光照和水分对白藤幼苗生长特性的影响路径关系研究

该研究以2年生白藤实生苗为研究对象,通过控制试验,设置4个光强梯度——S0(对照,全光照)、S1(75%~80%全光照)、S2(45%~50%全光照)、S3(20%~25%全光照)和3个水分梯度——W0(对照,RSWC85%)、W1(中度干旱,RSWC55%)、W2(重度干旱,RSWC25%),定期测定幼苗生长特性(株高、地径、叶片数),叶片光合能力净光合速率(Pn)、蒸腾速率(Tr)、胞间二氧化碳浓度(Ci)、气孔导度(Gs)]及吸收能力(根、茎、叶生物量),并利用结构方程模型进行路径分析,探讨光照和水分对白藤幼苗生长特性影响过程,为白藤育苗及资源恢复提供理论支撑。结果显示:(1)随着光照强度的降低,幼苗生长特性与吸收能力、光合能力表现出一致的变化趋势,即先增加后减少;在45%~50%光强条件下,幼苗株高、地径、叶片数,根、茎、叶和总生物量及叶片Pn、Gs、Tr和Ls均达最大值。(2)随着土壤含水量降低,幼苗株高、地径及茎和叶生物量均逐渐减少,而根、根冠比呈先增加后减少的趋势;光合能力方面的Pn、Ci、Tr比对照分别显著降低23.65%、20.61%和25.40%(P<0.05),Gs和WUE与对照差异不显著(P>0.05),Ls比对照显著升高170.00%(P<0.05)。(3)结构方程模型分析表明,光照主要通过影响幼苗叶片的光合能力,水分主要通过影响根系生物量来实现影响幼苗生长特性的作用。研究表明,SEM模型能有效对影响白藤幼苗生长的环境因子进行分析,定量解释环境因子影响的路径过程,光照和水分通过光合能力和吸收能力传递对生长特性的影响,且光照因子影响力大于水分因子,其路径系数分别为0.89和0.56;在白藤幼苗生长特性指标中,地径标准因子载荷为0.85,能够有效反映白藤幼苗生长特性;白藤幼苗培育在适度遮阴(45%~50%)和正常供水(RSWC85%)环境下生长最好。

Pathway Relationship between Light and Water on Growth Characteristics of Calamus tetradactylus Seedlings

In this study,the 2-year-old seedlings of Calamus tetradactylus were selected as the research object.Through the control experiment,we set four light intensity gradients—S0(control,full light),S1(75%to 80%full light),S2(45%to 50%full light),and S3(20%to 25%full light),and three water gradients-W0(control,RSWC 85%),W1(moderate drought,RSWC 55%),W2(severe drought,RSWC 25%),on a regular basis to determine seedling growth characteristics(plant height,ground diameter,leaf number),photosynthetic capacitynet photosynthetic rate(Pn),transpiration rate(Tr),intercellular CO2 concentration(Ci),stomatal conductance(Gs)]and absorptive capacity(root,stem and leaf biomass),and path analysis using structural equation model,to explore the pathway of light and water on the growth characteristics of C.tetradactylus seedlings,and to provide theoretical support for seedling cultivation and resource restoration.The results show that:(1)with the decrease of light intensities,the growth characteristics,absorption capacity and photosynthetic capacity of seedlings showed a consistent change trend,increased firstly and then decreased.(2)With the decrease of soil water content,the growth characteristics,stem and leaf biomass of seedlings decreased gradually,while the ratio of root and root crown increased firstly and then decreased.In terms of photosynthetic capacity,Pn,Ci and Tr were significantly reduced by 23.65%,20.61%and 25.40%compared to the control group(P<0.05).Gs and WUE were increased but not significantly different from the control group(P>0.05),and Ls was significantly increased by 170.00%compared to the control group(P<0.05).(3)Structural equation model analysis showed that light could affect the photosynthetic capacity of seedling leaves and water could affect the growth characteristics of seedlings by affecting the root biomass.This study shows that SEM model can effectively analyze the environmental factors that affect the growth of C.tetradactylus seedlings,and quantitatively explain the path process affected by environmental factors.Light and water transfer influence on growth characteristics through photosynthetic capacity and absorption capacity,and the influence of light factor is greater than that of water factor,with path coefficients of 0.89 and 0.56,respectively.During the cultivation of C.tetradactylus seedlings,the standard factor load of ground diameter was 0.85,which could effectively reflect the growth characteristics of C.tetradactylus seedlings.The seedlings grew best under moderate shade(45%-50%)plus normal water supply(RSWC 85%).