Souza Gustavo M, Ferreira Arlan S, Saraiva Gustavo F R, Toledo Gabriel R A
a Department of Botany , Federal University of Pelotas (IB/UFPel) , Pelotas - RS , Brazil.
b Department of Physics , Federal University of Pelotas (IFM/UFPel) , Pelotas - RS , Brazil.
Plant Signal Behav. 2017 Mar 4;12(3):e1290040. doi: 10.1080/15592324.2017.1290040.
In the present study, we have investigated how the low-voltage electrical signals of soybean seedlings change their temporal dynamic under different environmental conditions (cold, low light, and low osmotic potential). We have used electrophytografic technique (EPG) with sub-dermal electrodes inserted in 15-days-old seedlings located between root and shoot, accounting for a significant part of the individual seedlings. Herein, to work on a specific framework to settle this type of the study, we are adopting the term "electrome" as a reference to the totality of electrical activity measured. Taking into account the non-linear dynamic of the plants electrophysiology, we have hypothesized that the stimuli, as applied in a constant way, could push the system to a critical state, exhibiting spikes without a characteristic size, indicating self-organized criticality (SOC). The results from the power spectral density analysis (PSD), showed that the interval of the large majority of the β exponents were between 1.5 and 3, indicating that the time series, regardless environmental conditions, showed long-range temporal correlation (long memory for β≠0 and β≠2). The analyses from the histograms of the runs showed different patterns of distributions concerning the experimental conditions. However, the runs exhibiting typical spikes, mostly under low light and osmotic stress, showed power law distribution with exponent μ ≅ 2, which is an indicative for SOC. Overall, our results have confirmed that the temporal dynamic of the electrical signaling shows a complex non-linear behavior with long-range persistence. Moreover, the hypothesis that plant electrome can exhibit a self-organized critical state evoked by environmental cues, dissipating energy by bursts of electrical spikes without a characteristic size, was reinforced. Finally, new perspectives for research and additional hypothesis were presented.
在本研究中，我们探究了大豆幼苗的低压电信号在不同环境条件（寒冷、弱光和低渗透势）下如何改变其时间动态。我们使用了表皮下电极的电植物绘图技术（EPG），将电极插入15日龄幼苗根茎之间，该部位占单个幼苗的很大一部分。在此，为了在一个特定框架下开展此类研究，我们采用“电活动总量”这一术语来指代所测量的全部电活动。考虑到植物电生理学的非线性动态，我们假设以恒定方式施加的刺激可将系统推向临界状态，表现出无特征大小的尖峰，这表明自组织临界性（SOC）。功率谱密度分析（PSD）结果表明，绝大多数β指数的区间在1.5至3之间，这表明无论环境条件如何，时间序列都呈现出长程时间相关性（当β≠0且β≠2时具有长记忆性）。游程直方图分析显示了与实验条件相关的不同分布模式。然而，主要在弱光和渗透胁迫下出现典型尖峰的游程呈现出指数μ≅2的幂律分布，这是SOC的一个指标。总体而言，我们的结果证实了电信号的时间动态呈现出具有长程持续性的复杂非线性行为。此外，植物电活动总量可表现为由环境线索诱发的自组织临界状态，通过无特征大小的电尖峰爆发来耗散能量这一假设得到了加强。最后，提出了新的研究视角和其他假设。
