?A variety of corn from Oaxaca, Mexico, has aerial roots that harbor nitrogen-fixing bacteria, allowing the corn to suck nitrogen straight from the air. Christopher Intagliata reports.?墨西哥瓦哈卡(Oaxaca, Mexico)的許多種玉米都有氣生根,它們可以讓固氮細(xì)菌附著于上,這樣玉米就可以直接從空氣中吸收氮元素了。克里斯托弗·因塔利亞塔報(bào)道。 撰文\播音:克里斯托弗·因塔利亞塔(Christopher Intagliata) 翻譯:邱燕寧 審校:張清越
? Plants need three things to grow: air, water and nutrients. Farmers usually take care of the last bit by fertilizing their fields. But now scientists have found a type of corn that seems to thrive on air and water alone.? 植物需要三樣?xùn)|西才能生長:空氣、水和營養(yǎng)。為了保證最后一點(diǎn),農(nóng)民通常會給他們的田地施肥。但現(xiàn)在科學(xué)家們發(fā)現(xiàn)了一種玉米,它似乎只靠空氣和水就能茁壯成長。 "This has been sort of the holy grail, you know, if only I could grow corn and not put 200 pounds of nitrogen on it." Allen Van Deynze is a plant breeder at the University of California, Davis, and part of a team that analyzed this one corn’s unusual ability.? “如果我不用放200磅氮就能讓玉米茁壯生長,那簡直太好了。”Allen Van Deynze說。他是加州大學(xué)戴維斯分校的一名植物育種專家,也是一個研究小組的成員,該小組分析了這種玉米非同尋常的能力。 The corn variety hails from Oaxaca, Mexico, where it typically grows in nitrogen-poor soils. Nitrogen is needed for proteins, DNA and the chlorophyll that let plants perform photosynthesis. But the Oaxacan corn does well despite the bad soil, and with little or no fertilization.? 這種玉米來自墨西哥瓦哈卡,主要生長在氮貧瘠的土壤中。氮是蛋白質(zhì)、DNA和讓植物進(jìn)行光合作用的葉綠素所必需的。雖然土壤貧瘠,而且?guī)缀鯖]有施肥,但是瓦哈卡的玉米還是長得很好。 The plants pull off this trick via thick, red, aerial roots that protrude from its stem—above the ground—that ooze out a clear goo packed with sugars. That slime is the perfect habitat for nitrogen-fixing bacteria: a sugar-rich, oxygen-poor environment where the microbes transform nitrogen gas into a soluble form the corn plant can use. It’s an above-ground version of the nitrogen-fixation you might usually think of as happening in the underground roots of legumes, like peas and beans.? 植物通過從莖上伸出來的又厚又紅的氣生根系來解決這一難題。這種氣生根能夠滲出含糖的黏液,而這種黏液是固氮細(xì)菌的完美棲息地:這是一種含糖分高、含氧量低的環(huán)境,微生物可以在這里將氮?dú)廪D(zhuǎn)化為玉米植株可以利用的可溶性物質(zhì)。通常我們認(rèn)為固氮過程發(fā)生在豆類的地下根部,而這是一種地面上的固氮方式。 The researchers demonstrated the corn plants’ talent by exposing them to labeled isotopes of nitrogen. And they were able to track the movement of the distinctly identifiable nitrogen atoms from the air, to the root, and into the plant. This pathway allows the corn to obtain up to 80 percent of its nitrogen straight out of the air. The details are in the journal?PLOS Biology. [Allen Van Deynze et al.,?Nitrogen fixation in a landrace of maize is supported by a mucilage-associated diazotrophic microbiota] 研究人員通過將玉米暴露在標(biāo)記過的氮同位素中來展示和研究它們的這種能力。他們能夠追蹤到氮原子從空氣、到根部、到植物的運(yùn)動。玉米通過這一途徑直接從空氣中獲得80%的氮。詳情刊登在《PLOS Biology》雜志上。 Van Deynze says early plant breeders may have inadvertently got rid of corn’s nitrogen-fixing proficiency long ago. "When early man made some selections for bigger ears, higher yield, perhaps they lost this ability along the way. And we have the opportunity perhaps to bring it back." Van Deynze說,早期的植物育種家可能很久以前就在無意中拋棄了玉米的固氮能力。“早期人類在選擇大抽穗、高產(chǎn)量的過程中,它們可能使玉米失去了這種能力。我們或許有機(jī)會把它帶回來。”