氮磷供给比例对长白落叶松苗木磷素吸收和利用效率的影响

Abstract

The effect of supply ratio of nitrogen(N): phosphorus(P) on P uptake and utilization in germinated Changbai larch(Larix olgensis Henry.) was analyzed in our research.The seedlings were cultivated in a greenhouse where fertilizers were supplied according to N ∶ P ratios of 1 ∶3,1 ∶2,1 ∶1,2 ∶1 and 3 ∶1.Seedling morphology and biomass accumulation,P content and concentration of needles and roots were measured.The method of vector diagnosis was used to analyze the interactions among biomass,P content and P concentration.Some seedlings were cultivated in hydroponic solutions for six hours to detect their kinetic characteristics.Two inorganic N sources,NH+4-N and NO-3-N,were employed to create the same N ∶ P ratios in the greenhouse experiment with the P source of PO3-4,separately.The results showed that root biomass accumulation and diameter increased significantly with the increase of N ∶ P ratio(P=0.0027 and 0.10013,respectively).Compared to the N ∶ P ratio of 1 ∶1,the N ∶ P ratio of 3 ∶1 increased the fine root length,surface area and volume by 14%(P=0.0178),21%(P=0.0004) and 5%(P=0.0009),respectively.Root P concentration,root P content and needle P content were not affected by N ∶ P ratios(P0.05).However,needle P concentration was higher in N ∶ P ratio of 1 ∶2 than 2 ∶1(P=0.0270) and 3 ∶1(P=0.0014),but it was not significantly different from that in N ∶ P ratios of 1 ∶3(P=0.0669) and 1 ∶1(P=0.0804).In N ∶ P ratios of 2 ∶1 and 3 ∶1,P utilization index was higher than the N ∶ P ratio of 1 ∶2 by 84%(P=0.0002) and 37%(P=0.0014),respectively.With the increase of N ∶ P ratio,P uptake efficiency increased linearly.N ∶ P ratio positively correlated with P uptake efficiency(R2=0.978).Vector diagnosis indicated that,compared to the N ∶ P ratio of 1 ∶2,the N ∶ P ratio of 1 ∶1 resulted in a nutrient dilution while the N ∶ P ratios of 3 ∶1,2 ∶1 and 1 ∶3 resulted in a nutrient deficiency for needles;the N ∶ P ratio of 2 ∶1,1 ∶1 and 1 ∶3 resulted in a nutrient excess while the N ∶ P ratio of 3 ∶1 resulted in a nutrient dilution for roots.The activity of acid phosphatase of needles in the N ∶ P ratios of 2 ∶1 and 3 ∶1 was higher than that in the N ∶ P ratio of 1 ∶1(P=0.0026) while the activity of acid phosphatase of roots in the N ∶ P ratio of 1 ∶2 was higher than that in 1 ∶1(P=0.0003).In solutions containing NH+4-N or NO-3-N,the P uptake rate did not change among N ∶ P ratios(P=0.3247 and 0.0934,respectively).However,the P uptake rate linearly and positively correlated with the ratio of NH+4-N ∶ P(R2=0.908),while there was no significant correlation between P uptake rate and NO-3-N ∶ P ratios(R2=0.005).In solutions supplied with NH+4-N and NO-3-N,Vmax and Km were regressed to be 0.89 and 0.60 mmol/h/g FM and 0.15 and 0.03 mmol/L,respectively.In conclusion,for improving the efficiencies of P uptake and utilization of larch seedlings under the circumstance of both supplied N and P,nitrification should be avoided and the N ∶ P ratio should be increased within a certain range.