不同芹菜品种镉吸收和运转差异研究

【目的】 研究镉胁迫下芹菜生长、镉吸收和向上运转品种间差异,为筛选镉低积累型芹菜品种减少镉对人体的危害提供依据。 【方法】 以10个芹菜品种为试材进行基质无土栽培试验,基质为蛭石,营养液采用1/2华南农业大学叶菜类营养液配方,以只浇灌营养液的处理作为对照,浇灌含15 mg/L氯化镉（CdCl₂）的营养液为Cd胁迫处理;每3 d浇灌一次,每次浇灌0.2 L,累计浇灌15次,每盆Cd施用量为45 mg。移栽45 d后,测定生长指标与根、叶柄和叶片Cd含量。计算相对生长量（relative growth yield,RGY）和转运系数（translocation factor,TF）,并筛选出高、低Cd积累品种。分别对高、低Cd积累品种进行穴盘基育苗,14 d后采用华南农业大学叶菜类营养液配方进行营养液栽培,21 d后利用非损伤微测技术（non-invasive micro-test technology,NMT）测定根系分生区、伸长区和根毛区Cd2+离子流速。 【结果】 与非Cd胁迫相比,Cd胁迫使‘速生四季西芹王’、文图拉西芹’、‘四季小香芹’、‘实心香芹’、 ‘雪白芹菜’ 地下部受到显著抑制,对地上部无显著影响;Cd胁迫促进了 ‘四季小香芹’ 地上部生长;而 ‘种都金黄芹菜’、‘红芹’、‘鲍芹’ 地上部受到显著抑制,对地下部则无显著影响;‘马家沟芹菜’ 和 ‘速生香芹’ 地上部和地下部均生长均受到抑制。食用器官叶柄中Cd含量以 ‘种都金黄芹菜’ 和 ‘雪白芹菜’ 最高;‘速生香芹’ 和 ‘实心香芹’ 最低。地上部Cd含量高的 ‘种都金黄芹菜’ 和 ‘雪白芹菜’ 对Cd转运能力也最高;Cd含量低的 ‘速生香芹’ 对Cd转运能力也最低。在根系成熟区（根毛区）,‘种都金黄芹菜’ 较 ‘速生香芹’ 有更高Cd2+ 离子流速。 【结论】 Cd胁迫下,芹菜不同品种生长、Cd吸收、转运和积累存在显著差异。‘四季小香芹’、‘速生四季西芹王’、‘文图拉芹菜’、‘实心香芹’ 和 ‘雪白芹菜’ 较为耐镉;而 ‘种都金黄芹菜’、‘红芹’、‘鲍芹’、‘马家沟芹菜’ 和 ‘速生香芹’ 对镉敏感。‘雪白芹菜’ 和 ‘种都金黄芹菜’ 为高Cd积累型,‘实心香芹’ 和 ‘速生香芹’ 为低Cd积累型,其中 ‘实心香芹’ 表现为低Cd含量和高生长量。高Cd积累型芹菜较低Cd积累型芹菜有更强Cd2+ 吸收能力和Cd转运能力,根部Cd2+ 流速可用于低积累品种的快速筛选。      

东北地区不同水稻品种对Cd的累积特性研究

采用土培盆栽试验方法,以东北地区大面积种植的32个水稻品种为试验材料,在土壤中未添加和添加Cd（5mg.kg-1Cd）的条件下,研究水稻生长、籽粒产量和Cd在水稻植株不同部位的分配规律。结果表明,土壤中添加Cd后,多数水稻籽粒产量和植株总生物量下降,只有少数品种籽粒产量和生物量有所上升。Cd在水稻植株中的含量遵循根系〉茎叶〉颖壳〉籽粒的规律,但从分配比例来看,土壤中未添加Cd时根系中Cd的分配比例较高,添加Cd后茎叶中Cd的分配比例明显增加。从稻米产量和质量安全角度综合考虑,认为越路早生（3号）品种为农业生产中较理想的种植品种,沈农265（1号）、农林315（30号）、屉锦（31号）、沈稻12（32号）品种可以在中轻度污染的农田土壤条件下种植,而千重浪-1（8号）、辽盐2（14号）、辽盐283（17号）、辽恢190（19号）以及吉03-2843（27号）品种尽量避免在污染土壤上种植。研究结果对东北地区镉污染稻田选择水稻品种,保障稻米安全具有重要意义。     

Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Arbuscular Mycorrhizal Fungi Contribute to Resistance of Upland Rice to Combined Metal Contamination of Soil

A greenhouse pot experiment was conducted to investigate heavy metal [copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd)] uptake by two upland rice cultivars, ‘91B3’ and ‘277’, grown in a sterilized field soil contaminated by a mixture of Cu, Zn, Pb, and Cd. Rice plants were inoculated with each of three arbuscular mycorrhizal fungi (AMF), Glomus versiforme (GV), Glomus mosseae (GM), and Glomus diaphanum (GD), or remained noninoculated (NM). Both rice cultivars could be colonized by the three AMF used in this experiment. The percentage of mycorrhizal colonization by the three AMFs on the two rice cultivars ranged from 30% to 70%. Mycorrhizal colonization of both upland rice cultivars had a large influence on plant growth by increasing the shoot and root biomass compared with non-inoculated (NM) plants. The results indicate that mycorrhiza exert some protective effects against the combined toxicity of Cu, Zn, Pb, and Cd in the contaminated soil. This conclusion is supported by the partitioning of heavy metals (HMs) in the two cultivars. In the two cultivars, colonization by AMF reduced the translocation of HMs from root to shoot (except that the colonization of AMF increased the Cu translocation of HMs in cultivar ‘277’). Immobilization of the HMs in roots can alleviate the potential toxicity to shoots induced by the mixture of Cu, Zn, Pb, and Cd. The two rice cultivars showed significant differences in uptake of Cu, Zn, Pb, and Cd when uninoculated. GM inoculation gave the most protective effects on the two cultivars under the combined soil contamination.     

Genetic Variation in Cadmium Accumulation and Tolerance among Wheat Cultivars at the Seedling Stage

Exploitation of genetic differences to select wheat cultivars’ pollution-safe from cadmium (Cd) contamination requires better understanding of Cd uptake and translocation patterns. For this purpose, 15 wheat cultivars were grown in nutrient solution and exposed to four levels of Cd, i.e., 0, 15, 30, and 45 µM. The plants were harvested after 2 weeks of Cd exposure. Root and shoot relative dry matter (DM) was decreased in most of the cultivars, but some cultivars did not exhibit any toxic symptoms. The lowest Cd concentration in shoots was recorded for Lasani-2008 and Iqbal-2000 while the highest for Sehar-2006 and Inqlab-91. Both root absorption and translocation accounted for regulating Cd concentration in shoots. There was no relationship between relative DM and Cd concentrations in roots and shoots. The results suggest that wheat cultivars with low shoot Cd concentration but higher tolerance, i.e. Lasani-2008 and Iqbal-2000, could be used in breading programs for low Cd wheat.     

Genetic line effects on parameters influencing cadmium concentration in lettuce (Lactuca sativa L.)

Cd uptake rates, translocation percentages, and shoot:root ratios were determined for 4 lettuce lines known to concentrate different levels of leaf Cd. Uptake rates were measured for one hr on 14‐day‐old plants exposed to Cd concentrations ranging from 2.5 to 100.00 nM. PI 278080, the high Cd line, had the highest uptake rate; PI 140398 and PI 169493, 2 low‐Cd lines, had intermediate uptake rates; and ‘Ruby’, a low‐to‐intermediate line, had the lowest overall uptake rate. Translocation percentages and shootrroot ratios were measured from one to 7 days on 15‐ to 21‐day‐old seedlings grown at 0.4 μM Cd. PI 278080 and ‘Ruby’ translocated about 40% of absorbed Cd to shoots, whereas PI 140398 and PI 169493 translocated about 30%. The shoot:root ratios of PI 278080, PI 140398 and PI 169493 ranged from 2.5 to 2.7, and these values were significantly lower than the ratio of 3.4 for ‘Ruby’.     

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.     

Tropical Rice Cultivars from Lowland and Upland Cropping Systems Differ in Iron Plaque Formation

In iron toxic wetlands, ferric hydroxide is commonly deposited on rice roots. This study aims to to evaluate the differences in iron plaque formation in rice cultivars from different cropping systems. Thirty days old seedlings of Brazilian rice cultivars from the lowland cropping system (‘BRS Atalanta’ and ‘Epagri 107’) and upland cropping system (‘Canastra’) or both systems (‘BRSMG Curinga’) and the cultivar ‘Nipponbare’ were exposed to iron excess [4 mM iron sulfate heptahydrate (FeSO₄.7H₂O)] for seven days in nutrient solution. It was observed iron plaque formation and ruptures of the root epidermal cells. The lowland cultivars showed higher Fe content in iron plaque. Iron stain was detected in the root hairs, epidermis, hypodermis, and exodermis. The root exodermis may be contributed to prevent the deposit of iron in the cortex of the lowland cultivars and in the cultivar ‘BRSMG Curinga’. It was observed in plants with iron plaque formation significant reductions in the shoot content of phosphorous, manganese and magnesium due to different causes. The differences in iron plaque formation among the cultivars might be an indicative of variations in exodermis selectivity, root oxidative capacity, and iron nutrition mechanisms.     

Effect of Cadmium and Iron on Rice (Oryza Sativa L.) Plant in Chelator-Buffered Nutrient Solution

ABSTRACT

To better understand the mechanisms responsible for differences in uptake and distribution of cadmium (Cd), nutrient-solution experiments were conducted with different varieties of rice (Oryza sativa), ‘Khitish’ and ‘CNRH3’. The plants were grown in a complete nutrient solution with different levels of pCd (-log free Cd⁺² activity) and pFe [-log free iron (Fe⁺²) activity]. The required concentrations of chelating agent and metals were determined using a computerized chemical equilibrium model such as Geochem-PC. Experimental treatments included a combination of four pCd activity levels (0, 7.9, 8.2, and 8.5) applied as Cd (NO₃)₂ 4H₂O, and two pFe activity levels (17.0 and 17.8) applied as FeCl₃. The application of both Cd and Fe in solution culture significantly affected plant growth, yield, and Cd accumulation in plant tissue. In general, yield of rice was decreased by an increase in amount of solution Cd; however, yield response varied among the cultivars. At the 7.9 pCd level, yields of rice cultivars ‘Khitish’ and ‘CNRH3’ were reduced to 69% and 65%, respectively, compared with control plants. Root Cd concentrations ranged from 2.6 mg kg^?1 (control plants) to 505.7 mg kg^?1 and were directly related to solution Cd concentrations. In rice plants, Cd toxicity symptoms resembled Fe chlorosis. Differential tolerance of varieties to phytotoxicity was not readily visible, but a significant interaction of substrate Cd and variety was obtained from dry-matter yields. Significant interactions indicated that response of tissue Cd concentration, plant Cd uptake, and translocation of Cd to the aerial parts were dependent on variety as well as substrate Cd. Uptake of Cd by roots was significantly higher than by shoots. Higher Cd uptake by rice plants decreased the uptake of other beneficial metals.

The effect of Cd and Fe on the rate of phytometallophore release was also studied in the nutrient solution. Among the rice genotypes, ‘Khitish’ was the most sensitive to Cd toxicity. In both genotypes, with the onset of visual Cd-toxicity symptoms, the release of phytometallophore (PM) was enhanced. Among the rice varieties, ‘Khitish’ had the highest rate of PM release. Treatments with the metal ions studied produced a decrease in chlorophyll and enzyme activity. A decrease in concentrations of chlorophyll pigments in the third leaf was observed due to the highest activity level of Cd (pCd 7.9). Activities of enzymes such as peroxidase (POD) and superoxide dismutase (SOD) are altered by toxic amounts of Cd. Changes in enzyme activities occurred at the lowest activity of Cd (pCd 8.5) in solution. Peroxidase activity increased in the third leaf. Results showed that in contrast with growth parameters, the measurements of enzyme activities may be included as early biomarkers in a plant bioassay to assess the phytotoxicity of Cd-contaminated solution on rice plants. Evidence that Cd uptake and translocation are genetically controlled warrants the selection of varieties that assimilate the least Cd and that translocate the least metal to the plant part to be used for human and animal consumption.     

外源Cd在不同品种水稻组织中的细胞分布和化学形态特征研究

采用水培试验,以低镉(Cd)积累水稻品种‘D83A/R527’和高Cd积累水稻品种‘辐优838’为供试材料,设置3个Cd浓度(5μmol·L~(-1)、10μmol·L~(-1)、25μmol·L~(-1))处理,从Cd亚细胞及化学形态分布角度研究了不同基因型水稻品种的Cd积累特性,为探讨水稻对Cd的吸收积累生理机制提供科学依据。结果表明:(1)水稻‘D83A/R527’的根系和茎叶Cd含量及根系-茎叶转移系数均显著低于‘辐优838’(P0.05)。(2)两水稻根系各亚细胞组分中Cd含量表现为可溶部分(F3)细胞壁(F1)细胞器(F2),茎叶表现为细胞壁(F1)可溶部分(F3)细胞器(F2);‘D83A/R527’根系和茎叶细胞壁Cd的质量分数(36.76%~51.75%)高于‘辐优838’(31.29%~49.07%)。(3)两水稻品种Cd化学形态含量均表现为氯化钠提取态(F_(NaCl)-Cd)醋酸提取态(F_(HAc)-Cd)去离子水提取态(F_W-Cd)乙醇提取态(F_E-Cd)盐酸提取态(F_(HCl)-Cd);随Cd处理浓度的增加,‘D83A/R527’根系F_E-Cd和F_W-Cd(活性态Cd)质量分数逐渐下降(24.75%~18.34%),‘辐优838’活性态Cd逐渐上升(27.18%~28.68%),茎叶F_(HAc)-Cd和F_(HCl)-Cd(惰性态Cd)质量分数(32.41%~38.98%)逐渐上升且高于‘辐优838’(28.44%~31.22%),‘D83A/R527’根系和茎叶F_(NaCl)-Cd质量分数(32.71%~51.17%)均高于‘辐优838’(32.14%~47.63%)。综上,‘D83A/R527’水稻幼苗Cd积累量低;与‘辐优838’相比,‘D83A/R527’水稻幼苗根系和茎叶细胞壁质量分数较高,"活性态"Cd质量分数较低,"惰性态"Cd则更高,表明‘D83A/R527’水稻对Cd有更强的固持能力。     

Influence of Iron Fertilization on Cadmium Uptake by Rice Seedlings Irrigated with Cadmium Solution

A pot experiment investigated the effects of iron (Fe) fertilization on cadmium (Cd) uptake by rice seedlings irrigated with Cd solution. Shoot dry weight was significantly affected by Fe addition, and root dry weight was affected by Cd addition. Iron supply was the dominant factor affecting the length of the longest leaf and the soil and plant analyzer development (SPAD) value. Cadmium concentrations were much greater in roots than in dithionite–citrate–bicarbonate (DCB) extracts or shoots, and a significant correlation was found between shoot Fe and Cd concentrations. Enhanced Cd uptake observed at high Fe supply implies that enhanced Fe nutrition may counteract the adverse effects of Cd on plants.     

Sulfur Alleviates Growth Inhibition and Oxidative Stress Caused by Cadmium Toxicity in Rice

A hydroponic experiment was conducted to investigate the effect of sulfur (S) on growth inhibition and oxidative stress caused by Cd²⁺ toxicity, using two rice cultivars with different grain Cd²⁺ content. Treatments consisted of factorial arrangement of three S levels (0.2, 0.4, and 0.8 mmol), two cadmium (Cd) levels (0 and 1 μ mol), and two rice cultivars (‘Bing 97252,’ a cultivar with low grain Cd²⁺ content, and ‘Xiushui 63,’ a cultivar with high grain Cd²⁺ content). The results showed that Cd²⁺ addition in the medium generally increased Cd²⁺ and malondialdehyde (MDA) content in both roots and shoots; the increases were more pronounced in ‘Xuishui 63’ than in ‘Bing 97252.’ Dramatic reductions in growth parameters, including plant height, root and shoot weight, tillers per plant, chlorophyll content, and net photosynthetic rate were found in the plants exposed to Cd stress relative to the plants without Cd²⁺ treatment. ‘Xiushui 63’ showed more sensitivity than ‘Bing 97252’ under Cd²⁺ exposure. In comparison with the lower S level (0.2 mmol), the higher S levels (0.4 and 0.6 mmol) helped alleviate Cd toxicity, characterized by a significant increase in growth parameters, and a decrease in Cd²⁺ and MDA content in both roots and shoots. In addition, superoxide dismutase (SOD) activity in the plants varied among tissues, cultivars, and Cd treatments. High Cd²⁺ and MDA content was consistently accompanied by higher SOD activity, and higher S levels caused a marked increase in glutathione content and a reduction in SOD activity, indicating a positive effect of S in alleviating oxidative stress.     

Growth and cadmium accumulation in two durum wheat cultivars

Abstract

A solution culture study was conducted to determine the effects of cadmium (Cd) application on Cd accumulation and growth of two durum wheat (Triticum turgidum L. var durum) cultivars. Arcola and DT618 were grown in nutrient solution for 13 days. Cadmium application to nutrient solution significantly (P ≤ 0.05) decreased root and shoot biomass, leaf area, leaf mass, total root length, and chlorophyll a and b concentration of the first leaf. The deleterious effects of Cd on plant growth were explained by a modified version of Weibull distribution function of the form, y = a.exp(b.√Cd), where ‘y’ is the growth parameter, ‘a’ is plant growth in the absence of Cd, and ‘b’ is reduction in growth with per unit increase in solution Cd. Total root length was decreased the most (80%) and chlorophyll b concentration of the first leaf decreased the least (9%) with per unit increase in solution Cd. Although the two cultivars were significantly different in some growth characteristics, both responded similarly to increase of Cd concentration in solution. Cadmium concentration in roots and shoots increased significantly (P ≤ 0.05) with Cd application, but due to concomitant decrease in growth the Cd content of plants remained constant at solution Cd concentrations of 5 μm or above. We concluded that seedlings of durum cultivars with different growth potential responded similarly to Cd application in nutrient solution.     

EFFECT OF ARSENIC ON GERMINATION,PHOTOSYNTHESIS AND GROWTH PARAMETERS OF TWO WINTER WHEAT VARIETIES IN IRAN

□ Effects of different arsenic (As) concentration (0–30 mg L^?1) on seed germination, root tolerance index, relative shoot height, root and shoot biomass, photosynthetic pigments and arsenic accumulation in two wheat varieties were investigated. Low concentrations of arsenic (0–2.5 mg L^?1) stimulated germination percentage, shoot and root elongation, plant biomass as well as chlorophyll content as compared with control, however, these factors all decreased gradually at high concentrations of arsenic (5–30 mg L^?1). ‘Zarin’ variety had a significantly higher tolerance to arsenic than ‘Sardari.’ Arsenic accumulation by plants root and shoot increased with the increasing arsenic concentrations in medium, which ‘Zarin’ had a higher ability to absorb and translocate arsenic to the shoots. Root accumulated more arsenic than shoot. The similar trend of chlorophyll content and wheat growth under different arsenic concentration suggesting that arsenic toxicity affects the photosynthesis which ultimately results in the reduction of wheat growth and yield.     

Arsenic uptake is suppressed in a rice mutant defective in silicon uptake

Possible mechanisms of the effects of silicon (Si) on arsenic (As) uptake were explored using a wild‐type rice and its low‐Si mutant (lsi1). Hydroponic experiments were carried out to investigate the effects of internal and external Si on the As accumulation and uptake by rice in excised roots (28 d–old seedlings) and xylem sap (61 d–old plants). The presence of Si significantly decreased the As concentrations in both shoots and roots of the wild type but not in the mutant with 13.3 μM–arsenite or 10/20 μM–arsenate treatments. The Si‐defective mutant rice (lsi1) also showed a significant reduction in arsenite or arsenate uptake. Moreover, As concentrations in xylem sap of the wild type were reduced by 51% with 1 mM Si– and 15 μM–arsenate treatments, while Si had no effect on As concentrations in the xylem sap of the mutant. Arsenic‐species analysis further indicated that the addition of 1 mM Si significantly decreased As(III) concentrations but had little effect on As(V) concentrations in the xylem sap of the wild type with 15 μM–arsenate treatments. These results indicated that external Si‐mediated reduction in arsenite uptake by rice is due to the direct competition between Si and arsenite during uptake. This is because both share the same influx transporter Lsi1. In addition, internal Si‐mediated reduction in arsenite uptake by rice is due to competition of the Si/arsenite efflux transporter Lsi2 during the As(III)‐transportation process. Silicon also inhibited arsenate uptake by rice. It is proposed that this could actually be due not to the inhibition of arsenate uptake per se but rather the inhibition of arsenite transformed from arsenate, either in the external solution or in rice roots.     

Genotypic differences in effects of cadmium on growth and nutrient compositions in wheat

Abstract

A solution culture study was conducted to determine the genotypic difference in the effects of cadmium (Cd) addition on growth and on the uptake and distribution of Cd and other 11 nutrients in wheat plants. Cadmium addition at a rate of 1 mg L^?1 significantly reduced root and shoot dry matter production, shoot height, root length, chlorophyll content, and tillers per plant. On the average of 16 wheat genotypes used in study, Cd concentrations of Cd‐treated plants were 48.1 and 459 μg g^?1 dry weight (DW) in shoots and roots, respectively, and retained 77.91% of total Cd taken up in the roots. On the whole, Cd addition reduced the concentration of sulfur (S), phosphorus (P), magnesium (Mg), molybdenum (Mo), manganese (Mn), and boron (B), and increased iron (Fe), irrespective of the plant parts. The effect of Cd on the concentration of potassium (K), calcium (Ca), and copper (Cu) differed in shoots and roots. The significant difference existed among 16 wheat genotypes in their response to Cd in terms of growth and nutrient concentrations. Genotype E81513, which showed relatively less inhibition in growth, had the lowest shoot Cd concentration and more Cd accumulation in roots, while Ailuyuang had the highest Cd concentration and accumulation in shoot with lower Cd concentration in root. The significant interaction was found between Cd treatment and genotype for all nutrient concentrations in both shoot and root, except S and Zn in root.     

Genotypic Difference of Germination and Early Seedling Growth in Response to Cd Stress and its Relation to Cd Accumulation

A greenhouse experiment was conducted using twelve Japonica rice genotypes differing in grain Cd concentration, to study the genotypic difference in germination and early seedling growth in response to Cd stress and its relation to Cd accumulation. The results showed that under low Cd level (0.5 mM), germination was significantly enhanced for most rice genotypes, but higher Cd levels (2.5 and 10.0 mM) inhibited germination dramatically. When exposed to 10.0 mM Cd, a few genotypes could still germinate, but the seedlings of all genotypes would die in early stage. Shoot height and dry weight, and root length and dry weight of seedling were significantly inhibited at 0.5 and 2.5 mM Cd levels, irrespectively of genotypes, and the inhibition became more severe under higher Cd level. There was a significant genotypic difference in response of germination, early seedling growth and shoot Cd concentration to Cd stress. The difference was the largest for germination, followed by root growth, the least for shoot growth. A cluster analysis of tolerance indices, including germination rate, shoot height and weight, root length and weight of the plants exposed to 2.5 mM Cd level showed that 12 rice genotypes may be grouped into three clusters, i.e. high-, intermediate- and weak Cd-tolerance. No significant correlation was found between grain Cd concentration and Cd-tolerance in terms of germination and seedling growth, and shoot Cd concentrations, suggesting that it is possible to develop rice cultivars with high Cd-tolerance and low grain Cd accumulation.     

Effect of cadmium on growth and the uptake of cadmium and other elements by durum wheat

A solution culture study was conducted to determine the effects of cadmium (Cd) application on the uptake of Cd, potassium (K), zinc (Zn), manganese (Mn), copper (Cu), iron (Fe) and on the growth of seedlings of three wheat (Triticum turgidum L. var Durum) cultivars, Kyle, Nile, and SC84–994. Cadmium application decreased shoot and root biomass, root length, and leaf area. Cadmium application did not produce any differences among cultivars in these growth parameters. There were differential cultivar responses in the uptake of Cd and K but not for Zn, Mn, Cu, and Fe uptake. A solution Cd concentration of 0.1 μM did not affect the concentration of Cd and K compared to zero Cd but at and above 0.5 μM Cd, Nile had a higher concentration and contents of Cd and K in root and shoot than SC84–994 and Kyle. Kyle and SC84–994 were not different in any of the elements tested except K concentration in shoot where the order was SC84–994<Kyle<Nile. Cadmium application increased the Cd concentration but decreased the concentration of K, Zn, and Mn in root and shoot, while the Fe and Cu concentrations in shoot and root were not affected. Cultivar differences were observed in the translocation of Cd from root to shoot. In SC84–994 and Kyle, 0.5 μmole Cd/L decreased the total Cd translocated to shoot, Further addition of Cd did not affect Cd translocation, whereas in Nile, increased Cd concentration in solution did not affect Cd translocation to the shoot. A modified version of Weibull frequency distribution [y = a exp.(b.Cd^c)] was applied to explain the effect of Cd on plant growth parameters and on the uptake of K, Mn, Zn, and Cu in plants.     

镉胁迫对两个水稻品种幼苗光合参数、可溶性糖和植株生长的影响

以较耐镉(武育粳3号,WYJ)和镉敏感(汕优63,SY63)的2个不同耐性水稻品种为材料,采用溶液培养试验,研究了镉处理(Cd.1.0和5.0mol/L)对水稻幼苗光合作用、可溶性糖和生长的影响。结果表明,镉胁迫下,水稻幼苗的光合作用显著地受到抑制。与不加镉的对照相比,随镉水平的提高水稻幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls)逐步下降,尤其是在Cd.5.0mol/L处理下的植株,下降幅度武育粳3号显著小于汕优63。蒸腾效率(Te)也随镉浓度的增加而降低,但变化与净光合速率等不同,武育粳3号的下降速率要大于汕优63的。加镉处理使2个水稻品种幼苗叶片可溶性糖含量均显著升高,而叶绿素含量仅汕优63在Cd.5.0mol/L处理下与对照差异显著。加镉处理使汕优63根系生长(根长)显著受到抑制,而株高仅在Cd.5.0mol/L时显著降低。武育粳3号生长与对照差异不显著。本研究结果表明,随着镉处理水平的提高,镉对水稻幼苗的毒害作用增加,但是水稻对镉毒害的响应存在明显的基因型差异。     

Zinc alleviates growth inhibition and oxidative stress caused by cadmium in rice

A hydroponic experiment with two rice cultivars differing in cadmium (Cd) tolerance was conducted to investigate the alleviating effect of zinc (Zn) on growth inhibition and oxidative stress caused by Cd. Treatments consisted of all combinations of two Zn concentrations (0.2 and 1 μM), three Cd concentrations (0, 1, and 5 μM), and two rice cultivars (Bing 97252, Cd‐tolerant; Xiushui 63, Cd‐sensitive). Cd toxicity caused a dramatic reduction in plant height and biomass, chlorophyll concentration and photosynthetic rate, and an increase in Cd concentration in both roots and shoots, malondialdehyde (MDA) concentration, and superoxide dismutase (SOD) and peroxidase (POD) activities in shoots. The response of all these parameters was much larger for Xiushui 63 than for Bing 97252. Addition of Zn to the medium solution alleviated Cd toxicity, which was reflected in a significant increase in plant height, biomass, chlorophyll concentration, and photosynthetic rate, and a marked decrease in MDA concentration and activity of anti‐oxidative enzymes. However, it was noted that Zn increased shoot Cd concentration at higher Cd supply, probably due to the enhancement of Cd translocation from roots to shoots. Therefore, further studies are necessary to determine the effect of Zn supply on Cd translocation from vegetative organs to grains or grain Cd accumulation before Zn fertilizer is applied to Cd‐contaminated soils to alleviate Cd toxicity in rice.