Nutrient uptake strategy selection by first-order roots of Juglans mandshurica under shading and phosphorus limitation
We investigated root growth of 1-year-old Juglans mandshurica seedlings under different light environ-ments and varying doses of phosphorus fertilizer,to understand the relationship between root resource acquisition strategies and the variations of light and phosphorus availability.There were four shading intensities(full light,65％full light,35％full light,and 20％full light)along with three doses of phosphate fertilizer(0(CK),200％soil background available phosphorus,and 500％soil background available phosphorus).We measured in root mor-phology characteristics,architectural characteristics,and mycorrhizal colonization rates of first-order roots.The re-sults showed that average diameter,average root length,and mycorrhizal colonization rates of first-order roots grad-ually decreased,and the specific root length,specific surface area,branching ratio and branching intensity showed a trend of first increasing and then decreasing with the increases of shading degree.As the phosphorus content decreased,the first-order root diameter gradually became thinner,and the mycorrhizal infection rate gradually increased.Root morphology and architecture of J.mandshurica would undergo adaptive changes under shade,adap-ting to the shading environment by expanding specific root length,specific surface area,branching ratio and branching intensity.Under phosphorus limitation,root system of J.mandshurica would increase phosphorus absorp-tion through symbiosis with mycorrhizal fungi.When J.mandshurica was artificially regenerate in forest land with a light transmittance of 35％,root morphology and architecture would adapt to the shading environment.The symbio-sis between J.mandshurica and mycorrhizal fungi would be enhanced under phosphorus limitation,which could improve phosphorus absorption of roots.
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