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- Author or Editor: Jia Chen x
- HortScience x
The abscisic acid (ABA) has a key role in the regulation of grapevine fruit ripening, but the cellular and molecular biological mechanism of the hormone action in the fruit ripening remains unknown. By means of differential centrifugation, microsomes were prepared from Kyoho grapevine (Vitis vinifera L. × V. Labrusca L.) berries, and using the microsomes, we have obtained evidence for the occurrence of specific ABA-binding sites on the membranes with the microvolume radio-ligand binding assay. The binding sites had saturability, high affinity, and low capacity. The results of trypsin and dithiothreitol treatments to the microsomes suggested that ABA binding sites had the properties of proteins that might have disulfide group located at or near the binding site. The binding maximum amount of ABA in the microsomes was at pH 6.0 and the activity of ABA binding proteins was higher at 25 than at 0°C (temperature). The amount of ABA bound reached 54% of the ABA binding maximum (Bmax) for 10 minutes of incubation and Bmax reached for 30 minutes. The dissociation constant (Ka) and Bmax of ABA binding proteins in the microsomes were 17.5 nmol/L and 98.4 fmol/mg protein, respectively.
By using the micro-volume radio-ligand binding essay, the changes in the kinetic characteristics of the abscisic acid (ABA)-binding protein(s) of the Kyhoh grapevine (Vitis vinifera × V. labrusca) fruit during the different stages of fruit development have been studied. The changes in the berry volume growth, concentration of sugar, organic acids, and ABA in fruit mesocarp have been surveyed, especially for studies of ABA-binding protein. The dissociation constant (Kd) and ABA binding maximum (Bmax) were determined by the Scatchard plots for ABA binding in microsomes of the fruit. They are Kd = 17.5, 50.0, 6.3, 13.3 nmol·L–1; Bmax = 98.6, 523.0, 41.6, 85.4 μmol·mg–1 protein, respectively, for the fruit developmental phase I, II, veraison, and phase III. The Scatchard plots showed a rectilinear function for all of the developmental phases including veraison, which suggests the sole ABA-binding site of high affinity for ABA in the fruit microsomes, but this site could either be only one kind of the same protein or consist of more kinds of different proteins for different developmental stages. The binding affinity of ABA-binding protein(s) for ABA was shown to be higher at veraison time than during other developmental phases; this binding affinity increased nearly by 10 times from phase II to veraison, while the concentration (Bmax) of the ABA-binding protein(s) decreased to the minimum at veraison. The very low concentration of ABA at veraison may be able to trigger the onset of fruit ripening due to the increase of the binding affinity of ABA-binding protein(s) for ABA at this time. The possible functions of the ABA-binding protein(s) for fruit development during the different developmental stages were discussed, and it is suggested that the protein(s) detected could be the putative ABA receptor(s) or transporter(s) for the action of this plant hormone in grapevine.
Paphiopedilum Clair de Lune ‘Edgard Van Belle’, an excellent Maudiae-type hybrid that has been propagated by artificial division for a long time. We studied its flower bud initiation, development of floral organs, and flowering habits with a view to providing information for flowering control and efficient commercial production. According to our research, the flower bud initiation phase of this cultivar begins in February every year, and 80% of the plants completed sepal primordium differentiation in March, The flower bud differentiation lasts for 6 to 7 months, until flowering in August. Within 1 to 3 months after flower bud differentiation, all tested plants differentiated lateral buds. After 5 to 6 months, the new, aboveground vegetative shoots reached their maximum growth, with an average plant height of 20 cm, five leaves, and a shoot dry weight of more than 3 g. From February to April of the following year, a new cycle of flower development and vegetative growth began. In addition, this cultivar was notably sensitivity to high ambient temperature during the late phase of flower development, with a flower bud drop rate as high as 33.3% under average day/night temperatures of 29.0/26.5 °C.
The rare species Magnolia wufengensis frequently suffers from freezing injury in northern China. To investigate the influence of exogenous abscisic acid (ABA) application on the natural cold acclimation of M. wufengensis, physiological and biochemical changes in field-grown M. wufengensis seedlings subjected to foliar ABA treatments at four concentrations (0, 300, 600, and 900 mg·L−1) were evaluated from Sept. 2012 to Jan. 2013. The optimum foliar application concentrations of ABA for M. wufengensis were between 600 and 900 mg·L−1, which led to faster shoot growth cessation, leaf senescence, and development rates of bud endodormancy level and shoot freezing tolerance. The improved freezing tolerance under exogenous ABA application was associated with promoted dehydration and accumulation of proline, soluble protein, and certain soluble sugars such as glucose and fructose. Foliar ABA treatments initiated a cascade of steps for advancing the cold acclimation process of M. wufengensis. We suggest that exogenous ABA application may be used on M. wufengensis grown in northern China, where there are short growing seasons and early fall frost events.