Photosynthetic efficiency, growth and secondary metabolism of common buckwheat (Fagopyrum esculentum Moench) in different controlled-environment production systems

Abstract

Light-emitting diodes (LEDs) and high-pressure sodium lamps (HPS) are among the most commonly used light sources for plant cultivation. The objective of this study was to evaluate the effect of two controlled-environment production systems differing in light sources on growth, photosynthetic activity, and secondary metabolism of common buckwheat. We hypothesized that LED light with the majority of red and blue waves would increase physiological and biochemical parameters compared to sunlight supplemented with HPS lamps. The experiment was performed in a phytotronic chamber (LEDs) and in a greenhouse (solar radiation supplemented with HPS lamps as a control). The effects were analyzed at the flowering phase with biometric measurements, leaf chlorophyll index, the kinetics of chlorophyll a fluorescence, content of soluble carbohydrates and phenolics in the leaves. Applied LED light decreased the biomass but stimulated the production of phenolics compared to control plants. In control plants, a positive correlation between flavonoid content and energy dissipation from photosystem II (DI_o/CS_m) was found, while in plants under LEDs total pool of phenolic content correlated with this parameter and the quantum yield of electron transport (φ Ro and ψ Ro) was lower than that of the control, probably affecting buckwheat biomass.

Figure 1

Differences in the leaf area in the plants grown in greenhouse conditions under solar light supplemented with HPS Agro Philips lamps (upper row) and the plants grown in phytotron chambers under LED light (bottom row). All presented leaves were collected at the same time from 8-week-old plants. The sample was the third, fully developed leaf in order from the top inflorescence.

Figure 2

Individual sugar content in leaves of common buckwheat cv. ‘Panda’ under different controlled-environment production systems. Control—solar light supplemented with HPS (High-Pressure Sodium) lamps; LED (Light-Emitting Diodes), Raf—raffinose, Stach—stachyose, Kest—1-kestose, Mal—maltose, Glu—glucose, Fru—fructose, Suc—sucrose. Values represent means (n = 3) ± SE. Stars indicate significant difference between means; *p < 0.05, **p < 0.01, ***p < 0.001 (Student's t test).

Figure 3

The percentage share of individual colours in the tested spectra. Greenhouse—solar radiation; Greenhouse + HPS—solar radiation supplemented with HPS lamps (High-Pressure Sodium); Phytotronic chamber—solo LED lamps (Light-Emitting diodes). Plants were grown in a greenhouse in the daylight (under 16-h photoperiod) supplemented with HPS lamps’ spectrum from 6.00 to 10.00 a.m., and in a phytotronic chamber with only LED spectrum. Greenhouse and Greenhouse + HPS were presented to demonstrate the influence of HPS spectrum on daylight.

Figure 4

Light spectrum in a greenhouse under solar light supplemented with HPS Agro Phillips lamps (A; control), phytotron chamber with LED light (B), and the light spectrum emitted by solo HPS (C).