A cultivation experiment was conducted to investigate the change of chemical forms of Cu, Fe, and Zn in compost produced from horse dung (HDC) and that produced from swine manure (SMC). A mixture of silica gel and sieved HDC and that of silica gel and sieved SMC were used as media to cultivate peas (Pisum sativam L.) in order to determine bioavailable chemical forms of Cu, Fe, and Zn. Cu and Fe were primarily found in an organic complex fraction and residue fraction of HDC and SMC. Zn was primarily found in an iron and manganese oxide fraction and an organic-complex fraction. There was little change in the concentration of “bioavailable fractions,” such as water-soluble, exchangeable, and carbonate. However, the amount of Cu and Fe in the organic complex fraction decreased significantly and that Zn in the iron and manganese oxide and organic complex fractions also decreased significantly. These results indicated that the transportation of Cu, Fe, and Zn to plants affected their chemical forms. The associated fraction played a role in the storage (sink) of Cu, Fe, and Zn when the amount decreased significantly.
Appropriate methods for breaking down the seed hardness that interferes with the breeding of Pelargonium were carried out. Treatment with concentrated H2SO4 for 20 min for P. vitifolium seeds achieved a high germination rate of 90%, and with 60 min of treatment, the seeds of P.×domesticum achieved a germination rate of 70%. In the case of scarification by a homogenizer, with 5–10 min of treatment these two species both absorbed sufficient water and showed high germination rates. However, as the degree of seed hardness considerably differs among species (strains), it will be necessary to treat them accordingly in regard to length of treatment time. Germination was more effective when seed treated with concentrated H2SO4 or homogenizer was sown on vermiculite beds, compared with in petri dishes. The seeds of P. appendiculatum are not much harder than those of other Pelargonium species, and were germinated slowly at 10–15°C, after which healthy seedlings could be obtained. Regarding the other 5 species used in this trial, the germination rates were extremely haphazard according to species and sowing date (0–100%), indicating that plants under natural conditions need seed with the diversity to adapt to intense environmental changes.
Leaflet inclination angle before paraheliotropism controls seed production of soybean plants. We examined the effect of water condition on the inclination angle of leaflets and petioles of two soybean cultivars. Angles measured in the morning were larger in 2008, a wetter season, than in 2009, a drier season. Angles were similarly larger in irrigated plants than in unirrigated plants. The imposition of drought stress on plants grown in pots reduced these angles with the decline in water content of these tissues. There were significant correlations between inclination angle and water content in leaflets and petioles of plants grown both in the field and in pots. These results indicate that water condition controls leaflet and petiole inclination.
Light interception by leaves is crucial to crop production. In order to compare the light-intercepting characteristics of soybean ‘Misato-zairai’ (unstable yield) with those of ‘Fukuyutaka’ (stable yield), we cultivated these cultivars under the different soil water condition and measured the light extinction coefficient (K) with two different photometers. In 2010, ‘Misato-zairai’ had a higher proportion of upper-layer LAI and a significantly lower leaf inclination angle (closer to horizontal), but there was no difference in K between the cultivars. In 2011, irrigation increased LAI, but there was no difference in LAI between the cultivars. As before, ‘Misato-zairai’ had a significantly higher upper-layer LAI and a lower leaf inclination angle, but there was no difference in K. These suggested that unstable yield of ‘Misato-zairai’ should not be due to low light capture in spite of a higher proportion of upper-layer LAI and unerect leaflets.
In a farmer's strawberry greenhouse, seasonal changes in solar radiation and air conditions (temperature, humidity, and CO2 concentration) were measured, and it became clear that the stable year-round production of strawberry was depressed by low temperature and low solar radiation in the cold season and by excessively high temperature in early autumn. Furthermore, dew formations during the nighttime and inappropriate application of CO2 enrichment were also related to the depression of stable production. Therefore, a local environmental control system was newly developed for strawberry crops based on air circulation and heat exchange between the constant soil temperature layer and the ambient air. The system consisted of an underground air pipe (UAP) and perforated inter-row air ducts (IAD) connected to the UAP; the UAP was set at a depth of 1.5 m, where soil temperature remained suitable for year-round strawberry growth. The greenhouse air was drawn into the UAP, and the air flowing through the UAP exchanged heat with the constant soil temperature layer and was dispersed to the ambient environment of the strawberry crops through the perforated IAD. In the nighttime during the cold season, air flowing through the system was heated by 8°C, and a heating effect of 3°C was observed in the ambient air. The proposed system of applying the constant soil temperature layer can be expected to reduce the nighttime heating load by 50% and enable energy-saving environmental control.
A comparative analysis of stunting was conducted at various temperatures to develop a simple and reliable method for evaluating the disease symptoms of the chrysanthemum stunt viroid (CSVd). CSVd-free plants had significantly greater plant height than CSVd-carrying plants at 22°C and 24°C. No significant differences in plant height were detected at high and low temperatures. These results suggest that the in vitro evaluation of plant growth at an appropriate temperature might provide a useful method for CSVd diagnosis. In addition, the intensity of the small RNA hybridization signal obtained by northern blot analysis using a full-length CSVd RNA as a probe indicated synchronous behavior that correlated with the degree of growth suppression. These results suggest that a small RNA from CSVd may lead directly to the suppression of plant growth, with a similar function to siRNAs in chrysanthemum.