The taproot

leteral root and the growth of hypocotyl and root/shoot ratio of plant seedlings are important characteristics relevant to seedling drought tolerance. The N+ ion beams with 25keV energy and the doses of 600-3600 × 2.6 × 1013 · cm-2 were implanted into the liquorice dry seeds

among which 1800 × 2.6 × 1013 · cm-2 could improve effectively the taproot growth of liquorice seedlings at period of 6d and root/shoot ratio (dry weight and fresh weight) and promote the development of lateral roots of liquorice seedlings at the period of 30d

and stimulate obviously the growth of hypocotyl and taproot and stem height of seedlings at the period of 6d and 30d. The parameters can be considered as those of energy and dose of N+ ion beam irradiation whose M1 mutagenesis effect on liquorice plant vegetation in desert area is to be studied for reference. Within the implantation parameter ranges in this experiment

the response of N+ implantation to drought tolerant characteristics of liquorice seedlings also shows the "damage-repair-damage" effect.