Observation on the viability of root apex cells treated with different pH and aluminum in highbush blueberry (Vaccinium corymbosum L.) and Maruba kaido (Malus prunifolia Borkh. var. Ringo) cultured in vitro

The viable root apices of highbush blueberry and apple rootstock were obser ved by staining with fluorescein diacetate (FDA) and propidium iodide (PI) to assess their pH and aluminum (Al) tolerance. In the pH treatment, roots were dipped in phosphate buffer solution ranging in pH from 3.5 to 6.0 for 2 to 6 hours. About 15 to 40 % of the blueberry root epidermis in all treat ments except pH 6.0 for 2 hours were damaged, but the rest of the roots rem ained healthy. The apple rootstock 'Maruba kaido' suffered more damage at p H 3.5 than did the blueberry. In the Al treatment, blueberry roots dipped i n an acetate buffer solution without Al, the root tip or the whole root was damaged; but roots treated with 1 mM Al retained its viability similar to the untreated root; almost ail roots treated with 10 mM Al were injured. 'M aruba kaido' exhibited a tolerance to 1 mM Al. Observation of root tissue by staining with FDA and PI is a simple techniqu e that allows visible differentiation between viable and injured cells. Fur thermore, because it is a nondestructive method, it is very useful for dete rmining root viability.