilic chemical studied, and were then greatest for the more lipophilic chemicals. Amounts in the leaves generally increased up to 72 or 96 h, when degradation balanced translocation. The accumulation of chemical in the lower section of shoots can be ascribed to a partitioning process similar to that in roots, the chemical being partitioned between the shoot and the xylem transpiration stream; this uptake could be estimated from the octan-1-01/water distribution coefficients, and was predicted to be greatest for compounds for which log K_ow=4. 5.     

Partial characterization and insecticidal properties of Ricinus communis L foliage flavonoids

Aqueous leaf extract of Ricinus communis L (Euphorbiaceae), a cultivated plant in tropical countries, showed excellent insecticidal activity against Callosobruchus chinensis L (Coleoptera: Bruchidae). We have isolated and tested flavonoids as insecticidal and antimicrobial agents. The isolated flavonoids showed potential insecticidal, ovicidal and oviposition deterrent activities against C chinensis L. However, antimicrobial activity against the common microbial infestants of stored pulses, of which C chinensis is a major pest, was found to be insignificant. Two bands having Rf 0.63 and 0.69 were seen on HPTLC plates using mobile phase benzene + ethyl acetate + methanol + formic acid (12 + 4.5 + 2 + 1.5 by volume) as eluant. The Rf values and scanning of the spectrum in the ultraviolet region, showed identity with the flavonoids quercetin and kaempferol. This was further confirmed using HPLC and IR and UV spectrometry. HPLC and HPTLC chromatograms also suggested quercetin to be the major flavonoid present in the hydrolyzed aqueous leaf extract of R communis.     

Evaluation of world castor (Ricinus communis L.) germplasm for resistance to Fusarium wilt (Fusarium oxysporum f. sp. ricini)

Castor (Ricinus communis L.) is an important industrial oilseed crop grown worldwide. Wilt caused by Fusarium oxysporum f. sp. ricini is a devastating disease of this crop. The objective of this research was to identify stable sources of wilt resistance among the global castor germplasm collections available in India for use in cultivar improvement. The global collections comprising 1,779 Indian and 190 exotic accessions from 36 countries were screened against wilt in wilt sick plots at two sites in India in preliminary screening. None of the accessions showed high resistance to wilt, 133 accessions comprising 111 Indian and 22 exotic accessions representing 13 countries exhibited resistance. Thirteen of the 133 resistant accessions were tested further for multiple years in wilt sick plots and glasshouse under controlled artificial inoculation at two sites. All the 13 accessions consistently showed wilt resistance in both wilt sick plot and glasshouse at both sites in multiple years. Eleven of these 13 accessions were from India and two were from former USSR. Evaluation for agro-morphological traits identified high seed yielding and early maturing resistant accessions. Diversity analyses precisely revealed diversity among the resistant accessions. These 13 resistant accessions would be great value as donors of resistance.     

Activity of Ricinus communis (Euphorbiaceae) and ricinine against the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae) and the symbiotic fungus Leucoagaricus gongylophorus

The focus of this study was the identification of compounds from plant extracts for use in crop protection. This paper reports on the toxic activity of fractions of leaf extracts of Ricinus communis L (Euphorbiaceae) and isolated active compounds in the leaf-cutting ant Atta sexdens rubropilosa Forel and its symbiotic fungus Leucoagaricus gongylophorus (Singer) M?ller. The main compounds responsible for activity against the fungus and ant in leaf extracts of R communis were found to be fatty acids for the former and ricinine for the ants.     

Relationships between chemical structure and phloem mobility in Ricinus communis var. Gibsonii with reference to a series of ω-(1-naphthoxy)alkanoic acids

The phloem translocation of an homologous series of ω-(1-[1-⁴C]naphthoxy)alkanoic acids relative to that of applied [6,6′-³H] sucrose was measured in Ricinus communis var. Gibsonii. Relative phloem mobility decreased with increase in octan-l-ol/water partition coefficients. However, non-ionisable compounds with partition coefficients similar to the readily translocated acids were not phloem mobile. These results are explained in terms of an ion-trap mechanism subject to limitations on the partition coefficients of the acids and possibly their anions.     

不同培养条件下甲霜灵在蓖麻幼苗韧皮部的输导性

甲霜灵是一种能通过植物叶片吸收后在韧皮部向下传导的杀菌剂,为了探明其在韧皮部的传导规律,以蓖麻幼苗为模式植物,通过改变试验过程培养液中甲霜灵含量、pH值以及培养的温度、时间及光照等因子,采用气相色谱-质谱联用 (GC-MS) 方法,检测了不同培养条件下蓖麻幼苗韧皮部渗出液中甲霜灵的含量。结果表明:光照对甲霜灵在蓖麻幼苗韧皮部中的输导性无显著影响;当培养液中甲霜灵质量浓度为400 mg/L时,其在蓖麻幼苗韧皮部中输导量最大;当培养液pH值为5.5时,甲霜灵在蓖麻幼苗韧皮部中输导量最大;当培养温度为28 ℃时培养效果最佳,温度过高或过低均会使甲霜灵在蓖麻幼苗韧皮部中的输导量减少;培养3 h以上,蓖麻幼苗韧皮部渗出液中甲霜灵的含量显著高于前2 h渗出液中甲霜灵的含量。该研究优化了蓖麻幼苗获得药剂最大吸收时的适宜培养条件,为检测其他未知化合物在植株韧皮部中的输导性提供了参考。     

12种除草剂对玉米田鸭跖草的防效

采用田间小区试验方法,测定12种除草剂对玉米田鸭跖草的防效。在玉米3~5叶期、鸭跖草3~7叶期进行茎叶喷雾处理,施药后观察鸭跖草的药害症状并定时调查除草效果。试验结果表明:氯氟吡氧乙酸、苯唑草酮、硝磺草酮以及含有以上成分的复配制剂对鸭跖草有较高防效。因此,防除玉米田鸭跖草可选择氯氟吡氧乙酸、苯唑草酮、硝磺草酮等除草剂单剂或含有以上成分的除草剂混剂。     

乌梁素海芦苇湿地遥感生物量估算研究

以定量遥感的手段实现对内蒙古乌梁素海湿地生物量的估算。在定点监测芦苇生长周期内的生物量基础上,分析了各监测点生物量(鲜重和干重)实测数据与同期4种植被指数NDVI、DVI、PVI、RVI的相关关系。建立一元线性估算模型及多种非线性估算模型并进行对比分析。结果表明:对于乌梁素海而言,芦苇地上生物量(鲜重与干重)与所选4种植被指数均存在显著正相关关系,鲜重、干重的最优模型均是基于NDVI的三次多项式估算模型。精度检验结果显示:用NDVI三次多项式估算模型计算出的鲜重和干重的预测值与实测值较接近,鲜重的平均误差为19.90%,拟合精度达到80.10%;干重的平均误差为18.71%,拟合精度达到81.29%,可以满足乌梁素海地区芦苇生物量宏观估测的需要。通过分析2013年7月研究区芦苇总生物量干鲜重的空间分布图可得,乌梁素海地区芦苇干重在1 000~1 500 g·m~(-2),鲜重在3 000~4 500 g·m~(-2),且高生物量和低生物量相对较少。     

Modelling the application of chemicals in box potato stores

Chemicals are applied in crop stores for the control of diseases and, in the case of potatoes, sprouting. Non‐uniform deposition of chemicals on crop surfaces can lead to excessive chemical residues in parts of the store and impaired efficacy in those parts of the store where deposition is low. With the aim of improving the efficiency of chemical applications, this paper presents a transient three‐dimensional model consisting of the mass, momentum and energy equations which were solved to predict the air flows, temperature and moisture changes of the air and crops and the movements and deposits of small airborne particles of chemical in box potato stores. The crop was treated as a porous medium and the interaction between the air flow and crop was described by the Ergun equation. The movements of three sizes of chemical particles were predicted and the results validated against measurements of deposits of CIPC (a common potato sprout suppressant) in a 3‐tonne experimental store. The predictions showed good agreement with the measured trends in the spatial variation of deposits. Measured deposits varied between 16.3 and 176.0 mg CIPC per kg of potatoes while predicted values varied between 13.1 and 140.3 mg CIPC per kg of potatoes. The largest difference between measured and predicted deposit was 37.2%. © 2000 Society of Chemical Industry     

Enhancement of natural disease resistance in potatoes by chemicals

The mechanism involved in systemic acquired resistance (SAR) can be non-specifically induced in susceptible plants. In response to pathogens, plants' natural defence mechanisms include the production of lignin and phytoalexins and the induction of plant enzymes. The aim of this research was to study the induction of SAR mediated by the chemical activator DL-3-aminobutyric acid (BABA) and the fungicide fosetyl-aluminium in potato cultivars with different levels of resistance against Phytophthora infestans (Mont) de Bary. To study the chemical induction of the resistance, the foliage of several potato cultivars was sprayed with BABA, fosetyl-aluminium or water (as a control treatment). After 3 days the foliage was inoculated with P. infestans. Seven days after inoculation, development of disease symptoms in the foliage was assessed. In postharvest tuber samples, evidence for enhancement of the defence response was evaluated by measuring the protein content of several hydrolytic enzymes as well as the phenol and phytoalexin content. The highest level of protection against late blight was observed when the chemicals were applied at early stages of crop development. An increase in resistance to late blight was also detected in tubers after harvest. There was also an increase in the protein level of beta-1,3-glucanase and aspartic protease as well as in the phenol and phytoalexin content of potato tuber discs obtained from postharvest tubers of treated plants. Thus the protective effect seemed to persist throughout the whole crop cycle. This treatment may offer the possibility of controlling both foliage and tuber blight and could have a major impact in reducing over-winter survival of P. infestans in tubers.     

鸭跖草生物学特性初步研究

通过田间试验和系统调查,初步明确了鸭跖草的生物学特性。在黑龙江省哈尔滨市和佳木斯市,鸭跖草的发生高峰期为5月中下旬,发生盛期出苗的鸭跖草生长发育速度快。鸭跖草植株可多次分枝,分枝数可多达几十个,着地节能生根,植株生长较繁茂,种子随熟随落。鸭跖草种子出苗的适应播种深度为5－10cm,将7－10叶期的鸭跖草苗拔出晾晒3d后移栽,成活率达100％,晾晒7d成活率也在50％以上。     

Role of insect haemolymph in translocation of insecticides

A ligature round the “waist” of the housefly was shown to block effectively the flow of haemolymph between the abdomen and the rest of the body, but it did not prevent the toxic action of certain contact insecticides. These included representatives of four major chemical types. The ligature appeared to have little effect on the speed of action of these compounds, suggesting that the haemolymph is not important in their transport to the site of action.