IAA and zeatin controls cell division and endoreduplication process in quiescent center cells of Allium cepa root

Abstract

Role of endogenous IAA and zeatin level in regulation of cell division and endoreduplication processes was studied in quiescent center cells of Allium cepa using colchicine by considering morphological and cytological parameters. This resulted in formation of c-tumor at root tips, which contained endoreduplicated cells. Different concentrations of NAA and BAP (1–250 μM) were exogenously applied to these endoreduplicated root tips to depolyploidize endoreduplicated quiescent center cells. Exogenous NAA treatment showed negative response on depolyploidization of quiescent center cells of root tips. However, elongation of cells, and decrease in nucleus size was observed after exogenous NAA treatment. There was no change in length of endoreduplicated roots, and growth of root at the tip of c-tumor. Exogenous BAP showed positive response in depolyploidization of quiescent center cells of root tips. There was remarkable increase in length of roots, growth of root at tip of c-tumor and decrease in cell size and nucleus size after BAP treatment. It induced cytokinesis process in endoreduplicated meristematic cells and started cell division and differentiation process in quiescent center cells. Endogenous IAA and zeatin measured from normal, endoreduplicated and depolyploidized quiescent center root tip cells suggested that when endogenous IAA/zeatin ratio is high in meristematic cells then cell cycle shifts towards endoreduplication process but when it decreases cell cycle shifts towards cell division process.