Fig. 2. Branch dilation does not account for dendrite growth.

(A) Top: Internal branches are branches that lie between two branch points, as distinct from terminal branches that end in a tip. Bottom two panels: Two models for dendrite growth. Middle: Elongation of existing branches and infilling with new branches. Bottom: Maintenance of internal branches and growth and infilling with new branches. (B) Maximum projection image of a GFP-labeled class IV neuron cell (genotype ;;ppkCD4-tdGFP) at 24 hours (magenta color) and same cell imaged at 48 hours (green color). Twenty-four– and 48-hour images are combined with a leftward displacement of the latter. The area in the gray boundary (inset) is enlarged in (C) and (D), where conserved internal branches are marked with the same color circle and number (see Materials and Methods). (E) The fractional length changes of the hemisegments along the AP and LR axes were calculated from 24 to 48 hours and from 48 to 96 hours, together with the fractional length changes of the internal branches. Each blue and green circle is a different larva; the red circles correspond to several branch measurements in each of six larvae.