Характеристики сезонной изменчивости хлорофилла и спектра листьев Populus euphratica при водном стрессе

Chlorophyll content is an important index for monitoring the health status of vegetation growth. Revealing the variation characteristics of the chlorophyll content in leaves of Populus euphratica plays an important role in evaluating the health and ecological conservation of Populus euphratica. In this study, leaves of healthy Populus euphratica and water-stressed Populus euphratica were collected from May to October, and the spectral reflectance was obtained at 390-1100 nm. At the same time, the chlorophyll content of Populus euphratica leaves was analyzed. The results indicated that from May to October, the chlorophyll content showed a trend of “two peaks and two valleys,” which decreased first, then increased and then decreased. In general, the chlorophyll content of healthy Populus euphratica leaves was higher than that of water-stressed Populus eu-phratica leaves. The ratio of chlorophyll a to chlorophyll b was maintained between 3.0 and 3.4 from May to August, while there was a significant increase in September and October. The ratio of chlorophyll a to chlorophyll b in healthy Populus euphratica leaves was significantly lower than that in water-stressed Populus euphratica leaves from June to September. The spectral curves of healthy Populus euphratica leaves were relatively consistent from May to August, and the curves in the near-infrared band were also concentrated. For the water-stressed Populus euphratica leaves, the curve in the near-infrared band was more dispersed. There were two absorption valleys at wavelengths of 500 and 675 nm, and some of the absorption characteristic parameters of the two absorption valleys had a significant correlation with the chlorophyll content. A partial least squares regression model constructed by these absorption parameters roughly estimated the chlorophyll content of the water-stressed Populus euphratica leaves.