Difference of Ca distribution before and after the onset of tipburn in lisianthus [Eustoma grandiflorum (Raf.) Shinn.] cultivars.

• Ca concentrations and distributivity before and after tipburn were determined. • The influence of plant growth rate on the tipburn was evaluated by new approach. • Tipburn was caused by the decrease in the distribution of Ca in new leaves. Tipburn (leaf-tip necrosis) is severe problem for the production of lisianthus [ Eustoma grandiflorum (Raf.) Shinn.] cultivars. A previous study has suggested that tipburn of 14 lisianthus cultivars are caused by the inability to translocate sufficient quantities of calcium (Ca) to the tips of the upper leaves. However, systematic studies are not available that identify the differences in Ca concentrations and distributivity before and after the onset of tipburn. To address this insufficiency in our knowledge, we used the lisianthus cultivars 'Umihonoka' (UH), 'Voyage green' (VG), and 'Voyage pink' (VP) and determined Ca concentrations and the dry weight of each organ at weekly intervals for 8 weeks. In addition, we evaluated the Ca distributivity from the ratios of the relative Ca increase rate (RGR Ca) to the relative plant growth rate (RGR) by applying growth analysis methods. UH did not exhibit tipburn. In contrast, VG and VP exhibited tipburn after 4 and 5 weeks, respectively. At the same time, the concentrations and distributions of Ca in the roots increased and those of whole and new leaves decreased in each cultivar. Thus, it is suggested that the distribution of Ca in new leaves of the tipburn-sensitive cultivars VG and VP was below the threshold, which caused tipburn. Moreover, it was demonstrated that decreases in the distribution of Ca in whole and new leaves were mainly caused by not increase of the relative leaf growth rate (RGR leaf) but decrease of the relative leaf Ca increase rate (RGR leaf-Ca). We conclude that this approach more rigorously evaluates the influence of plant growth rate on the incidence of tipburn. Thefore, tipburn exhibited by lisianthus cultivars was caused by decreased distributions of Ca in new leaves, which was associated with an increase in the distribution of Ca in roots. [ABSTRACT FROM AUTHOR]