納米生物技術的新用途：肥料

發布日期：2009-11-12

核心提示：Carbon nanotubes find an unusual use as fertilisers Manure, compost and ash were used as fertilisers for centuries before the 1800s, but people did not understand how they worked until the science of chemistry was developed in the 19th century and i

Carbon nanotubes find an unusual use as fertilisers

Manure, compost and ash were used as fertilisers for centuries before the 1800s, but people did not understand how they worked until the science of chemistry was developed in the 19th century and it became clear that they supply plants with nitrogen, phosphorous and potassium. Today, something similar may be happening with a different sort of fertiliser altogether. For reasons that are not yet entirely clear, it looks as though exposing seeds to carbon nanotubes before they germinate makes the seedlings that subsequently sprout grow faster and larger.

A carbon nanotube is, as its name suggests, a tiny cylinder of carbon atoms. Such tubes have been proposed for all sorts of fancy uses, particularly in electronics, but they and other nanoparticles （so called because their dimensions are measured in nanometres, or billionths of a metre） have also been objects of concern. The fear is that if they became ubiquitous, they might damage living creatures, people included, by interfering with the way cells work.

In the case of plants, a few studies over the past decade have suggested that some nanoparticles can, indeed, breach the rigid walls that surround plant cells. Instead of viewing that as a threat, however, Mariya Khodakovskaya and Alex Biris of the University of Arkansas at Little Rock wondered if it might be an opportunity. They therefore considered the possibility of using nanoparticles to penetrate the tough coats that surround unsprouted seeds.

The reason for their interest was that these coats are something of a mixed blessing. They are there to protect the seed-and the germinating seedling-from desiccation and physical harm. They also, however, slow the absorption of nutrients when a seed eventually finds soil that is good enough to grow in. That is sensible for a wild seed, but unnecessary for a pampered cultivar. Nor is the reduction in initial growth something that even the finest fertilisers can get around.

But nanotubes, if Dr Khodakovskaya and Dr Biris are correct, may be able to. The researchers reasoned that if such tubes do penetrate conventional cell walls, they might also be able to pierce the even-tougher coat of a seed. That would let both water and dissolved nutrients in, and might promote rapid initial growth.

And so it proved. The researchers and their colleagues did the experiment on tomato seeds, germinating them in standard plant-growth medium that had been doped with nanotubes and comparing the result with seeds grown in undoped medium. As they report in ACS Nano, the seeds exposed to the nanotubes started to germinate within three days. The untreated seeds took six.

Moreover, this head start was reflected in subsequent growth. On the 27th day of the experiment, the researchers measured stem length, root-system length and the overall weight of the plants. The root systems were all the same, but the stems of the treated plants had an average length of 6cm, compared with 3.5cm for the untreated plants. The difference in weight was even greater. Treated plants weighed an average of more than 150 milligrams while untreated plants averaged 60 milligrams.

Whether this accelerated early growth was due only to penetration of the seed coat, or was a more complex phenomenon, is still unclear. Certainly, during the early days of germination, the treated seeds were absorbing nearly 50% more water （and thus nutrients） than the untreated ones. When the researchers looked at the seedling tissues under an electron microscope, however, they could see the nanotubes had actually entered living cells. They speculate that it is not just a question of letting more water into the seed, but also into the cells themselves. Possibly, the nanotubes are acting as analogues of the natural protein channels that pump water in and out of cells. As with conventional fertilisers before the 19th century, though, no one knows exactly how they do work.

Nor is it clear whether the early spurt of growth that Dr Khodakovskaya and Dr Biris have observed will translate into faster maturity or bigger crops. That remains to be seen in further experiments. And, crucially, it is not yet known if the nanotubes will find their way into the fruit of fully grown plants. Since this experiment shows that carbon nanotubes can, indeed, have significant effects on living organisms, that would be a good thing to find out.

碳納米管不同尋常的用途：肥料

在19世紀初期以前，人們使用糞、堆肥以及灰燼作為肥料已有很長的曆史了。但是，人們一直不明白這些肥料是如何起作用的，到19世紀化學科學發展起來以後，人們才弄清楚這些肥料為植物體提供了氮、磷、鉀jia這zhe些xie植zhi物wu成cheng長chang所suo需xu要yao的de營ying養yang元yuan素su。現xian在zai，類lei似si的de情qing況kuang可ke能neng正zheng在zai發fa生sheng，隻zhi不bu過guo這zhe一yi次ci是shi與yu一yi種zhong完wan全quan不bu同tong的de肥fei料liao有you關guan。在zai種zhong子zi發fa芽ya之zhi前qian，如ru果guo把ba種zhong子zi用yong碳tan納na米mi管guan處chu理li之zhi後hou，這zhe些xie後hou來lai發fa芽ya的de種zhong子zi幼you苗miao生sheng長chang得de更geng快kuai、更大，但是其中的原因目前還沒有完全弄清楚。

碳tan納na米mi管guan恰qia如ru其qi名ming字zi所suo揭jie示shi的de一yi樣yang，是shi由you碳tan原yuan子zi構gou成cheng的de一yi種zhong圓yuan柱zhu體ti。人ren們men認ren為wei碳tan納na米mi管guan會hui有you許xu多duo意yi想xiang不bu到dao的de用yong途tu，尤you其qi是shi在zai電dian子zi學xue領ling域yu，但dan是shi碳tan納na米mi管guan和he其qi它ta的de納na米mi粒li子zi（之所以稱之為納米粒子，是因為測量它們的大小是以納米為單位，一納米是10億分之一米）同(tong)時(shi)也(ye)讓(rang)人(ren)們(men)擔(dan)心(xin)，因(yin)為(wei)如(ru)果(guo)碳(tan)納(na)米(mi)管(guan)和(he)其(qi)它(ta)的(de)納(na)米(mi)粒(li)子(zi)變(bian)得(de)無(wu)處(chu)不(bu)在(zai)的(de)話(hua)，人(ren)們(men)害(hai)怕(pa)它(ta)們(men)會(hui)幹(gan)擾(rao)細(xi)胞(bao)的(de)正(zheng)常(chang)工(gong)作(zuo)，從(cong)而(er)會(hui)對(dui)生(sheng)物(wu)有(you)害(hai)，其(qi)中(zhong)也(ye)包(bao)括(kuo)對(dui)人(ren)不(bu)利(li)。

對dui於yu植zhi物wu來lai說shuo，過guo去qu十shi年nian裏li的de少shao數shu幾ji項xiang研yan究jiu表biao明ming，有you些xie納na米mi粒li子zi確que實shi能neng突tu破po圍wei繞rao在zai植zhi物wu細xi胞bao周zhou圍wei的de堅jian硬ying的de細xi胞bao壁bi。不bu過guo，來lai自zi阿e肯ken色se大da學xue小xiao石shi城cheng分fen校xiao的de（University of Arkansas at Little Rock） Mariya Khodakovskaya 和 Alex Biris認為這說不準也是一個好事。因此他們想到納米粒子有可能透過圍繞在不發芽種子周圍的堅硬外殼。

他們在這方麵的研究之所以有興趣是因為這些植物種子周圍的外殼的作用有好有壞。這些外殼能保護種子---以及正在發芽的幼苗---不bu失shi掉diao水shui分fen以yi及ji免mian於yu其qi它ta的de物wu理li上shang的de破po壞huai。不bu過guo在zai種zhong子zi最zui終zhong遇yu到dao適shi合he生sheng長chang的de土tu壤rang時shi候hou，這zhe些xie外wai殼ke減jian慢man了le種zhong子zi吸xi收shou營ying養yang的de速su度du。對dui於yu野ye生sheng種zhong子zi來lai說shuo，這zhe種zhong作zuo用yong是shi有you意yi義yi的de，但dan是shi對dui於yu莊zhuang稼jia用yong的de種zhong子zi而er言yan，這zhe種zhong作zuo用yong就jiu沒mei有you必bi要yao了le。而er且qie對dui於yu即ji使shi是shi最zui好hao的de肥fei料liao來lai說shuo，如ru果guo種zhong子zi在zai初chu期qi不bu能neng發fa芽ya成cheng長chang，它ta們men也ye無wu能neng為wei力li。

但是如果Khodakovskaya 和Biris博bo士shi的de研yan究jiu結jie果guo正zheng確que無wu誤wu的de話hua，那na麼me納na米mi管guan或huo許xu可ke以yi解jie決jue上shang述shu問wen題ti。研yan究jiu人ren員yuan們men推tui理li認ren為wei，如ru果guo碳tan納na米mi管guan的de確que能neng穿chuan透tou一yi般ban的de細xi胞bao壁bi的de話hua，那na麼me它ta們men或huo許xu也ye能neng穿chuan透tou更geng加jia堅jian固gu的de種zhong子zi外wai殼ke。這zhe樣yang的de話hua，水shui以yi及ji溶rong解jie在zai水shui中zhong的de營ying養yang物wu質zhi都dou能neng進jin入ru到dao種zhong子zi內nei部bu，從cong而er提ti高gao種zhong子zi在zai初chu始shi階jie段duan的de快kuai速su成cheng長chang。

上述想法得到了研究證實。Khodakovskaya 和Biris博bo士shi以yi及ji他ta們men的de同tong事shi們men對dui西xi紅hong柿shi種zhong子zi做zuo了le實shi驗yan，他ta們men讓rang西xi紅hong柿shi種zhong子zi在zai標biao準zhun的de植zhi物wu生sheng長chang環huan境jing中zhong發fa芽ya，然ran後hou對dui比bi在zai摻chan有you納na米mi管guan的de生sheng長chang環huan境jing下xia和he沒mei有you摻chan納na米mi管guan的de生sheng長chang環huan境jing下xia的de結jie果guo。他ta們men的de研yan究jiu結jie果guo發fa表biao在zai美mei國guo化hua學xue學xue會hui（ACS）雜誌《納米》（Nano）上。研究顯示在有碳納米管存在的環境中，種子在3天內就開始發芽了。在沒有碳納米管存在的環境中，種子6天後後才開始發芽。而且，發芽早的種子對隨後的生長也有利。在第二十七天的實驗中，研究者們測量了這些植物的幹莖長度、genxichangduyijizhenggezhiwudezhongliang。duibiliangzhongtiaojianxiadezhiwushengchangqingkuang，tamendegenxichangdushiyiyangde，danshishoudaotannamiguanchuliguodezhiwudepingjunganjingchangduwei6厘米，而沒有受到碳納米管處理過的植物的平均幹莖長度為3厘米。兩種條件下生長的植物的重量差別更大。受到碳納米管處理過的植物，其平均重量超過了150毫克，而沒有收到處理的植物的平均重量隻有60毫克。

種子的這種提早生長是否僅僅歸因於碳納米管對種子外殼的穿透、huozheshiyizhonggengweifuzadexianxiang，muqianrengranbudeerzhi。keyikendingdeshi，zaifayadeqianjitianli，shoutannamiguanchuliguodezhongziyaobimeiyouchuliguodezhongziduoxishoulejiangjin50%的水（因此也多吸收了近50%營養）.不(bu)過(guo)，當(dang)研(yan)究(jiu)者(zhe)們(men)在(zai)電(dian)子(zi)顯(xian)微(wei)鏡(jing)下(xia)觀(guan)察(cha)種(zhong)子(zi)幼(you)苗(miao)的(de)組(zu)織(zhi)的(de)時(shi)候(hou)，他(ta)們(men)發(fa)現(xian)碳(tan)納(na)米(mi)管(guan)實(shi)際(ji)上(shang)進(jin)入(ru)到(dao)了(le)活(huo)的(de)細(xi)胞(bao)中(zhong)。他(ta)們(men)推(tui)測(ce)，這(zhe)不(bu)僅(jin)僅(jin)是(shi)讓(rang)更(geng)多(duo)的(de)水(shui)進(jin)入(ru)到(dao)種(zhong)子(zi)中(zhong)的(de)問(wen)題(ti)，也(ye)關(guan)係(xi)到(dao)讓(rang)碳(tan)納(na)米(mi)管(guan)本(ben)身(shen)進(jin)入(ru)到(dao)細(xi)胞(bao)裏(li)麵(mian)的(de)問(wen)題(ti)。也(ye)許(xu)碳(tan)納(na)米(mi)管(guan)扮(ban)演(yan)著(zhe)和(he)天(tian)然(ran)蛋(dan)白(bai)質(zhi)通(tong)道(dao)類(lei)似(si)的(de)角(jiao)色(se)，這(zhe)些(xie)通(tong)道(dao)控(kong)製(zhi)著(zhe)水(shui)進(jin)出(chu)細(xi)胞(bao)。然(ran)而(er)，這(zhe)就(jiu)和(he)在(zai)19世紀之前人們對傳統肥料的認識一樣，沒有人確切知道它們是如何工作的。

Khodakovskaya 和 Dr Biris博士觀察到種子在早期有這種突飛猛進的生長，但是人們同樣也不知道這種"快長"是(shi)否(fou)導(dao)致(zhi)植(zhi)物(wu)早(zao)熟(shu)或(huo)者(zhe)作(zuo)物(wu)產(chan)量(liang)更(geng)高(gao)。這(zhe)還(hai)需(xu)要(yao)進(jin)一(yi)步(bu)的(de)實(shi)驗(yan)來(lai)證(zheng)實(shi)。關(guan)鍵(jian)是(shi)目(mu)前(qian)還(hai)不(bu)知(zhi)道(dao)這(zhe)些(xie)碳(tan)納(na)米(mi)管(guan)是(shi)否(fou)會(hui)進(jin)入(ru)成(cheng)熟(shu)植(zhi)物(wu)的(de)果(guo)實(shi)中(zhong)。因(yin)為(wei)Khodakovskaya 和 Dr Biris博(bo)士(shi)的(de)實(shi)驗(yan)表(biao)明(ming)，碳(tan)納(na)米(mi)管(guan)確(que)實(shi)能(neng)對(dui)生(sheng)物(wu)體(ti)有(you)顯(xian)著(zhe)的(de)影(ying)響(xiang)，如(ru)果(guo)能(neng)知(zhi)道(dao)碳(tan)納(na)米(mi)管(guan)是(shi)否(fou)會(hui)進(jin)入(ru)成(cheng)熟(shu)植(zhi)物(wu)的(de)果(guo)實(shi)中(zhong)的(de)話(hua)，這(zhe)將(jiang)是(shi)個(ge)了(le)不(bu)起(qi)的(de)發(fa)現(xian)。

Vocabulary:

Carbon Nanotube:碳納米管

Unusual:不同尋常的

Fertiliser:肥料

Manure:糞

Compost:堆肥

Nitrogen:（化學元素）氮

Phosphorous:（化學元素）磷

Potassium:（化學元素）鉀

Expose: 暴露；顯露

Germinate: 發芽

Seedling: 幼苗；秧苗