掌叶木幼苗根瘤形成及土壤石砾含量对根瘤形成的影响

Root Nodule Formation of Handeliodendron bodinieri Seedlings and Effects of Soil Gravel Content on Root Nodule Formation

为探究掌叶木(Handeliodendron bodinieri)幼苗根瘤形成及土壤石砾含量对根瘤形成的影响,以掌叶木幼苗为研究对象,采用石蜡切片技术,结合体视显微镜,观察掌叶木幼苗根瘤形成及发育过程;设置不同的土壤石砾含量,分别为0%(CK)、20%、40%、60%和80%,探讨土壤石砾含量对根瘤形成的影响。结果表明,掌叶木幼苗根瘤属内源性根瘤,起源于中柱鞘细胞,多为圆形或椭圆形;幼嫩根瘤呈黄白色或淡黄色,表面光滑有光泽;衰老根瘤多呈深红棕色或褐色,质地较硬,有矿化或腐烂现象;部分新瘤叠生于老瘤之上,呈串珠状或叠生状;根瘤上有瘤毛。土壤石砾含量对掌叶木幼苗根瘤形成影响显著。随土壤石砾含量增加,根瘤数量和重量均呈先升后降的趋势;石砾含量为60%时,根瘤数量最多,最重。随土壤石砾含量增加,根瘤长度呈先升后降再升的趋势;石砾含量为80%时,根瘤最长。随土壤石砾含量增加,根瘤宽度呈先升后降的趋势;石砾含量为60%时,根瘤最宽。综合评价表明,掌叶木幼苗根瘤各形态指标在土壤石砾含量为60%时得分最高,说明适当增加土壤石砾含量,有助于掌叶木幼苗根瘤形成。

In order to explore root nodule formation of Handeliodendron bodinieri seedlings and effects of soil gravel content on root nodule formation,taking H.bodinieri seedlings as object,by paraffin section method and stereomicroscope,formation and development process of root nodules on H.bodinieri seedlings were observed and effects of soil gravel content on root nodule formation were discussed by setting different soil gravel con⁃tents including 0%(CK),20%,40%,60%and 80%.Results showed that root nodules on H.bodinieri seedlings were endogenous,which originated from pericycle cells.Shapes of root nodules were mostly round or oval.Young root nodules were yellowish-white or light yellow,and surfaces were smooth and shiny.Senescent root nodules were mostly dark reddish-brown or brown,with hard texture and mineralization or decay.Some new root nodules were superimposed on old rood nodules,which were beaded or superimposed.Root nodules had root hairs.Soil gravel content had significant effects on formation of root nodules on H.bodinieri seedlings.Numbers and weights of root nodules increased firstly and then decreased with increase of soil gravel content.When gravel content increased to 60%,number and weight of root nodule were the largest.Lengths of root nod⁃ules tended to increase firstly,then decrease and increase with increase of soil gravel content.When soil gravel content was 80%,root nodule was the longest.Widths of root nodules tended to increase firstly and then de⁃crease with increase of soil gravel content.When soil gravel content reached 60%,root nodule was the widest.Comprehensive evaluation showed that when soil gravel content was 60%,morphological indexes of root nod⁃ules on H.bodinieri seedlings were the highest,which indicated that increasing soil gravel content proporly could help root nodule formation of H.bodinieri seedlings.