LED and HPS Supplementary Light Differentially Affect Gas Exchange in Tomato Leaves

Abstract

Using light emitting diodes (LED) instead of conventionally used high pressure sodium (HPS) lamps as a supplemental light source in greenhouses results in a higher efficacy (µmol light per J electricity) and makes it possible to customize the light spectrum. To explore the effects of LED and HPS on gas exchange, thermal relations, photosynthesis, and water status of young tomato plants, seven genotypes were grown in a greenhouse under LED (95% red, 5% blue) or HPS lamps in four experiments differing in the fraction of lamp light over natural light. HPS lights emit a broader spectrum of red (40%), green–yellow (50%), blue (5%), and far-red (5%) and a substantial amount of infrared radiation (heat). Young tomato plants grown under LED showed lower leaf temperature and higher stomatal density, stomatal conductance (gs) and transpiration rate (E) than plants grown under HPS; this may be due to the different supplemental light spectrum. The young plants grown under LED tended to have increased photosynthetic capacity. Furthermore, the water stress indices CWSI and IG, which were obtained using thermal imaging, were positively correlated with gas exchange-derived gs and E, putting forward the use of thermal imaging for the phenotyping of transpiration. Under LED light, photosynthetic gas exchange was generally increased, which agreed with the water stress indices. The extent of this increase was genotype-dependent. All differences between LED and HPS were smaller in the experiments where the fraction of lamp light over natural light was smaller.

Effect of Photoconversion Coatings for Greenhouses on Electrical Signal-Induced Resistance to Heat Stress of Tomato Plants

“…The coatings used in this work have photoluminescence maxima at 450 and nm, which quite well correspond to the absorption maxima of tomato plants, locate the region of 440 and 675 nm [29]. Stimulating photosynthesis by increasing the pro tion of light in the blue and red regions of the spectrum has been shown in a large num of works [1][2][3][4][5][6]10,11,14]. Such stimulation can be caused both by a direct increase in amount of energy available for photosynthesis and by the adjustment of physiolo processes due to signaling pathways starting from photoreceptors.…”

“…In temperate and polar latitudes, one of the most serious problems is insufficient illumination, in particular at wavelengths used in the course of photosynthetic reactions. This problem can be solved by active backlighting using LEDs or other light sources [1][2][3][4][5][6]. However, this approach requires high economic and energy costs, which leads to an increase in carbon footprint [7].…”

Effects of Greenhouse vs. Growth Chamber and Different Blue-Light Percentages on the Growth Performance and Quality of Broccoli Microgreens

“…In particular, after examining the effects of blue spectra on microgreens' growth and yield, it was found that their action was genotypic dependent [28], but this result was contradictory between experiments [29]. More generally, it was found that monochromatic blue light increased stomatal conductance [30], induced a more compact plant size [31], increased the net photosynthesis rate [32], reduced the plants' height, and increased the leaf area [33].…”

Comparison of Supplemental LED Top- and Interlighting for Year-Round Production of Cherry Tomato

“…However, these studies were experiments comparing HPS and LED, and no study measured the effect of SL using LED for both top-and interlighting. LED and HPS SL differentially affect photosynthetic capacity in young tomatoes [20]. Therefore, we examined the effects of different LED SL positions on cherry tomato fruit yield and quality under high irradiance.…”