Relative toxicities of inorganic aluminum complexes to barley
Relative toxicities of inorganic aluminum complexes to barley
复制标题
DOI：
10.2136/sssaj1986.03615995005000050029x
复制
发表时间：
1986-09
影响因子：
2.9
通讯作者：
R. Cameron;G. Ritchie;A. Robson
中科院分区：
文献类型：
--
作者：
R. Cameron;G. Ritchie;A. Robson
在酸性土壤中，土壤溶液中降低植物生长的无机形式的铝还没有被清楚地识别出来。因此，我们研究了在pH为4.5的含有3333 nmol Ca L ‘和6 /imol B L ’的营养液中，Al及其与F和SOI'的配合物对大麦（Hordeum vulgare）根系伸长的影响。选择阴离子是因为阴离子在土壤溶液中的含量足以使Al复合。研究了0 ~ 100 pmol Al L ‘在0 ~ 10 /imol F L ’或0 ~ 3300 /unol SOI L '存在下的毒性。大麦幼苗根系伸长与A1浓度相关，但与总可溶性Al或Al与F和SOJ~复合无关。这可能是使用络合剂测量不稳定铝并不总是能成功区分铝有毒和无毒土壤的原因之一。附加索引词：pH， Ca, F~, SOJ~，营养液，土壤酸度，紫花苜蓿，Hordeum vulgare L. Camerpn, r.c.， G.S.P. Ritchie, a.d Robson. 1986。无机铝配合物对大麦的相对毒性。土壤科学。Soc。点。j . 50:1231 - 1236。毒性是限制植物在酸性土壤上生长的一个主要因素（Foy, 1984）。尽管进行了大量的研究，但由于我们缺乏对哪种形式的可溶性铝导致植物生长下降的了解，鉴定含有铝毒性水平的土壤仍然受到限制。总可溶性铝（A1T）的活性与根伸长的相关性大于总可溶性铝浓度[A1T] （Adams and Lund, 1966; Helyar, 1978）。最近对营养液的研究表明，“自由”离子A1或不稳定的单体形式（即A1、A1（OH）、A1(OH)J）可能是主要的有毒物质（Pavan and Bingham, 1982; Blarney et al., 1983）。上述工作在自然土壤条件下的应用取得了部分成功，根据所有可溶性离子的总浓度和热力学稳定性常数计算A1 （A1）的活性（例如，Pavan等人，1982年；Sheppard和Floate， 1984年）。然而，当土壤中的有毒铝通过与络合试剂反应的速度来估计时，比较结果就不那么令人鼓舞了（Adams和Hathcock， 1984）。这种测量的Al（不稳定Al）被认为是由A1和无机阴离子的单体配合物组成的（James et Al ., 1983）。造成这种异常的原因可能是由于溶液中无机形式的Al的不同毒性。硫酸盐和F~都能与土壤溶液中的Al形成可溶络合物（Ritchie, 1986）。这项工作的目的是比较A1及其复合物与F~和SO的毒性作用。1 .西澳大利亚大学土壤科学与植物营养学院，西澳尼德兰6009这项工作是由澳大利亚羊毛公司资助的。1986年1月2日收到。2西澳大学农学院前研究员，讲师，农业（土壤科学），土壤科学与植物营养学教授，西澳尼德兰，西澳6009。首先，我们研究了pH、离子强度和Ca浓度对大麦（Hordeum vulgare L., cv.）幼苗初生根伸长的影响。比彻)和苜蓿(Medicago唾液L., cv。cuf101)，因此我们可以开发一种合适的生物测定方法来检测铝对根生长的影响。材料与方法幼苗的萌发与生长所有种子经过筛选，在25±3°C的200 nmol CaSO4-2H2O L~'曝气溶液中浸泡发芽。当胚根长到约3mm时，将6株幼苗移栽到每个试验溶液中。将植物悬浮在营养液表面的粗棉布上，棉布拉伸在丝网模板上。这确保了根尖始终浸泡在溶液中。溶液中Ca <1600 ^mol L~‘和B < 6jwnol ~’，以及实验处理。钙和B在植物体内是固定不动的，对根生长至关重要，因为它们维持根膜的完整性（Haynes和Robbins， 1948）。在实验的短时间内，种子提供了所有其他营养物质的充足来源。这避免了计算（A1）的并发症，如果添加了H2POj等营养物质，可能会出现这种并发症。营养液装在5 l塑料瓶中，置于根冷却槽中，温度为23±2℃。在植物生长期间，溶液不断充气，每天更新，以确保离子的恒定水平。这些处理在所有实验中都是重复的。生物测定法的发展生物测定法的目的是研究外部因素对铝毒性的影响，而不是设计用于监测可能仅影响茎部生长的内部效应。开发该程序的标准是建立一种营养液，该营养液含有在短时间内（3天）足够的幼苗生长所需的最低营养，但含有可能影响根系对Al反应的最低离子。没有努力使用正常营养液或模拟土壤溶液，因为这两种溶液太复杂，无法区分所研究的机制。设计三因子试验，研究pH、Al、Ca和离子强度对苜蓿和大麦初生根伸长的影响（表1）。选择这些植物是因为它们对铝毒性敏感（Russell, 1973）。试验1研究了pH值对苜蓿和大麦幼苗根伸长的影响，以及pH值仅为4.0时铝对根系伸长的影响。随后，选择苜蓿进行Al-H相互作用的进一步研究（Exp. 2），而选择大麦进行Al-Ca相互作用的研究（Exp. 3）。必要时，通过添加17.3 mmol HC1 L~‘或1.4 mmol NaHCO3 L~’来控制pH。用CaQ2和KC1保持离子强度。加入氯化铝，得到（A1）值范围从0到16 nmol L-'。初步试验表明，施钠、施钾对根伸长无影响。因此，在随后的实验中，F~和SO.”被添加为Na、K或Ca盐，以确保1231是l
The inorganic forms of Al in the soil solution that decrease plant growth in acid soils have not been clearly identified. Therefore, we examined the effects of Al and its complexes with F and SOI' on the root elongation of barley (Hordeum vulgare) in nutrient solutions containing 3333 nmol Ca L ' and 6 /imol B L ' at pH 4.5. The anions were chosen because of their presence in the soil solution at levels sufficient to complex Al. The toxicity of 0 to 100 pmol Al L ' was studied in the presence of 0 to 10 /imol F L ' or 0-3300 /unol SOI L '• The elongation of roots of barley seedlings was correlated with A1 concentrations but not with total soluble Al or Al com plexed with F and SOJ~. This could be one of the reasons why measurements of labile Al using complexing agents have not always been successful at distinguishing between Al-toxic and nontoxic soils. Additional Index Words: pH, Ca, F~, SOJ~, nutrient solutions, soil acidity, alfalfa, Hordeum vulgare L. Camerpn, R.C., G.S.P. Ritchie, and A.D. Robson. 1986. Relative toxicities of inorganic aluminum complexes to barley. Soil Sci. Soc. Am. J. 50:1231-1236. A TOXICITY is a major factor limiting the growth of plants on acid soils (Foy, 1984). Despite considerable research, the identification of soils containing toxic levels of Al is still limited by our lack of understanding of which forms of soluble Al are responsible for decreased plant growth. The activity of total soluble aluminum, (A1T), has been shown to be more correlated with root elongation than total soluble Al concentration, [A1T] (Adams and Lund, 1966; Helyar, 1978). More recent studies with nutrient solutions have indicated that the "free" ion, A1, or the labile monomeric forms (i.e., A1, A1(OH), A1(OH)J may be the major toxic species (Pavan and Bingham, 1982; Blarney et al., 1983). The application of the above work to natural soil conditions has met with partial success when the activity of A1, (A1), is calculated from the total concentrations of all soluble ions and thermodynamic stability constants (e.g., Pavan et al., 1982; Sheppard and Floate, 1984). However, comparisons have not been so encouraging when toxic Al in soil is estimated by the speed with which it reacts with a complexing reagent (Adams and Hathcock, 1984). This measure of Al (labile Al) is thought to consist of A1 and monomeric complexes with inorganic anions (James et al., 1983). The cause of such an anomaly could be due to the different toxicities of the inorganic forms of Al in solutions. Sulphate and F~ are both capable of forming soluble complexes with Al at levels found in the soil solution (Ritchie, 1986). The purpose of this work was to compare the toxic effect of A1 and its complexes with F~ and SO.". 1 Contribution from Soil Science and Plant Nutrition, School of Agriculture, Univ. of Western Australia, Nedlands, WA Australia 6009. This work was funded by the Australian Wool Corporation. Received 2 Jan. 1986. 2 Former Research Officer, Lecturer and Professor of Agriculture (Soil Science), Soil Science and Plant Nutrition, School of Agriculture, Univ. of Western Australia, Nedlands, WA Australia 6009. Initially, we examined the effect of pH, ionic strength, and Ca concentration on the elongation of the primary root of seedlings of barley (Hordeum vulgare L., cv. Beecher) and alfalfa (Medicago saliva L., cv. CUF 101) so that we could develop a suitable bioassay for examining the effects of Al on root growth. MATERIALS AND METHODS Germination and Growth of Seedlings All seeds were sieved and germinated by immersion in an aerated, 200 nmol CaSO4-2H2O L~' solution at 25 ± 3°C. Six seedlings were transplanted to each test solution when the radicles had emerged to approximately 3 mm. The plants were suspended at the surface of the nutrient solution on cheesecloth stretched over a wire mesh template. This ensured that the root tips were always immersed in the solution. The solutions contained only <1600 ^mol Ca L~' and 6 jwnol B L~', as well as the experimental treatments. Calcium and B are immobile in plants and are essential for root growth because they maintain the integrity of the root membrane (Haynes and Robbins, 1948). The seed provided an adequate source of all other nutrients over the short time period of the experiment. This prevented complications in the calculation of (A1), which may have occurred if nutrients such as H2POj had been added. The nutrient solutions were contained in 5-L plastic pots placed in root cooling tanks at 23 ± 2°C. During plant growth, the solutions were aerated continuously and renewed daily to ensure constant levels of the ions present. The treatments were duplicated in all experiments. Development of Bioassay The purpose of the bioassay was to study the influence of external factors on Al toxicity and was not designed to monitor internal effects that may influence shoot growth only. The criterion for the development of the procedure was to establish a nutrient solution that contained the minimum nutrients required for adequate seedling growth over short time periods (3 d) but contained a minimum of ions that could affect the response of roots to Al. No effort was made to use normal nutrient solutions or simulate the soil solution because both solutions are too complex to differentiate between the mechanisms under investigation. Three factorial experiments were designed to study the effect of pH, Al, Ca, and ionic strength on primary root elongation of alfalfa and barley (Table 1). These plant species were chosen because of their sensitivity to Al toxicity (Russell, 1973). Experiment 1 investigated the effect of pH on root elongation of alfalfa and barley seedlings and also the effect of Al at pH 4.0 only. Subsequently, alfalfa was chosen for further studies of the Al-H interaction (Exp. 2), whereas barley was selected to study the Al-Ca interaction (Exp. 3). Where necessary, pH was controlled by the addition of 17.3 mmol HC1 L~' or 1.4 mmol NaHCO3 L~'. Ionic strength was maintained with CaQ2 and KC1. Aluminum chloride was added to give a range of values of (A1) from 0 to 16 nmol L-'. A preliminary experiment indicated that there was no effect of Na or K on root elongation at the levels used. Hence, in the subsequent experiments, F~ and SO." were added as either the Na, K, or Ca salts to ensure that 1231 i l l