Comparison of acid and alkaline soil and liquid culture growth systems for studies of shoot and root characteristics of white lupin (Lupinus albus L.) genotypes

Current agronomic cultivars of white lupin (Lupinus albus L.) in the European Union are intolerant of calcareous soils, producing poor yields. Intolerant genotypes of L. albus, and a tolerant genotype of L. pilosus Murr. were grown in liquid culture varied for pH, or pot and chamber soil systems varied for lime. Chlorosis, determined visually as leaf interveinal yellowing, was shown to be an unsuitable genotype screen. However, leaf greenness measured electronically at a sub-chlorotic level, provided a quantifiable estimate of stress. Shoot Ca concentration increased when plants were grown in the limed compared with non-limed soil, but remained unchanged between the liquid culture treatments. The root systems in the pots and liquid culture showed growth abnormalities, whereas important differences between L. albus and L. pilosus root systems were seen in the soil chambers. The tap and lateral root dry weights of both species were lower in the limed soil than in the non-limed soil. The dry weight per plant of the cluster roots was comparable between the treatments in both species, although when grown in the limed soil they accounted for a larger proportion of the L. albus root system. In contrast, the proportion of the root system that was cluster root in L. pilosus was comparable between the treatments. In limed soil, both species showed increased levels of extractable citrate from the soil adhering to the cluster roots compared with that in the acid-pH soil. However this did not result in higher shoot P concentrations in the limed compared with acid-soil grown plants. These results demonstrated the importance of analysing a developed and unrestricted root system when determining the physiological responses of these species to limed soil.