Spatial reconstructions of pine leucoplasts were obtained from thin serial sections of resin duct cells. Plastid volume and envelope surface were estimated using morphometric methods and compared to chloroplasts of adjacent parenchyma cells. The high number of plastid sections in secretory cells is not related to leucoplast division occurring during the secretory stage, but to the differentiation of complex, amoeboid plastids, closely imbricated with each other. Furthermore, there is no “leucoplast network” resulting from the fusion of preexisting plastids. In contrast to chloroplasts, leucoplast shape is not ruled by a single morphogenetic program but results from rapid growth in all directions, filling most of the free cytoplasmic space. The plastid surface is enclosed by a continuous sheath of endoplasmic reticulum. The leucoplast volume per cytoplasm volume unit in a secretory cell is 2.5 times that of chloroplasts in a parenchyma cell. Owing to the overlapping of plastid structures, the leucoplast surface is more than 3 times larger than that of chloroplasts with the same space factor. The active production of terpenes during the short period of secretion is supported by a very specialized structure, the leucoplastidome, where the biosynthetic process is optimized by an increase in plastid volume and enlargement of the plastid surface allowing rapid processing of precursors and free outflow of the end products.