Study of the Spectral Absorption Characteristics of Wild Lancea tibetica under Intense Solar Radiation on the Tibetan Plateau

Abstract

Lancea tibetica is a valuable medicinal herb uniquely found in the Tibetan plateau. The photosynthetic pigments within its leaves are one of the indispensable substances for photosynthesis. However, The Tibetan plateau is one of the regions with the most intense solar radiation in the world. It has extreme solar radiation conditions. These extreme solar radiation conditions have multiple effects on local ecological conditions. In this study, the absorption spectrum of wild and laboratory Lancea tibetica leaves was observed using equipment like a spectrometer, followed by analyzing its characteristics. The results show that short-wavelength solar ultraviolet radiation has considerable small energy penetrating through plant leaves, and most of the energy is reflected by leaves or only a small proportion of energy is absorbed. Within the visible solar spectrum, most of the energy of the purple and indigo light is absorbed by leaves, with the absorbance of carotenoids being 0.731 at the maximum absorbent peak of 470nm. The transmitted intensity of the solar spectrum at this point is 0.38W·m -2·nm -1, accounting for an absorption of nearly 81.42%. In the green light spectrum, the transmitted intensity is relatively high given the leaves’ ability to retain the stability of their systems. The absorption of chlorophyll a and b is mainly concentrated in the red-light part, with transmitted intensity at 665nm and 649 nm being 0.80W·m -2·nm -1 and 0.34W·m -2·nm -1 only, playing a significant part in photosynthesis. The near infrared spectrum mainly consists of solar thermal energy, and the leaves of Lancea tibetica absorb less thermal radiation compared with ultraviolet and visible spectra.