The effects of light quality on the flowering need to be investigated for the efficient use of light-emitting diodes (LEDs) in cut flower production because of the environmentally friendly features of LEDs. Assuming long-day treatments in cut flower production, we used Delphinium species, popular long-day plants, and treated the plants at night with relatively weak light to investigate the effects of light quality. We used reproductive experimental conditions with phytotrons and long-day treatments, mainly monochromatic light, to establish an experimental system to elucidate physiological and molecular mechanisms in the near future. Before investigating the effect of monochromatic light, we first performed a long-day treatment with a widely used white LED. A similar effect to the incandescent lamp on bolting was observed, suggesting the possibility that red or blue light, but not far-red light, are adequate to promote flowering from the spectra of both light sources. Next, long-day treatments were performed with LEDs emitting monochromatic blue, red, and far-red light. In the model plant Arabidopsis thaliana, flowering is well known to be promoted by far-red and blue light and inhibited by red light. However, long-day treatment with red light for Delphinium effectively promoted flowering. Treatment with far-red light, which shows an opposite flowering response to red light in A. thaliana, also promoted the flowering of Delphinium. As for blue light, the flower budding rate of D. grandiflorum reached 100%, and that of D. elatum was lower. Compared to far-red and blue lights, long-day treatment with red light did not negatively impact cut flower quality, including cut flower length and number of florets. Our results on light quality impact on flowering response will contribute to technology for regulating Delphinium flowering and potentially also lead to the elucidation of the mechanism of unique flowering promotion by red light.

　Upland soils are an important methane (CH₄) sink at the global scale, but their responses to rising CH₄ concentrations are not well understood. In this study, we developed a system for the in situ evaluation of the responses in CH₄ uptake in forest soils to rising CH₄ concentrations, and applied this system to a temperate forest in Japan. The system was used to precisely inject air with a high CH₄ concentration into an automated closed chamber, and was used to quasi-continuously measure CH₄ uptake under higher CH₄ concentrations than ambient air up to 2.6 ppm. Artificial diffusion associated with a sudden increase in CH₄ concentrations within the chamber was compensated for with a diffusive flux calculated with a multi-layer diffusion model. We also conducted a long-enclosure experiment, in which CH₄ concentrations within the chamber were gradually decreased from 3.0 ppm to 1.9 ppm over two to four hours to minimize artificial diffusion. The measured responses in CH₄ uptake to CH₄ concentration ranged from 0.10 to 2.47 nmol m^-2 s^-1 ppm^-1 or varied from 1.3 to 1.6 times ppm^-1 in four plots that chamber experiments were conducted. Based on the CH₄ concentration profiles within soils, CH₄ oxidation was estimated to occur within the top 10-cm soil. To further obtain accurate estimates in soil responses to rising CH₄ concentrations, the effect of artificial diffusion must be minimized in experiments, as this was the greatest source of uncertainty in this study.

　The net photosynthetic rate (NPR) of cos lettuce plants at an average photosynthetic (wavelength range: 400-700 nm) photon flux density of 100 µmol m^-2 s^-1 under pulsed light generated with full-wave rectification of 50 Hz sine-wave alternating-current power (FWR pulsed light) was compared with those under square-wave (SW) pulsed light at a frequency of 100 Hz and duty ratio of 50%, and under constant continuous light. The NPR under FWR pulsed light was significantly greater than that under SW pulsed light and not significantly different from that under continuous light. Considering that FWR pulsed light is producible using a simple driving circuit, and therefore low cost and low energy loss are expected compared with continuous light, FWR pulsed light is an option for plant cultivation by artificial lighting with light-emitting diodes.

　The large genotypic differences in yield response within crop species to elevated CO₂ concentration (e[CO₂]) suggest that there is potential to ensure food security under future e[CO₂], by actively selecting and breeding cultivars that maximize yield under e[CO₂]. Identifying the determinants of yield response is important for breeding these cultivars. In soybean, genotypic variations in yield response to e[CO₂] may be explained by increased pod number. However, the relative contributions of other yield components, such as node number, number of pods per node, number of seeds per pod, and single-seed mass, to yield increase are not fully understood. Increased node number in response to e[CO₂] has also been observed and hypothesized to be a determinant of the genotypic increase in yield due to e[CO₂]. This was tested using six cultivars grown in controlled-environment chambers. Surprisingly, it was the increase in pods per node, rather than increased node number per se, that was most strongly associated with yield increase. This emphasizes the importance of studying the responses to e[CO₂] of the components which contribute to yield, including flower number and pod set (both of which can affect pods per node), to develop cultivars that can maximize yield under e[CO₂].

　Greenness indices derived from near-surface photography are increasingly being used for the continuous and automated monitoring of vegetation within various ecosystems. In the present study, we examined the characteristics and applicability of the green chromatic coordinate (GCC) index for monitoring vegetation parameters in semi-arid grasslands. From 2016 to 2019, digital images were collected using time-lapse cameras at 10-min intervals at two grassland sites in Mongolia. The GCC was calculated from the digital number values of red, green, and blue channels of the images. The results demonstrated that GCC values on sunny days were nearly constant between 1100 local time (LT) and 1500 LT regardless of solar altitude and direction. However, the GCC showed erroneous values under low illumination conditions on cloudy and rainy days. In addition, the GCC showed clear seasonal changes similar to the satellite-based normalized difference vegetation index (NDVI) and greenery ratio (GR). The variation in GCC agreed better with that in GR than in NDVI. Finally, the GCC value was highly correlated with plant aboveground biomass and was probably related to CO₂ fluxes. Thus, our findings suggest the feasibility of using a digital camera system for continuous long-term monitoring of vegetation parameters and phenology in semi-arid grasslands.

　The occurrence dates of crop phenological events are closely related to the timing of agronomic management and therefore are key information for agricultural monitoring and forecasting as well as for climate change impact assessment and adaptation planning. However, sowing and harvesting dates are only variables available in current global datasets. Here, we present the 0.5° grid global dataset of crop phenology in 2000 (the average of 1996-2005), called the GCPE, developed using a crop phenology model, potential sowing windows estimated from agroclimatic conditions, and site observations worldwide collected from 319 literature. Crops considered include maize, rice, wheat, and soybean. This dataset offers the plausible peak dates of sowing, emergence, maturity and harvesting as well as those of silking for maize, flowering for soybean, heading and flowering for wheat, and transplanting, heading and flowering for rice. Distinctions are made between fully irrigated and rainfed conditions and winter and spring wheat as well as between dry- and wet-season rice in the tropics. The GCPE dataset gives users opportunities to improve any applications in which crop calendars are a key input and is useful for regions where calendar information is currently sparse.