Changes in soluble and non-cellulosic carbohydrates composition and calcium content during stem tip cuttings propagation and production of Eustoma grandiflorum

Abstract

Stem tip cuttings of Eustoma grandiflorum (Raf.) Shinn. ‘Kiri no Mine’ were rooted under a mist to determine the feasibility of vegetative propagation and to produce acceptable plants without showing any physiological disorder at flowering. Stem tip cuttings were rooted with 50 mm 2-(1H-indol-3-yl)acetic acid (IAA) treatment. However, physiological disorders, such as die-back symptoms at the shoot apex and scorches at the margin of leaves, developed from the smallest leaves and affected nearly 50% of the cuttings. These disorders were from either leaching of macro- and micro-elements, particularly calcium (Ca), coupled with little or no translocation of radioactive Ca from the base of the cuttings to the young leaves and growing point. Plants from rooted cuttings that did not show any physiological disorder symptoms flowered later and produced fewer flowers than seed-propagated plants. Due to a reduction in growth vigor of some plants exhibiting a reduced number of top breaks and flowers, plants flowered 16 days later than plants without reduced vigor and produced only 4.3 flowers, as compared to 14.2 flowers of normal plants without showing reduced growth vigor. Although concentrations of the macro- and micro-elements of rooted plants were similar to those of seeded plants after planting rooted cuttings in a growing medium, reduction in growth vigor observed in some rooted plants cannot be explained by the leaching of macro- and micro-elements during the mist. Thus, carbohydrate and protein, which may have been leached from the cuttings were analyzed. Soluble carbohydrate content and monosaccharide composition hydrolyzed from polysaccharides after DEAE-cellulose anion-exchange chromatography was analyzed. Leachate contained primarily glucose, uronic acid, galactose, and protein in fraction III, suggesting that leaching of calcium in conjunction with carbohydrates and glycoprotein may be the cause of the expression of physiological disorder symptoms that affect the development of rooted cuttings. The reduction in growth vigor could be related to the leaching of free carbohydrates or polysaccharides, and some of the polysaccharides could be cell wall components rich in uronic acid. Calcium could be leached from cell wall fragments as a calcium-glycoprotein complex and the Ca concentration may not be restored during the resumption of new growth in 20 days when rooted cuttings were planted. Limiting factors for stem tip cutting propagation were physiological disorders, especially die-back of the shoot apex and reduced growth vigor observed at flowering when no physiological disorder symptoms were observed in rooted cuttings.