Light micrographs of soybean root tips. Roots were exposed to Ca (A), 10 μm
Al (B), napthylphthalamic acid (NPA; C), 1-aminocyclopropane-1-carboxylic acid (ACC; D), Al plus AVG (E), Al plus NPA (F), 75 μm
Al (G), or 30 μm
Al (H and I) for the periods indicated. Bars in A to H = 1 mm.