Mountain streams with water temperatures lower than 10°C can be easily found in the southern part of Japan from late autumn to early summer. In this study, the potential of cool water of the mountain streams to produce value-added vegetables was examined by applying low temperature stress only to roots in a soil-less culture of spinach plants (Spinacia oleracea L.). The root treatment with a moderately low temperature of 10°C subsequent to the short term pre-treatment with a moderately high temperature of 30°C brought the moderate low temperature stress in roots and induced adaptive functions of osmoregulation and antioxidation in shoots. This effect enabled to produce value-added spinach with high contents of healthful substances (sugars, Fe, ASA and SOD) and low contents of harmful substances (NO3− and oxalic acid) without significant depression in growth. These results suggest the possibility of production of value-added vegetables by applying cool water of mountain streams to the root zone.
The ornamental banana plant Musa velutina Wendl. & Drude produces many seeds, but they do not germinate. To mass seedling production using seeds, we investigated the effects of seed harvest time on embryo development and seed germinability. Seeds harvested in August contained mushroom-shaped embryos with first and/or second leaf primordia. These seeds required scarification for germination, but not gibberellic acid 3 (GA3) treatment. Seeds harvested in November contained mushroom-shaped embryos with no leaf primordia. These seeds required scarification and 2.9 μM GA3 treatments for germination. Seeds harvested in February contained immature globular embryos and did not germinate after both treatments, but only 30% of the globular and mushroom-shaped embryos germinated in embryo culture. These results indicate that seeds harvested in August contain well-developed embryos that synthesize endogenous GA after imbibition, but are unable to germinate because of the hard seed coat. Seeds harvested in November and February contained immature embryos that do not synthesize endogenous GA after imbibition. Embryos without leaf primordia germinated in vitro, but globular embryos did not. High germination percentage for mass seedling production can be obtained by harvesting seeds from August to November and treating them with scarification and GA3.
The hydraulic acclimation of napiergrass (Pennisetum purpureum Schumach.) shoots to shading depends on that of stem. In this study, we measured the hydraulic and morphological properties of a stem segment (a node+an internode), node and internode of napiergrass and compared these properties among treatments to investigate the effect of shading on the hydraulic acclimation of stems. Plants were grown under shade conditions (30% of full sunlight) for 30 d (S plants), shade conditions for 24 d followed by full-sunlight conditions for 6 d (SF plants), or full sunlight for 30 d (control, C plants). The response of total hydraulic resistance (R) of stem segment was similar to that of internode, S plants showed the highest R and SF plants had an intermediate value between the other plants. Shading made internode long and narrow, resulting in the increase in R. In addition, normalizing internodal R by length and cross-sectional area (Rsp) was co-related with cross-sectional area. While, there was no significant difference in R of node among the treatments, Rsp was co-related with vascular bundle density. The response of R to light treatment in napiergrass stems depended on that of internode through the morphological changes.
A medicinal species, Dioscorea tokoro (Dioscoreaceae), distributes in temperate eastern Asia including the entire Japan Islands. To determine the colonizing history of this species into Japan, we investigated the geographic pattern of its nucleotide sequence variations in Japan. To reveal the genetic relationships between the species, forty-five Dioscorea species were reconstructed molecular phylogenetic tree using the rbcL and matK sequences, indicating that D. tokoro is the sister to D. tenuipes. Moreover, the result of network analysis of the Adh sequences using thirty individuals of D. tokoro indicates that there are two genetic groups in Japan, suggesting that this species had independently colonized into Japan at least twice.
The circadian clock controls many physiological states in plants by synchronization with environmental changes. The clock can be controlled artificially by imposing various light conditions in a closed system for plant cultivation. The plant circadian rhythm is formed by enormous self-sustained cellular circadian oscillators, so that the synchronization of circadian oscillators is of great importance to the formation of individual circadian rhythms. Therefore, the study of synchronization phenomena is important for precise control of the circadian rhythm. In this study, we have investigated the spatiotemporal dynamics of circadian oscillators in lettuce (Lactuca sativa L.). Bioluminescence of transgenic lettuce carrying a CCA1::LUC construct as a reporter of a circadian gene expression was measured in the leaf and root. We observed phase wave propagation in the leaf with a phase delay in the region of the primary vein, with the primary vein region showing lower amplitude than the other regions. Wave propagation occurred from the edge of the leaf inward. In addition, a striped wave traveled from the base to the tip along the roots, which were grown under continuous dark or light conditions. The features observed in the lettuce plants could be explained by phase oscillator models established in the study of Arabidopsis thaliana. The results of this study show the possibility of applying circadian clock control in a model plant for plant production.
Cymbidium protocorm-like bodies (PLBs) were cultured in modified MS (1962) medium (Shimasaki and Uemoto, 1990) to investigate the effect of light quality on organogenesis in PLBs, and the changes in superoxide dismutase (SOD). Of the different light treatments used in the research, six times of weekly light breaking by one day of green LED lighting (green LED interval lighting) during red LED illumination showed optimal number (14.1) and formation rate (93.1%) of PLB cultures. Optimal shoot formation of PLB cultures obtained at treatments of fluorescent lamp+interval lighting of green LED and blue LED+interval lighting of green LED. The highest fresh weight was achieved under fluorescent lamp condition. Except for red LED lighting treatment, interval lighting of green LED enhanced increase in antioxidant enzyme SOD activity of PLB cultures, and showed the highest SOD activity at blue LED+green LED interval lighting treatment. The study concludes that except for red LED lighting condition, interval lighting using green LED could stimulate proliferation, shoot formation in PLB cultures which accompanying with increase in SOD enzymes.
As an alternative to agricultural adjuvant, the influence of aluminum oxide (Al2O3) on the detection of chlorpyrifos dried on apple skin using UV was investigated. UV spectral reflectance was measured in the range 240–400 nm from a mixture of chlorpyrifos and Al2O3 dried on apple skin. It was determined that chlorpyrifos reduced the reflectance at 290 nm, and Al2O3 raised the spectral reflectance in the UV test range. Reflectance at 380 nm was used for estimating the amount of Al2O3 dried on apple skin. The relationship between the depth of a valley appearing at approximately 290 nm in the UV spectral reflectance and the reflectance value at 380 nm was modeled using the saturation curve. This relationship was effective in constructing an accurate prediction model for chlorpyrifos amounts in the range 0.00491–0.0490 mg•cm−2. Reflectance data at 380 nm ranged from 0.051–0.41 for calibration. The proposed model could predict the amount of chlorpyrifos with a correlation coefficient of 0.84. Furthermore, the standard error of prediction is 8.40×10−3 mg•cm−2. Conversely, the model was valid in the range 0.079–0.38 for reflectance at 380 nm.
Pretreatment of soybean (Glycine max (L.) Merr.) seeds with hydrogen peroxide (H2O2) promoted their growth rates at low water potentials. Seeds were pretreated with H2O2 and sowed in vermiculite medium with water potential of −0.02 MPa (as the control with adequate water in vermiculite) and −0.18 MPa (as the low amount of water in vermiculite). Among examined concentrations, 20 mM of H2O2 had the highest effects on the growth of seedlings at low water potential. Roots exhibited more elongation improvement than hypocotyls at low water potential. The osmotic adjustment was extremely promoted in seedlings with H2O2-pretreatment in seeds in 50 h after sowing. The data indicate that such extreme osmotic adjustment was associated with a large size of the growth-induced water potential in roots and hypocotyls. Furthermore, water permeability in the zone of elongation was decreased in seedlings H2O2-pretreated. At low water potential, seedlings with H2O2-pretreatment in seeds could import more solutes and water in cells in the zone of elongation while faster cell elongation went on by absorbing water from the low amount of water in vermiculite.
The availability of agricultural land use information allows decision makers and managers to establish short-term and to long-term plans for land conservation and sustainable use. The objective of this study was to develop a method for extraction of agricultural land use information based on remote sensing imagery. By combining particle swarm optimization (PSO), k-means clustering algorithm and minimum distance classifier, a PSO-k-means-based minimum distance classifier for agricultural land use classification was developed. Crop planting information was collected and divided into five classes: water bodies, paddy fields, bean fields, wheat fields and others (windbreak, roads, rare areas, and buildings, etc.). K-means, a widely used algorithm in pattern recognition for unsupervised classification, became a part of supervised classification by using PSO to find the optimal initial position vectors in a training sample pretreatment process. The optimal cluster of each subclass was finally used for minimum distance classification. The results obtained from Miyajimanuma wetland land use information extraction showed that merely using a small feature space composed of the first three principal components of a SPOT 5 image enabled classification accuracy of 93%.
Micropropagation of two clones of rabbiteye blueberry (Vaccinium virgatum Aiton) developed for leaf tea production was investigated for supply in high quantities to plantations and plant factories. Shoots of a new cultivar, ‘Kunisato 35 Gou’, were multiplied efficiently on MW, a mixture of equal parts of MS and WPM, supplemented with 20 μM zeatin by using 2-node segments. For No. 19, another promising clone, 5-node segments were the most productive for shoot multiplication. Among basal media tested for micropropagation, MW medium was found to be the most efficient. Although shoots of ‘Kunisato 35 Gou’ grew better in vitro than those of No. 19, both clones had equivalent rooting abilities. More than 90% of the shoots rooted and survived in vermiculite after culturing in Gellan gum-solidified rooting medium without plant growth regulators. The growth of shoots with roots in pots was significantly influenced by the potting soil. The plantlets in the soils mixed with peat moss, which made the soil acid, grew vigorously, while those in the soils without peat moss grew moderately or poorly, depending on soil type.
Tuberous root growth and antioxidant contents of 2 sweetpotato (Ipomoea batatas (L.) Lam.) cultivars were examined using 2 different irrigation schemes: surface-irrigation and sub-irrigation. Coarse silica sand was used for root media, which maintained well the gas permeability and water drainage around the roots. The root surface was periodically wetted for watering in the surface-irrigated roots, while the sub-irrigated roots were not. The irrigation methods did not affect the oxygen concentration around the roots. No differences in plant growth were observed between the 2 irrigation methods. However, the content of α-tocopherol in the tuberous root was significantly higher in the ordinary-irrigated roots for both of two cultivars. Thus, the periodical wetting increased the α-tocopherol content in the tuberous root of sweetpotato cultivars without any apparent changes in tuberous root development.
The areas along rivers and streams are composed of particular environmental characteristics, and plants growing within this environment, called rheophytes, are subjected to flash floods after heavy rainfall as a strong selective pressure. To identify potential hybridization of the rheophytic Rhododendron ripense Makino and its allied dryland species R. macrosepalum Maxim., we conducted morphological and molecular analyses of these plant species. These analyses revealed a high rate of hybridization and introgression from R. ripense into R. macrosepalum, suggesting that hybrid plants arising from R. ripense and R. macrosepalum may develop broader leaves than R. ripense and may affect the flooding of river waters along the riverside.
The effects of defoliation timing on fruit growth and abortion were monitored in gynoecious, parthenocarpic ‘NK×AN8’ cucumber. In control, non-defoliated plants, fruit attained marketable size at 14 days after anthesis (DAA), whereas some of the fruit from the plants (leaf-to-fruit ratio=2) defoliated at different time points were either stunted or aborted. Stunted and aborted fruit ceased to grow at about 7–8 DAA and at 4 DAA, respectively. When plants were defoliated at 4 DAA or earlier, more than 20% of the fruit aborted, whereas no fruit aborted when defoliated at 6 DAA or later. For fruits neither aborted nor stunted, the relative growth rate (RGR) of a fruit was almost the same for the period between 8 and 14 DAA irrespective of defoliation timing. In plants defoliated at 0 to 8 DAA, however, RGR decreased temporarily after defoliation. These results suggested that sufficient amount of photoassimilates should be continuously transported into fruits up to 4 DAA and 7–8 DAA in order to prevent fruit abortion and stunting, respectively.