XVI International Botanical Congess

Plants respond to a large variety of external stimuli by changes in theconcentration of cytosolic calcium (?[Ca]c). These variations are converted into biological adaptive response through a cascade of events leading ultimately to gene expression. We will present and discuss experimental data showing that calcium entry through plasma-membrane (PM) is modulated by the organization of microtubules which has a profound influence on ?[Ca]c by controlling the activity and the stability of calcium channels. We will also present results indicating that the amplitude of ?[Ca]c depends upon the intensity of the applied stimulus that may act either on PM or on intracellular transport systems. The effects of these gradual and controlled ?[Ca]c from different origins on cellular activity will be discussed.