Fine Structural Studies on the Pycnidiospores of Botryodiplodia theobromae Pat.

The structure of the pycnidiospores of B. theobromae was investigatedby a combination of light microscope, a scanning electron microscopeand a transmission electron microscope observations. As observedwith the light microscope the hyaline non-septate pycnidiosporeis highly vesiculated while the pigmented septate one exhibitslongitudinal hyaline striations. Investigations with the scanningelectron microscope showed the hyaline non-septate pycnidiosporeto be smooth-walled without any form of ornamentation. The pigmentedseptate pycnidiospore on the other hand had a rough outer surfacewith a transverse groove, which probably indicated the positionof the septum. The longitudinal striations seen on such pycnidiosporeswith the light microscope were not observed under these conditions.Observations with the transmission electron microscope showedthat the outermost layer of the hyaline pycnidiospore was smootherthan that of the pigmented one. The pigment was on the outerlayer of the double-layered wall of the pigmented pycnidiospore.The inner non-pigmented wall layer was continuous with the septum.The septum tapered gradually to a thin layer in the centre whereit was perforated by a simple pore. The observations indicatedthat the pigmented spore was multinucleate while the hyalineone was uninucleate.     

Effect of External Supply of Growth Substances on Axillary Proliferation and Development in Dioscorea bulbifera

Bulbil development in cultured nodes of D. bulbifera proceededin the absence of growth substances from the medium. When IAAwas incorporated into the medium at the concentrations of 5mg l^–1 and 10 mg l^–1 the cultured nodes producedlarger bulbils than in its absences. When the concentrationof IAA was increased to 15 mg l^–1, however, the culturednodes produced a callus instead of a properly organized bulbil.The dry weight of bulbils increased when kinetin was added tothe medium at the concentrations of 0.05, 0.5, and 2.5 mg l^–1.The greatest increase was with 0.5 mg l^–1 kinetin. Onincreasing the concentration of kinetin in the medium to 5.0mg l^–1 the tissue produced had smaller dry weight thanthose produced in the absence of growth substances. Additionof different combinations of IAA and kinetin to the basal mediumresulted in the production of normal bulbils, roots, and shootsin some instances (suitable combinations) and in the productionof callus and abnormal shoots in others (non suitable combinations).