Summary pH 5.9 is optimal for tobacco pollen tube growth in suspension culture. Little pH
changes of sugar-mineral medium result from the release of surface-linked compounds from
pollen grains. Germination and pollen tube growth bring about a progressive medium
acidification resulting in total growth inhibition. An increase of the buffering capacity of the
culture medium enhances pollen tube growth. When the pH was kept near the optimum by
25 mM MES-KOH buffer, pollen tubes grew for 4 days and in the presence of casein …