Persea americana, Mesocarp Cell Structure, Light and Electron Microscope Study

The bulk of the mesocarp of the fruit of the avocado (Persea americana) consists of polyhedral parenchymatous cells and scattered oil idioblasts. Oil is abundant in the cytoplasm of the parenchyma and also fills the oil sacs of the idioblasts. 2. In young fruits all cell walls consist principally of cellulose. The thick walls of idioblasts in the mature fruit are heavily suberized. Intercellular spaces are lined with a suberin pellicle.3. Plasmodesmata are ubiquitous; the pits on the interparenchymatous walls are large, in contrast to those of the parenchyma-idioblast cell faces. 4. In fresh material of the mature fruit the suberized idioblasts are frequently impermeable to aqueous stains and to standard microchemical reagents that react immediately with parenchymatous elements. At what stage of growth this impermeability develops is not known, nor is it known to what extent wall suberization slows down or blocks the transport of materials from chlorophyll-containing parenchyma to idioblast. 5. The details of interparenchymatous and of parenchyma-idioblast microfibrillar pit patterns are evident under the electron microscope. 6. Chloroplasts with lamellae and starch and elaioplasts with coronae of oil droplets occur in the parenchymatous cytoplasm. 7. The oil sac is ensheathed by cytoplasm from which strands radiate to the peripheral cytoplasm and the cell wall with its plasmodesmata. Plasmodesmata also occur at the base of the stalk. 8. Pores in the suberized layer of the cell wall of the idioblast mark the path of plasmodesmata.