Abscisic acid modifies boron stress in cultured maize kernels

Fertilized ovules of maize (Zea mays L.) were cultured at 14 days after anthesis in MS medium devoid of growth regulators. The developing kernels were supplied boron at three levels 0.01mM (low), 0.1mM (normal) and 0.5mM (high), each without or with 1mg l⁻¹ abscisic acid (ABA). Growth of kernels, after 8 days in culture, was observed as increase in length, breadth, fresh and dry weight with concomitant decrease in concentration of sugars and increase in that of nitrogen, protein and starch. Maize kernels cultured in absence of ABA showed growth enhancement at low B and poor growth at high B from those at normal B. In kernels at low B the concentration of sugars and phenols increased and that of nitrogen, proteins and starch decreased, while at high B protein nitrogen and starch contents increased. A supply of ABA increased the level of seed reserves and almost reversed the effects of boron stress in maize kernels cultured in vitro.