夏季水涝对白皮松根系电阻抗特性及生长生理的影响

Effects of waterlogging in summer on electrical impedance characteristics,growth and physiology of roots in Pinus bungeana seedlings

气候变化背景下夏季极端降水发生频率增加,夏季水涝通过影响根系,从而影响树木生长和存活,对森林生态造成严重破坏。树木根系埋于地下,水涝后根系变化不易观测。研究目的是利用电阻抗图谱法非破坏性测定根系电阻抗特性,通过分析电阻抗参数与根系生长生理指标的相关性,为快速了解水涝胁迫后白皮松地下根系的受害程度提供新方法。本研究以我国北方造林常用的白皮松四年生苗木为试验材料,于夏季进行水涝处理:i)对照(CK),正常管理;ii)连续水涝3周(CWL);iii)间歇水涝3周(IWL,水涝1周+排水1周,循环3次,总计水涝时长3周)。水涝后及后续恢复生长期对白皮松根系进行了电阻抗图谱测定及图谱归类分析(CLAFIC,Class-Featuring Information Compression)。对根系形态指标、非结构性碳水化合物、丙二醛含量进行了测定并分析与电阻抗参数的相关性。CWL和IWL处理下白皮松的根系形态指标较CK降低,且IWL处理下根系形态指标在恢复期显著低于CK和CWL处理,表明连续和间歇水涝3周均抑制了白皮松的根系生长,间歇水涝对根系的伤害较连续水涝更严重,与根系丙二醛含量更高相印证。CWL和IWL处理下白皮松根系的电阻抗图谱表现出明显的变化,电阻值(Re(Z))低于CK,容抗值(Im(Z))高于CK,恢复生长期间以上参数变化相反。CLAFIC归类结果显示CWL和IWL在水涝处理期间图谱相似比例最高,在恢复一个月后分别与CK相似比例较高。低频下阻抗损耗系数(δ)与根体积呈线性正相关,与淀粉含量呈线性负相关,表明水涝胁迫后白皮松苗木根系的阻抗损耗系数具有反映根大小和生理状态的潜力。

Extreme precipitation in summer occurs more frequently in the context of climate change.Waterlogging in summer affects the growth and survival of trees by affecting their roots,thus causing serious damage to forest ecology.Since tree roots are buried underground,changes of roots after waterlogging are not easy to observe.The aim of this study was to use electrical impedance spectrum(EIS)method to non-destructively measure the electrical impedance characteristics of roots,and therefore providing a new method for quickly understanding the damage degree of underground roots after waterlogging stress by analyzing the correlation between electrical impedance parameters and root growth and physiological indexes.In the study,four-year-old lacebark pine(Pinus bungeana Zucc.)seedlings,commonly used in afforestation in north China,were exposed to waterlogging treatments in summer:i)Control(CK),normal management;ii)Continuous waterlogging for 3 weeks(CWL);and iii)Intermittent waterlogging for 3 weeks(IWL,waterlogging of 1 week+drainage of 1 week,a total of 3 cycles,cumulative waterlogging for 3 weeks).After waterlogging and during the subsequent recovery growth period,the EIS of the root system were measured and the spectra were classified by Class-Featuring Information Compression(CLAFIC).Morphological indexes,non-structural carbohydrates,and malondialdehyde content of roots were measured and their correlations with the EIS parameters were analyzed.Root morphological indexes in CWL and IWL treatments were lower than that in CK,and the root morphological indexes in IWL treatment were significantly lower than that in CK and CWL treatment during the recovery period.The results indicated that both continuous and intermittent waterlogging for 3 weeks inhibited the root growth,and intermittent waterlogging had more serious damage to roots than continuous waterlogging,which were confirmed by the higher content of malondialdehyde in roots.The EIS of the roots showed clear changes in CWL and IWL treatments,therein,the resistance value(Re(Z))was lower,the reactance value(Im(Z))was higher than that in CK,and the above parameters during the recovery growth stage changed in the opposite direction.The CLAFIC classification results showed that EIS of roots in CWL and IWL had the highest similarity during the waterlogging period,and their similarity with CK was higher after one month of recovery.The impedance loss factor(δ)at low frequency was linearly and positively correlated with root volume,whereas it was negatively correlated with starch content.The results suggest that impedance loss factor has the potential to characterize the root growth and physiological changes of lacebark pine seedlings after waterlogging stress.