Stability of chemical parameters of tissue culture medium (pH, osmolarity,electrical conductivity) as a function of time of growth

Changes in medium pH, osmolarity (OS), and electrical conductivity (EC) wer e studied as a function of time in Murashige and Skoog (MS) liquid prolifer ation and rooting medium. Microshoots of wild pear (Pyrus syriaca), bitter almond, and 'Spunta' potato were targeted. Results indicated an acidic drif t in pH in the different species on both proliferation and rooting medium. The EC was increased significantly with time whereas solution OS was decrea sed. Different species caused different effects on EC or OS depending on gr owth medium. The decline in OS in the proliferation medium was higher when pear and almond were grown, while on rooting medium the decline was sharper with potato and almond. The EC of proliferation medium was increased more when almond was grown; while on the rooting medium all species had similar effects. Under these saline conditions, low nutrient elements availability, poor plant growth, and nutrient element imbalance are expected. This study illustrates that the change in the: chemical parameters of the culture med ium could lead to undesirable effects on plant growth and nutrient element availability. Therefore, it is recommended to monitor the change in these p arameters of the medium over the incubation time.