Cell and nuclear area, RNA and protein content, and chromosome counts in meristematic cells of secondary roots and callus of Cocos nucifera

Abstract

The relationships between cell area, nuclear area, and cellular RNA and protein content were determined for mitotic cells in callus lines D-80, D-81, H-81, and H-83, for which ploidy levels were determined, and compared with the corresponding relationships for cells in the secondary root meristem of dwarf, hybrid, and tall varieties of Cocos nucifera L. Mitotic cells in hypotetraploid line D-80 and diploid H-83 showed increases in cell size and cellular RNA and protein content compared with mitotic cells from dwarf and hybrid root tips. However, there was a disproportionate increase in cell size in lines D-80 and H-83. Probit analysis revealed that cell size and protein and RNA content per cell were less tightly coupled in these callus lines. Apart from line D-80, nuclear area for prophase cells in the other three diploid callus lines was very similar to that in cells of the variety from which each was established. Overall, our results suggest that nuclear and cellular parameters are free to change independently of each other when cells are transferred to culture media. Furthermore, the failure to increase RNA and protein contents by amounts equivalent to changes in cell size may have detrimental effects on the cell cycle in callus cells.