The Influence of Different Carbon Sources, Photohetero-, Photoauto- and Photomixotrophic Conditions on ProtocormLike Body Organogenesis and Callus Formation in Thin Cell Layer Culture of Hybrid Cymbidium (Orchidaceae)

摘要

It is common to utilize sucrose as a carbon source in the induction of Cymbidium PLB and callus, and as an energy source in the tissue culture of other orchids. This study found carbon sources to be clustered into 4 groups according to their suitability for PLB and/or callus induction: cluster A (high PLB and callus inducers): fructose, sucrose; cluster B (intermediate PLB and callus inducers): galactose, glucose, turanose (a rare sugar); cluster C (intermediate PLB and low callus inducers): lactose,maltose, starch, mannitol, sorbitol; cluster D (poor PLB and callus inducers): mannose, xylose, raffmose, cellulose. Plants regenerated from control PLB-derived shoots were cytology-cally (using flow cytometry) and genetically (using 10mer RAPD) identical, despite varying photosynthetic capacities. Callus exhibited high levels of polysomaty. Plants could root under photoauto-, photohetero- and photomixotrophic conditions, with the latter showing the highest photosynthetic capacity at almost all photosynthetic photon fluxes (0-300 mumol CO_2.m~(-2).s~(-1)). Plants were acclimatized from all treatments with a 100% survival rate, although those derived from photomixo- and photoautotrophic conditions appeared (visually) to be much stronger, sturdier and more robust.