Temporal Changes of Leaf Spectral Properties and Rapid Chlorophyll—A Fluorescence under Natural Cold Stress in Rice Seedlings

Abstract

Nowadays, hyperspectral remote sensing data are widely used in nutrient management, crop yield forecasting and stress monitoring. These data can be acquired with satellites, drones and handheld spectrometers. In this research, handheld spectrometer data were validated by chlorophyll-a fluorescence measurements under natural cold stress. The performance of 16 rice cultivars with different origins and tolerances was monitored in the seedling stage. The studies were carried out under field conditions across two seasons to simulate different temperature regimes. Twenty-four spectral indices and eleven rapid chlorophyll-a fluorescence parameters were compared with albino plants. We identified which wavelengths are affected by low temperatures. Furthermore, the differences between genotypes were characterized by certain well-known and two newly developed (AAR and RAR) indices based on the spectral difference between the genotype and albino plant. The absorbance, reflectance and transmittance differences from the control are suitable for the discrimination of tolerant-sensitive varieties, especially based on their shape, peak and shifting distance. The following wavelengths are capable of determining the tolerant varieties, namely 548–553 nm, 667–670 nm, 687–688 nm and 800–950 nm in case of absorbance; above 700 nm for reflectance; and the whole spectrum (400–1100 nm) for transmittance.

Indirect Estimation of Heavy Metal Contamination in Rice Soil Using Spectral Techniques

“…When the concentration of heavy metals in the soil increases, the content of heavy metals in different parts of rice usually increases as well, resulting in a stress effect [ 43 ]. As the stress of heavy metals in rice increases, some of the cellular structures are damaged, resulting in a decrease in chlorophyll content, which is reflected in differences in leaf spectra [ 44 , 45 ]. Therefore, we successfully inverted the content of heavy metals (Cd and As) in soil by spectral transformation, characteristic analysis, and modeling of rice leaf spectra.…”

Crop-Specific Responses to Cold Stress and Priming: Insights from Chlorophyll Fluorescence and Spectral Reflectance Analysis in Maize and Soybean

“…Numerous studies have investigated the impact of cold stress on chlorophyll a fluorescence and leaf reflectance across various crop species [37][38][39][40][41][42][43][44]. For instance, research on winter oilseed rape cultivars under cold stress has shown declines in the maximal fluorescence and electron transport rate, coupled with changes in quantum yield and non-photochemical quenching [37].…”

“…Soybean exhibited a decreased maximum quantum efficiency of PSII in the dark-adapted state and impaired photosynthesis due to cold stress [41,42]. Variations in absorbance, reflectance, and transmittance under cold stress in rice have been used to distinguish between tolerant and sensitive genotypes, with the range of 525-535 nm proving the most stable and wavelengths above 700 nm being the most sensitive in the reflectance curve [43]. In maize, cold stress mainly affected reflectance between 500 and 600 nm, as well as around 700 nm, with spectral indices indicating decreased chlorophyll levels and an increased carotenoid/chlorophyll ratio in cold-exposed plants [44].…”

Reference field spectrometric data of albino rice plants

“…This dataset was captured by the CI-710 s SpectraVue Leaf Spectrometer (Cid-Bioscience, Camas, WA, U.S.A.). The absorbance, reflectance, and transmittance of albino plants were measured under natural cold stress in a temperate rice-growing area [1] . The experiment was carried out in field conditions at the seedling stage.…”