Abstract

STUDIES ON SOMATIC EMBRYOGENESIS OF STEVIA REBAUDIANA (BERTONI). BY SCANNING ELECTRON MICROSCOPE (SEM)

Humera Nazneen*, Samala Sridhar and S. Karnakar Reddy

Abstract

Development of somatic embryos from nodal and leaf callus of Stevia rebaudiana plant has been studied in detailed by Scanning Electron Microscope (SEM). Friable embryogenic callus by single spherical shaped cell aggregates with a diameter of about 20μm diameter is observed. They act as initial cell of somatic embryos or embryo mother cells. The fine structure of somatic embryos was clearly identified during the following sequential developmental stages: single spherical cell, early globular shape with conspicuous suspensor, typical globular shape, elongated shape, early heart shape, typical heart shape, torpedo shape. The high frequency of somatic embryos was found in callus tissues derived from mature leaves under a two step culture method. Low frequency of somatic embryogenesis was found on the leaf edges associated with very small callus formation and also from the callus tissues derived from young leaves under the one step culture method. In the SEM investigation, it is demonstrated that the sequential events leading to Stevia somatic embryogenesis arise through one unicellular pathway derived from Stevia somatic embryo mother cells.

Keywords: Stevia rebaudiana, Tissue culture and Scanning Electron Microscope (SEM).