摘要
Tissue proliferation is a fundamental process in plant growth and development.As a relatively undifferentiated cell type,the cortex makes up the bulk of the ground tissue in most plant species.In the root of Arabidopsis thaliana,however,the cortex has a limited ability to proliferate.In the apical meristem of young seedlings(within 1 week of seed germination),only one layer of the cortex is present;as the root matures,a second layer of the cortex starts to form in the elongation zone as a result of an asymmetric cell division of the endodermis,another cell type in the ground tissue(Cui and Benfey,2009a,Figure 1A).In the roots of rice and maize,the cortex/endodermis initial(CEI)undergoes multiple rounds of division.Only the innermost cell layer is differentiated into the endodermis;the outer layers of cells become the cortex by default.
