The effect of darkening of the nutrient medium on in vitro rooting of GF 677 rootstock (Prunus amygdalus x P. persica) and kiwi (Actinidia chinensis, cv. Hayward) explants was studied. Two different dyes, Brilliant Black MN-SIGMA (BB) ( 50, 100 and 200 mg L-1) and active charcoal (AC) ( 200 and 500 mg L-1) were added in the Murashige and Skoog medium. Moreover, the rooting medium of the control treatment was darkened by covering the outside of the test tubes with black electrical tape. In both plant species, adding 50 mg L-1 BB in the nutrient medium had the same positive results as did the black electrical tape, enhancing rooting percentage, root number and growth. On the other hand, AC did not promote in vitro rooting of the explants. Finally, increasing the concentration of BB it reduces the amount of total chlorophyll in the leaves of kiwi explants.
Effect of medium darkening on in vitro rooting of GF 677 and kiwi explants