Medicinal and Aromatic Plants - vol 45 - Turmeric- The Genus Curcuma

30 Turmeric: The Genus Curcuma
FIGURE 2.6 Ontogeny of oil cells and ducts in turmeric: (A) Lysigenous development of duct in the intercalary
meristem. (B) Darkening of cell content and vacuole formation. (C,D) Complete disintegration of central
cell. (E) LS of oil duct filled with secretory substances. (F) Mature oil duct and neighboring cell containing
starch grains.
2.4.1.2.1 Initiation and Differentiation
Some of the cells in the meristematic shoot apex differentiate into oil cell mother cells, which are
distinguishable by their larger size, dense cytoplasm, and prominent nucleus. A group of oil initials
arise from the mother cells through anticlinal and periclinal division. These initials undergo cytoplasmic
vacuolation at a distance of 410 to 130 μm from the shoot apex. Subsequently the
surrounding cells also enlarge, undergoing cytoplasmic and nuclear disintegration. In due course
the central cell enlarges and then gets lysed, thereby leading to the formation of a duct, which can
be either an articulated or a nonarticulated type. The ducts get filled up with the contents of the
lysed cells. Often the wall dissolves completely and the entire process leads to the formation of
long ducts. Subsequently the cells surrounding the duct also get lysed, thereby leading to the
widening of the duct lumen. These stages can be seen about 3500 μm behind the apex.
2.4.1.2.2 Secretion
The oil cells that differentiate from the initials start a holocrine type of secretion and expel content
into the duct. Then the adjacent cell undergoes differentiation and the process continues. Simulta-