By Henry Fountain PETERSHAM, Massachusetts – Not every scientist would choose to spend a peaceful summer Sunday morning perched on a jittery scaffold 12 meters up a red oak tree, peering through a microscope to jab a leaf with a tiny glass needle filled with oil.
並不是每一位科學家都會選擇在一個平靜的夏日早晨，站在高12公尺、靠著一棵紅橡樹的搖搖晃晃的架子上，透過顯微鏡以一根注滿油的細小玻璃針戮刺一片樹葉。
But Michael Knoblauch, a plant cell biologist at Washington State University, is nearing the end of a 20-year quest to prove a hypothesis about how nutrients are transported in plants. He is also nearing the end of a sabbatical year, much of which he has spent here at Harvard Forest, a 1,400-hectare research plot in Massachusetts.
然而，華盛頓州立大學的植物細胞生物學家諾布勞奇即將完成一項長達20年的研究，證明一項有關植物如何輸送養分的假設。他同時即將結束一個休假年。在這段期間，他把許多時間花在占地1400公頃的麻州實驗林「哈佛森林」。
Proving the hypothesis would be far more than an academic exercise. Fully understanding how plants function – how they circulate the sugars made in the leaves – could lead to improvements in crop yields or resistance to pests and disease.
證明這項假設，絕不只是為了學術研究。徹底瞭解植物如何運作（如何輸送在葉子製造的糖），可能有助於提高農作的產量或對害蟲與疾病的抵抗力。
So he found himself up in the tree on a recent Sunday, accompanied by his 19-year-old son, Jan. While his son monitored the image from the microscope on a laptop, Dr. Knoblauch fiddled with a device that held the glass needle.
因為如此，他最近一個周日在19歲的兒子詹恩陪伴下，爬到樹上。詹恩透過一台筆電監控來自顯微鏡的影像時，諾布勞奇撥弄一個固定玻璃針的裝置。
The tip of the glass needle is delicate and tiny and has to be impaled in a specific kind of cell. Even though the microscope sits on a device that senses the vibrations and counteracts them, Dr. Knoblauch remains as motionless as possible.
玻璃針的尖端很精細微小，而且必須刺穿特定種類的細胞。雖然固定顯微鏡的裝置可以察覺震動並予以反制，諾布勞奇還是盡可能保持不動。
He and his son hoped to make at least one successful measurement of the pressure inside the long tubes of living cells, called phloem, that deliver the sugars produced by photosynthesis in the leaves through the branches and the trunk to fruits and roots.
他們父子希望，至少可以成功測量名為韌皮部的活體細胞長管內的壓力。韌皮部負責將樹葉光合作用製造的糖經由枝幹輸送到果實與根部。
The glass needle acts something like a tire gauge: When it punctures the cell wall, the pressure of the water inside instantly compresses the oil in the needle by a tiny amount. Dr. Knoblauch then uses before and after images to calculate the amount of compression, and thus determine the pressure.
玻璃針的作用有如輪胎胎壓測量器。當它刺穿細胞壁時，內部水的壓力會立刻微量壓縮玻璃針內的油。接著，諾布勞奇比較前後的影像估算壓縮的量，據以估計壓力。
Dr. Knoblauch spent more than three years in his laboratory developing the needles, which he calls picogauges because they contain less than 100 picoliters of oil. (The oil from about 50 million picogauges would fill a teaspoon.) And it's just one of several techniques he has devised to test the hypothesis that what drives the flow of nutrients in the phloem is pressure differential.
諾布勞奇以三年多的時間在他的實驗室開發這種玻璃針。他稱它皮升計量器，因為它只含不到100皮升的油（約五千萬個皮升計量器的油才能注滿一個茶匙）。為驗證促使韌皮部養分流動的力量來自壓力差異的假設，他開發了數項技術，這是其中之一。
That hypothesis was developed in 1930 by a German plant physiologist, Ernst Munch, and it has been widely accepted because it makes sense: The nutrients should flow from areas with higher pressure (the leaves, where sugars are added) to areas with lower pressure (the roots and fruits, where sugars are taken out).
德國植物生理學家蒙克1930年首次提出這項假設，此後獲學術界認同，因為它言之成理：養分應該自壓力較高部位（糖分增加所在的葉子）流向壓力較低部位（糖分抽出所在的根部與果實）。
"If you can figure out what the plant does to allocate its resources on a 24-hour basis, then you can think about all sorts of changes in yield," said William J. Lucas, a plant biologist at the University of California, Davis. "The future in terms of population and food security lies in us getting a thorough understanding of this."
戴維斯加州大學植物生物學家路卡斯說：「如能釐清植物如何全天候分配它的資源，你一定可以思索農作產量的各種變化。人口與糧食安全的未來繫於我們能否徹底瞭解其中原理。」
Over the decades, there have been many attempts to test the Munch hypothesis, but definitive proof has eluded researchers. With the human circulatory system, pressure measurements are easy because there are blood vessels near the skin, and everything is elastic. But the phloem is found in the tree, and is more rigid.
數十年來科學家多次嘗試驗證蒙克提出的假設，卻始終找不到確切證據。以人體的循環系統而言，壓力很容易測量，因為血管位於皮膚附近，而且每個部位都有彈性。然而樹木的韌皮部位於它的內部，而且比較堅硬。
"You can't get to it," Dr. Lucas said. "And generally, anybody who tried to get to it destroyed the system."
路卡斯博士說：「我們無法接觸到韌皮部。大致而言，曾經試圖接觸韌皮部的科學家最後都把整個系統給毀了。」
Dr. Knoblauch's gauges are so small and the measurement is made so quickly that any damage to the system is slight.
諾布勞奇博士的計量器很小，測量也很快。這使整個系統只受輕微損傷。
But things can go wrong. During his sabbatical, Dr. Knoblauch said, he had spent about five months "optimizing the system," which is shorthand for trying to figure out how to avoid all the ways measurements could be foiled. The work is so trying that he and his son had gotten fewer than 20 valid pressure measurements in the oak.
然而事情可能搞砸。諾布勞奇說，在他的休假年期間，他以大約五個月的時間「盡量改善系統」，亦即設法想出避免測量失敗的方法。由於這個過程很麻煩，他和兒子最後只能有效測量橡樹壓力不到20次。
But he has also worked with a morning glory vine that he hauls inside to make the measurements in the calm of the lab. The oak measurements, combined with pressure measurements from the morning glory (as well as other data, like phloem cell diameters and flow rates), should be enough to come to a conclusion.
他還曾經在安靜的實驗室測量一種牽牛花藤。橡樹與牽牛花藤的壓力測量（還有其他相關資料，例如韌皮部細胞的直徑與流動率）應該足以達成結論。
"In about half a year, we will have all the data to say whether Munch is right or wrong, finally and definitively," he said.
他說：「大約半年內，我們就會握有各項必要資料，據以最終斷定蒙克是對還是錯。」
He's still cautious, Dr. Knoblauch said, "but now it's looking like he was right."
諾布勞奇說，他還是很審慎，「不過目前看來，他（蒙克）是對的」。
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