The Impact of Far-Red Light Supplementation on Hormonal Responses to Cold Acclimation in Barley

Abstract

Cold acclimation, the necessary prerequisite for promotion of freezing tolerance, is affected by both low temperature and enhanced far-red/red light (FR/R) ratio. The impact of FR supplementation to white light, created by artificial LED light sources, on the hormone levels, metabolism, and expression of the key hormone metabolism-related genes was determined in winter barley at moderate (15 °C) and low (5 °C) temperature. FR-enhanced freezing tolerance at 15 °C was associated with promotion of abscisic acid (ABA) levels, and accompanied by a moderate increase in indole-3-acetic acid (IAA) and cis-zeatin levels. The most prominent impact on the plants’ freezing tolerance was found after FR pre-treatment at 15 °C (for 10 days) followed by cold treatment at FR supplementation (7 days). The response of ABA was diminished in comparison with white light treatment, probably due to the elevation of stress tolerance during FR pre-treatment. Jasmonic acid (JA) and salicylic acid (SA) were transiently reduced. When the plants were exposed directly to a combination of cold (5 °C) and FR supplementation, ABA increase was higher than in white light, and was associated with enhanced elevation of JA and, in the longer term (after 7 days), with IAA and cis-zeatin increase, which indicates a stronger stress response and better acclimation. Cold hardening was more efficient when FR light was applied in the early developmental stage of the barley plants (three-leaf stage, 18 days), rather than in later stages (28-days). The dynamics of the phytohormone changes are well supported by the expression profiles of the key hormone metabolism-related genes. This series of treatments serves as evidence for the close relationship between plant hormones, light quality, and low temperature at the beginning of cold acclimation. Besides the timing of the FR treatments, plant age also represents a key factor during light spectrum-dependent cold acclimation.

Effect of low-temperature stress on the growth of plants of Secale cereale (Poaceae) and endogenous cytokinin content in roots and shoots

“…Prolonged acclimation (21 d) of Carpobrotus edulis plants at 5 °C results in the increase of endogenous contents of trans-zeatin and trans-zeatin riboside (Fenollosa et al, 2018). Acclimation of barley plants at 5 °C during 7 d is accompanied by a decrease in the transzeatin content and an increase in cis-zeatin (Ahres et al, 2021). In winter wheat, elevation in active cytokinins content has been found during 7-31 d of acclimation at 4 °C after its transient drop at the alarm phase of stress response (Vanková et al, 2014).…”

“…Recently, it has been shown that the combination of dark and cold arrests the growth of Arabidopsis plants and leads to a strong decrease of cytokinin levels (Prerostova et al, 2021). Treatment of young barley plants with far-red light stimulates better cold acclimation and is associated with significant changes in phytohormone balance, in particular, an increased ciszeatin concentration (Ahres et al, 2021). Unfortunately, in most studies of plant adaptation to cold stress, the role of light is often not taken into account.…”

Light regulation of quality and growth of basil

“…To improve postharvest chilling tolerance several studies have investigated the use of pre-harvest light treatments such as modifying the light spectrum to increase the percentage of blue (400-500 nm) and far-red (FR, 700-800 nm) light (Affandi et al, 2020(Affandi et al, , 2022Kovács et al, 2020;Ahres et al, 2021). In this thesis it was investigated if light intensity and spectra influenced chilling tolerance.…”

“…The involvement of far-red (FR) light in acclimation to chilling has gained increasing interest. Most authors relate the proposed mechanism of FR to the induction of the C-repeat-binding factors CBF pathway which function upstream of the cold responsive (COR) genes (Franklin and Whitelam, 2007;Wang et al, 2016a;Ahres et al, 2021). COR genes have a vast function in plants such as inducing enzymes for the biosynthesis of osmoprotectants and proteins related to lipid metabolism (Liu et al, 2019).…”

“…Schwend et al (2016) found that FR increased the content of rosmarinic acid in basil and suggested phytochromes to be involved in the regulation. In barley, additional FR improved freezing tolerance, reflected in a lower ion leakage (Ahres et al, 2021). Additional FR at moderate temperature (15 °C) also upregulated the content of abscisic acid (ABA) (Ahres et al, 2021).…”