Abstract
BackgroundThe sunfleck is an important light environmental factor for plants that live under the shade of trees. Currently, the smartfarm has a system that can artificially create these sunfleks. Therefore, it was intended to find optimal light conditions by measuring and analyzing photosynthetic responses of Eutrema japonica (Miq.) Koidz., a plant living in shade with high economic value under artificial sunflecks.ResultsFor this purpose, we used LED pulsed light as the simulated sunflecks and set the light frequency levels of six chambers to 20 Hz, 60 Hz, 180 Hz, 540 Hz, 1620 Hz, and 4860 Hz of a pulsed LED grow system in a plant factory and the duty ratio of the all chambers was set to 30%, 50%, and 70% every 2 weeks. We measured the photosynthetic rate, transpiration rate, stomatal conductance, and substomatal CO2 partial pressure of E. japonica under each light condition. We also calculated the results of measurement, A/Ci, and water use efficiency. According to our results, the photosynthetic rate was not different among different duty ratios, the transpiration rate was higher at the duty ratio of 70% than 30% and 50%, and stomatal conductance was higher at 50% and 70% than at 30%. In addition, the substomatal CO2 partial pressure was higher at the duty ratio of 50% than 30% and 70%, and A/Ci was higher at 30% than 50% and 70%. Water use efficiency was higher at 30% and 50% than at 70%. While the transpiration rate and stomatal conductance generally tended to become higher as the frequency level decreased, other physiological items did not change with different frequency levels.ConclusionsOur results showed that 30% and 50% duty ratios could be better in the cultivation of E. japonica due to suffering from water stress as well as light stress in environments with the 70% duty ratio by decreasing water use efficiency. These results suggest that E. japonica is adapted under the light environment with nature sunflecks around 30–50% duty ratio and low light frequency around 20 Hz.
Highlights
The sunfleck is an important light environmental factor for plants that live under the shade of trees
The gs was higher at the duty ratios of 50% and 70% than at 30% and the CO2 partial pressure (Ci) was highest at 50% (Fig. 1)
The A/Ci was highest at 30% and the Water use efficiency (WUE) was higher at 30% and 50% than at 70% (Fig. 1)
Summary
The sunfleck is an important light environmental factor for plants that live under the shade of trees. Park et al Journal of Ecology and Environment Because of these advantages, studies on system automation, light wavelengths for optimal plant growth conditions, and breeding of varieties are being carried out in South Korea at national and private research institutes using plant factories. In the case of Japan, plant factories that can produce large quantities of plants regardless of weather or place have attracted attention because Japan’s food self-sufficiency rate was about 41% and grain self-sufficiency rate was about 28% as of 2008, which were the lowest among OECD countries This presents serious problems in securing food resources, but large-scale farming is difficult in Japan due to the characteristics of Japanese smallscale agriculture because of the considerable amount of deserted land (Takatsuji 2010). The fully controlled types only use artificial light to produce plants, and they are optimal for cultivation studies using LED light (Watanabe 1997)
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