In: Phyton, 53 Fasc. 1 (2013), S. 133-149, with 3 figures
Key words: Cambium, growth regulators, Kigelia africana, vascular differentiation.
Mishra P., Pramod S. & Rao K. S. 2013. Effect of exogenous growth regulators on secondary vascular tissue differentiation in the twigs of (Lam.) Benth. – Phyton (Horn, Austria) 53 (1): 133–149, with 3 figures.
The effect of gibberellic acid (GA), naphthalene acetic acid (NAA) and ethephon on dormant and actively growing twigs of was studied by histological and histochemical staining methods. Application of GA and ethephon alone on dormant twigs did not initiate cambial cell division and differentiation, while application of NAA lead to cambial cell division but failed to differentiate cells towards xylem and phloem. Application of GA together with NAA and the combination of GA, NAA and ethephon induced rapid cambial cell division and differentiation of xylem and phloem elements. In the upper portion of twigs close to the point of GA, NAA and ethephon application the cell walls of cambium and phloem elements underwent lignification, while formation of earlywood and latewood was observed in the lower portion. Moreover the application of this hormone combination on actively growing twigs resulted in the formation of tyloses in vessels and differentiation of parenchyma cells with intercellular spaces towards phloem. The combination of GA-NAA promoted rapid cambial cell division and differentiation towards xylem. Maule’s reaction revealed increase in ‘S’ type of lignin in the walls of newly formed vessels and associated parenchyma cells following GA+NAA treatment.