Abstract
SummaryAbscisic acid (ABA) promoted a significant increase of the heterocyst frequency in cultures of Nostoc 6720. A significant interaction between ABA and the concentration of Ca2+ in the growth medium was detected. Studies using 45Ca2+ confirmed that the intracellular Ca2+ content was raised by 20% in the presence of 10−6 M ABA. Verapamil, a Ca2+ channel antagonist, inhibited the ABA‐induced increase in heterocyst frequency. Trifluoroperazine, a known inhibitor of Ca2+/protein binding, also inhibited the response to ABA.The characteristics of the response to ABA were similar to those of the Ca2+ ionophore, A23187. Both promote an increase in the total nitrogenase activity of the culture, which, it is suggested, may result from a Ca2+‐dependent protective mechanism similar to that proposed for Gleocapsa. A Ca2+‐dependent repression of dinitrogen fixation is suggested to account for the increased nitrogenase activity in cultures induced to form heterocysts in the presence of lanthanum or when the concentration of Ca2+ in the growth medium is less than 10−4 M.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
