Evaluation of resistance to Al toxicity in wild graminae of acid meadows

In acid soils, aluminium toxicity is the primary factor limiting crop and forage production. At soil pH < 5.0, Al solubility increases and Al appears to be rhizotoxic. The objectives of the present study were to compare Al tolerance among wild graminae of acid meadows and to evaluate the relation between a plant functional trait and the Al resistance, in nutrient solution. In addition, a sensitive Lolium perenne variety was included as a control. There was a great difference among the graminaceous species tested, when compared by relative root elongation and critical Al activity corresponding to 50% root elongation reduction. The {Al 3+}50 activities were 3, 13, 14 et 26 µM for Lolium perenne, Molinia coerulea, Holcus lanatus and Danthonia decumbens, respectively. No relation was found between the functional trait leaf dry matter content (LDMC) and Al resistance. Holcus lanatus, tolerant to Al toxicity, with a low LDMC, would deserve a further study of its nutritional qualities for cattle. The very tolerant D. decumbens, with a high LDMC, would present an interest for a later study of the mechanisms of tolerance to Al and possibly, for other applications like the protection of the very acid soils against erosion.