Physiological and mineralogical properties of arsenic-induced chlorosis in rice seedlings grown hydroponically

Abstract

A hydroponic experiment was conducted to observe the effect of arsenic (As) on a number of physiological and mineralogical properties of rice (Oryza sativa L. cv. Akihikari) seedlings. Seedlings were treated with 0, 6.7, 13.4 and 26.8 µmol L^?1 As (0, 0.5, 1.0 and 2.0 mg As L^?1) for 14 days in a greenhouse. Shoot dry matter yield decreased by 23, 56 and 64%; however, the values for roots were 15, 35 and 42% for the 6.7, 13.4 and 26.8 µmol L^?1 As treatments, respectively. Shoot height decreased by 11, 35 and 43%, while that of the roots decreased by 6, 11 and 33%, respectively. These results indicated that the shoot was more sensitive to As than the root in rice. Leaf number and width of leaf blade also decreased with As toxicity. Arsenic toxicity induced chlorosis symptoms in the youngest leaves of rice seedlings by decreasing chlorophyll content. Concentrations and accumulations of K, Mg, Fe, Mn, Zn and Cu decreased significantly in shoots in the 26.8 µmol L^?1 As treatment. However, the concentration of P increased in shoots at 6.7 and 13.4 µmol L^?1 As levels, indicating a cooperative rather than antagonistic relationship. Arsenic and Fe concentration increased in roots at higher As treatments. Arsenic translocation (%) decreased in the 13.4 and 26.8 µmol L^?1 As treatments compared with the 6.7 µmol L^?1 As treatment. Arsenic and Fe were mostly concentrated in the roots of rice seedlings, assuming co-existence of these two elements. Roots contained an almost 8–16-fold higher As concentration than shoots in plants in the As treatments. Considering the concentration of Mn, Zn and Cu, it was suggested that chlorosis resulted from Fe deficiency induced by As and not heavy-metal-induced Fe deficiency.     

Effects of Nickel on Growth and Composition of Metal Micronutrients in Barley Plants Grown in Nutrient Solution

Abstract

A hydroponic experiment was conducted in a phytotron at pH 5.5 to study the effects of nickel (Ni) on the growth and composition of metal micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), of barley (Hordeum vulgare L. cv. Minorimugi). Four Ni treatments were conducted (0, 1.0, 10, and 100 μM) for 14 d. Plants grown in 100 μM Ni showed typical visual symptoms of Ni toxicity such as chlorosis, necrosis of leaves, and browning of the root system, while other plants were free from any symptoms. Dry weights were the highest in plants grown in 1.0 μM Ni, with a corresponding increase in the chlorophyll index of the plants, suggesting that 1.0～10 μM Ni needs to be added to the nutrient solution for optimum growth of barley plants. The increase of Ni in the nutrient solutions increased the concentrations of Cu and Fe in roots, while a decrease was observed in shoots. The concentrations of Mn and Zn in shoots and roots of plants decreased with increasing Ni supply in the nutrient solution. Shoot concentrations of Cu, Fe, Mn, and Zn in plants grown at 100 μ M Ni were below the critical levels for deficiency. Plants grown at 1.0 μ M Ni accumulated higher amounts of Cu, Fe, Mn and Zn, indicating that nutrient accumulation in plants was more influenced by dry weights than by nutrient concentrations. The translocation of Cu and Fe from roots to shoots was repressed, while that of Mn and Zn was not repressed with increasing Ni concentration in the nutrient solution.     

Physiological basis of iron chlorosis tolerance in rice (Oryza sativa) in relation to the root exudation capacity

Micronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R² = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.     

Alleviation of Manganese Phytotoxicity in Barley with Calcium

In order to clarify the mechanism by which calcium (Ca) alleviates manganese (Mn) phytotoxicity, barley plants were grown under the following conditions: (1) nutrient solution alone (control), (2) nutrient solution + 25 μM Mn (Mn-toxic), and (3) nutrient solution + 25 μ M Mn + 20 mM Ca (Ca-alleviated). Feeding experiments using ⁵⁴Mn and ⁵⁹Fe (iron) with 2.0 or 20 mM Ca to the plant roots were also conducted. The absorption and translocation of ⁵⁴Mn in the control plants were lowered by the high-Ca (20 mM) feeding condition. The translocation of ⁵⁴Mn to shoots of Mn-toxic or Ca-alleviated plants was also lowered by the high-Ca feeding condition, but ⁵⁴Mn absorption by roots of the plants was unaffected. The absorption and translocation of ⁵⁹Fe in the plants was unaffected by the high-Ca feeding condition. Calcium alleviation of Mn phytotoxicity in barley may be induced mainly by the inhibition of Mn translocation to shoots.     

The Tolerance Index and Translocation Factor were Used to Identify the Barley Genotypes with High Arsenic Stress Tolerance

Ninety-four barley genotypes were used to investigate the genotypic differences in arsenic (As) uptake and translocation and their relationships with As tolerance index (TI) and translocation factor (TF). Two As treatments (300 µM and 500 µM) were applied in the initial screening and the confirmatory experiments, respectively. The results showed significant (p < 0.05) differences in tissue biomass, shoot height, root length, As TI and TF among genotypes. Based on As TI, 11 barley genotypes were selected and divided into 3 groups, i.e. tolerant, mildly tolerant and sensitive. There was more As uptake in the roots of the As tolerant genotypes, while the As sensitive genotypes contained more As in shoots, which was further proved by the greater TF. Significantly negative correlation was observed between shoot and root As concentration. The results showed that As tolerant genotypes are able to restrict the upward movement of As, thus developing their tolerance.     

Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

Abstract

The objective of this study was to compare iron (Fe) concentrations (mg kg^?1) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg^?1) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg^?1) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg^?1) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg^?1) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg^?1) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg^?1) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.     

冬大麦花后穗部氮素积累及转移的研究

在大田条件下,以扬饲麦3、扬饲麦1、苏啤2号和扬农啤2号等4个品种为供试材料,在07、5、1502、25.kg/hm24个氮肥处理水平下,研究了大麦花后穗部氮积累及转移的规律。结果表明,在扬饲麦3、扬饲麦1、苏啤2号和扬农啤2号4个品种各氮肥处理的平均值中,开花期绿叶的含氮量依次为2.64%、2.76%、2.63%和2.45%,穗部含氮量依次为1.43%、1.83%、1.69%和1.51%。成熟期子粒含氮量分别为2.65%、2.63%、2.48%和2.14%。氮的花前积累量(NABF)依次为17.68、15.27、19.80和14.85.mg/plant,总积累量(NTA)分别为33.75、25.51、54.24和28.83mg/plant,花后积累量(NAAF)依次为16.061、0.25、34.45和13.98.mg/plant,转移量(NT)依次为12.60、10.551、3.48和9.54.mg/plant,转移效率(NTE)分别为71.49%、69.84%、68.42%和64.97%。收获指数(NHI)分别为84.91%、81.95%、88.47%和81.90%;随着施氮水平的提高,各品种的花前氮积累量、总积累量、花后积累量和氮转移量均呈上升趋势,而氮转移效率、氮转移对子粒的贡献(NCR)率则成下降趋势;大麦花后穗部氮积累过程可以用Richards方程W=A/(1+be-kt)m来描述,通径分析方程各特征参数与氮积累和转移的关系表明,影响大麦穗部氮积累和转移的主要因素是最大积累速率,其次是起始积累势,最大积累速率越高,起始积累势越小,越有利于氮的积累和转移。同时,积累中期和前期的积累速率和积累量对大麦穗部氮积累和转移的影响也较大。     

Differential Zinc Efficiency of Barley Genotypes Grown in Soil and Chelator-Buffered Nutrient Solution

Genotypic variation to zinc (Zn) deficiency in barley indicates that selection for Zn efficiency is possible. Sahara (Zn-efficient) and Clipper (Zn-inefficient) were evaluated at different Zn nutrition in soil and chelator-buffered nutrient. Zinc deficiency symptoms appeared first in Clipper and later in Sahara. At 0.8 mg Zn/kg soil, shoot and root Zn concentration and content were higher in Sahara than Clipper. The root:shoot dry matter ratio of genotypes increased as Zn application decreased. The 4th and 5th leaf elongation were depressed greater in Clipper than Sahara by Zn deficiency. The genotypes responses to Zn in solution and soil were consistent in all parameters except root growth. In contrast to soil, root drymatter was greater in Clipper than Sahara in solution under Zn deficiency. Shoot Zn concentration and content can be used in assessment of barley genotypes, and may be useful criteria in screening large genotypes aimed at developing molecular markers for Zn efficiency.     

Genotypic Difference in Arsenic and Cadmium Accumulation by Rice Seedlings Grown in Hydroponics

Genotypic differences in arsenic (As) and cadmium (Cd) uptake and their translocation within rice seedlings grown in solution culture were investigated. Arsenic uptake and its translocation differed significantly between eight cultivars. The largest shoot and root As concentrations were found in cultivar ‘TN1’ and ‘ZYQ8’, while cultivar ‘JX-17’ had the lowest As concentration. Arsenic concentration in shoot or root of ‘JX-17’ was about 50% of that in cultivar ‘ZYQ8’. Specific Arsenic uptake (SAU) was found significantly different between rice cultivars, which was about 2-fold higher of ‘ZYQ8’ than that of ‘JX-17’. The Cd accumulation also differed significantly between cultivars. Rice cultivar ‘JX-17’ had the highest ability in Cd uptake, but the lowest ability in Cd translocation from root to shoot. The transfer factor (TF) of Cd had an important effect on Cd accumulation by rice seedlings. Arsenic can competitively inhibit P uptake by rice seedlings, P concentrations in shoots, or roots treated with As were significantly lower than those without As addition. However, the concentrations of P and As were positively correlated within these genotypes. The Cd immobilization by cell wall was an important mechanism for Cd detoxification. The cell wall bound 21–44% of total Cd in shoots and 25–59% of total Cd in roots of these tested genotypes. The genotypic differences in As and Cd uptake and translocation within rice seedlings provide the possibility of selecting and breeding genotypes and /or cultivars with reduced levels of As and Cd in rice grains.     

UV-B辐射增强对大麦生理生态的影响

在大田条件下,研究了UV-B辐射增强对大麦的生长发育、光合作用、蒸腾作用及其产量构成的影响。结果表明,UV-B辐射增强明显抑制大麦生长,使株高变矮、绿叶数减少、叶面积和干物质量下降,但抑制程度随生育期而异。在UV-B辐射增强条件下,大麦叶片叶绿素含量、净光合速率、气孔导度和蒸腾速率都有不同程度的降低,水分利用率也随之降低。UV-B辐射增强对大麦形态学和生理学上的不利影响,导致了大麦产量下降24.96%。     

Catch Crop and Animal Slurry in Spring Barley Grown with Straw Incorporation

Abstract

Four rates of straw (0, 4, 8 and 12 t ha^?1 yr^?1) were incorporated in a field experiment with continuous spring barley. The experiment was conducted on a sandy soil (5.5% clay) and a sandy loam soil (11.2% clay). After eight years, the straw incorporation was combined with catch-crop growing with and without winter application of animal slurry and also spring fertilization with mineral fertilizer (0, 50, 100 or 125 kg N ha^?1 yr^?1). The combined experiment was conducted for three lyears on the sandy soil and for four years on the sandy loam soil. The effects on barley dry matter yield and N uptake are presented together with the long-term effects of the straw incorporations on crop growth and soil C and N. Grain yield on the sandy loam was unaffected by straw incorporation. On the sandy soil the highest straw application rates reduced grain yield in the unfertilized barley. When the barley received mineral fertilizer at recommended levels (100 kg N ha^?1 yr^?1), grain yield on this soil was also unaffected by the high straw rates. Including a catch crop had a positive effect on the grain yield of barley on both soils. The total N uptake in grain and straw generally increased with straw application up to 8 t ha^?1 yr^?1. With the highest straw application rate (12 t ha^?1 yr^?1), the total N uptake decreased but still exceeded N uptake in barley grown with straw removal. The barley accumulated higher amounts of N when a catch crop was included. The total N uptake in the barley was significantly higher after animal slurry application. The extra N uptake, however, was much lower than the amounts of N applied with the slurry. Incorporation of straw had only a small influence on N uptake after slurry application. The straw, therefore, was not able to store the applied N during winter. In the two four-year periods before the combined experiment, grain yield on the sandy loam was generally negatively affected by straw incorporations. In the second period, N uptake began to show a positive effect of the straw. On the sandy soil, grain yield and N uptake during the whole period were generally positively affected by the straw incorporations except for the highest straw rate (12 t ha^?1 yr^?1). The sandy loam soil showed higher increases in C and N content after the repeated straw incorporations and catch-crop growing than the sandy soil. When application of animal slurry was combined with the catch crop, no further increases in soil C and N were found relative to soil where a catch crop was grown without slurry application. Large amounts of the N applied with the slurry may therefore have been lost by denitrification or nitrate leaching.     

Quantitative Trait Loci (QTL) of Seed Zn Accumulation in Barley Population Clipper X Sahara

There is little information regarding the chromosomal regions conferring zinc (Zn) accumulation in barley. With the aim of developing markers for Zn accumulation, 150 lines derived from cross between ‘Clipper’ (low-Zn-accumulator) and ‘Sahara’ (high-Zn-accumulator) were screened. In field-grown plants, two regions located on 2HS and 2HL were associated with seed Zn concentration and content. 2HS was flanked by Xbcd175 and Xpsr108; 2HL was flanked by vrs1 and XksuF15 markers. These two regions accounted for 45% of total variation in seed Zn concentration and 59% of total variation in seed Zn content. In a glasshouse experiment, 2HS and 2HL were also associated with seed Zn concentration and content, and explained 37% and 55% of the total variation in seed Zn concentration and content, respectively. The identification of these Quantitative Trait Loci (QTL) provides an important starting point for transferring and pyramiding genes that may contribute to the improvement of barley productivity and nutritional quality in Zn-deficient environments.     

Response of Cadmium Uptake in Different Barley Genotypes to Cadmium Level

A greenhouse hydroponic experiment was performed out to study the cadmium (Cd) uptake by four different barley cultivars at two Cd levels. The results showed that Cd concentrations in roots and shoots increased with Cd levels in the solution and Cd concentration in roots was much higher than that in shoots. The amount of Cd accumulated by plants increased continually with the duration of treatment, and the highest Cd concentration in roots and aboveground tissues was found approximately at the 100th and 70th day after Cd addition, respectively. Genotypes differed significantly in relation to Cd concentration in roots and aboveground tissues. Wumaoliuling showed a higher Cd concentration than the other three genotypes, while Mimai 114 had the lowest concentration. Cadmium uptake rate per plant increased slowly before the booting stage, then increased sharply during the 70–100 d period (approximately late elongation to booting stage), and after that Cd uptake rate tended to slow dramatically. However, the Cd uptake rate per unit of dry biomass showed a significant reduction after booting stage (70 d after Cd exposure), and the Cd uptake pattern varied by Cd levels in the medium. At the lower Cd level (0.1 μM), there were two peaks in Cd uptake rate, appearing at the seedling (20–30 d after Cd exposure) and stem elongation stages (50–70 d after Cd exposure), respectively, while there was only one peak at the stem elongation stage at the higher Cd level (1 μ M).     

Diurnal variations in absorption and translocation of a ferrated phytosiderophore in barley as affected by iron deficiency

The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe³⁺ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with ⁵⁹Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of ⁵⁹Fe, The absorption of ⁵⁹Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of ⁵⁹Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of ⁵⁹Fe by roots, The formation of root apoplastic ⁵⁹Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe³⁺ complex by roots did not follow the PS release pattern.     

改良剂对柴油污染土壤中黑麦草生理代谢的调节

开展了土壤柴油污染的单因素盆栽实验和柴油污染盐渍化土壤中添加锯末-硝酸铵-磷酸二氢钾的三因素正交盆栽实验,对黑麦草幼苗抗氧化酶活性和叶绿素含量进行了分析,探究了柴油污染土壤中黑麦草幼苗的生理变化与调节。结果表明,土壤柴油污染显著减小了黑麦草幼苗生物量,与对照相比,叶SOD活性在柴油浓度0.3%和0.9%时显著降低,POD和CAT活性在0.6%和0.9%柴油浓度下显著降低;根SOD活性在0.9%柴油浓度下显著增大,POD活性在0.6%和0.9%柴油浓度下显著下降。受柴油污染的盐渍化土壤,施加锯末体积分数为10%时,黑麦草幼苗叶POD和CAT活性显著增强,叶绿素a和叶绿素b含量显著增加;施氮量为0.3 g·kg~(-1)土时,黑麦草幼苗叶绿素a和叶绿素b含量显著增加。可见,土壤受柴油污染时,添加锯末和硝酸铵可有效调节黑麦草幼苗的生理代谢。     

Cadmium Accumulation and Tolerance of Two Salix Genotypes Hydroponically Grown in Presence of Cadmium

Abstract

In general, according to previous studies, pioneer species do not require arbuscular mycorrhizal fungi (AMF) to increase their growth and survival in tropical systems. The aim of this study was to determine the dependence response to AMF of Heliocarpus appendiculatus, a pioneer species, at different phosphorus (P) levels. In a greenhouse experiment, H. appendiculatus seedlings were grown in pots with a sterile vermiculite-sand mixture (1:1). Two sets of pots were set up: One set was inoculated (150 spores per pot) with indigenous AMF from a tropical rain forest at “Los Tuxtlas” (Veracruz, Mexico); the other set was not inoculated. To each set, 0, 0.02, 0.2, and 2 g L^?1P was added. All pots were watered with 250 mL of nutrient solution. Mycorrhizal plants showed a higher total dry weight and relative growth rate in 0.02 g L^?1P concentration, while nonmycorrhizal plants responded positively at 0.2 g L^?1P; a decrease in plant responses at higher P levels was observed in both treatments. H. appendiculatus showed to have higher relative dependence at lower P concentration (≈50%). As levels of P increased, mycorrhizal colonization decreased. Successful growth of pioneer species during succession process may be improved if there is AMF content in soils, prior to disturbance.     

辐照处理对蔺草苗期生理生化特性的影响

分别以500、1000、1500和2000Gy的60Coγ射线处理不同蔺草品种成熟干种子,并将其培养成实生苗,进行根系活力、叶绿素含量及多酚氧化酶和过氧化氢酶活性的检测,观察蔺草苗期的生长状况,从而研究不同辐射剂量对蔺草苗期生长及生理生化特性的影响,确定蔺草的适宜辐射诱变剂量,为下一步开展蔺草品种诱变改良奠定基础。结果发现,CK（对照组）的根系活力、叶绿素含量和多酚氧化酶活性都大大高于同等条件下培养的的辐射处理组。表明辐照会影响蔺草的根系活力、多酚氧化酶活性和叶绿素含量。过氧化氢酶活性测定表明,500Gy处理的过氧化氢酶活性高于CK和其他辐射处理组。从蔺草苗期的生长状况来看,随着辐剂量的增加,草茎长度有不断增加的趋势。由此表明,在一定剂量范围内,辐射处理可促进蔺草苗期的生长,500Gy是较适宜的处理剂量。