Callus of Pinus roxburghii (Chir pine) and its cytology

Callus was initiated form different vegetative parts of 3 to 5-week-old seedlings of Pinus roxburghii Sargent. Best results were obtained on Murashige and Skoog's revised medium supplemented with 4 mg1⁻¹ NAA or 2,4-D, 1 mg1⁻¹ kinetin and 15% coconut milk. Callus was grown successfully for more than a year without deterioration in its growth. Growth rate studies on the calli form cytoledon explants were undertaken with different concentrations of auxins and cytokinins. Histogenic differentiation of tracheids ocurred in all the calli, with the formation of bordered pits preceding the reticulate thickenings of the tracherary walls. Cells in the 4 to 12-week-old calli were predominantly diploid, though a few polyploid and aneuploid cells were also noticed. Chromosome bridges and laggards were observed in a number of cells.