Senescence of Dendrobium `Pompadour' flowers following pollination

Summary

Flowers of Dendrobium `Pompadour' developed premature petal and sepal senescence following pollination. Pollination induced an ethylene climacteric accompanied by a small respiratory climacteric, epinasty and increased flower or inflorescence fresh weight and water uptake. Pollination did not alter petal and sepal anthocyanin content and ion leakage, and lip, petal and sepal fresh weight and dry weight. The fresh weight and dry weight of stigmas (columns) together with pedicels increased significantly after pollination. Ovary growth of pollinated orchid flowers with petals and sepals intact was greater than that of pollinated orchid flowers without petals and sepals, while their water uptake was not significantly different.     

Salicylic acid alleviates chilling injury in anthurium (Anthurium andraeanum L.) flowers

We tested if salicylic acid (SA) can alleviate chilling injury in anthurium flowers (Anthurium andraeanum). Cut flowers of five cultivars, individually placed in water, were held at 4 °C and 12 °C. Symptoms of chilling injury (CI) were found in the flowers stored at 4 °C. These symptoms included desiccation of the spadix (the compound floral stalk) and a colour change of the spathe (the large floral bract) to pink and then to brown. The time to the CI symptoms depended on the cultivar. CI symptoms were accompanied by an increase in electrolyte leakage, by loss of fresh weight, and by an increase in catalase (CAT) and superoxide dismutase (SOD) activity. SA at 2.0 mM in water was applied as a 15 min dip. It delayed the CI symptoms, as well as the loss of fresh weight, the increase in electrolyte leakage, and the increase CAT and SOD activity. The data suggest that CI in this system is related to an increase in the concentrations of active oxygen species.     

Effects of fruit size on juice content and chemical composition of tangerine

Summary

The relationship between fruit size and juice content and chemical composition of tangerine was studied. The results showed an increase in juice content and in the total soluble solids: titrable acidity ratio. There was a decline in total soluble solids and in titrable acidity with increasing fruit size but there was an inconsistent change in ascorbic acid with increasing fruit size.     

The relationship between chilling injury and membrane damage in lemon basil (Ocimum × citriodourum) leaves

Leaves of lemon basil (Ocimum × citriodourum) were stored in sealed polyethylene bags at 4 °C and 12 °C. At 4 °C, leaf browning, the visible symptom of chilling injury, occurred earlier and was more severe in mature leaves than in young leaves. No positive correlation was found, when comparing young and mature leaves stored at 4 °C, between browning and either substrate levels (free phenolics) or the activities of peroxidase or catechol oxidase, which might catalyse these reactions. The levels of saturated and unsaturated fatty acids differed only slightly and were not correlated with chilling injury. Compared to young leaves, mature ones showed higher lipoxygenase activity throughout the period of low temperature storage. This might indicate more degradation of membrane unsaturated fatty acids. In addition, mature leaves exhibited lower catalase activity than young ones. This suggests lower protection against membrane oxidation in mature leaves. The data thus suggest a correlation between lipoxygenase activity, antioxidant defense, and chilling injury.     

Colour development and quality of mangosteen (Garcinia mangostana L.) fruit during ripening and after harvest

The colour of mangosteen (Garcinia mangostana L.) fruit changes from green to purple black after harvest as the fruit ripens, and is used as a quality guide for growers and consumers. We determined the relationship between anthocyanin composition and content during fruit colour development in relation to fruit maturity and postharvest quality. Fruit at different stages of maturity (light greenish yellow with 5% scattered pink spots to purple black) were harvested and kept at 25 °C (85–90% RH). Fruit from each maturity stage all developed to the final purple black stage. During the postharvest period, hue angle values and pericarp firmness decreased significantly, while soluble solids contents increased. Anthocyanin contents in the outer pericarp were higher than in the inner pericarp and increased to a maximum at the final colour stage. Sensory evaluation and fruit quality (hue angle values, soluble solids and titratable acidity) of fruit harvested at the different stages did not differ once the fruit had finally developed to the purple black stage. The anthocyanins in the outer pericarp mainly consisted of five compounds, identified by HPLC/MS as cyanidin-sophoroside, cyanidin-glucoside, cyanidin-glucoside-pentoside, cyanidin-glucoside-X, cyanidin-X₂ and cyanidin-X, where X denotes an unidentified residue of m/z 190, a mass which does not correspond to any common sugar residue. Cyanidin-3-sophoroside and cyanidin-3-glucoside were the major compounds and the only ones that increased with fruit colour development.     

Ethylene-regulated hastening of perianth senescence after pollination in Dendrobium flowers is not due to an increase in perianth ethylene production

Flowers of Dendrobium cv. Kenny were hand-pollinated using pollinia from cv. Sakura. This resulted in a large increase in flower ethylene emission and rapid perianth (tepal) senescence. The increase in flower ethylene emission was correlated in time with an increase in ethylene emitted by the column (the fused stigma, style and stamens) plus the ovary. No ethylene emission was observed from perianth parts that were isolated at various periods after pollination. The increased ethylene emission by the column plus ovary was correlated with an increase in ACC synthase and ACC oxidase activity in these flower parts. The perianth parts, in contrast, only showed an increase in ACC oxidase activity, following pollination. The data show that pollination-induced early perianth senescence in Dendrobium is mediated by increased ethylene biosynthesis by the column + ovary, and not due to increased ethylene biosynthesis in the perianth parts. Apparently, ethylene synthesized in the gynoecium diffuses to the perianth parts where it induces senescence. The data are very similar to those found previously in pollinated Phaleanopsis orchids and in emasculated Cymbidium orchids, with the exception that ethylene was emitted from the tepals of these two orchids and not from Dendrobium.     

Firmness,pectin components and cell wall hydrolases of mango fruit following low-temperature stress

Summary

Mango (Mangifera indica L. cv. Nam Dokmai) fruits chilled for 21 d at 48C were firmer than non-chilled fruits during subsequent ripening at 258C. The cell wall contents of chilled fruit contained less water-soluble pectin, more ammonium oxalate-soluble pectin and less alkali-soluble pectin than non-chilled fruits. The increase in ammonium oxalate-soluble pectin was at the expense of the alkali-soluble pectin and correlated with high pectinesterase activity in the fruit from low-temperature storage. Polygalacturonase and b-galactosidase activities were inhibited in chilled fruits. The relationships between delay in loss of firmness, and differences between activity of cell wall enzymes and pectin content of chilled and non-chilled fruits are discussed.     

龙眼果实商业化采后处理系统的建立

基于国际上龙眼果实采后技术的研究结果,尤其是中国和泰国的观点,建立了龙眼果实采后处理系统;介绍了龙眼果实采后处理系统技术如耐贮运品种选择,采收成熟度和采收方法,选别和分级,杀菌剂或熏硫处理,检疫杀虫处理,预冷,包装,贮藏,运输和销售。指出了龙眼果实采后处理存在的问题和今后需进一步研究的领域     

Chilling injury in mango fruit peel: Cultivar differences are related to the activity of phenylalanine ammonia lyase

In mango (Mangifera indica) cv. Nam Dok Mai fruit, stored at 4 °C, peel browning occurred within 9 d, while no browning was found in cv. Choke Anan fruit stored at 4 °C for 30 d. During 6 d of shelf life at 27-28 °C, following various periods of low temperature storage, the peel browning in cv. Nam Dok Mai (if not yet maximal) became worse, whereas little browning was observed in cv. Choke Anan fruit. The pulp of the fruit of both cultivars did not show browning during the 4 °C storage, but the pulp of cv. Nam Dok Mai exhibited some browning during shelf life if the fruit had been stored at 4 °C for more than 18 d. Peel and pulp color were not correlated with total free phenolics. A high correlation coefficient was observed between peel browning and PAL activity in the peel, while a very low correlation was found with peel catechol oxidase activity. The browning in the pulp was not correlated with the measured enzyme activities. The data therefore show a relation between PAL activity in the peel and low temperature-induced peel browning.     

1-MCP extends the storage and shelf life of mangosteen (Garcinia mangostana L.) fruit

Mangosteen (Garcinia mangostana L.) fruit were harvested when the peel (pericarp) was light greenish yellow with scattered pinkish spots. Fruit were exposed to 1 μL L⁻¹ 1-methylcyclopropene (1-MCP) for 6 h at 25 °C and were then stored at 25 °C (control) or 15 °C. The 1-MCP treatment only temporarily delayed softening of the fruit flesh, during storage. Storage life, defined as the time until the pericarp was dark purple, was much longer in fruit stored at 15 °C than in fruit stored at 25 °C. It was also longer in 1-MCP treated fruit (storage life at 15 °C: control 18 d, 1-MCP-treated fruit 27 d). The 1-MCP treatment also increased the length of shelf life, defined as the time until the pericarp turned blackish purple or showed calyx wilting, at 25 °C. 1-MCP treatment reduced ethylene production. It also reduced pericarp levels of 1-aminocyclopropane-1-carboxylic acid (ACC), and the pericarp activities of ACC synthase (ACS) and ACC oxidase (ACO). In the fruit flesh, in contrast, 1-MCP did not affect ACC levels and ACS activity, but the treatment reduced ACO activity. Taken together, both the storage life and the shelf life of the fruit were extended by the 1-MCP treatment. A decrease in ACO activity largely accounted for the effects of the 1-MCP on ethylene production in the pericarp.