6个白杨无性系水力效率与气体交换及生长的关系

Relationship between Hydraulic Efficiency and Gas Exchange and Growth of Six Poplar Clones

【目的】探究6个白杨无性系水力效率对气体交换和生长性能的影响,阐明水力效率与气体交换和生长的内在关系,为林木抗旱新品种选育提供理论指导。【方法】对6个白杨杂交无性系的2年生苗木,测定气体交换参数(净光合速率A_(net)、气孔导度g_(s)、参比气孔导度g_(s-ref)、水分利用效率WUE)、叶片水分状况(中午叶水势Ψ_(md))、水力效率(整个树冠水力效率K_(CL)、主枝水力效率K_(MSL)和根系水力效率KRL)、气孔特征(气孔密度SD、气孔长度SL、气孔面积指数SPI)和生长指标(地径绝对生长速率AGRD和相对生长速率RGRD)。【结果】1)6个白杨无性系的水力效率差异显著,且根、主枝及树冠的水力效率变化具有一致性,即高或低水力效率的无性系其KRL、K_(MSL)及K_(CL)均较高或较低。2)Ψ_(md)与g_(s)的变化密切相关,在Ψ_(md)下降至-1.1 MPa后g_(s)急剧下降,导致A_(net)相应下降,而AGRD与A_(net)呈显著正相关。3)SL与K_(CL)、K_(MSL)、g_(s-ref)、AGRD及RGRD显著正相关,SD与K_(MSL)、A_(net)及AGRD显著负相关。4)K_(CL)、K_(MSL)与g_(s-ref)显著相关,且K_(CL)与g_(s-ref)的相关性更强,表明较高的水力效率利于气孔开放。5)K_(CL)和K_(MSL)呈显著正相关,两者均与AGRD及RGRD显著正相关,其中K_(CL)与RGRD相关性更强。【结论】本研究在白杨无性系水平发现,树木各部分的水力效率相协调,根系、主枝、树冠等水平的水力效率均能反映树木运输水分的能力;水分运输效率与叶片气体交换过程密切相关,并且叶片气孔结构特征与木质部水分运输能力相匹配,高效的水分运输改善了叶片水分状况,促进了气孔开放,提高碳同化能力,从而促进生长。

【Objective】Xylem water transport is the basis of photosynthetic process and tree growth.Exploring the effect of hydraulic efficiency on gas exchange and growth performance will help to deepen the understanding of the internal relationship between hydraulic efficiency and gas exchange and growth,and provide a theoretical basis for the breeding of new drought-resistant forest varieties.【Method】The 2-year-old seedlings of six poplar hybrid clones【Populus alba‘I-101’×(P.alba×P.Glandulosa‘84K’)】were used to measure gas exchange parameters(net photosynthetic rate A_(net),stomatal conductance g_(s),reference stomatal conductance g_(s-ref),water use efficiency WUE),leaf water status(midday leaf water potentialΨ_(md)),hydraulic efficiency(whole crown hydraulic efficiency KCL,main branch hydraulic efficiency K_(MSL)and root hydraulic efficiency KRL),stomatal characteristics(stomatal density SD,stomatal length SL,stomatal area index SPI)and growth parameters(ground diameter absolute growth rate AGRD and relative growth rate RGRD).【Results】1)Six poplar clones showed significant difference in hydraulic efficiency,and the changes of the hydraulic efficiency of roots,main branches and crowns were consistent,that is,the clones with high or low hydraulic efficiency had higher or lower KRL,K_(MSL)and KCL.2)The change inΨ_(md)was closely related to that of g_(s).AfterΨ_(md)decreased to-1.1 Mpa,g_(s)decreased sharply,resulting in a corresponding decrease in A_(net).AGRD was significantly positively correlated with A_(net).3)SL was significantly positively correlated with KCL,K_(MSL),g_(s-ref),AGRD and RGRD,and SD was significantly negatively correlated with K_(MSL),A_(net)and AGRD.4)K_(CL)and K_(MSL)were significantly correlated with g_(s-re),and K_(CL)had a stronger correlation with g_(s-ref),indicating that higher hydraulic efficiency was beneficial to stomatal opening.5)K_(CL)was significantly positively correlated with K_(MSL),and K_(MSL)was always greater than KCL(about 37.3%higher on average).K_(CL)and K_(MSL)were significantly positively correlated with AGRD and RGRD,among which K_(CL)had a stronger correlation with RGRD.【Conclusion】In this study,,it is found that the hydraulic efficiency of each part of the tree is coordinated at the intraspecific clonal level,and the hydraulic efficiency of the root system,main branch,crown can reflect the ability of the tree to transport water.The water transport efficiency is closely related to the gas exchange process of leaves,and the structural characteristics of leaf stomata are coordinated with the water transport capacity.Efficient water transport improves the leaf water status,promotes stomatal opening,and improves carbon assimilation capacity,and thereby promotes growth.