Abstract: TA could stimulate NK activity induction by KNO3 in Pinus elliottii Engelm. seedlings at different ages. TA could not induce NR activity alone, but could enhance NR induction by NO3. TA eliminated partially the inhibition of arsenate (an oxidate phosphorylation decoupler). The accumulation of chlorophyll accelerated by TA or BA closely paralleled to the increase of NRA accelerated by TA or BA. Cycloheximide (CHM) could inhibit the effect of TA on NRA in roots and excised etiolated leaves exposed to light and NO3. Lincomycin (LCMC, an inhibitor of chloroplast protein synthesis) could only inhibit the effect of TA in etiolated leaves, but did not inhibit the effect of TA on NRA in roots. The inhibition of CHM was much stronger than LCMC.TA(0.5ppm, l.0ppm) could increase the height of seedlings in the field experiment. The root system of TA treated seedlings was superior to the control.