EFFECT OF ALUMINUM AND PH ON RELATIVE YIELD AND PLANT-CHEMICAL CONCENTRATIONS OF 7 DICOTYLEDONOUS SPECIES GROWN IN SOLUTION CULTURE AT LOW IONIC-STRENGTH

The effects of aluminum (Al) on yield and plant chemical concentrations were determined for 7 species (18 cultivars) of dicotyledons using a low ionic strength solution culture technique. The relationship between relative yield and solution Al activity was determined using polynomial exponential splines, and the Al activity (mu-M) at which yields were reduced by 50% (Al(RY50)) were determined. Based on the yields of the plant tops, Arabadopis thaliana, Lycopersicon esculentum (tomato) and Nicotiana plumaginifolia were all sensitive to Al (Al(RY50) < 1). Petunia cultivars (Al(RY50) mean 3.1, range 2.4-4) and beans (Phaseolus vulgaris) (Al(RY50) mean 6.3, range 4.4-9.4) were intermediate in their tolerance to Al. Lima beans (Phaseolus lunatus) were the most tolerant of the species tested (Al(RY50) 15.6). Pepper (Capsicum annum var annum) was unusual in that it was the only species sensitive to solution pH. For this species, top and root yields increased with increasing Al rates. In the plant tops, increasing Al in solution increased Mg and K concentrations in tomato, increased N, S and Ca in petunia and decreased Mg and K concentrations in beans (except for K in the cultivar Black Turtle). In the roots, increasing Al in solution increased Mg, Ca and K concentrations in tomato, decreased P, S, Mg and Ca concentrations in nicotiana, increased P, S, Mg, and K and decreased Ca concentrations in petunias, and decreased Mg, Ca, and K concentrations in beans. Increasing solution Al decreased the top Fe concentrations in all cultivars and increased the concentration of Mn, Zn, and Cu in the tops, and Cu in the roots in all species except Nicotiana plumaginifolia.