Callose biosynthesis in developing gemmalings of the liverwort Riella helicophylla: effects of aromatic nitroso-compounds

Abstract

The vegetative life cycle of the aquatic liverwort Riella helicophylla consists of three stages: adult plantlet, gemma and gemmaling (asexual reproductive structure). In meristematic cells of 8-day-old gemmalings that were grown in a 12 h light/12 h dark-cycle, the number of callosic cell plates displayed a minimum at 2 pm (day) and a maximum at 2 am (night). We compared the effects of two drugs on the enhancement of callose biosynthesis: the nitroso-derivative of the calcium antagonist nifedipine and the simplest aromatic nitroso-compound, nitrosobenzene. Callose synthesis (deposition of β-1,3-glucan) was promoted in cell plates by both substances. Moreover, nitrosobenzene is capable of inducing callose synthesis in juvenile walls of elongating cells, whereas the effect of nifedipine is restricted to the meristem. T-, H- and net-like callose structures could be observed in the meristem of drug-treated gemmalings. Our results indicate that the differences in the observed cytotoxic effects depend on the steric properties (chemical structure) and thus the reactive behaviours of the two nitroso-compounds.

Keywords:

• CALLOSE
• CYTOKINESIS
• DEVELOPMENT
• NIFEDIPINE
• NITROSOBENZENE
• RIELLA HELICOPHYLLA.