The effects of LEDs and duty ratio on the growth and physiological responses of Silene capitata Kom., endangered plant, in a plant factory

Abstract

Background: In this study, we observed their growth and physiological responses using a variety of duty ratio under the mixed light using red, blue, and white lights. The red+blue mixed light was treated with 95%, 90%, 85%, 80%, and 75% duty ratios and red+blue+white mixed light with 85% and 70% duty ratios. We examined the width and length of leaves, total number of leaves, and number of shoots to examine their growth responses. The physiological responses were studied by measuring their photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, chlorophyll content, and fluorescence (F o , F m , and F v /F m). Results: We found that lower duty ratio caused the length and width of the leaves to grow longer under red+blue mixed light but that it did not cause any difference in the red+blue+white mixed light condition. In addition, there was no difference in the number of leaves and shoots among all treatments. In the red+blue mixed light condition, the photosynthetic rate was no difference, but both transpiration rate and stomatal conductance were the highest at 95% duty ratio than in other ratios. Water use efficiency pattern was similar to that of photosynthetic rate; water use efficiency was no difference. Chlorophyll content was the highest at 95% duty ratios, and it was the least at 90%, 85%, and 75% duty ratio. F o and F m values were relatively high at 85% and 80% duty ratio and low at 90% duty ratio while F v /F m showed no difference. Conclusions: Under the red+blue+white mixed light, all physiological items showed no difference between 70 and 85% treatments. But, photosynthetic rate, water use efficiency, chlorophyll content, and F v /F m were relatively greater in the red+blue+white mixed light than in the red+blue mixed light. Therefore, red+blue+white mixed light treated with 70% duty ratio could lessen the environmental stress and save more power when cultivating Silene capitata in a plant factory.

Comparative Growth, Photosynthetic Pigments, and Osmolytes Analysis of Hemp (Cannabis sativa L.) Seedlings under an Aeroponics System with Different LED Light Sources

“…Besides light stress, a decreasing trend in Fv/Fm by reducing Fm was also observed under stress from heat, ozone, and other pollutants [49,51]. Interestingly, Fv/Fm was found higher in the white, R:B:W, and R:B:G ratio in some previous studies [41,52], which quite supports our present findings. PCA analysis revealed that Chl a, Chl b, and Fv/Fm were negatively correlated with Pro, AsA, RL, PFW, and Car (Figure 7).…”

“…Similar results from a previous study described that a high ratio of both R:B and R:B:W manifested higher chlorophyll compared to natural light in Silene capitate Kom. [41]. Each of the plant pigments has been characterized by an absorbance pattern in wavelength called the absorbance spectrum, where the blue and red regions are absorbed strongly by Chl a and b, with less absorbance of other wavelengths [42].…”