Abstract:

Malus hupehensis Rehd. seedlings were used as test materials，study the effect of different
boron concentrations（0，1.0，2.0，3.0，4.0，5.0 and 6.0 mg · L-1 boric acid）to Malus hupehensis Rehd.
seedlings root growth，nitrogen uptake，utilization and distribution using 15N isotope tracer and
non-damage microtest techniques. The results showed that root vigor and root morphological index of
seedlings treated with 3.0 mg · L-1 boric acid treatment were significantly higher than those of other
treatments. Compared with the control，the total N and 15N uptake of 3.0 mg · L-1 boric acid treatment
increased by 19.4% and 75.0%，respectively. With the increase of boron supply，the nitrogen use efficiency
of plants increased first and then decreased，and it was 14.8% at 3.0 mg · L-1 boric acid treatment，which was 1.8 times of the control. The effect of boron treatment on the 15N partitioning rate of seedlings was
significant，and the root partition rate of 3.0 mg · L-1 boric acid treatment was the highest and significantly
higher than that of the control. The results of non-damage microtest showed that the root absorption of
NO3
- was strong and the influx velocity was the highest in 3.0 mg · L-1 boric acid treatment，and obvious
efflux in the treatments of boron deficiency（0 mg · L-1 boric acid） and high boron（6.0 mg · L-1 boric
acid）. Therefore，3.0 mg · L-1 boric acid treatment was most beneficial to the root growth，root activity and
nitrogen absorption and utilization of Malus hupehensis，while low boron and excess boron could inhibit
roots growth and nitrogen uptake and utilization.

Key words: apple, boron, NO3-, absorption, utilization, distribution