Evaluation of Growth and Photosynthetic Rate of Cucumber Seedlings Affected by Far-Red Light Using a Semi-Open Chamber and Imaging System

Abstract

Far-red light was excluded in photosynthetic photon flux; however, recent studies have shown that it increases photosynthetic capacity. In addition, there were few studies on the whole canopy photosynthetic rate and continuous changes of morphology on cucumber seedlings affected by far-red light. This study evaluated the effect of conventional white LEDs adding far-red light on cucumber seedlings using a semi-open chamber system for the measurement of the whole canopy gas exchange rate, and the Raspberry Pi-based imaging system for the analysis of a continuous image. In the image, through the imaging system, it was confirmed that far-red light promoted the germination rate of cucumber seedlings and enhanced early growth. However, the dry weight of the shoot and root did not increase. The measured net apparent CO2 assimilation rate was improved by an increasing leaf area during the cultivation period. The conventional white LED light source with added far-red light increased the photosynthetic rate of cucumber seedlings’ whole canopy. However, at the early seedling stage, plant height and leaf area of the whole canopy was increased by far-red light, and it was revealed that the image data saturated faster. It was considered that the photosynthetic efficiency decreased due to a shading effect of the limited planting density of the cell tray. The results found that using appropriate far-red light, considering planting density, could increase the photosynthetic rate of the whole canopy of crops, thereby promoting crop growth, but it was judged that the use of far-red light in the early growth stage of cucumber seedlings should be considered carefully.

Development of a semi-open chamber system for the gas exchange measurement of whole-canopy under steady and unsteady states in cucumber seedlings

“…However, extending leaf-level measurements of photosynthetic rate to the whole-canopy level can vary depending on light interception due to leaf position and distribution [ 27 , 28 ]. [ 29 ] showed that the photosynthetic rate of whole-canopy in cucumber seedlings decreased with decreasing light interception due to the shading effect of leaf morphology. This experiment determined that there were no shading effects due to the growth of cucumber seedlings.…”

Far-red light modulates grapevine growth by increasing leaf photosynthesis efficiency and triggering organ-specific transcriptome remodelling

“…Conversely, filtering far-red solar light could inhibit internode growth and leaf area enlargement in chrysanthemum and bell pepper [12]. In addition, the low R/FR treatment could increase the content of carbohydrates in many species, including tomato [13,14], turnip (Brassica rapa L. ) [15], onion [16] and cucumber [17,18]. Similarly, supplemental farred light could significantly increase the fresh weight, dry weight and stem length of lettuce [19].…”