镉胁迫对刺槐幼苗生长与光合生理特性的影响

Effects of Cadmium Stress on Growth and Photosynthetic Physiological Characteristics of Robinia pseudoacacia Seedlings

[目的]探究镉胁迫对刺槐生长与光合生理特性的影响。[方法]以刺槐幼苗为研究对象,测定不同浓度镉处理下刺槐生长、叶绿素含量、叶绿素荧光参数、呼吸速率和气孔特性等。[结果]在镉胁迫下,刺槐幼苗地径、株高受到明显抑制;高浓度处理植株的鲜质量、干质量下降,低浓度处理植株则略微上升,但均与对照差异不显著。随着镉浓度增加,刺槐叶绿素a、叶绿素总量呈下降趋势,而叶绿素b、类胡萝卜素变化无规则,但与对照差异不显著;初始荧光(F0)与最大荧光产量(Fm)先升后降,最大光化学效率(Fv/Fm)逐步下降,非光化学淬灭系数(qN)逐步上升,实际光化学量子效率(ΦPSII)均低于对照值,但差异不显著;胁迫植株气孔宽度、气孔面积降低,气孔逐步闭合,呼吸效率受到显著抑制;通过相关分析显示,多数指标之间显著性相关;经随机森林回归分析,初始荧光(F0)、根系镉含量、气孔宽度和叶绿素a的重要性分别在叶绿素荧光参数、植株富集镉含量、气孔特性、光合色素中最强,成为影响刺槐光合功能的最关键因子。[结论]刺槐幼苗生长与光合生理受到一定影响,但仍表现出较强的镉胁迫耐受性,可为镉污染地区的园林应用提供参考。

[Objective]To explore the effects of cadmium(Cd)stress on the growth and photosynthetic physiological characteristics of Robinia pseudoacacia.[Method]The characteristics on the growth,chlorophyll content,chlorophyll fluorescence parameters,respiration rate and stomatal indices of Cd-stressed R.pseudoacacia seedlings were studied in this experiment.[Result]Under Cd stress,the stem diameter and plant height of these seedlings were obviously inhibited.The fresh weight and dry weight of treated plants with high concentration decreased,while those with low concentration increased slightly,but all the differences were insignificant between them and the control treatment.With an increase of cadmium concentration,the contents of chlorophyll a and total chlorophyll decreased,chlorophyll b and carotenoids changed irregularly,but there were insignificant differences between them and the control for R.pseudoacacia seedlings.However,the initial fluorescence(F0)and the maximum fluorescence yield(Fm)increased first and then decreased.The maximum photochemical efficiency(Fv/Fm)gradually decreased,the non-photochemical quenching coefficient(qN)gradually increased,and the actual photochemical quantum efficiencies(ΦPSII)were all lower than the control with insignificant-difference for those stressed plants during this experiment.Simultaneously,the stomatal width and stomatal area decreased,the stomata gradually closed in the treated-seedlings,and their respiratory efficiency was significantly inhibited.It was shown that the most of indicators were significantly correlated each other by correlation analysis.Through random forest regression analysis,the importance of initial fluorescence(F0),root cadmium content,stomatal width and chlorophyll a were the strongest among chlorophyll fluorescence parameters,plant cadmium enrichment content,stomatal characteristics and photosynthetic pigments,respectively,and became the most critical factors affecting the photosynthetic function of R.pseudoacacia seedlings.[Conclusion]Although the growth and photosynthetic physiology of R.pseudoacacia seedlings are affected by cadmium concentration to some extent,the seedlings still show strong tolerance to cadmium stress.It provides a reference for garden application in cadmium polluted areas.