Effects of auxin application on the lignification of xylem parenchymatous cells and the development of hollowness in the root of Japanese radish (Raphanus sativusL.)

Abstract

SummaryThe effects of auxin application at different stages of growth on the development of hollowing in the root of Japanese radish, cv. Gensuke, was evaluated by foliar-spraying with the Na-salt of a-naphthaleneacetic acid (NAA) every three days for 15 days during four different growth periods. The treatment from day 16 after sowing to 30 days after sowing (DAS) slowed the rate of thickening of roots and resulted in a higher density of vessels, active lignin formation and a large hollow cavity. In contrast, the same treatment during the other growth periods exerted none of these effects. In the second experiment, to investigate cultivar differences in the development of hollowing in Japanese radish treated with NAA, the leaves of plants of three cultivars were sprayed with this compound. A treatment of 1 mg l−1 of NAA limited thickening of root of cv. Yamada and caused it to form a high density of vessels. This resulted in active lignin formation and production of a large hollow cavity. The same treatme...