Abstract
Chlorophyll content is an important indicator of winter wheat health status. It is valuable to investigate whether the relationship between spectral reflectance and the chlorophyll content differs under elevated CO2 condition. In this open-top chamber experiment, the CO2 treatments were categorized into ambient (aCO2; about 400 μmol⋅mol–1) or elevated (eCO2; ambient + 200 μmol⋅mol–1) levels. The correlation between the spectral reflectance and the chlorophyll content of the winter wheat were analyzed by constructing the estimation model based on red edge position, sensitive band and spectral index methods, respectively. The results showed that there was a close relationship between chlorophyll content and the canopy spectral curve characteristics of winter wheat. Chlorophyll content was better estimated based on sensitive spectral bands and difference vegetation index (DVI) under both aCO2 and eCO2 conditions, though the accuracy of the models varied under different CO2 conditions. The results suggested that the hyperspectral measurement can be effectively used to estimate the chlorophyll content under both aCO2 and eCO2 conditionsand could provide a useful tool for monitoring plants physiology and growth.
Highlights
It is expected that the atmospheric CO2 concentration will rise to 550 μmol·mol−1 in 2050 and reach or exceed 700 μmol·mol−1 at the end of the 21st century due to the increase of human population, energy production and utilization, deforestation and other intensive human activities (IPCC, 2013)
In order to establish statistical models to study the relationship between the optical properties and chlorophyll content of winter wheat under elevated CO2 conditions, we measured the chlorophyll content and spectral reflectance in winter wheat canopy under ambient CO2 (aCO2) and eCO2 conditions throughout the growing season for 2 years
The effects of elevated CO2 on the chlorophyll content and spectral reflectance depended upon growing stages
Summary
It is expected that the atmospheric CO2 concentration will rise to 550 μmol·mol−1 in 2050 and reach or exceed 700 μmol·mol−1 at the end of the 21st century due to the increase of human population, energy production and utilization, deforestation and other intensive human activities (IPCC, 2013). Under elevated CO2, the physiology, growth and yield of wheat and other species are affected (Long et al, 2006; Wang et al, 2012). Chlorophyll content was closely related to crop health, photosynthetic capacity and crop yield (Lukas et al, 2014). The chlorophyll content and photosynthetic rate of varieties of C3 species, including crops and trees, was increased by elevated CO2 (Zhang et al, 2013; Madhana et al, 2014; Fathurrahman et al, 2016; Choi et al, 2017). Previous studies had shown a positive (Dubey et al, 2015) or negative (Wang et al, 2013) CO2 effects on the chlorophyll content and the difference might be resulted from the different experimental settings or CO2 increasing levels used in different studies
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