Stem bending in cut gerbera under the condition of suppressing bacterial proliferation is associated with the weakening of the stem strength

Bacterial proliferation causes stem bending, which shortens the vase life of cut gerbera (Gerbera jamesonii Bolus ex Hook. F.). We investigated the effect of an antimicrobial compound on the symptoms of ornamental value loss using 8 gerbera cultivars. In five different cultivars, the vase life of 11-44% and 11% cut flowers held in distilled water and antimicrobial solution, respectively, was terminated by stem bending. To explore in detail variations in the occurrence of stem bending under condition in which bacterial proliferation is suppressed, the occurrence of stem bending was investigated using cut flowers from 31 cultivars in the presence of the antimicrobial compound. The occurrence of stem bending varied significantly between cultivars. Following that, the stem diameter, stem elongation, and maximum breaking strength of stems were investigated using 'Kentucky', which is prone to stem bending, and 'Kimsey', which is less prone to it. The flower stem diameter of 'Kentucky' became smaller than that of 'Kimsey'. In addition, the maximum breaking strength of the stem became lower in 'Ken-tucky' compared to 'Kimsey'. Treatment with calcium chloride (CaCl2) suppressed the occurrence of stem bending in 'Kentucky'. In 'Kentucky' and 'Kimsey', CaCl2 treatment suppressed transpiration and increased stem diameter and maximum breaking strength. These results suggest stem bending in cut gerbera 'Kentucky' may be caused by a decrease in flower stem diameter and a weakening of stem strength under conditions of suppressing bacterial proliferation.