Changes of chlorophyll (Chl) and carotenoid (Car) contents and their ratio (Car/Chl) represent a sensitive indicator of vegetation photosynthetic activity, developmental changes, and stress responses. The goal of this study was to design methods for estimating Car/Chl in plants across species, seasonal changes and ontogenetic phases requiring no species-specific parameterization. Four tree species (maple, chestnut, beech, and elm), wild vine shrub, and two crops species (maize and soybean) featuring contrasting leaf structure and photosynthetic pathways, a wide variation of pigment content and composition were studied. Two models based on leaf pigment absorption coefficients retrieved from reflectance spectra were proposed and tested. The first model uses the ratio of absorption coefficients at 500 and 700 nm and the second one-the difference between absorption coefficients at 500 and 660 nm. Both models accurately described Car/Chl changes in the range from 0.15 to 0.6 with determination coefficients R2 of 0.87 for the first model and 0.82 for the second; algorithms for Car/Chl estimation did not require parameterization for each species accurately assessing Car/Chl with normalized root mean square error below 11 % and 14 %, respectively. The findings of a close relationship between leaf absorption coefficients, retrieved from reflectance, and Car/Chl present the first step towards accurate generic quantification of pigment composition and hence the progression of developmental stages, impact of stresses, and potential photosynthetic activity.

中文翻译：

---

一种对叶类胡萝卜素与叶绿素比值进行远程无创估计的通用方法

叶绿素 (Chl) 和类胡萝卜素 (Car) 含量及其比值 (Car/Chl) 的变化代表了植被光合活动、发育变化和胁迫反应的敏感指标。本研究的目标是设计用于估计植物中跨物种、季节性变化和个体发育阶段的 Car/Chl 的方法，不需要物种特定的参数化。研究了四种树种（枫树、栗树、山毛榉和榆树）、野生藤本灌木和两种作物（玉米和大豆），它们的叶子结构和光合作用途径截然不同，色素含量和成分的变化范围很广。提出并测试了两种基于从反射光谱中检索到的叶色素吸收系数的模型。第一个模型使用 500 和 700 nm 处吸收系数的比率，第二个模型使用 500 和 660 nm 处吸收系数之间的差异。两个模型都准确地描述了范围从 0.15 到 0.6 的 Car/Chl 变化，第一个模型的决定系数 R2 为 0.87，第二个模型的决定系数 R2 为 0.82；Car/Chl 估计算法不需要对每个物种进行参数化，准确评估 Car/Chl 的归一化均方根误差分别低于 11% 和 14%。从反射率中检索到的叶子吸收系数与 Car/Chl 之间存在密切关系的发现，为色素成分的准确通用量化以及发育阶段的进展、压力的影响和潜在的光合作用活动迈出了第一步。