The remote sensing of a plant's physiological state is a key problem of precision agriculture. The photochemical reflectance index (PRI), which is based on the intensities of the reflected light at 531 and 570 nm, is an important tool for the remote sensing of photosynthetic processes in plants. In particular, the PRI can be strongly connected with the non-photochemical quenching of chlorophyll fluorescence (NPQ) and the quantum yield of photosystem II (ФPSII); however, this connection is dependent on illumination, the intensity of stressor actions, the time scale of measurements, etc. The aim of the present work was to analyze the connection of PRI with the energy-dependent component of NPQ (NPQF) and ФPSII under heating and soil drought conditions. Pea, wheat, and pumpkin seedlings, which were grown under controlled conditions, were investigated. A PAM fluorometer Dual-PAM-100 and spectrometer S-100 were used for measurements of photosynthetic parameters and PRI, respectively. It was shown that heat stress increased the NPQF and the magnitude of light-induced changes in PRI (ΔPRI) and decreased ФPSII in pea seedlings. The decreased ФPSII and increased ΔPRI were observed in wheat after heating, but significant changes in NPQF were absent; the significant decrease in ФPSII was observed in pumpkin seedlings, while there were no significant changes in the other parameters. ΔPRI and NPQF after heating were significantly correlated. However, a significant correlation of the absolute values of PRI with photosynthetic parameters was absent. The soil drought increased NPQF and the magnitude of ΔPRI and decreased ФPSII in peas. ΔPRI was strongly correlated with photosynthetic parameters, but this correlation was absent for the absolute value of PRI. Thus, ΔPRI is strongly connected with the magnitude of NPQF and can be used as an estimator of this parameter.

中文翻译：

---

光引起的光化学反射指数（PRI）下降可用于估计豌豆、小麦和南瓜在热胁迫和土壤干旱条件下非光化学猝灭的能量依赖部分。


植物生理状态的遥感是精准农业的关键问题。光化学反射指数 (PRI) 基于 531 和 570 nm 的反射光强度，是遥感植物光合作用过程的重要工具。特别是，PRI与叶绿素荧光的非光化学猝灭（NPQ）和光系统II的量子产率（ФPSII）密切相关；然而，这种联系取决于光照、压力源行为的强度、测量的时间尺度等。本工作的目的是分析 PRI 与 NPQ (NPQF) 和 ФPSII 的能量依赖分量之间的联系供暖和土壤干旱条件。研究人员对在受控条件下生长的豌豆、小麦和南瓜幼苗进行了研究。 PAM 荧光计 Dual-PAM-100 和光谱仪 S-100 分别用于测量光合参数和 PRI。结果表明，热应激增加了豌豆幼苗的 NPQF 和光诱导的 PRI 变化幅度 (ΔPRI)，并降低了 ФPSII。小麦加热后，ФPSII 降低，ΔPRI 升高，但 NPQF 没有显着变化；南瓜幼苗中ФPSII显着下降，而其他参数没有显着变化。加热后的ΔPRI和NPQF显着相关。然而，PRI 绝对值与光合参数之间不存在显着相关性。土壤干旱增加了豌豆的 NPQF 和 ΔPRI 幅度，并降低了 ФPSII。 ΔPRI 与光合参数密切相关，但 PRI 的绝对值不存在这种相关性。 因此，ΔPRI 与 NPQF 的大小密切相关，可以用作该参数的估计量。