UV-B增强下施硅对水稻冠层反射光谱特征的影响

通过田间试验,在UV-B增强和施硅条件下,利用ASD便携式手持光谱仪在水稻分蘖期、拔节期、抽穗期和灌浆期选择典型晴天观测冠层光谱曲线,通过计算一阶导数曲线分析光谱的红边参数特征。UV-B辐射设2个水平,即对照(自然光,ambient UV-B,A)和UV-B增强(比自然光增强20%,elevated UV-B,E);施硅设2个水平,即不施硅和施硅(硅酸钠,200kg SiO_2·hm~(-2))。结果表明:UV-B增强下水稻叶面积指数(LAI)和叶绿素含量(SPAD值)降低,而施硅可提高叶面积指数(LAI)和SPAD值,缓解UV-B增强对水稻生长的抑制作用。各处理间水稻冠层光谱的差异主要体现在近红外波段,UV-B增强使水稻近红外波段反射率降低,施硅使近红外波段反射率上升。UV-B增强使水稻光谱红边位置蓝移,施硅使红边位置红移。随着生育期推移,水稻光谱红边位置、红边幅值和红边面积均呈现先增后减的趋势,且在拔节期达最大。

Effects of Silicon Supply on Reflectance Spectroscopy Characteristics of Rice Canopy under Elevated UV-B Radiation

A field experiment was conducted to observe the canopy spectra of rice by using ASD FieldSpec HandHeld spectrometer on typical sunny days and analyze the characteristics of red edge parameters by calculating the first derivative spectrum at tillering, jointing, heading and grain-filling stages under the conditions of elevated UV-B radiation and silicon supply. The experiment was designed with two UV-B radiation levels, i.e. ambient UV-B (ambient, A) and elevated UV-B (elevated by 20%, E);with two silicon supply levels, i.e. control and +Si (200kgSiO2?ha-1 as sodium silicate). The results indicated that LAI (leaf area index) and chlorophyll content (value of SPAD) were decreased under elevated UV-B radiation, but silicon supply increased and could alleviate the depressive effect of elevated UV-B radiation on rice growth. The differences of rice canopy spectra were mainly reflected in near-infrared band under each treatment, the reflectance of near-infrared band was decreased under elevated UV-B radiation, but increased by silicon application. The red edge position showed blue shift under elevated UV-B radiation and red shift by silicon application. The rice red edge position, red edge amplitude and red edge area showed a trend with an increase firstly and then a decrease, and reached the maximum at jointing stage.