Effects Of Root Control Treatments On Morphological And Physiological Straits Of 1-yr-old Juglans Mandshurica Seedling

The main roots of 1-yr-old Juglans mandshurica seedlings are longer and the lateral roots are less,which affects the quality and efficiency of transplanting.In order to shorten the length of main root,promote the development of lateral root and improve the survival rate of transplanting,three kinds of root control treatments were set up in this study:① radicle short cutting(RC1:cut 1/2,RC2:cut 1/3,CK1:control,not short cutting);②physical root pruning(linoleum paper buried under the soil of seedbed,PP1:depth 15 cm;PP2:depth 20 cm;CK1:control);③ chemical root pruning(15 cm depth of soil is embedded in felt paper coated with CuSO4 root control agent,CP1:100 mgCuSO4+1 L latex paint,CP2:150 mgCuSO4+1 L latex paint,CP3:200 mgCuSO4+1L latex paint,CK2:1 1 latex paint).The seedling height,ground diameter,biomass,root configuration,length of main root,number of lateral root and physiological indexes such as chlorophyll content,nutrient element content of each organ and non-structural carbohydrate content were measured,and the effects of different root control treatments on seedling morphology and physiology were analyzed.The results show that:(1)Different root control treatments had no significant effect on 1-yr-old seedling height,ground diameter,height diameter ratio,root mean diameter,leaf area and seedling quality index,but they inhibited the growth of main root and promoted the development of lateral root(P<0.05).RC1,RC2 and chemical root control significantly inhibited the length of main root(RC1:13.17 cm;RC2:13.06 cm;CP1;11.90 cm;CP2:11.13 cm;CP3:11.66 cm);RC2 significantly increased leaf area,total root length,root surface area,root volume,number of primary lateral roots and root tip;RC1 and PP1 inhibited the growth of leaf area.(2)Different root control treatments had significant effect on the dry weight and stem root ratio of roots,but had no effect on the fresh weight and dry weight of leaves and stems and the fresh weight of roots(P>0.05).The total root dry weight of RC2 and the root dry weight of d<2 mm were significantly higher than that of PP1(RC2:7.35 g,2.04 g;PP1:5.22 g,1.32 g respectively);the stem root ratio of CP1 was significantly higher than that of the control(CP1:2.49;CP2;2.02).(3)Different root control treatments had significant differences in the content of elements in each organ.RC1 and RC2 increased the C and N content of leaves,CP1 and CP2 reduced the C content of stems,PP1 reduced the N content of roots with d≥4 mm.RC1、RC2 and PP1 reduced the C/N content of organs and the P content of roots with 2≤d<4 mm,and chemical controlled roots decreased d≥4 of P content in mm root system.K content in root system increased in all treatments of radicle cutting and physical root control,while K content in root system increased only in chemical root control.(4)Different root control treatments had significant effects on leaf area and soluble sugar,soluble starch and NSC content of each organ,but no significant effects on chlorophyll content of leaves.RC2 increased leaf area,while RC1 and PP1 decreased leaf area.Radicle short section and physical root control increased soluble sugar content in roots with d≥4 mm.RC1,RC2 and PP1 decreased soluble starch content in stems,CP1 and CP3 reduced soluble starch content in roots with d<2 mm and d≥4 mm;RC1,RC2 and PP1 reduced leaf,stem and 2≤d<4 mm CP1 and CP3 decreased NSC content of d≥4 mm roots.To sum up,among all root control treatments,radicle short cutting and chemical root control had the best inhibition effect on the main root,among which RC2 and CP1 had good effects on promoting lateral root,number of first-order lateral root,number of root tips and seedling quality index,while radicle short cutting increased the fine root biomass by 1/3.In physiology,RC1 and RC2 increased the content of C and N in leaves and stems and K in roots of different diameters.RC2 also increased the area of leaves and the content of soluble sugar in roots.Generally speaking,the treatments of radicle short cutting and chemical root control can inhibit the growth of main root and promote the development of lateral root.Among them,the effects of short cutting 1/3(RC1)and 100 mg/LCuSO4(CP1)are the best,but chemical root control can reduce the physiological status of seedlings.Therefore,this study considers that the short cutting 1/3 of radicle is the most suitable root control measure for the seedlings of Juglans mandshurica.