花怎么知道什么时候该开？

Researchers have uncovered exactly where a key protein forms before it triggers the flowering process in plants.Until now, no one has pinpointed which cells produce the small protein, called Flowering Locus T (FT).The study also points to an extensive intercellular signaling system that regulates FT production.

在植物中，Flowering Locus T(FT)是一种关键蛋白质，它的形成会触发开花过程。最近，研究人员发现了FT的准确形成位置，以及调控FT分泌的大规模细胞间信号系统。在此之前，没有人知道它到底由哪些细胞分泌。

"Understanding where FT is located and how it coordinates with other flowering factors is important to breeders; it's useful for breeders for the fine manipulation of flowering times," says Qingguo Chen, the paper's first author and a research associate in the lab of Robert Turgeon, the paper's senior author and professor of plant biology at Cornell University.

本研究由康奈尔大学植物学教授Robert Turgeon(资深作者)和实验室研究助理Qingguo Chen(第一作者)共同完成。Qingguo Chen表示：对培植者来说，了解FT的位置以及它如何和其它开花因素协同作用很重要;他们能够以此精细控制植物的开花时间。

Flowering in many plants begins with the perception of day-length, which occurs in the leaves. Some plants flower in short days and others in long days.

许多植物的开花过程始于叶子对白昼长度的感知。有些植物在昼短的日子里开花，有些植物在昼长的日子里开花。

It was previously known that in Arabidopsis plants, long day-length starts a process where leaves synthesize and transmit FT in the plant's vascular tissue, called the phloem, which carries sugars and nutrients from leaves to the rest of the plant.

科学家早就知道，在拟南芥这种植物中，长昼会使叶子合成FT，并并通过韧皮部进行运输——韧皮部负责将糖分和营养物质从叶子运输到其它植物部位;

FT travels to the shoot apex, the highest point of new leaves and stems, where it promotes the formation of flowers.

FT来到枝条尖，即新茎叶的最高点，并在那里触发开花过程。

Flowering regulation is complex, with the release of FT controlled by more than 30 proteins in interacting cascades.

开花过程的调控非常复杂，FT的释放由30多种蛋白质控制。

"There's a complicated network and you can't unravel it until you realize what is going on with these particular cells, so the geography is very important," says Turgeon.

它们相互作用，形成复杂网络。只有确切了解这些特定细胞所发生的事情，才能够解释整个过程。所以，“(细胞)地理”很重要。

Because leaf veins are very small and covered by photosynthetic cells rich in green chlorophyll, identifying the FT-producing cells was difficult.

由于叶脉非常小，又被大量富含叶绿素的光合细胞所覆盖;因此，识别分泌FT的细胞非常困难。

In the study, Turgeon and colleagues used fluorescent proteins to identify the cells in the phloem (veins) where FT was produced.

这回，研究人员采用荧光蛋白，识别出韧皮部(叶脉)里分泌FT的细胞。

The researchers discovered that FT was also produced in the same type of companion cells in the phloem of Maryland Mammoth tobacco.

他们发现，在马里兰猛犸烟草的韧皮部中，一种同类型的伴细胞也会分泌FT。

Furthermore, when they killed these companion cells, it delayed flowering in both Arabidopisis and the tobacco plants.

当研究人员破坏这些伴细胞时，拟南芥和马里兰猛犸的开花过程都推迟了。

When they looked more closely at the pathways that lead to flowering, they found that killing these companion cells stopped the process downstream of FT, but not upstream, confirming that FT originates in these cells and that the synthesis of FT is regulated by an extensive intercellular signaling system.

当他们仔细观察开花通道时，发现破坏伴细胞会终止FT的下游过程，但不终止它的上游过程。这证明FT发源于这些细胞，而FT的合成受到大规模细胞间信号系统的调控。