红砂幼苗根系形态特征和水分利用效率对土壤水分变化的响应

Response of Root Morphology and Water Use Efficiency of Reaumuria soongorica to Soil Water Change

为探讨干旱与半干旱区受损红砂种群幼苗适宜生长的土壤水分条件,采用盆栽方法,研究了红砂幼苗在充分灌溉(FI)、适度灌溉(MI)、干旱处理(DT)3个水分处理下根系形态和水分利用效率的变化特征。结果表明:(1)红砂幼苗根系形态因水分条件和根序的不同而各异;随灌溉量的减少红砂幼苗根系直径和根体积均表现为FI>MI>DT,但干旱处理促进了根系的伸长生长和比表面积和比根长增加,根系形态的可塑性是红砂幼苗获取水分适应干旱环境的重要策略之一。(2)随根序的升高,各处理水平下红砂幼苗根长、比根长均显著减少,而其根直径和体积却显著增加,表明红砂幼苗根系内部具有高度的形态异质性。(3)与FI处理相比,MI和DT处理下红砂幼苗根系总生物量分别增加了50.00%、19.23%,但MI和DT处理却显著降低了红砂幼苗地上生物量,特别是叶片生物量下降幅度最大,分别降低了62.15%、83.28%,导致根冠比随灌溉量的减少而逐渐增加。(4)干旱处理显著提高了红砂幼苗的水分利用效率。研究认为,在灌溉量减少的情况下,红砂幼苗可通过根长、根系表面积和体积、直径等形态变化来优化其空间分布构型,以调节植株对水分的利用,提高水分利用效率。

Reaumuria soongorica population is facing a serious degradation at arid and semi-arid region of Northwest.Deficient water conditions impose restrictions on seedling establishment and survival of R.soongorica.In order to study root morphology and water use efficiency of R.soongorica seedlings to provide suggestions for rehabilitating degraded ecosystem,we studied the root morphology and water use efficiency of R.soongorica seedling under different water conditions（full irrigation,FI;moderate irrigation,MI;drought treatment,DT） by pot experiment.The results showed that：（1）R.soongorica seedling root morphology demonstrated great variations under different water gradient and root order.With the decrease of irrigation amounts,R.soongorica root diameter and root volume were FI＞MI＞DT,but drought treatment promoted the elongation growth of root and increased its specific surface area and specific root length,which indicated that R.soongorica seedling through the changes of morphological characteristics such as root elongation growth,root surface area increase,root volume and root diameter decrease to adapt to drought stress.（2）With increasing of root orders,the root length and specific root length significantly decreased in different soil water conditions.However,the root with higher order had greater root diameter and volume,these phenomena indicated the highly morphological variation of fine root system of R.soongorica.（3）Compared with full irrigation,moderate irrigation and drought treatment made the total root biomass and lateral root biomass of R.soongorica seedling increased 50.00% and 19.23%,respectively.However,the above ground growths of R.soongorica were depressed with the decrease of soil water,especially the leaves biomass reduced at maximum,which decreased 62.15% and 83.28%,respectively,which resulted in the root shoot ratio increased with the reduced of irrigation amounts.（4）Drought treatment significantly increased the R.soongorica seedling water use efficiency.We conclude that R.soongorica seedling through the changes of morphological characteristics such as root length,root surface area and volume,and diameter to optimize the spatial distribution of configurations in order to adjust the plant to improve water use efficiency.