pulse labeling of carrot root phloem parenchyma ( daucus carota l. cv . nantes ) tissue with ( 14 ) c-proline followed by fractionation of the cytoplasmic organelles on sucrose gradients was used to determine the identity of the membranous organelles involved in the secretion of the hydroxyproline-rich glycoproteins of the cell wall .
C0033382
proline
C0020388
hydroxyproline