(B) Sieve plate P-protein Sieve tube Sieve plate element Lateral sieve Modified plastid Sieve tube 日日日 element Companion Smooth ell endoplasmic reticulum Branched Cytoplasm plasmodesma Plasma Vacuole membrane Chloroplast Figure 6-1 Thickened一 primary wall Nucleus Sieve plate pore Mitochondria Sieve plateFigure 6-1