Response and tolerance to flooding of potted open-pollinated seedlings, four ungrafted dwarfing clonal selections of Pyrus betulaefolia Bunge (PB), six of P. calleryana Decne (PC), and the same topworked to the Japanese pear ‘Kosui’ were investigated. The 3-yr-old trees were flooded for 15 days or 12 weeks and then examined for tree survival, growth cessation, shoot growth, adventitious root formation, and defoliation. Although the tolerance to water stress was higher in PC than in PB, the responses varied within and between the species. Some SPRB clones with greater tolerance than the PC control and SPRC clones developed adventitious roots on the trunk above the water surface. This may be a morphological adaptation to the stress. Prolonged flooding separated the rootstocks into 4 overall rankings: most tolerant (SPRB22), very tolerant (SPRB13, SPRB15, PC1, PC2, SPRC15, and SPRC20), moderately tolerant (SPRC3 and SPRC8) and least tolerant (PB seedling, PB4, SPRB1, SPRC5, and SPRC13). PC and its selection flooded for 30 days had significantly higher shoot growth, new roots, and higher 2,3,5-triphenyltetrazolium chloride (TTC) reducing activity in the fine roots than the PB ones. Within the SPRB clones, SPRB15 and SPRB22 exhibited the most shoot and new root growth. From the analyses of long and short-term flooding data, we categorized the selections SPRB15, SPRB22, SPRC15, and SPRC20 that developed adventitious roots with extended root activity as having superior ability to withstand water stress.

View full abstract

The relationship between the shallot strains in Vietnam and those in the surrounding countries was studied by comparing their morphological and physiological characteristics and DNA polymorphisms. The morphological and physiological observations demonstrated that the strain from Taiwan was similar to those of the North type cultivated in northern Vietnam while those from Thailand, the Philippines, Malaysia, and Indonesia were akin to the South type cultivated in central and southern Vietnam. The strain from China (Kunmin) was similar to the North type rather than the South type although it had characteristics of both types. In the RAPD analysis, the strains from Taiwan, China, and the North type were formed into one group, whereas those from Thailand, the Philippines, Malaysia, Indonesia, and the South type formed the other group. With the unique characteristics, restricted distribution and long history of cultivation, it is supposed that the North type shallot had differentiated in the North region of Vietnam, while the South type seems to be a variant of the shallot strain distributed universally in the tropical zone of Southeast Asia.

View full abstract

The effects of rolC on morphogenesis of Chrysanthemum morifolium Ramat. ‘Ogura-nishiki’ were studied. The ray flowerets in the rolC-transformed plants were shorter than those in wild-type plants, but the transformation enhanced outgrowth of lateral shoots and reduced internode elongation. Studies on adventitious shoot and root formation from leaf segments revealed that the rolC transgene led to reduced root formation but enhanced adventitious bud formation. This enhanced cytokinin-like activity was consistent with phenotypes observed in the rolC-transformed plants.

View full abstract

Expanded, young leaf blades of Begonia Tuberhybrida Group ‘Clips Yellow’ were cut into four pieces radially from the junction with the petiole; each piece was inserted in various media in nursery trays. The surviving percentage of the leaf pieces, grown in rockwool beds, was higher than in other media; about half of them formed adventitious buds. When the leaf piece was cut into the proximal and distal halves, several adventitious buds were formed on the former, but only a few on the latter. Many leaf pieces, inserted in April, May, and October formed adventitious buds, but only a few leaf pieces inserted in July, did. The optimum temperature for adventitious bud formation was around 15–20°C. The results suggest that the adventitious bud formation is affected by temperature rather than day length.

View full abstract

Petal wilting, which involves the degradation of cell constituents, such as proteins, polysaccharides, lipids, and nucleic acids, is a determinant of the vase-life of carnation (Dianthus caryophyllus L.) flowers. In this study, a cDNA fragment, encoding a putative nuclease (DcNUC1), was isolated from carnation petals. In the petals of senescing carnation flowers, the level of the DcNUC1 transcript increased, corresponding to the increase of ethylene production. It became maximal in wilted flowers, which suggested the association of DcNUC1 expression with the wilting in carnation flowers.

View full abstract

Ultraviolet (UV) radiation induced the production of the phytoalexin, scoparone (6,7-dimethoxycoumarin), in the flavedo of various kinds of citrus fruits. We measured the changes in scoparone concentration after UV radiation in citrus leaves and fruits harvested in August and December. The changes in scoparone concentration were lower in young leaves (August) than in mature ones (December). Young leaves of all cultivars harvested in August, except for those of ‘Eureka’ lemon, produced less than 100 μg·g⁻¹FW. The concentration in the fruits was also lower in young than in mature specimens. Changes in the scoparone concentration and the rate of increase varied with cultivars, organs, and the time of harvest.

View full abstract

Varietal difference on forced- and fall-cropped greenhouse-grown cucumbers by reducing assimilation competition between lateral branches and fruits was investigated. The treatments consisted of exposing cucumber plants to different amounts of ventilation in greenhouses to keep them at 29°C and 70% relative humidity (RH) or 25°C and 55% RH. For all cultivars, the number of days from the first female flower bloom to harvest in the 29°C/70% plot was less than that in the 25°C/55% plot. ‘Pandex’ matured in the least number of days from the opening of the first female flower to harvest in the 25°C/55% plot. These results indicated that the fruit growth was regulated by the fruit growth ability calculated as the number of days of female flower blooming until harvest of each cultivar rather than the number of lateral branches.

View full abstract

Three different treatments, which are known to promote shoot formation in temperate Cymbidium species, were applied to the protocorm-like bodies (PLBs) of Cymbidium Sleeping Beauty × Cymbidium sinense (Andr.) Willd, a hybrid between tropical and temperate Cymbidium species. Shoot formation from the PLBs was promoted on Murashige and Skoog (MS) medium in which NH₄NO₃ and KNO₃ were reduced to 25 and 50%, respectively. The highest shoot formation rate (77%) was obtained on MS medium supplemented with 0.1 mg·L⁻¹ AgNO₃. The most favorable combination for shoot formation was 10 mg·L⁻¹ of 6-benzyladenine (BA) and 0.1 mg·L⁻¹ α-naphthaleneacetic acid (NAA).

View full abstract

The purpose of this study was to determine the minimum air temperature to conserve energy under covering in forcing culture of ‘Maekawa Jiro’ persimmon. The plastic house was covered with a film and heated annually from 1997 to 2001 beginning in early January to keep the minimum air temperature above 10, 15, 18, or 20°C, until heating became unnecessary. Such temperatures affected the time of bud break and full bloom, but not the growth and quality of fruits. The number of days from covering to bud break (period I) and from bud break to full bloom (period II) was quadratically correlated with the mean minimum air temperatures during the respective periods. The quadratic regression equation suggests that bud break and full bloom was the earliest if the minimum air temperatures during periods I and II were kept at 16.5 and 16.7°C, respectively. However, lowering of the minimum air temperature by 3 and 2°C, respectively, would delay bud break and full bloom by only one day. Thus, by taking the heating cost into account, setting the thermostat at 13.5°C and 14.7°C during the periods I and II, respectively, is recommended.

View full abstract

The present experiments tested the effects of root zone substrates consisting of coir and peat mixture (peat moss : vermiculite : perlite = 6 : 1 : 1, v/v/v) on the growth, yield, and water relations of the strawberry ‘Akihime’. Treatments consisted of four different ratios of coir and peat mixture as follows: 3 : 7, 5 : 5, 7 : 3, and 10 : 0. The liquid phase in the substrate at −1.5 kPa of matric potential decreased with increasing coir ratios, whereas the gaseous phase increased. The marketable yield of strawberries decreased with increasing coir ratios during the whole experimental period which is attributed to the significant reduction in water absorption and stomatal conductance during February and March. There is a high correlation between the marketable yield and the liquid phase in substrates during the February–March period (r = 0.74) and also during the whole period (r = 0.69). In January, the marketable yield, water uptake, and leaf water potential of strawberry plants decreased in all treatments compared with other periods. As a result, it was considered that the significant reduction of marketable yield during the February–March period was caused by restricted water absorption and transpiration from the substrate with low liquid phase, when the root growth and water absorption ability were inhibited by the previous excess fruit load.

View full abstract

To follow the partitioning of ¹³C-labeled photosynthates, the roles of the treated leaf, new leaf, bulb, basal stem and roots of Chinese chive were examined. The aerial part was cut 10 h after ¹³C was administered to a leaf. The distribution and content of ¹³C in the each organ were recorded daily for 3 days, while the dry matter assimilated by the organs stored in the light or dark was weighed every 5 days for 20 days. After the ¹³CO₂ feeding, the amount and partition rate of ¹³C in the leaf decreased for 72 h, but that in the roots increased. After removing the treated leaf, the amount and partition rate of ¹³C in the leaf increased, but decreased in the bulb and roots as a new leaf developed. After cutting, the decrease of the amount and the partition rate of ¹³C in the roots became small in the light compared to the kept in the dark. Their difference between the light and dark treatments became larger from 10 days after cutting. It is thought that the photosynthates are translocated and accumulated by the bulb and roots because they are storage organs. The new leaf, developing with a limited photosynthetic capacity, relies on being supplied stored products from the bulb and roots immediately after cutting; this dependency on stored food decreases from about 10 days after cutting because its photosynthetic capacity increases.

View full abstract