Fig. 4.

Root apical meristem size and cell division parameters in wild-type plants and in plants either overexpressing CLEL genes or treated with CLEL peptides. (A) Root tip from a 7-d-old wild type (WT) (Left) and CLEL6-overexpressing plant (CLEL6-ox) (Right). (B–E) Quantitative analysis of RAM in roots of 7-d-old plants overexpressing a CLEL gene (CLEL-ox) (B and D) or in wild-type plants treated with an unmodified synthetic 12- or 13-aa CLEL peptide (C and E). (D and E) Number of cortical cells in the RAM. (F) Regression analysis of RAM length and number of cortical cells in the RAM (red line) and RAM length and length of cortical cells in the RAM (blue line) from 7-d-old wild-type plants and plants overexpressing a CLEL gene. (G) Number of cells undergoing cell division in the RAM of roots grown on MS medium (red line) and in MS medium containing 1.0 μM unmodified synthetic 13-aa CLEL6 peptide (blue line). Age of the seedlings was defined as days post planting. (H) Roots of 7-d-old seedlings of Arabidopsis pCYCB1::CYCB1-GFP marker line grown on MS medium (Left) or on medium containing an 1.0-μM unmodified synthetic 13-aa CLEL6 peptide (Right) to illustrate cells undergoing division. The black arrows in A point to RAM borders in a primary root from wild type (WT) (Left) and a plant overexpressing CLEL6 (CLEL6-ox) (Right), respectively. (Scale bar, 50 μm.) Error bars indicate the SD. One, two, and three asterisks indicate which values are significantly different from the control at P < 0.05, P < 0.01, and P < 0.001, respectively. ns, not significant. n = 8–12.