Rongpipi Sintu, Barnes William J, Siemianowski Oskar, Del Mundo Joshua T, Wang Cheng, Freychet Guillaume, Zhernenkov Mikhail, Anderson Charles T, Gomez Esther W, Gomez Enrique D
Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, United States.
Department of Biology, The Pennsylvania State University, University Park, PA, United States.
Front Plant Sci. 2023 Aug 16;14:1212126. doi: 10.3389/fpls.2023.1212126. eCollection 2023.
Calcium is important for the growth and development of plants. It serves crucial functions in cell wall and cell membrane structure and serves as a secondary messenger in signaling pathways relevant to nutrient and immunity responses. Thus, measuring calcium levels in plants is important for studies of plant biology and for technology development in food, agriculture, energy, and forest industries. Often, calcium in plants has been measured through techniques such as atomic absorption spectrophotometry (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and electrophysiology. These techniques, however, require large sample sizes, chemical extraction of samples or have limited spatial resolution. Here, we used near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the calcium L- and K-edges to measure the calcium to carbon mass ratio with spatial resolution in plant samples without requiring chemical extraction or large sample sizes. We demonstrate that the integrated absorbance at the calcium L-edge and the edge jump in the fluorescence yield at the calcium K-edge can be used to quantify the calcium content as the calcium mass fraction, and validate this approach with onion epidermal peels and ICP-MS. We also used NEXAFS to estimate the calcium mass ratio in hypocotyls of a model plant, , which has a cell wall composition that is similar to that of onion epidermal peels. These results show that NEXAFS spectroscopy performed at the calcium edge provides an approach to quantify calcium levels within plants, which is crucial for understanding plant physiology and advancing plant-based materials.
钙对植物的生长和发育至关重要。它在细胞壁和细胞膜结构中发挥着关键作用,并在与养分和免疫反应相关的信号通路中作为第二信使。因此,测量植物中的钙含量对于植物生物学研究以及食品、农业、能源和林业等行业的技术发展都很重要。通常,植物中的钙是通过原子吸收分光光度法(AAS)、电感耦合等离子体质谱法(ICP-MS)和电生理学等技术来测量的。然而,这些技术需要大量样本、对样本进行化学提取或空间分辨率有限。在这里,我们利用钙L边和K边的近边X射线吸收精细结构(NEXAFS)光谱,在无需化学提取或大量样本的情况下,测量植物样本中钙与碳的质量比,并具有空间分辨率。我们证明,钙L边的积分吸光度和钙K边荧光产率的边跳变可用于将钙含量量化为钙质量分数,并用洋葱表皮和ICP-MS验证了这种方法。我们还使用NEXAFS估计了模式植物下胚轴中的钙质量比,该植物的细胞壁组成与洋葱表皮相似。这些结果表明,在钙边进行的NEXAFS光谱提供了一种量化植物体内钙水平的方法,这对于理解植物生理学和推进基于植物的材料至关重要。