Abstract

Orchid plants are thought to be glycophytes. Oncidium hybridum var. Gower Ramsey (OhGR) plants were tested for the halotolerance by cultivation in 0-5000mM NaCl solutions. Phenotypes such as leaf morphology and electrical conductivity of the salt treated plants for a week, and gene expression spectrums of different parts of those plants were analyzed. Electron transfer carrier genes OhFNR and OhFD as an example of house-keeping genes, a transcription factor OhMYB1R1 and a phospholipase D gene OhPLDζ1 as tolerance responsive genes, were investigated with qPCR. It was found that OhGR plants absorbed salt without secretion, the leaves turned yellow in the salt treatment with a basal to upper manner and the electrical conductivity of the leave tissues increased accordingly with the leaf morphological change. The genes assessed showed stress timing and tissue specific differential spectrums in which OhFD -OhFNR were co-inhibited by salt stress, OhMYB1R1 and OhPLDs were stress inducible and enhanced. At the meanwhile, the upper leaves, the pseudobulbs and the roots kept morphologically normal and alive in most tested OhGR plants in various salt conditions tested, even a high amount of salt had been accumulated in the plants as revealed by electroconductivity measures. Our results show that OhGR plants have high salt tolerance potential based on their ordered cell and molecular mechanisms.

Keywords: Halotolerance; Halogenomics; Ferredoxin; Phospholipase D; MYB