The chloroplast as a photonic structure

2017年，惠特尼和奥尔顿团队合作证明，海棠物种叶片中的改性叶绿体（称为虹膜质体）具有片状结构，排列成能够反射蓝光的周期性光子结构。研究表明，这些虹膜质体在弱光条件下具有更高的光合效率，并假设光子结构改变了虹膜质体在弱光条件下对合适波长的光的吸收。这项研究首次表明，植物进化出了有助于光合作用的光子结构。这些结构被发现是因为叶子的蓝色外观。然而，在其他光环境中，有很好的理由认为植物会进化出在光谱中反射绿色区域的叶绿体。这种影响可能是非常广泛的，因此是光合植物进化的一个重要因素。然而，通过叶片检查偶然发现几乎是不可能的。然而，这位候选人在他最后一年的项目中也发现了一些具有高反射性的绿色叶绿体（与蓝色叶绿体一起）的诱人证据。候选人的博士项目将涉及系统地搜索和测试不同种类的植物和藻类，以发现光子结构是否在叶绿体中广泛存在。他将从搜索已知的植物和藻类的电子显微镜图像数据库开始，寻找周期结构，表明这种结构可能是光子的。然后将寻找标本并测量反射率作为角度的函数，以确定叶绿体是否具有结构颜色以及由于色素而产生的颜色。我们预计结构颜色可能已经分别进化了几次。如果是这样的话，它将为更高效的作物基因工程提供另一条途径，并改变我们对地球上最重要的能源过程之一的基本理解。

In 2017 the Whitney and Oulton groups collaborated to show that modified chloroplasts (known as iridoplasts) in the leaves of Begonia species have lamellar structures that arrange into a periodic photonic structure capable of reflecting blue light. It was shown that these iridoplasts were more photosynthetically efficient at low light levels, with the hypothesis that the photonic structure modified the absorption to scavenge light at the right wavelength at low light levels. This work was the first of its kind to show that plants have evolved photonic structures to aid photosynthesis.These structures were discovered because of the blue appearance of the leaves. However, in other light environments there would be good reason to suggest that plants would evolve chloroplasts that reflect in the green area of the spectrum. This effect may be very widespread, and therefore an important factor in the evolution of photosynthesising plants. However, accidental discovery via leaf inspection would be almost impossible. Nevertheless, some tantalising evidence of highly reflective green chloroplasts (alongside the blue ones) have also been discovered by the candidate during his final year project.The candidate's PhD project will involve systematically searching for and testing different species of plants and algae to discover whether photonic structures are widespread in chloroplasts. He will begin by searching known databases of electron microscopy images of plants and algae to look for periodic structures, indicating that the structure may be photonic. Specimens will then be sought out and reflectivity measured as a function of angle to determine whether the chloroplasts have a structural colour as well as that due to pigment. We anticipate that structural colour may have evolved separately several times. If this were the case, it would provide another avenue to genetically engineering more efficient crops, as well as changing our fundamental understanding of one of the most important energy processes on the planet.