In Vitro Propagation of Origanum scabrum (Boiss. & Heldr.): An Endemic Medicinal Plant of Greece

The aim of the study was to develop an efficient micropropagation protocol of Origanum scabrum, which will allow its commercial exploitation in the pharmaceutical and horticultural industries. First, the effect of the date of the explant collection (20 April, 20 May, 20 June, 20 July, 20 August) and the position of the explant on the plant stem (shoot apex, 1st node, 3rd node, 5th node) on the establishment of in vitro cultures was studied (1st experiment: Stage I). Next, the effect of temperature (15 °C, 25 °C) and the node position (microshoot apex, 1st node, 5th node) on the microplant production and ex vitro survival of plantlets was studied (2nd experiment: Stage II). The optimum season to collect explants from wild plants was shown to be during the vegetative growth of the plants (April to May), while the shoot apex and the 1st node were the most suitable explants. For the proliferation and production of rooted microplants, the best results were obtained from single-node explants excised from microshoots produced from 1st node-explants collected on 20th of May. Temperature did not affect microshoot number, leaf number and the percentage of rooted microplants, while microshoot length was higher at 25 °C. Moreover, microshoot length and the percentage of rooted microplants were higher in those derived from apex explants, while the survival of plantlets was not affected by treatments and ranged between 67% and 100%.

Permeability of rod outer segment disk membranes as probed by Ficoll density gradient centrifugation and by turbidimetry

Osmotic volume changes of isolated disks prepared from bovine rod outer segments were investigated utilizing the capacity of osmotically intact disks to float on 2.5% (w/v) Ficoll under hypotonic conditions. The amount of floating disks decreases steadily and approximately linearly when the osmolarity is increased stepwise with an osmotically active solute. The slope of the decrease becomes smaller for partially permeable substances and no decrease in observed for fully permeable solutes. All ions assayed by this method as well as sucrose were osmotically fully active to disk membranes. The buffer molecules Tris and imidazole partially penetrated the disk membranes at pH 7, whereas the zwitterionic buffer Hepes was impermeable. Ethanol showed absolutely no osmotic activity to disk membranes and, therefore, can easily penetrate these membranes. concurrent turbidimetric measurements and, therefore, can easily penetrate these membranes. Concurrent turbidimetric measurements confirmed these results. Upon prolonged exposure of disk membranes to 5% (w/v) Ficoll, a considerable modification of the osmotic properties of disk membranes is observed, indicating a significant interaction of 5% (w/v) Ficoll with disk membranes. No influence of 2.5% (w/v) Ficoll on the osmotic properties of disk membranes was detected. The restriction of the use of Ficoll for disk membrane preparative purposes will be discussed.