[Effects of 6-BA on cluster root formation and organic acid exudation in white lupin grown under phosphorus deficiency].

Phosphorus deficiency results in cluster root formation and increased organic acid exudation. The regulatory mechanisms for these processes, however, are not yet clear. In the present study, influences of 6-BA (6-benzyl aminopurine) on cluster root formation, exudation of citrate and malate and their concentrations in the root clusters of P-deficient white lupin plants were studied by using non-destructive localized collection method and high-performance liquid chromatography (HPLC) technique. The results showed that application of exogenous 6-BA to P-deficient plants did not influence plant growth and P distribution within the plant (Tables 2,3), whereas the cluster root formation (Fig. 1, Table 1) and organic acid exudation (Table 4) were inhibited. The inhibitory effects could be reversed by omitting 6-BA from the growth medium, and even some stimulatory effects was observed, when lower concentration of 6-BA (10(-8) mol/L) was applied (Fig. 1, Tables 1 and 4). The inhibitory effects of higher concentration of 6-BA (10(-7) mol/L) were not reversible. (Table 4). Treatment with 6-BA also had some influence on organic acid concentration in the tissue of cluster roots (Table 5). The possible reasons for the effects on cluster root formation and organic acid exudation by 6-BA are discussed.