Effect of Top Grafting on Physiological Characteristics of Walnut Branches and Roots
To explore the effect of top grafting on the physiological characteristics of walnut branches and roots,10-year-old seeding rootstock+'Xiangling'walnut was used to be top grafted with'Qingxiang',with short cutting as the control.Physiological characteristics of annual branches and roots were compared and analyzed after 3 years of survival.The results showed that:(1)the vessel density,average length of annual branches after top grafting was 76.82 N/mm2,and 39.85 cm respectively,and the contents of N and K in leaves were 27.20 and 7.17 g/kg,which were significantly higher than those in regeneration treatments(P<0.05),indicating that top grafting improved the efficiency of nutrient transport and crown recovery.(2)The diameter of vessel of roots in 20-40 cm soil layer under regeneration treatment was 86.55 μm;the average density of vessel of roots in 0-20 cm soil layer reached 149.33 N/mm2,which were significantly higher than those in top grafting treatments(P<0.05),indicating that top grafting with'Qingxiang'changed the root structure to some extent.(3)The ratio of phloem thickness to branch radius in 0-20 cm soil layer after top grafting was 0.39,and the average length,diameter and the perimeter thickness of roots were 10.64 cm,2.36 mm and 70.09 μm,respectively,which were significantly higher than those in regeneration treatments,indicating that the photosynthetic products tended to be distributed to roots in 0-20 cm soil layer after top grafting with'Qingxiang'.(4)After top grafting with'Qingxiang',the cambium thickness of annual branches and roots in 20-40 cm soil layer reached 36.26 and 76.42 μm respectively,which were significantly higher than those in regeneration treatments.It means that it may have a strong thickening growth potential.So,'Xiangling'walnut top grafted with'Qingxiang'changed the annual branches and root transport structure,improved the nutrient transport efficiency,and then promoted the growth of crown and surface roots.
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