Abstract: By using river sand and mixed soil as growth media, and treating with different concentration IBA, ETH, and NAA, this paper studied the root-hair development of Poncirus trifoliate seedlings, and the development cycle and distribution pattern of the root-hairs under phosphorus deficiency in sand culture. The root-hairs had a development cycle of about 4 days, and formed block-shaped and clumped, mainly around root, and with uneven distribution. Sand culture gave rise to the production of more root hairs, with an average of 486.3 per tap root, and treating with 1.0 μmol·L^-1 of IBA and ETH notably promoted root-hair development. The phosphorous deficiency in sand culture induced more root hair formation (636.3 per tap root). Mixed soil culture produced lesser root-hairs (212.3 per tap root), and all the test growth regulators had no obvious effects on the root-hair development.

Key words: Poncirus trifoliate seedlings, root-hair, sand culture, mixed soil culture, phosphorus deficiency, growth regulator