Effects Of Phosphorus Supply On Phosphate Uptake Of Six Kinds Of Shrubs

Phosphorus is one of important nutrient elements and the main limiting factors which influence plant growth in arid desert region. Shrubs serve as a major component of arid desert vegetation and play an important role in the process of desertification control and grassland restoration. Researching the response mechanism of shrubs to low phosphorus, and excavating shrubs P utilization potential has great significance in maintaining the stability of the arid desert ecosystem and developing excellent low phosphorus-tolerantce genetic resources.Using 3 kinds of leguminous shrubs (Amorpha fruticosa, Lespedeza davurica and Caragana korshinskii) and 3 kinds of non-leguminous shrubs(Caryopteris mongholica, Zygophyllum xanthoxylum and Nitraria tangutorum) as experimental materials, soil culture method was employed to study the effects of different phosphorus levels (P0, PI, P2, P3 and P4 corresponding to 0,17.5,35.0,52.5 and 70 mg/kg soil respectively) on the growth, root morphology, acid phosphatase activity, phosphorus accumulation, homeostasis and activation. The main results were shown as follows:(1) Phosphorus supply significantly improved the growth of 6 kinds of shrubs except Z. xanthoxylum. With the phosphorus levels increased, the biomass, plant height and basal diameter in C. mongholica and A. fruticosa increased firstly and then declined, and reached the maximum in P1, P3 treatment respectively. The three indexes in C. korshinskii reached a higher level in P3 treatment, increased gradually in N. tangutorum, and showed no significant difference in both L. davurica and Z. xanthoxylum. The root-shoot ratios of 6 kinds of shrubs in phosphorus deficiency treatment were significantly higher than that in phosphorus supply treatment except A. fruticosa and Z. xanthoxylum.(2) With the phosphorus levels increased, the root total length, total surface area, total volume and average diameter in C. mongholica and A. fruticosa rised firstly and then decreased, and reached the maximum in PI, P3 treatment respectively. Under the control treatment, the four indexes in C. korshinskii and N. tangutorum were significantly smaller than that in phosphorus supply treatment except root average diameter, but there was no significant difference among phosphorus supply treatments. The root total length, total surface area and total volume of in L. davurica also increased firstly and then declined, and reached the maximum in P2 treatment, but the root average diameter reached the maximum in the control treatment.(3) In all the phosphorus levels, acid phosphatase(APA) activity in leaf were higher than that in root in 6 kinds of shrubs except L. davurica and Z. xanthoxylum. APA activity of C. mongholica in leaf was about 20 times higher than that in root. Great difference showed in the plant APA activities in 6 kinds of shrubs. Among them, APA activitives of Z. xanthoxylum were the lowest (<1 umol/g·min); APA activitives of C. korshinskii were the highest, ranged from 7.19 to 19.63 umol/g·min. Under low phosphorus levels (P0, P1 treatment), the leaf and root APA activitives of 6 kinds of shrubs reached a higher level. With the phosphorus levels increased, APA activitives declined. Under high phosphorus level (P4 treatment), leaf APA activitives of N. tangutorum and Z. xanthoxylum and both leaf and root APA activitives of L. davurica rebounded.(4) With the phosphorus levels increased, the shoot and root total P content of 6 kinds of shrubs gradually rised except Z. xanthoxylum and C. mongholica; The shoot, root and whole plant P accumulation of C. mongholica and A. fruticosa raised firstly and then decreased, and reached the maximum in P1, P3 treatment respectively. The three indexes increased gradually in L. davurica, C. korshinskii and N. tangutorum, and showed no significant difference in Z. xanthoxylum. The response of the shoot, root and whole plant P accumulation of 6 kinds of shrubs to phosphorus supply is basically consistent. The rank of the sensitivity of 6 kinds of shrubs to environmental phosphorus levels was N. tangutorum> L. davurica> A. fruticosa> C. korshinskii> C. mongholica> Z. xanthoxylum.(5) The homeostatic regulation coefficients (H) of phosphorus in 6 kinds of shrubs ranged from 1.32 to 5.78. The rank of HP of the shoot and root in 6 kinds of shrubs is consistent. The H values rank was Z. xanthoxylum> C. mongholica> N. tangutorum> A. fruticosa> C. korshinskii> L. davurica, that is:non-leguminous> leguminous. The aboveground H value were higher than that in belowground in 6 kinds of shrubs except C. mongholica.(6) With the phosphorus levels increased, the available P content in the rhizosphere and non-rhizosphere soils of 6 kinds of shrubs rised gradually except A. fruticosa and Z. xanthoxylum. Under the control treatment, there were consistently higher available P contents in the rhizosphere soils than that in the non-rhizosphere soils of Z. xanthoxylum, L. davurica and C. korshinskii, phosphorus enrichment phenomenon appeared in the rhizosphere, however, significant difference only showed in Z. xanthoxylum.