The growth characteristics and physiological activities of leaves and roots of lettuce cultivated in dry-fog aeroponics with different flow rates of nutrient dry-fog (FL, 1.0 m s−1; NF, 0.1 m s−1) were investigated under a controlled environment for two weeks and compared to lettuce cultivated using deep-flow technique (DFT). The growth of leaves of FL and DFT was not different and was significantly higher than that of NF. The amount of dry-fog particles adhering to the objects was higher in FL than in NF, so that the root growth in NF was significantly higher than that of FL. The respiration rate of roots was significantly higher in dry-fog aeroponics, but the dehydrogenase activity in the roots was significantly higher in DFT. There were no differences in the contents of chlorophyll and total soluble protein in the leaves or the specific leaf area. Photosynthetic rate and stomatal conductance were higher in dry-fog aeroponics. The contents of nitrate nitrogen, phosphate and potassium ions in the leaves were significantly higher in DFT, but the content of calcium ions was significantly higher in FL. Thus, changing the flow rate of the dry-fog in the rhizosphere can affect the growth and physiological activities of leaves and roots.
Lateral shoot growth generated at leaf axils was investigated in indeterminate and determinate tomatoes (Solanum lycopersicum L.) during spring and autumn-winter cultivation. In indeterminate cultivars, the lateral shoots at the first and second nodes below the terminal flower bud grew longer than those at the third or lower nodes in spring and at 5 weeks after transplanting in autumn-winter. In determinate cultivars, lateral shoots at the first node below the terminal flower bud were shorter than those at lower nodes. Stem lengths and lateral shoot lengths of indeterminate cultivars were longer than those of determinate cultivars. In indeterminate cultivars, the lateral shoot of the second node below the terminal flower bud was suppressed significantly by flower bud removal but not by shoot removal (the terminal flower bud and the axillary bud from first node below the terminal flower bud) compared with untreated plants. In determinate cultivars, the lateral shoot of the second node below the terminal flower bud was not promoted by flower bud removal, but was significantly promoted by shoot removal compared with untreated plants. Terminal flower bud emergence was affected during lateral shoot elongation of indeterminate cultivars, but was not affected during lateral shoot elongation of determinate cultivars.
A kinetic model for root ion absorption named as the evapotranspiration-integrated model was newly proposed in order to analyze the characteristics of ion absorption by crop roots in soil-based culture. The validity of the evapotranspiration-integrated model for simulation of the day-to-day dynamics of soil salinization was examined based on experiments with a large-sized soil column system cropped with maize plants, where the salinized nutrient solution was supplied as found in crop fields under desertification. The simulated time courses of salt accumulations in plants and soil were expressed reliably based on the specificity of ion types in root absorption: Cl −, Na +, Mg 2+ and Ca 2+more highly accumulated in the root zone soil than in plants because of the root low absorption of these ions. Accumulation of the major essential ion of K + was extremely higher in plants than in the root zone soil because of the root high absorption of K +. These results indicate that the evapotranspiration-integrated model is applicable for evaluating selective and active ion absorption by crop roots in the soil salinization process, which is considered to contribute to sustainable management of crop rotation systems.
The purpose of this study is to measure the time variation of nitrate concentration in whole lettuce plants throughout cultivation. Lettuce plants were cultivated in growth chambers under fluorescent or light-emitting diode (LED) lamps. Four different light/dark periods and two ratios of red to blue photon flux density (R/B ratio) were prepared. The cultivation terms utilized were 1 or 2 weeks, and 289 lettuce plants were harvested. The visible-near-infrared absorption spectrum and nitrate concentration were obtained for each sample by spectrometry and the RQflex method, respectively. A regression model for the nitrate concentration was constructed from the spectra, and the correlation coefficient and standard error between the measured and estimated concentrations were 0.77126 and 1100.4 mg L−1, respectively. The spectra of the lettuce plants under the LED lamps were obtained at intervals of 20 min for 14 d. The time variations of the nitrate concentrations in the lettuce plants were obtained by using the regression model. The time variation could be approximated by a concave-down quadratic function. It was found that the nitrate concentration at harvest was lower in the cases in which the peak concentration occurred earlier.
The leaves of Catharanthus roseus (L.) G. Don produce vindoline (VDL) and catharanthine (CAT). These two compounds are used as components of important and expensive anti-cancer drugs such as vinblastine and vincristine. Our previous study indicated the production of VDL and CAT under red light irradiation was greater than the production under blue light, a mixture of red and blue light, and fluorescent lamp-based white light (Fukuyama et al., 2013). The aim of this study was to determine the optimal red light intensity for maximizing production of VDL and CAT. The plants were cultivated hydroponically in an environmentally controlled room under a 16-h photoperiod and four different red light intensities: 75, 150, 300, and 600 μmol m−2 s−1. The fresh weight of total leaf of the plants grown under 300 μmol m−2 s−1 was the greatest, and VDL and CAT concentrations of the plants grown under 150 μmol m−2 s−1 were the greatest compared to the other treatments. Therefore, optimal red light intensity for VDL and CAT production was suggested to be between 150 and 300 μmol m−2 s−1. We expect that these results will contribute to the development of a stable material source for important and expensive pharmaceutical drugs.