Figure 1.

The experimental setup of the PVC-block technique used in the present study (A). One PVC block consisted of five vertical slits, allowing us to mount five seedlings simultaneously at five different ATS positions (B). The horizontal slits were filled with agarose medium after positioning the roots and sealing the vertical slits with petroleum jelly. The setup was immersed in an upright position into NS up to the level indicated by the arrow. Once the seedlings were in place, the roots were covered with filter paper and kept moistened by frequent spraying with NS. ATS in relation to described morphological and physiological organization of the root apex (see introduction) are shown in B. AEZ, Apical EZ; CEZ, central EZ.