EFFECT OF ATMOSPHERIC-PRESSURE ON SUNFLOWER (HELIANTHUS-ANNUUS-L) PROTOPLAST DIVISION

Sunflower protoplasts were cultured in liquid medium under high atmosp heric pressure (0.2 to 0.6 MPa) and the plating efficiency, cell wall synthesis and microtubule organization were assessed. In 7-day-old cul tures under a pressure of 0.4 MPa and above, the division rate was str ongly reduced by more than 60% as compared to the control. Although mo st of the protoplasts had begun to regenerate a new cell wall they wer e unable to complete this process. Pressure also had an inhibitory eff ect on microtubule synthesis. The percentage of protoplasts showing a disassembled cortical network of microtubules was significantly increa sed up to 60% of the population. These effects were reversible: when p rotoplasts were transferred to normal pressure most of them rapidly re covered their capacity to divide and afterwards developed normally. Cu lturing protoplasts under a pressurized atmosphere revealed to be a go od model system for studying cortical microtubule dynamics.