Shengrong YAN，Hairong HUA，Yuequn ZHANG，Qing ZHOU

1.Department of Environment and Resource，Nantong College of Science and Technology，Nantong 226007，China；

2.Jiangsu R&D center for Engineering Technology of Preventing and Curing Rural Environmental Pollution，Nantong 226007，China；

3.College of Environment and Civil Engineering，Jiangnan University，Wuxi 214122，China

Study on Absorptive Capacity to Formaldehyde and Physiological and Biochemical Changes of Scindapsus aureus Based on the Regulation of LaCl3

Shengrong YAN1，2，Hairong HUA1，2，Yuequn ZHANG2，Qing ZHOU3*

1.Department of Environment and Resource，Nantong College of Science and Technology，Nantong 226007，China；

2.Jiangsu R&D center for Engineering Technology of Preventing and Curing Rural Environmental Pollution，Nantong 226007，China；

3.College of Environment and Civil Engineering，Jiangnan University，Wuxi 214122，China

［Objective］This study was to analyze LaCl3sprayed onto Scindapsus aureus on Chlorophyll content and plasmamembrane permeability of leaves of Scindapsus aureus，in order to determinate a suitable dosage ofLaCl3.［Method］With Scindapsus aureus as the test subject，110 households of 20 communities in the New District of Nantong were selected to investigate formaldehyde concentration in indoor air；and effect of LaCl3on absorptive capacity to formaldehyde of Scindapsus aureus was studied through fumigating in laboratory.Simultaneously，its physiological and biochemical mechanism of formaldehyde resistance was studied.［Result］The results showed that formaldehyde pollution of indoor air was serious in the New District of Nantong，and the degree of pollution was related to the time after decoration.The suitable concentration of LaCl3for Scindapsus aureus was 20 mg/L.The ability to absorb formaldehyde of Scindapsus aureus，which was calculated by per unit leaf area，was enhanced after spraying the suitable concentration of LaCl3by 19.75%.When Scindapsus aureus was stressed by formaldehyde，chlorophyll content decreased by 39.87%，membrane permeability and cumulative MDA amount increased by 8.17% and 56.92%，respectively，and POD activity increased by 11.32%.However，by comparing the group pre-sprayed with LaCl3and the group not sprayed with LaCl3under formaldehyde stress，chlorophyll content of Scindapsus aureus reduced lessly，membrane permeability and MDA both increased lessly，while POD activity increased more.［Conclusion］This study provides a new thinking direction for broadening of rare earth application and control measures of indoor air pollution.

LaCl3；Scindapsus aureus；Absorptive capacity to formaldehyde；Physiological and biochemical mechanism

W ith rapid development of Nantong economy and greatlyincreasing living standard of people，the expenses for decorating their new homes have been improved year by year，resulting in non-optimistic indoor formaldehyde pollution，while the latest literature about indoor formaldehyde pollution in newly-decorated houses in Nantong was reported in 2001［1］.Compared with 10 years ago，current situation is more severe. On this basis，we performed investigation and analysis on the indoor formaldehyde pollution in 2010 in New District of Nantong developing rapidly.

After field investigation and review of literatures，we found that indoor ornamental plants were adopted to absorb formaldehyde widely，but the in-door ornamental plants exhibited injury symptoms and invisible injury after facing high-concentration or long-term formaldehyde stress［2］.In view of the unique biological regulatory effect and successfulapplication in adversity stress including acid rain，ozone，heavy metal，pesticide pollution and UV-B radiation［3］，this study simulated indoor environment by formaldehyde fumigation （with concentration of 1.52 ppm，hereinafter referred to as FF），and studied the absorptive capacity to formaldehyde and physiological and biochemical changes of Scindapsus aureus on the basis of LaCl3regulation，aiming at providing new thinking direction for broadening of rare earth application and control measures of indoor air pollution.

Materials and Methods

Materials

Scindapsus aureus which is an ornamental plant usually adopted by local residents of Nantong was selected and purchased from a flower market of Nantong.Scindapsus aureus has the characteristics of low price，vigorous growth，and the same growing period，and is free of pest and disease damage.

Material treatment

Selection of suitable concentration of LaCl3sprayed onto Scindapsus aureus The LaCl3solution with a concentration of 100 mg/L was prepared and titrated.The solution was diluted to obtained gradient solutions with concentrations of 10，20，30，40 and 50 mg/L，respectively.The solutions were sprayed onto leaves of Scindapsus aureus with sprayers within the limit of dropping liquid，the control plants was sprayed with the same amount of distilled water，and each treatment and corresponding control were designed with replications，respectively.After 48 h，a suitable concentration was determined according to chlorophyllcontent and plasmamembrane permeability.

Combined treatment of LaCl3and formaldehyde Multiple cuboid formaldehyde fumigation boxes with lengths of 40 cm，widths of 40 cm and heights of 60 cm were fabricated with ordinary glass with a thickness of 5 mm，with glass plates as covers，each of which was provided with a sampling port with a diameter of 1 cm.In order to prevent formaldehyde from leaking，the covers and sampling ports were sealed with transparent adhesive tapes，and air tightness was detected with an air inflation method.Five μl of 30%formaldehyde solution was added into a culture dish disposed at the bottom of each box to allow natural volatilization at room temperature.It was found that formaldehyde volatilized completely within half an hour，forming an initial concentration of formaldehyde stress.

The LaCl3solution with selected concentration was sprayed onto leaves of the indoor ornamental plant，Scindapsus aureus within the limit of dropping liquid，and the control plants were sprayed with distilled water.After 48 h，the flower pots were wrapped with plastic films together with soil to only expose the vegetative parts，and the plants were transferred into the formaldehyde fumigation boxes to perform formaldehyde stress treatment.

Groupingofexperiments The plants were divided into three groups: the control group （CK），the FF group（formaldehyde stress），and the FF+La group（sprayed with LaCl3solution followed by formaldehyde stress）.

Determination methods

The treated Scindapsus aureus was exposed to formaldehyde in the fumigation boxes for 4 h continuously.After the formaldehyde stress，the formaldehyde concentrations in the air in the boxes were determined with a 4160-19.99 m type digital portable formaldehyde analyzer produced by America INTERSCAN company；leaf areas of plants were calculated according to paper-cut weighing method［4-5］to calculate the amountof formaldehyde absorbed by unit leaf area；and the leaves in the same direction at the same positions were determined for chlorophyll contents（Chl），plasmamembrane permeability，malondialdehyde contents （MDA）and peroxidase activity（POD）.Chlorophyll contents were calculated according to Arnon formula［6］，the plasmamembrane permeability was determined according to the method by Zou［7］，MDA contents were determined according to the method in reference［8］，and the POD activity was determined according to the method in reference［9］.

Statistical method

Significance analysis of difference wasperformedwithSAS9.1.3（P＜0.05）.

Results and Analysis

lnvestigation of indoor formaldehyde pollution in the New District of Nantong

To investigate formaldehyde concentration in indoor air，110 households of 20 communities in the New District of Nantong were selected；and among them，50 households finished the decoration within half a year，the decoration of 30 households was finished 6 months to 3 years ago，and the decoration of the rest was finished earlier than above mentioned households. The result showed that in the 100 investigated households，the over standard rate of indoor formaldehyde was 24.5%，with the concentrations in the range of 0.01-0.54 mg/m3；the households had their decoration finished 3 years ago exhibited an over standard rate of indoor formaldehyde of 6.6%，with the concentrations in the range of 0.01-0.10 mg/m3，and the highest concentration being 1.25 times of the standard；the households had their decoration finished 6 months to 3 years ago showed an over standard rate of indoor formaldehyde of 13.3%，with the concentrations in the range of 0.03-0.23 mg/m3，and the highest concentration being 2.88 times of the standard；and the households had their decoration finished within 6 months exhibited an over standard rate of 42.0%，with the concentrations in the ranges of 0.03-0.54 mg/m3，and the highest concentration being 6.78 times of the standard.It was thus clear thatthe households finished their decoration within 6 months suffered the severest indoor formaldehyde pollution.

Selection of suitable LaCl3dosage to be sprayed onto Scindapsus aureus

Rare earth elements are chemical elements with physiological activity，a proper amount of which sprayed onto plants could affect the external morphology and growing development of plants，facilitating the increase of plant biomass，and in addition，rare earth el-ements have the effects of maintaining the permeability and stability of cytomembranes，improving the protection function of cytomembranes，and enhancing oxidase activity during metabolic process and the resistance of plants to harsh environments.The success of application of rare earth elements to plants depends on whether the dosage is proper，i.e.，a proper dosage is favorable，and a too-high dosage is harmful.Generally，the applied dosage is related to application manner，plant cultivar，plant growth stage，soil environment and so on［10］.

In order to select a LaCl3concentration suitable for the regulation of physiological function of Scindapsus aureus according to chlorophyll contents and plasmamembrane permeability，the solutions with concentrations of 10，20，30，40 and 50 mg/L were prepared.As shown in Fig.1，within the dosage range of 0-20 mg/L，the chlorophyll content of Scindapsus aureus exhibited an increasing trend with the increase of LaCl3dosage；and within the dosage range of 20-40 mg/L，the chlorophyllcontent of Scindapsus aureus exhibited an decreasing trend with the increase of LaCl3dosage.The statistical analysis showed that the chlorophyll content of the Scindapsus aureus sprayed with 20 mg/L LaCl3was significantly different with those of other dosage groups（P＜0.05），and 20 mg/L LaCl3greatest improved the chlorophyll content of Scindapsus aureus.Fig.2 showed that after spraying LaCl3，the 10 mg/L and 20 mg/L dosage groups less affected the plasmamembrane permeability of Scindapsus aureus，while the 30 mg/L and 40 mg/L dosage groups improved the plasmamembrane permeability of Scindapsus aureus instead.The statisticalanalysis showed that the Scindapsus aureus of the 0 mg/L，10 mg/L and 20 mg/L dosage groups had the plasmamembrane permeability different with that of the 30 mg/L and 40 mg/L dosage groups （P＜0.05）. Therefore，20 mg/L LaCl3was determined as the suitable concentration for Scindapsus aureus taking chlorophyll content into consideration.

Effect of LaCl3on absorptive capacity to formaldehyde of Scindapsus aureus

As described above，rare earth elements serves as a kind of growth regulatory substance currently，and the application of rare earth elements in a proper amount is beneficial to the growing development in that they can promote the physiological activity of plants and related biochemical reaction.In order to investigate whether LaCl3can improve the absorptive capacity to formaldehyde of Scindapsus aureus，we studied the effect of LaCl3on the absorptive capacity to formaldehyde of Scindapsus aureus under formaldehyde stress on the basis of the determined suitable LaCl3dosage for Scindapsus aureus.As shown in Table 1，after formaldehyde fumigation，the amount of formaldehyde absorbed by unit Scindapsus aureus leaf area of the FF+La group was improved by 19.75%compared with that of the FF group （P＜0.05），indicating that the absorptive capacity to formaldehyde of Scindapsus aureus was enhanced after the pretreatment with 20 mg/L LaCl3.

Table 1 Effect of LaCl3on absorptive capacity to formaldehyde of Scindapsus aureus

Table 2 Effect of LaCl3on physiological and biochemical indexes of Scindapsus aureus under formaldehyde stress

Effect of LaCl3on physiological and biochemical indexes of Scindapsus aureus under formaldehyde stress

It has been reported that indoor ornamental plants could absorb polluting gases including formaldehyde by many researches both at home and abroad.However，when facing highconcentration formaldehyde stress and long-term continuous exposure to formaldehyde， indoor ornamental plants exhibit injury symptoms and invisible injury.How to alleviate the injury in indoor ornamentalplants caused by formaldehyde stress to thereby give play to their formaldehyde reduction effect is an urgent problem to be solved.On the basis of former section，this study investigated the effects of LaCl3on physiological and biochemical indexes including chlorophyll content，plasmamembrane permeability，MDA content and POD activity of Scindapsus aureus under formaldehyde stress，to further expound the internal mechanism of LaCl3in alleviat-ing the injury of formaldehyde stress to plants.

The data in Table 2 showed that after the formaldehyde stress compared with CK，chlorophyll content decreased by 39.87%，membrane permeability and MDA concentration increased by 8.17%and 56.92%，respectively，and POD activity increased by 11.32%.These results indicated that Scindapsus aureus has suffered oxidative stress.Though POD activity increased under stress，active oxygen exhibited disequilibrium metabolism and accumulated，which triggered membrane lipid peroxidation，resulting in increased plasmamembrane permeability and MDA content and decreased chlorophyll content.

Under formaldehyde stress，the Scindapsus aureus subjected to pretreatmentwith LaCl3exhibited a chlorophyll content lower than CK but higher than the FF treatment group；its plasmamembrane permeability and MDA content were lower than CK but higher than the FF group；and the POD activity was higher than the FF group.It was thus clear that LaCl3could increase the chlorophyll content，improve the POD activity to accelerate removal of reactive oxygen and thereby decrease plasmamembrane electrolyte leakage and MAD content，effectively alleviating the injury of active oxygen to cytomembrane system.

Discusson

（1）In all monitored households，the overstandard rate ofindoor formaldehyde concentration was 24.5%，and especially，the households finished their decoration within 6 months exhibited an over standard rate up to 42.0%，with the greatest concentration being 6.78 time of the standard， indicating the indoor formaldehyde concentration in the New District of Nantong was severer and numerous residents（especially for the susceptible population including old people，infants and patients）have long faced the threat of formaldehyde. In addition，the households having their decoration finished 3 years ago also exhibited an over standard rate of indoor formaldehyde concentration up to 6.6%，indicating that the release of formaldehyde was a long slow process.To solve the problem of indoor formaldehyde pollution，other methods should be applied besides ventilation，such as usage of indoor ornamental plants for absorbing formaldehyde，to thereby ensure public health.

（2）According to both the indexes ofchlorophyllcontentand plasmamembrane permeability，20 mg/L LaCl3was selected as a suitable concentration.The following experiments about the effects of LaCl3on the absorptive capacity to formaldehyde and physiological and biochemical indexes of Scindapsus aureus both adopted this determined concentration.

（3）After the application of LaCl3with the suitable concentration，the ability of Scindapsus aureus to absorb formaldehyde，which was calculated by per unit leaf area，was enhanced by 19.75%.

（4）After formaldehyde fumigation，Scindapsus aureus exhibited decreased chlorophyllcontents，increased membrane permeability，and increased cumulative MDA amount and POD activity，indicating that Scindapsus aureus was injured by formaldehyde stress.LaCl3could enhance the resistance of Scindapsus aureus to formaldehyde stress by increasing chlorophyll content，improving POD activity，and decreasing plasmamembrane permeability and MDA content.

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Responsible editor：Yingzhi GUANG

Responsible proofreader：Xiaoyan WU

基于LaCl3調(diào)控作用下綠蘿凈化甲醛能力及生理生化變化研究

閆生榮1，2，花海蓉1，2，張躍群2，周青3*（1.南通科技職業(yè)學院環(huán)境與資源系，江蘇南通226007；2.江蘇省農(nóng)村環(huán)境污染防治工程技術(shù)研究開發(fā)中心，江蘇南通 226007；3.江南大學環(huán)境與土木工程學院，江蘇無錫214122）

［目的］分析噴施稀土LaCl3對綠蘿葉片葉綠素含量和質(zhì)膜透性的影響，進而確定綠蘿噴施LaCl3的適宜劑量。［方法］以室內(nèi)觀賞植物綠蘿作為受試對象，對南通市新城區(qū)20個居民小區(qū)共110家住戶，進行入戶調(diào)查與檢測空氣中甲醛污染狀況；采用熏蒸法考察LaCl3對甲醛脅迫下室內(nèi)觀賞植物綠蘿降醛能力的影響，并研究其甲醛抗性的生理生化機制。［結(jié)果］研究結(jié)果表明，南通市新城區(qū)居室空氣甲醛污染較為嚴重，污染程度與裝修后時間長短有關(guān)；綠蘿噴施LaCl3的適宜濃度為20 mg/L；在噴施適宜濃度LaCl3之后，室內(nèi)觀賞植物綠蘿單位葉面積吸收甲醛能力有所增強，提升幅度為19.75%；甲醛脅迫下，綠蘿葉綠素含量降低了39.87%，質(zhì)膜透性和MDA累積量分別增加了8.17%、56.92%，POD活性升高了11.32%；經(jīng)LaCl3預處理后，較甲醛脅迫組，綠蘿葉綠素含量降幅與質(zhì)膜透性、MDA濃度增幅均變小，而POD活性增幅變大。［結(jié)論］該研究為稀土應用拓展及室內(nèi)空氣污染防治對策提供了新的思考方向。

LaCl3；綠蘿；凈化甲醛能力；生理生化機制

江蘇省高?！扒嗨{工程”優(yōu)秀青年骨干教師培養(yǎng)對象資助項目（蘇教師〔2010〕27號）；江蘇省2014年高等學校大學生實踐創(chuàng)新訓練計劃項目（蘇教辦高〔2014〕8號）；江蘇省農(nóng)村環(huán)境污染防治工程技術(shù)研究開發(fā)中心資助項目（蘇教科〔2011〕13號）；南通市科技計劃資助項目（HS2014025）、南通市首批生態(tài)建設(shè)小額資助項目（通環(huán)〔2014〕33號）。

閆生榮（1981－），男，江蘇如皋人，副教授、碩士研究生，主要從事空氣污染防治、稀土環(huán)境生態(tài)效應的研究，E-mail：sofjnhqu@sina.com。*通訊作者，E-mail：zhouqeco@yahoo.com.cn。

2015-08-21

Supported by Qing Lan Project for Outstanding Young Teachers in Higher Education Institutions of Jiangsu Province（SJS［2010］27）；College Students’Innovative Entrepreneurial Training Program of Jiangsu Province in 2014（SJBG［2010］8）；Funding Project for Rural Environment Pollution Control Engineering and Technological Research Center of Jiangsu Province（SJK［2011］13）；Funding Project of Science and Technology Plan in Nantong City （HS2014025）；First Petty Funding Project for Ecological Construction of Nantong City（TH［2014］33）.

*Corresponding author.E-mail:zhouqeco@yahoo.com.cn

Received:August 21，2015 Accepted:October 19，2015

修回日期 2015-10-19