Ryo Norikoshi’s research while affiliated with Tokyo University of Agriculture and other places

The effects of gellan gum gels and Murashige and Skoog (MS) inorganic salts at various strengths on the vase life of 'Rote Rose' rose cut flowers were investigated. To form the gels, gellan gum was dissolved with MS salts at various concentrations. To simulate the transport of cut rose flowers, stems were placed in gellan gum gels and held at 23°C for 24 h or 48 h. Cut flowers were then transferred into distilled water and their fresh weight (FW) and vase life were determined. According to the observed vase life and changes in FW, gels formed with 0.2% gellan gum and standard-strength MS salts appear to be the most suitable for cut roses. Although the hardness of gellan gum gel increases with increased concentrations of gellan gum and MS salts, no correlation between vase life and gel hardness was observed. To determine the potential water availability of gellan gum gel, gels were placed in a centrifuge filter device, centrifuged at 3000 × g for 10 min and the amount of water released from the gel was measured. A highly positive correlation between the amount of water released from the gel and water uptake of flowers placed in gellan gum gels was observed. A positive correlation between the amount of water released and vase life was also observed. Thus, using centrifugation to measure the volume of water released from gellan gum gels appears to be a simple and rapid method for evaluating the performance of gellan gum gels as wetting agents. JSHS

There have been few reports on the morphology of flower opening, despite its horticultural significance. It is not clear when cell division stops during rose petal development or what changes occur in cell morphology. This study aims to clarify the details of cell morphological changes during rose petal development. Rose (Rosa hybrida L. 'Sonia') petals were sampled in six flower bud stages. Cell morphological changes were observed by light microscopy, transmission and scanning electron microscopy using cross sections of the petals, and the number of epidermal cells was measured using Nomarski differential interference contrast microscopy. The number of epidermal cells increased with flower opening, but the rate of increase in the number of abaxial epidermal cells slowed down at an earlier stage than in adaxial epidermal cells. The increase in the epidermal cell area was much more rapid in later stages compared with the increase in cell number, suggesting that petal growth in later stages is mainly due to cell expansion. During flower opening, the unique expansion of spongy parenchyma cells produced large air spaces. Epidermal cells of the upper part showed obvious lateral expansion. In particular, marked expansion of adaxial epidermal cells with enlargement of the central vacuole was observed. Differences in the patterns of cell expansion among cell types and locations would contribute to the reflex of petals during rose flower opening. JSHS

To establish a simple and rapid extraction method for soluble carbohydrate for determination of osmolar concentration in petals by HPLC analysis, a method using a centrifugal filter device with microwave heating was developed. Rose 'Sonia' petals were placed in a centrifugal filter device and heated in a microwave oven to boiling. The centrifugal filter device was centrifuged with the petals at 12,000 g for 10 min. The resulting leached solution was subjected to HPLC analysis. No significant difference in soluble carbohydrate composition was observed between the solution obtained from this method and that obtained from a conventional extraction method in which tissues are homogenized using hot ethanol solution. Changes in soluble carbohydrate concentration with flower opening in 'Rote Rose' roses were investigated using the new method. The osmolar concentrations of glucose and fructose in the petals increased during flower opening. This increase was roughly comparable to the increase in osmotic pressure in the petals. The results suggest that the method using the centrifugal filter device with microwave heating is a simple and rapid way to determine osmolar concentration of soluble carbohydrates of rose petals.

We developed a simple and rapid extraction method of soluble carbohydrates from petals for analysis by high performance liquid chromatography (HPLC), using a centrifugal filter device in a test tube without homogenization. Rose 'Sonia' petals were immersed in 99.5% ethanol solution in a test tube and kept at 75 degrees C for 20 min. Sorbitol was then added to the solution as an internal standard, and the petals were transferred to the centrifugal filter device and centrifuged at 12000 x g for 10 min. Following removal of the filtrate, 99.5% ethanol was added to the filter device and a second round of centrifugation performed. Filtrated solution obtained from both centrifugations was combined with the ethanol solution remaining in the test tube, heated to dryness at 80 degrees C, and used for HPLC analysis. Few differences in soluble carbohydrate content were observed between the new method and a conventional method in which soluble carbohydrates are extracted by homogenization. We confirmed that most carbohydrate was extracted by the new method. Moreover, the soluble carbohydrate content of samples extracted from 'Sonia' petals using the new method did not change during one week of storage at -30 degrees C, indicating the stability of the samples. Marked differences in soluble carbohydrate content were not observed among 'Chanel', 'New Bridal', 'Rote Rose', or 'Saturn' rose petals, carnations or Tweedia caerulea petals or Delphinium sepals, using either the new or conventional method. Marked differences in soluble carbohydrate content were also not observed among leaves and stems in carnations, Delphinium or rose 'Sonia' using either the new or conventional method. These results suggest that the new method, which does not require homogenization, appears to be a more simple and rapid method of extraction of soluble carbohydrates from various organs of floricultural plants.

A simple method using a vacuum manifold for extracting soluble carbohydrates for analysis by high performance liquid chromatography (HPLC) from various tissues of ornamental plants was developed. Rose ‘Sonia’ petals were immersed in ethanol solution at 75°C for 20 min. Sorbitol was added to the extraction as an internal standard, and extractions were transferred to filter holders on a vacuum manifold, and the manifold was then decompressed. The filtrate was evaporated to dryness, and used for HPLC analysis. In comparison to soluble carbohydrate extraction by conventional homogenization extraction, few differences in soluble carbohydrate content were observed. Carbohydrate content in the remaining plant tissue was confirmed to be very low, indicating that soluble carbohydrates are effectively extracted by this procedure. Few differences in soluble carbohydrate content were observed among rose stem and leaves between the new method and a conventional method. Also, few differences in soluble carbohydrate content were observed among petals or sepals, stems and leaves in carnation, Delphinium and snapdragon, using either the new or conventional method. These findings suggest that the new method, which does not require homogenization, is a very simple method for the extraction of soluble carbohydrates from various organs of several ornamental plants.

Cut rose (Rosa hybrida L.) cv. Rote Rose was treated with glucose, fructose or sucrose at 10 g L-1 in combination with a commercial preparation of isothiazolinonic germicide (a mixture of 5-chloro-2-methyl-4-isothiazolin-3- one and 2-methyl-4-isothiazolin-3-one; CMI/MI; Legend MK) at 0.25, 0.5 or 1 mL L-1. To stabilize germicidal activity, the solution was acidified by the addition of citric acid to a final concentration at 30 mg L-1. Of the sugars, glucose was the most effective in extending the vase life, followed by fructose. CMI/MI was most optimal at 0.5 mL L-1. The addition of aluminum sulphate at 50 mg L-1 to glucose plus CMI/MI considerably extended the vase life of cut roses more than glucose plus CMI/MI. Based on these results, a formulation comprising 10 g L-1 glucose, 0.5 mL L-1 CMI/MI, 30 mg L-1 citric acid and 50 mg L-1 aluminum sulphate was designated as GLCA and the effect of GLCA on the vase life of 8 cultivars was compared against 10 g L-1 glucose plus 200 mg L-1 8-hydroxyquinoline sulphate (HQS). Treatment with GLCA extended the vase life of all the tested cultivars more than glucose plus HQS. Hydraulic conductance of stem segments in the control 'Rote Rose' roses decreased rapidly after harvest, but those for GLCA and glucose plus HQS were maintained at near their initial levels. The extension of vase life in cut roses by the addition of GLCA is attributed to the supply of sugars and the suppression of vascular occlusion without toxicity to cut flowers.

Cut rose (Rosa hybrida L.) 'Sonia' flowers were placed in vases of which water temperatures were kept at 10,15 and 23°C under constant air temperature of 23°C. Vase life of cut roses became longer with lowering water temperature; the vase life was 5.2, 6.7 and 7.5 days at 23, 15 and 10°C, respectively. Fresh weight of cut flowers increased over the first 3, 4 and 5 days during the experimental period at 23, 15 and 10°C, respectively and decreased thereafter. Temperature of flower part was very slightly lowered by lowering water temperature. Hydraulic conductance of stem segments decreased on the third day after harvest, and this decrease was suppressed by lowering the temperature of vase water. Bacterial number in vase water increased with time, and this increase was suppressed by lowering the temperature of vase water. These results show that low temperature of vase water might improve the stem water relation and extended the vase life of cut rose flowers.

Post-harvest characteristics of Rosa hybrida L. cv. 'Delilah', a long-lived cultivar, were compared with those of cv. 'Sonia', a short-lived cultivar. The vase-life of 'Delilah' was 10.6 d whereas that of 'Sonia' was 5.6 d. Petals of 'Sonia' flowers kept in water did not reflect fully and showed blueing. However, treatment with sucrose plus 8-hydroxyquinoline sulphate (HQS) markedly promoted petal reflection and inhibited blueing. In contrast, 'Delilah' flowers kept in water reflected fully and did not show blueing. In both cultivars, hydraulic conductance of stem segments in the control treatment decreased rapidly after harvest. Treatment with HQS suppressed this decrease. Concentrations of glucose, fructose and sucrose in petals of 'Delilah' were much higher throughout the experimental period than those of 'Sonia'. There was no difference between 'Sonia' and 'Delilah' in soluble carbohydrate concentrations in stems and leaves. Starch concentration in petals of 'Sonia' was higher than in 'Delilah'. However, the starch concentration in both cultivars was much lower than the total soluble carbohydrate concentration in 'Delilah'. Sensitivity to ethylene in 'Delilah' was greater than in 'Sonia'. There was little difference in ethylene production trends between 'Sonia' and 'Delilah' flowers. The results suggest that complete petal reflection and the longer vase-life of 'Delilah' versus 'Sonia' flowers may be attributed to higher soluble carbohydrate concentrations in petals of the former.