Chromoplasts ultrastructure and estimated carotene content in root secondary phloem of different carrot varieties
Scanning (SEM) and transmission (TEM) electron microscopic studies in fresh and stored roots (4 months at an average temperature of +8 degrees C) of Daucus carota L. (carrots) were carried out. Chief stress was laid on the analysis of the histological and cytological structure of the secondary phloem parenchyma cell. SEM images show the three-dimensional histological arrangement of the cells. Moreover, the outlines of lipid droplets, mitochondria, starch grains, and carotin pigment crystals are visible within the parietal cytoplasmic layer. In TEM, besides the usual cell organelles (mitochondria, golgi-apparatus, ER, etc.) nuclei with several nuclear bodies can be recognised. The morphological structure of the chromoplasts shows a remarkable diversity. Within stored carrots a strong reduction of lipid droplets and starch grains within the chromoplasts takes place.