Welche Bedeutung Hat die OH−-Aktivität bei der Intoleranz von Lupinus — Arten Gegenüber Höheren pH-Werten im Wurzelraum ?

Lupin production in Germany is restricted by poor growth of this genus on neutral or alkaline soils. This intolerance towards higher pH values may be attributed to several soil chemical and physical factors. There is indication in the literature that OH− activity in the root medium negatively affects root growth of lupins even at moderate pH values. The aim of the experiments reported here was to examine whether variation in root growth exists among lupin genotypes regarding OH− activity in the root medium. The experiments were set up as nutrient solution cultures with seedlings of L. luteus L., L. angustifolius L., L. albus L., L. mutabilis L., Pisum sativum L. and Vicia faba L. The seedlings were grown for 48 h in unbuffered nutrient or test solutions. Their pH was adjusted to values between 5 and 8. Root growth within 48 h was determined and the rate of root growth calculated. There was no significant reduction in root elongation at pH 6. pH 7 caused a decrease of root elongation by less than 20%. Lupins and pea did not differ in this respect. No consistent species or cultivar differences were observed. The results indicate that OH− activity itself has no strong inhibitory effect on root elongation and thus seems not to be the major cause for the poor performance of lupins on neutral or alkaline soils.