We examined the effects of fertilizer concentration and irrigation amount on the growth of Nopalea cochenillifera (L.) Salm-Dyck, the edible cactus, under soil and gravel culture conditions. Although fertilizer supplementation was effective in promoting daughter cladode growth, high concentration led to growth inhibition in gravel culture. In gravel culture experiments, plants were watered at different frequencies: once a week (1/w), once every two weeks (1/2w) and once every four weeks (1/4w). Cladode growth was promoted at 1/w and 1/2w leading to increased harvest of daughter cladodes compared with 1/4w treatment when electrical conductivity of fertilizer was 2.6 dS m^-1 (gravel ×1). Under “gravel ×1”treatments, growth of daughter cladodes was significantly higher in gravel culture (gravel ×1, 1/w) compared with soil culture (soil ×2, 1/w), resulting in about 185% increase in fresh weight. We evaluated the effect of zinc (Zn) and iron (Fe) on cladodes growth and checked the metal accumulation in cladodes by exposing them to 100 ppm Zn and Fe under gravel culture. Subsequently, large amount of Zn and Fe accumulated in cladodes compared with those untreated with Zn and Fe as well as those in soil culture. These results suggested that gravel culture is effective in growth promotion and biofortification of N. cochenillifera.

　This study aimed to devise a non-destructive method to measure the potassium content of root vegetables using visible and near-infrared spectroscopy. The test materials included three varieties of radish, i.e., “New Comet”, “Isabell”, and “Ruby Comet”, and “Mifune” turnips. Visible light reflectance (400-700 nm) and near-infrared light reflectance (1,100-1,350 nm) of the embryo axes were measured, and analyzed using second-order derivatives. The actual potassium content was measured using an inductively coupled plasma emission spectrometer. Calibration curves were created using partial least squares regression analysis, and the predicted values were calculated. The correlation coefficients between the predicted and actual values were as follows: 0.801 for “New Comet”, 0.698 for “Isabell”, 0.820 for “Ruby Comet”, and 0.805 for “Mifune”; thus, a high correlation was observed for all tested varieties. The ‘ratio of standard deviation of reference data in prediction sample set to standard error of prediction (RPD)’, which determined the analytical precision of the calibration curve, were 11.0, 4.24, 4.58, and 5.92 for “New Comet”, “Isabell”, “Ruby Comet”, and “Mifune”, respectively. Therefore, non-destructive measurement of potassium content is possible using visible and near-infrared spectroscopy.

　In this study, I investigated the effect of sub-irrigation frequency on changes in xylem pressure potential and intumescence occurrence in tomato seedlings grow in closed seedling-production systems. Further, I explored the relationship between irrigation frequency and physiological responses in tomato seedlings. The tomato seeds were sown in a closed seedling-production system and subjected to varying irrigation frequencies. The results revealed that increasing irrigation frequency suppressed the decline in soil moisture content and mitigated the rise in xylem pressure potential, when humidity rises concurrently with irrigation. Moreover, higher irrigation frequency correlated with reduced incidence of intumescence during early growth stages and accelerated seedling growth. Thus, optimizing irrigation strategies is crucial to mitigate fluctuations in xylem pressure potential and suppress intumescence in closed seedling-production systems.

　This paper presents the effects of artificial periodic sound on the growth of Hatsuka daikon (radish). In our experiment, radishes were exposed to artificial periodic sound generated by vibration for 6 hours a day. In this experiment, three different frequencies of periodic sound (100, 500, and 1,000 Hz) were used, and the sound volume was set at 50 and 70 dBA. As a result, we found that when the periodic sound was applied, the growth of the tuberous root of the radish was promoted compared to the control, and that the higher the frequency, the more the tuberous roots grew. Also, we found that the conditions of 1,000 Hz and 50 dBA were most effective compared to other conditions, resulting in that the weight of the tuberous root was approximately 1.34 times greater than that of the control. In addition, the Dunnett’s test-based statistical assessment confirmed that there were statistically significant differences in the mean value between the control and the 1,000 Hz and 50 dBA condition-group at the significance level of 5%.