Variation in cadmium accumulation and translocation among peanut cultivars as affected by iron deficiency

Purpose

The current study aimed to test the hypothesis that the variations in shoot Cd accumulation among peanut cultivars was ascribed to the difference in capacity of competition with Fe transport, xylem loading and transpiration.

Methods

A hydroponics experiment was conducted to determine the plant biomass, gas exchange, and Cd accumulation in Fe-sufficient or -deficient plants of 12 peanut cultivars, at low Cd level (0.2 μM CdCl₂).

Results

Peanut varied among cultivars in morpho-physiological response to Cd stress as well as Cd accumulation, translocation and distribution. Qishan 208 and Xvhua 13 showed a higher capacity for accumulating Cd in their shoots. Fe deficiency increased the concentration and amount of Cd in plant organs, but decreased TF _{root to shoot} and TF _{root to stem}, while TF _{stem to leaf} remained unaffected. Fe deficiency-induced increase rates of Cd concentration and total Cd amount in roots and leaves were negatively correlated with the values in Fe-sufficient plants. Transpiration rate was positively correlated with leaf Cd concentration, TF _{root to shoot}, TF _{root to stem} and TF _{stem to leaf}.

Conclusions

The difference in shoot Cd concentration among peanut cultivars was mainly ascribed to the difference in Fe transport system, xylem loading capacity and transpiration.     

Effects of cadmium and salicylic acid on growth, spectral reflectance and photosynthesis of castor bean seedlings

Salicylic acid (SA) is a potent signaling molecule in plants and is involved in eliciting specific responses to biotic and abiotic stresses. The aim of this study is to investigate whether the exogenous application of SA can improve cadmium (Cd) induced inhibition of photosynthesis in castor bean (Ricinus communis L.) plants. The effects of SA and Cd on plant growth, spectral reflectance, pigment contents, chlorophyll fluorescence and gas exchange were examined in a hydroponic cultivation system. Results indicate that Cd exposure significantly decreased the dry biomass, photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), pigment contents, quantum yield of PS II photochemistry (F_v/F_m), and effective quantum yield of PS II (??PS II) in the plants. Pretreatment with SA alone reduced the biomass and P_n in castor bean plants, whereas pigment contents, F_v/F_m and ??PS II remained unaffected. Reduced G_s, C_i and E, as well as increased stomatal limitation (L_s) and water use efficiency (WUE), were observed in plants pretreated with 500???M SA alone, whereas plants treated with 250???M SA were unaffected. Under Cd stress, SA pretreatment led to a significant decrease in P_n, G_s, E, C_i, and chlorophyll contents (Chl a, Chl b, Chl a+b, Car, Chl a/b), and an increase in L_s and WUE. Cd exposure enhanced spectral reflectance in the range 550?C680?nm and 750?C1,050?nm. It also decreased the normalized difference vegetation index (_chlNDI), the modified red edge simple ratio index (mSR₇₀₅), the red edge position (REP), water band index, and red/green ratio, whereas the structure independent pigment index (SIPI) was increased. Significant correlations (P?<?0.01) between spectral indices (mSR₇₀₅, _chlNDI, REP, red/green ratio) and pigment contents. SA significantly worsened plant growth and photosynthesis in Cd-stressed castor bean plants, in which a stomatal limitation was involved. The leaf spectral reflectance is a sensitive indicator in determining Cd toxicity in plants.     

植物根系分泌物的生态效应

根系分泌物是在一定的生长条件下 ,活的且未被扰动的根系释放到根际环境中的有机物质的总称 ,在植物主动适应和抵御不良环境中具有重要作用 :(1)通过化感作用影响根际微生物和周围其它植物的生长 ,并进一步改善植物的生态环境 (生物因素 ) ;(2 )通过对土壤中矿质元素的溶解、螯合作用、迁移和活化等作用 ,不仅在营养缺乏的情况下提高矿质营养元素的有效性 ,而且在面临重金属胁迫时能降低根际中金属污染物的活性 ,减少植物对金属的吸收。根系分泌物在植物与环境的相互作用中起着传递信息的作用     

Silicon alleviates cadmium toxicity in peanut plants in relation to cadmium distribution and stimulation of antioxidative enzymes

Silicon (Si) is generally considered a beneficial element for the growth of higher plants, especially for those grown under stressed environments. Recently, the mitigating role of Si in cadmium (Cd) stress has received some attention. However, its mechanisms involved remain poorly understood. We studied the effects of Si on tissue and subcellular distribution of Cd, as well as the activities of major antioxidant enzymes (SOD, POD and CAT) with two contrasting peanut (Arachis hypogaea L.) cultivars (Luhua 11 and Luzi 101) differing in their Cd tolerance. The results showed that Cd exposure alone depressed plant growth and caused oxidative stress for both cultivars, and this toxicity was more obvious in Cd-sensitive cultivar (Luhua 11) than in Cd-tolerant cultivar (Luzi 101). Si supply significantly alleviated the toxicity of Cd in peanut seedlings; this was correlated with a reduction of shoot Cd accumulation, an alteration of Cd subcellular distribution in leaves, and a stimulation of antioxidative enzymes. The mechanisms of Si amelioration of Cd stress were cultivar and tissue dependent. For Luhua 11, Si-mediated inhibition of Cd transport from roots to shoots, reduction of Cd content in cell organelle fractions of leaves, and enhancement of the SOD, POD and CAT activities in roots, might responsible for the role of Si in alleviating Cd toxicity. For Luzi 101, Si alleviation of Cd toxicity is mainly attributed to the decrease in Cd concentration in shoot and stimulation of antioxidants systems.     

142例支气管肺泡灌洗液真菌免疫荧光染色检测结果与G/GM试验结果对比分析

目的探讨真菌免疫荧光染色检测支气管肺泡灌洗液(brondioalveolar lavage fluid,BALF)在肺部真菌感染诊断中的意义。方法对2019年1月至12月送检至本所的142例BALF标本进行G/GM试验及真菌免疫荧光染色检测。结果142例BALF中免疫荧光染色检测阳性为52例(占36.62%),G试验同时阳性者为49例,GM试验同时阳性者为11例。免疫荧光染色检测阳性例数与KOH湿片镜检阳性27例(占19.01%)比较检出率明显提高。结论真菌免疫荧光染色检测作为一种快速方便高效直观的真菌常规检测方法,是BALF标本中真菌检测的1个重要补充,为临床肺部真菌感染的诊断提供了1种快速检测方法。     

Leaf responses to iron nutrition and low cadmium in peanut: anatomical properties in relation to gas exchange

Aims

This study evaluated how iron nutrition affect leaf anatomical and photosynthetic responses to low cadmium and its accumulation in peanut plants.

Methods

Seedlings were treated with Cd (0 and 0.2 μM CdCl₂) and Fe (0, 10, 25, 50 or 100 μM EDTA-Na₂Fe) in hydroponic culture.

Results

Cadmium accumulation is highest in Fe-deficient plants, and dramatically decreased with increasing Fe supply. The biomass, gas exchange, and reflectance indices were highest at 25 μM Fe²⁺ treatments, indicating the concentration is favorable for the growth of peanut plants. Both Fe deficiency and Cd exposure impair photosynthesis and reduce reflectance indices. However, they show different effects on leaf anatomical traits. Fe deficiency induces more and smaller stomata in the leaf surface, but does not affect the inner structure. Low Cd results in a thicker lamina with smaller stomata, thicker palisade and spongy tissues, and lower palisade to spongy thickness ratio. The stomatal length and length/width ratio in the upper epidermis, spongy tissue thickness, and palisade to spongy thickness ratio were closely correlated with net photosynthetic rate, stomatal conductance, and transpiration rate.

Conclusions

Cd accumulation rather than Fe deficiency alters leaf anatomy that may increase water use efficiency but inhibit photosynthesis.     

Peanut as a potential crop for bioenergy production via Cd-phytoextraction: A life-cycle pot experiment

Aims

The current study aimed to assess the potential of peanut (Arachis hypogaea L.) for bioenergy production via phytoextraction in cadmium (Cd) -contaminated soils and screen appropriate cultivars for this approach.

Methods

A life-cycle pot experiment was conducted to determine the biomass, seed yield, oil content and Cd accumulation of seven peanut cultivars under Cd concentration gradients of 0, 2, and 4 mg kg^?1.

Results

Peanut exhibits genotypic variations in Cd tolerance, seed production, oil content, and Cd accumulation. Exposure of plants to 2 and 4 mg kg^?1 Cd did not inhibit shoot biomass, seed yield, and oil content for most of the cultivars tested. There are large amounts of Cd accumulated in the shoots. Although the seed Cd concentration of peanut was relatively high, the Cd concentration in seed oils was very low (0.04-0.08 mg kg^?1). Among the cultivars, Qishan 208 showed significant Cd tolerance, high shoot biomass, high pod and seed yield, high seed oil content, considerable shoot Cd concentration, and the largest translocation factor and total Cd in shoots.

Conclusions

The cultivation of peanut in Cd-contaminated farmland was confirmed to be feasible for bioenergy production via phytoextraction, and Qishan 208 is a good candidate for this approach.     

Cadmium-induced alterations in morpho-physiology of two peanut cultivars differing in cadmium accumulation

This study examines differences in the morpho-physiological responses of low- and high-cadmium (Cd) accumulating peanut (Arachis hypogaea L.) cultivars to Cd stress. The biomass, Cd accumulation, leaf gas exchange, root morphology, root respiration, and hydraulic conductivity of Qishan 208 (low-Cd accumulator) and Haihua 1 (high-Cd accumulator) were determined via a hydroponic experiment. Exposure of peanut plants to 2 and 20 μM Cd considerably decreased their shoot biomass, net photosynthetic rate, transpiration rate, stomatal conductance, total root length, number of root tips, root respiration, and hydraulic conductivity. The root biomass, root surface area, and average diameter were unaffected by Cd exposure. The two cultivars differed in Cd accumulation and morpho-physiological responses to Cd stress. Qishan 208 accumulated less Cd in plant tissues but was more sensitive to Cd stress than Haihua 1. The total root length, surface area, average diameter, number of root tips, and root respiration rate of Haihua 1 were significantly higher than those of Qishan 208. The well-developed root system and higher root respiration of Haihua 1 may be responsible for its high Cd accumulation capacity.     

Differential Responses of two Bamboo Species (Phyllostachys Auresulcata `Spectabilis' and Pleioblastus Chino `Hisauchii') to Excess Copper

Pot experiments were carried out to examine the responses of growth, physiological properties, copper (Cu) absorption and translocation in two bamboo species, Phyllostachys auresulcata ‘Spectabilis’ and Pleioblastus chino ‘Hisauchii’ Two-year old plants with similar size were exposed to excess Cu treatments, in order to demonstrate their Cu tolerance and potential ability of phytoremediation under Cu-polluted soil as biofuel feedstock. Pots were irrigated with aqueous solutions of Cu in concentrations of 500, 1000 and 2000 mg CuSO₄·5H₂O kg^?1, against the control (tap water). Plant growth, chlorophyll contents, photosynthesis rate, malondialdehyde (MDA) content, Cu concentrations in leave, stem and root, and Cu contents in shoot per pot were measured after transplanted plants were grown under excess Cu treatments for 60 days. Two bamboo species had different responses to tolerance and allocation of supplied Cu. As Cu treatments rose, the percentage of senescent shoot and MDA content increased, and the chlorophyll content and photosynthetic capacity decreased. Such changes in Hisauchii were more obvious than in Spectabilis. However, number of emerged shoots did not differ between the two species across four Cu treatments. In the efficiency of decontamination, Hisauchii was more effective than Spectabilis, since either the Cu concentrations in leaves, stems and roots or Cu contents in shoot per pot in Cu treatments from 500 to 2000 mg?kg^?1 were higher in Hisauchii than in Spectabilis It is suggested that the potential capability of absorbing Cu might cause the different response to cu stress between the two bamboo species. Both bamboo species can be considered to exhibit enough potential to develop in Cu-polluted areas of China as bioenergy resources and phytoremediation plants.     

Leaf plasticity in peanut (Arachis hypogaea L.) in response to heavy metal stress

Phenotypic plasticity in morphological, anatomical and physiological traits of peanut (Arachis hypogaea L.) leaves was tested at four different concentrations of Cd, Cu and Zn under greenhouse conditions. Among 18 characteristics tested, nine were found to be the most sensitive and demonstrate the greatest phenotypic plasticity. These were: the leaf area (LA), the leaf mass per area (LMA), chlorophyll a concentration (Chl a), chlorophyll b concentration (Chl b), total chlorophyll concentration (Chl t), the effective quantum yield of photosystem II (ΦPS II), stomatal density of upper epidermis (SDU), palisade thickness (PT), and palisade to spongy thickness ratio (P/S). The plasticity of chlorophyll concentration and fluorescence parameters may be maladaptive and reflects metal toxicity to leaves, whereas the anatomical plasticity is adaptive, indicative of a tradeoff between the physiological and anatomic plasticity. The anatomical plasticity resulted in a xerophyte feature of leaves (i.e. small leaflets, thick lamina, upper epidermis, palisade mesophyll, as well as abundant and small stomata), which enhanced the capacity to resist drought caused by heavy metals via a decrease in root growth.