Peroxidase leakage and pollen tube growth inhibition in aged Nicotiana alata styles

An attempt was made to explain the influence of stylar age on the growth of compatible pollen tubes based on peroxidase data. The growth of compatible pollen tubes in Nicotiana alata styles varied with the physiological age of the style. Especially in detached styles ageing caused changes by which the tube growth was retarded, or even totally inhibited. One of these changes might be the increase in the activity of several stylar peroxidase isoenzymes. Among them, there was the isoenzyme 10 which has previously been suggested to be involved in the inhibition of the growth of incompatible pollen tubes. The senescence-induced increase in the activity of this isoenzyme in unpollinated styles was 3 to 4 times higher when the styles were detached from the flower. An in situ extraction of walls and intercellular material by centrifugation after vacuum infiltration of stylar sections revealed that after ageing during 7 days, the detached styles contained 9 times more extracellular peroxidase 10 than the styles which remained attached to the flower. A possible relationship between peroxidase release from cytoplasm to walls and intercellular spaces, and inhibition of pollen tube growth was discussed.