Abstract:
Both
lrn1 and
prl1, two
Brassica napus root mutants insensitive to exogenous cytokinin, show phosphorus efficiency. Compared with‘Ningyou 7’(WT) plants,
lrn1 produces more lateral roots and
prl1 has longer primary roots under 0.2 μmol/L cytokinins (6-BA) treatment by hydroponics. In this study, differences in root hair, differentiation of epidermal cells and anatomical structure of the root tip of all three genotypes under ddH
2O and 0.2 μmol/L 6-BA were studied with stereomicroscopy, non-sliced squash method and paraffin sectioning. Results showed that the root hair number at the zone of maturation in
lrn1,
prl1 and WT at ddH
2O was significantly less than that under 0.2 μmol/L 6-BA treatment. Under 0.2 μmol/L 6-BA treatment, the root hair length and density of WT was the longest and highest, while that of
prl1 was the shortest and lowest, and that of
lrn1 was between WT and
prl1 3 days after germination (DAG3). The zone of cell division and cell elongation of
lrn1,
prl1 and WT were shortened under 0.2 μmol/L 6-BA DAG6. The meristem areas of
lrn1 and
prl1 were greater than that of WT, and there were no differences between these two mutants. Moreover, cell structure of the root cap of
lrn1 and
prl1 were normal, whereas, that of WT was abnormal. Periblem cell arrangements of
lrn1 were closer than that of WT and
prl1. Under 0.2 μmol/L 6-BA DAG9,
lrn1 had four lateral roots, whereas
prl1 and WT had no lateral roots. Longer primary root length of
prl1 was closely related to its larger meristem area; and more lateral roots in
lrn1 under 0.2 μmol/L 6-BA treatment were due to higher cell density in the plerome in the zone of cell division.