Developmental Aspects of Roots of Pisum Sativum Influenced by the G2 Factor From Cotyledons

A G2 Factor present in cotyledons of Pisum sativum influences several developmental events in roots. G2 Factor present in dry seeds (cotyledons and radicles) is transported to roots after germination and promotes cell arrest in G2 in about 35% of all root meristem cells. Present evidence suggests the G2 Factor promotes cell arrest in G2 only in cells that undergo normal cell differentiation (arrest) because the proportion of cells labeled with 3 H‐TdR after 16 hr does not differ among both seedlings or excised roots in the presence or absence of this substance. In this manner, trigonelline differs from chalones of animal tissues that usually suppress cell proliferation by cell arrest either in G1 or in G2. Experimental results suggest that cortex cells and not cells of vascular tissues in mature root tissues (20–22 mm from the meristem) are influenced by G2 Factor. Other recent publications indicate that the G2 Factor is trigonelline (N‐methyl nicotinic acid) and concentrations of synthetic trigonelline from 10 −5 to 10 −7 m are effective in promoting cell arrest in G2 in one of the G2 Factor bioassays.