Rapid Propagation of Pteris vittata L.via Tissue Culture

[Objective] The study had developed a means of rapid propagation Pteris vittata L.by tissue culture. The species was a perennial fern belonging to the genus Pteris. [Metbed] The leaf bud of P. vittata collected in field conditions as explantsand the 1/2 MS ＋ 3% sucrose ＋ 0.7% agar as the basic medium were used to screen the medium formula of the phytohormone ratio for callus induction and subculture of P. vittata. [Result] The best medium formula for each step was list below： 1/2 MS ＋ 3% sucrose ＋ 0.7% agar ＋ 0.5 g/L PVP ＋ 0.1 mg/L KT ＋ 0.5 mg/L 2, 4-D for in- ducing the callus from explants; 1/2MS ＋ 3% sucrose ＋ 0.7% agar ＋ 0.5 g/L PVP ＋ 1.0 mg/L KT ＋ 0.01 mg/L 2,4-D for inducing the GGB from callus and the seedlings from GGB. In addition, 1/2 MS ＋ 3% sucrose ＋ 0.7% agar ＋ 0.5 g/L PVP ＋ 0.5 mg/L 2,4-D for the subculture could make the continued proliferation of callus. [Cen- clusioa] This study makes an applicable procedure by the direct use of field materi- als, for propagating P. vittata in a simplified and rapid mode.

Potential of Pteris vittata L. for phytoremediation of sites co-contaminated with cadmium and arsenic: The tolerance and accumulation

Field investigation and greenhouse experiments were conducted to study the tolerance of Pteris vittata L. （Chinese brake） to cadmium （Cd） and its feasibility for remediating sites co-contaminated with Cd and arsenic （As）. The results showed that P. vittata could survive in pot soils spiked with 80 mg/kg of Cd and tolerated as great as 301 mg/kg of total Cd and 26.8 mg/kg of diethyltriaminepenta acetic acid （DTPA）-extractable Cd under field conditions. The highest concentration of Cd in fronds was 186 mg/kg under a total soil concentration of 920 mg As/kg and 98.6 mg Cd/kg in the field, whereas just 2.6 mg/kg under greenhouse conditions. Ecotypes of P. vittata were differentiated in tolerance and accumulation of Cd, and some of them could not only tolerate high concentrations of soil Cd, but also accumulated high concentrations of Cd in their fronds. Arsenic uptake and transportation by P. vittata was not inhibited at lower levels （〈20 mg/kg） of Cd addition. Compared to the treatment without addition of Cd, the frond As concentration was increased by 103.8% at 20 mg Cd/kg, with the highest level of 6434 mg/kg. The results suggested that the Cd-tolerant ecotype of P. vittata extracted effectively As and Cd from the site co-contaminated with Cd and As, and might be used to remediate and revegetate this type of site.

Arsenic uptake and transport of Pteris vittata L.as influenced by phosphate and inorganic arsenic species under sand culture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in Ashyperaccumulator, uptake and transport of arsenate （As（V）） and arsenite （As（Ⅲ）） were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As（Ⅲ） more than As（Ⅴ）, while the reverse was observed at high concentrations of phosphate （≥1.0 mmol/L）. Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As（Ⅴ）. It may in part be due to competition between phosphorus and As（Ⅴ） during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As（Ⅲ）. Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposed to As（Ⅴ）, but the suppression of phosphate to As transport may be insignificant when P. vittata exposed to As（Ⅲ） under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.

Role of trichome of Pteris vittata L.in arsenic hyperaccu-mulation

Environmental scanning electron microscope(ESEM)fitted with an energy disper-sive X-ray microanalyzer(EDX)was used to investigate the surface micromorphology and arse-nic(As)micro-distribution in Chinese brake(Pteris vittata L.).It was found that amounts of trichome,which possessed multicellular structure with the average length of 160μm and with an average diameter of 28μm,existed in the frond of P.vittata,and the density of trichome on the pinnate axial surface was higher than that on the petiole.Visible X-ray peak of As was recorded in the epidermal cell and trichome.The relative weight of As in the pinnate trichome,which con-tained the highest concentration of As among all tissues of the plant,was 2.4 and 3.9 times as much as that in the epidermal and mesophyllous cells,respectively.The As concentrations in the basal and stalk cells of the same trichome were higher than that in its cap cell.This is the first time to report that the trichome of P.vittata plays an important role in arsenic hyperaccumulation.The finding from the present study implies that much attention should be paid to the role of the trichome in understanding the hyperaccumulation and detoxicity of As in the hyperaccumulator and improving the ability of As accumulation.

A combined process coupling phytoremediation and in situ flushing for removal of arsenic in contaminated soil

Phytoremediation and soil washing are both potentially useful for remediating arsenic（As）-contaminated soils.We evaluated the effectiveness of a combined process coupling phytoremediation and in situ soil flushing for removal of As in contaminated soil through a pilot study.The results showed that growing Pteris vittata L.（P.v.） accompanied by soil flushing of phosphate（P.v./Flushing treatment） could significantly decrease the total As concentration of soil over a 37 day flushing period compared with the single flushing（Flushing treatment）.The P.v./Flushing treatment removed 54.04% of soil As from contaminated soil compared to 47.16% in Flushing treatment,suggesting that the growth of P.vittata was beneficial for promoting the removal efficiency.We analyzed the As fractionation in soil and As concentration in soil solution to reveal the mechanism behind this combined process.Results showed that comparing with the control treatment,the percent of labile arsenate fraction significantly increased by 17% under P.v./Flushing treatment.As concentration in soil solution remained a high lever during the middle and later periods（51.26–56.22 mg/L）,which was significantly higher than the Flushing treatment.Although soil flushing of phosphate for more than a month,P.vittata still had good accumulation and transfer capacity of As of the soil.The results of the research revealed that combination of phytoremediation and in situ soil flushing is available to remediate As-contaminated soils.

蜈蚣草细胞壁对锑的吸附固定机制

蜈蚣草(Pteris vittata L.)是锑高富集植物,细胞壁是其吸收积累锑的重要场所。本研究利用细胞壁化学改性结合吸附实验和红外光谱学研究蜈蚣草细胞壁及其组分对锑的吸附特征,以及吸附固定锑的主要组分。吸附实验表明,在30 mg/L的锑溶液处理下,当吸附时长为100 min时根细胞壁中的锑含量已趋近于饱和,此时细胞壁中的锑含量是饱和吸附量的95%左右;在吸附实验进行450 min后,根细胞壁中的锑的含量达到饱和,饱和吸附量为25.01 mg/g。通过蜈蚣草细胞壁改性实验表明,果胶是细胞壁吸附固定锑的主要组分,降低果胶甲基酯化程度,吸附锑的效果会降低14.63%。此外,由傅立叶红外表征可知,在水培状态下胁迫蜈蚣草,胁迫浓度为40 mg/L为蜈蚣草根部的临界值,60 mg/L为蜈蚣草茎、叶部的临界值,当胁迫浓度超过此临界值时,蜈蚣草会受到一定的毒害作用,从而影响其正常的生理生化活动。通过研究细胞壁对锑的吸附固定机制,有利于进一步探究蜈蚣草亚细胞对锑的富集机理。