Effects of aluminum, calcium, and phosphate on shoot growth, viability, and aluminum distribution in the root apices in highbush blueberry cultured in vitro

The viability, Al distribution in root apices, shoot growth, and excreted organic acid contents in blueberry cultured in vitro were examined to study the effects of aluminum (Al), calcium (Ca), and phosphate (P) ions on the plant's tolerance to Al. 1. Roots in the control, exposed to an Al-free acetate buffer were significantly damaged, bur roots treated with 1mM Al or 1mM Al plus ImM Ca retained their viability. 2. Al could not be detected in the root apex in the control, but the roots treated with 1mM Al and 1mM Al+Ca accumulated Al in the cortical area but not to the interior cortex as the treatment progressed. Thus, the accumulation of Al on the root surface seems to have protected the plant from the damage of low pH and acetate ions. 3. 1 mM Al in the medium hastened both the shoot and root growth for fifty days. The elimination of P from the medium inhibited root growth more than shoot growth. 4. The amount of organic acids excreted did not differ whether Al was present or nor indicating that 1mM Al is not injurious.