Abstract:

The processes and the influence factors of phosphorus absorbed by one-year seedling roots of Platycladus orientalis from three provenances, Taian, Shandong (ST), Liping, Guizhou(GL), Baotou, Inner Mongolia (NB), were studied with isotope atom indicator, ³²P. As a result, the patterns of the P uptaken in the three provenances were similar, while the quntities uptaken were different. The absorption rate of -H₂PO₄ (³²P) varied according to V= V₀exp (K_t). The efflux rate according to E=E₀/ (K_m +t)2, where V₀, E₀, K, K_m are constants, t is time variable. The absorption of phosphorus is influenced by some factors, such as the genetic variation, the physiological activities and the surroundings of the provenances. The half-time (T_1/2) of P(³²P) absorption for ST, Gl and NB were 6. 4, 6. 1 and 5. 8h respectively when cultured in nutrient solution, but they are 40. 7, 18. 4 and 7. 5h, partyly when cultured in soil. The half-time for P(³²P)maxium efflux (K_m) are 0. 9, 53, and 14 min separately. When the parts of root from root-tip to upper 0- 0. 5cm, 0. 5-7. 5cm and 7. 5-14. 5cm Were determined to root-tip or white, yellow-brown and brown sections, respectivly, at the brown section of the root more P (³²P) were uptaken by ST and GL than NB, at the yellow-brown were similar but at the root-tip zone, white section, less were uptaken by the formers than the latter. Most of P(³²P) had entered the seedlings remained in the roots and less were transported up to the part above the ground. The speed of movementin ST, GL and NB were 3. 0, 4. 0 and 2. 2cm/h and the mass removed were GL > ST > NB.

Key words: Platycladus orientalis (L.) Franco. Seedlings, Mineral absorption, Phosphorus, ³²P, Isotope method