利用小波软阈值消噪法和快速傅里叶变换研究不同温度条件下芦荟叶片电信号的基本特征及变化规律。通过植物电信号谱边缘频率(SEF)、谱重心频率(SGF)和功率谱熵(PSE)研究不同温度下芦荟(Aloe vera L.)叶片电信号功率谱的变化。结果表明,芦荟的电信号是一种强度为mV数量级、频率分布在5 Hz以下的低频信号;随着温度的升高,电信号的SEF和SGF向高频段移动,细胞活动受到激发,PSE急剧增加;在升温过程中SEF、SGF和PSE三者的变化趋势趋于一致,PSE与SGF的变化之间有很强的关联性,因而植物电信号PSE或SGF的变化可以作为叶片细胞响应外界环境变化的灵敏指标,而对植物生长发育的生理生化过程实施科学调控。
To quantify the characteristics of the power spectrum of plant electrical signals, we defined the following concepts:spectral edge frequency (SEF), spectral center frequency (SCF), power index (PI) and power spectral entropy (PSE). These parameters were used to examine and quantify changes in the power spectrum of electrical signals in maize leaves under osmotic stress. In the absence of osmotic stress, the SEF of the electrical signal in maize leaves was approx. 0.2 Hz and the SCF was approx. 0.1 Hz. The electrical signal in maize leaves was mainly a slow wave signal with a frequency of 0-0.1 Hz. After 2 h osmotic stress, the SEF and SCF of the electrical signal increased to higher frequencies. The proportion of the fast wave frequency also increased to 0.1-0.2 Hz, resulting in a dramatic increase in PSE. We also found that the changes in PSE and SCF were significantly correlated during osmotic stress. We propose that the changes in the PSE and SCF in maize leaves can be used as a sensitive signal indicating water deficit in leaf cells under osmotic stress. Thus, measurement of SCF or PSE of electrical signals in maize leaves could be used to develop early warning and rapid diagnosis techniques for the water demands of plants.
