Chloroplast ultrastructural development in vascular bundle sheath cells of two different maize (Zea mays L.) genotypes

The leaves of maize have two photosynthesizing tissues with two types of chloroplasts, mesophyll cells (MC) and vascular bundle sheaths cells (BSC). The development of chloroplasts in BSC was followed by transmission electron microscopy and point counting method in the middle part of the third leaf of maize plants. From young (Y) to mature (M) leaves, volume density of photosynthetic membrane system (thylakoids) increased, to senescing (S) leaves it did not significantly change. During the whole leaf ontogeny, small thylakoid appression regions (grana) were present in BSC chloroplasts, currently assumed to be agranal. From M to S leaves, volume density of starch inclusions strongly decreased and that of plastoglobuli strongly increased.