Pyrus Pyrifolia Nakai Cv Research Articles

Effects of Chitosan Coating on the Storage of Peach, Japanese Pear, and Kiwifruit.

The effects of chitosan coating on respiration, ethylene production, and storage of peach (Prunus persica Batsch. var. vulgaris Maxim cv. Hakuho), Japanese pear (Pyrus pyrifolia Nakai cv. Shinko and Housui), and kiwifruit (Actinidia deliciosa L. cv. Hayward) during storage were investigated. Acetic acid was found to be a suitable solvent of chitosan for coating fresh fruits. Chitosan coating significantly reduced the respiration rate of peach and 'Shinko' pear in storage and of kiwifruit after storage. Coating reduced the ethylene production of the peach markedly, increased the internal CO2, and decreased the internal O2 levels of 'Shinko' pear. Chitosan significantly inhibited the growth of Botrytis cinerea and fungi isolated from decaying 'Housui' pear. This resulted in a decrease of post-harvested spoilage of peach, 'Housui' pear, and kiwifruit. Chitosan-coated peach and 'Shinko' pear were markedly firmer and less mature at the end of storage, indicating that the treatment could be an alternative means of preserving fresh fruits.

ニホンナシ‘豊水’のみつ症発生に及ぼす果実生長初期の高温とジベレリンの影響

The effect of high temperature and/or gibberellin (GA) treatments during the early period of fruit development on the occurrence of watercore in Japanese Pear (Pyrus pyrifolia Nakai cv. Hosui) fruit was examined.1. Trees or fruits covered with polyvinyl chloride film during the early period of fruit development yielded heavier fruits with smaller specific gravity, and higher incidence of watercore compared with the control fruits. The occurrence of watercore was especially severe in fruits covered with film.2. When gibberellin was sprayed on the fruit surface or applied on the pedicel 30 days after full bloom, the fruits were heavier and softer with a smaller specific gravity compared with the control. GA treatment led to severe cases of watercore, especially when combined with the film treatment.3. The fruit sprayed with paclobutrazol (PP-333), a gibberellin inhibitor, at 30 days after full bloom significantly suppressed the occurrence of watercore. Thus, the occurrence of watercore is considered to be related to high temperature and gibberellin contents during the early period of fruit development in addition to the exposure to lower temperature during early summer.

ニホンナシの花芽分化に伴う茎頂細胞の微細構造の変化

To elucidate the mechanism of flower differentiation, ultrastructural changes, particularly the changes in amount and shape of organelles were investigated in the apical meristem of the buds of Japanese pear (Pyrus pyrifolia Nakai cv. Shinsui) during flower bud differentiation.1. The most important stages in the flower bud differentiation were from the beginning of activation of corpus cells on June 26 to the differentiation of sepal primordia on July 17. During these periods all the organelles in the cell underwent remarkable changes.2. During flower differentiation the number of dictiosomes markedly increased with concomitant cytomorphological changes such as many larger vesicles and the reduction in length of dictiosome itself. Distribution of endoplasmic reticulum (ER) also increased with the increase in ribosome. ER evolved into a kind of network from a discontinuous linear shape. There also existed active dictiosomes associated with ER.3. The number and size of mitochondria increased during flower differentiation. As the size increased the shape became spherical or oval. The number and size of plastids in the cells of active tissues did not differ between flower buds and vegetative buds. The size of plastids in the cells of quiescent zone changed markedly, increasing initially and then decreasing, because the size was closely related to the amount of starch grains the plastids contained.4. While flower differentiation progressed, chromatin in the nucleus increased and became densely stained in the cells of apical meristem of the flower buds. Nucleoli also increased in size, and occasionally two nucleoli were observed in a nucleus. Actively dividing cells in the apical meristem of flower buds were also characterized by many small vacuoles.5. These ultrastructural changes of the organelles in the cell of flower buds were discussed in relation to their physiological roles.

ニホンナシ‘豊水’のみつ症の発生条件の解明に関する研究

The interrelationships between the development of watercore, fruit maturity, and diur-nal temperature during July, and the use of plant growth regulators, ethephon and GA, were studied in the Japanese pear (Pyrus pyrifolia Nakai cv. Hosui).1. When potted pear trees were transferred to a phytotron in July to expose them to 23°/15 °C (day/night), severe watercore symptoms developed in four out of five years, as compared to fruits on trees exposed to 33°/25 °C or field-grown potted trees (control). In these afflicted fruits, the flesh was more physiologically mature than was the skin.2. There is a high degree of correlation between the development of watercore and the exposure of pear trees to relatively cool temperatures 80 to 100 days after full bloom.3. The percentage of fruits displaying watercore increased with the advancement of fruit maturity ; fruit with large affected areas in their flesh had lower specific gravity and softer flesh.4. Treatments with ethephon and gibberellic acid which accelerated maturity also fos-tered the development of large watercores.

ニホンナシ‘豊水’のみつ症の発生と膜の透過性との関係

The development of watercore in fruits of potted trees of the Japanese pear (Pyrus pyrifolia Nakai cv. Hosui) in relation to a change in the membrane permeability as influ-enced by diurnal temperatures was investigated. The levels of K + efflux through the membranes of fruits with watercore were compared with fruits without the watercore symptoms.1. The optimal condition for measuring the K+ efflux through the membrane of flesh samples was to shake the tissues in 0.3 M or 0.5 M glycerin solution at 25 °C. The con-centration of Ca2+ in the shaking solutions had no relation to K+ efflux.2. Tissue samples from fruits with watercore leaked K+ faster than did those without watercore.3. When the ground color at the calyx end of fruits reached level 2 or 4, the mem-branes of fruits exposed to 23°/15 °C (day/night) in July were found to be more perme-able than were those from fruits on trees which had been exposed to 33°/25 °C or were continuously field-grown (control trees). Furthermore, the membrane permeability of fruits, exposed to relatively low summer diurnal temperatures, began at an earlier stage of fruit development than did that from the control fruits.4. In those years during which there were more cool summer days, the membrane was more permeable in 'Hosui' fruits than it was in fruits which matured in warmer summer temperatures.5. When fruits were treated with ethephon and GA, K + efflux was accelerated and occurred earlier than they did in control fruits.