Roots turnover times

The control could be established if at any one time there was at the membrane more vesicles than those that were fusing. However in order to sustain the increase in secretion it would be necessary to transmit the signal back to the synthetic system and packaging process at the Golgi apparatus so that a new steady state system was obtained. This would produce the requisite number of vesicles containing the polysaccharides necessary to maintain the new rate of fusion and secretion. The turnover of the Golgi apparatus can be very fast in plant cells and times of 5-40 minutes have been calculated (36). In vitro experiments which involved isolation of membrane fractions from maize-root cells also showed that Ca was necessary for membrane fusion (37). Analysis of the membranes indicated that the Ca dependence involved membrane proteins and one of these was a Ca and Mg -dependent ATPase (38). 

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