Time Course and Polarity of Primary Phloem Fibre Differentiation in Pisum sativum

Primary phloem fibres of Pisum sativum deposit lignified cellwalls, 2 and 5 days after germination in root and stem, respectively.Fibre bundles reach their final size within 4–6 days.The differentiation of the bundles as a whole is faster in thestem compared with the root. In the special diverging bundlesof the lower internodes of the stem the peripheral portionsmature earlier than the inner portions. A wound in the rootas well as in the stem, interrrupts the differentiation of fibresdirectly below it. At least one bundle below a wound is disturbedand often a whole bundle is missing. The meaning of these findingsconcerning the control of cell size is discussed. Pisum sativum, differentiation, induction, phloem fibres, polarity, time course