Effect of blue light on the photosynthesis and flavonoid accumulation in leaves of Hedyotis corymbosa (L.) Lam.

Abstract

In plants, blue light with a short wavelength can promote light reaction in photosynthesis and increase dry mass. Photosynthesis plays an important role in supporting carbohydrates for primary and secondary metabolism processes. Flavonoids are phenolic compounds, a class of plant secondary metabolites, that can be obtained from many medicinal herbs. These phenolic compounds are involved in the reactive oxygen species scavenging system, inhibit lipid peroxidation by free-radical, chelate redox-active metals resulting in their antioxidant ability and cardioprotective effects. In this study, H. corymbosa (L.) Lam., one of the common medicinal herbs, was cultured for 4 weeks under conditions of 450 nm blue LED (light-emitting diode) lights at the different light intensity as treatments and fluorescent lamp light as a control to investigate the effects of blue light on photosynthesis and flavonoid accumulation in leaves. The results show that blue light at 450 nm promoted photosynthetic rate by enhancing stomatal opening, electron transport rate in light reaction. Blue light also enhanced photoprotection by decrease the quantum yield of non-photochemical losses, increase the quantum yield of non-photochemical quenching and gained 24% more in dry mass. The accumulation of flavonoid and total phenolic compounds in leaves was followed by a decrease in sucrose. These events proved that blue light enhances photosynthesis and increase carbohydrate and flavonoid accumulation in leaves.

Colored LED Lights: Use One Color Alone or with Others for Growth in Hedyotis corymbosa In Vitro?

“…Blue LEDs, which have a short wavelength and a high energy light [ 36 ], played as a strong light environment condition that caused a decrease in the LHC amount and chlorophyll-b biosynthesis from chlorophyll-a through the enzyme chlorophyllide, an oxygenase [ 37 ]. A reduction in the chlorophyll-b content in the leaves of ex vitro plants grown under blue LEDs compared with a control was previously reported [ 27 , 28 ]. Plants that were exposed to a long-term red LED light (660 nm) treatment showed “red light syndrome”, which had a lower chlorophyll-a concentration in the leaves compared with the control in cucumbers and lettuce [ 12 , 31 ].…”

“…These molecules fuel the Calvin–Benson cycle for CO 2 fixation to produce carbohydrates and other assimilatory processes [ 42 ]. An increase in the photosynthetic product accumulation (such as sugar or starch) led to the rise of the fresh and dry weight of the leaf of H. corymbosa [ 27 , 28 ]. Plants grown under a high proportion of blue LEDs had greater F v /F m , Y(II), qP, and ETR values compared with the red LEDs, which correlated with a high biomass under those light treatments [ 30 ].…”

“…However, the raw materials collected in the wild are heterogeneous, have a high post-harvest cost, and mainly depend on environmental conditions. According to previous studies, a change in the light quality could lead to increased levels of the total phenolic and flavonoid compounds in H. corymbosa [ 27 , 28 , 29 ].…”

The Role of Pigments and Cryptochrome 1 in the Adaptation of Solanum lycopersicum Photosynthetic Apparatus to High-Intensity Blue Light

“…Thus, the study by Le et al (2021) showed that BL enhanced photosynthesis, likely by increasing stomatal conductance and the rate of photosynthetic electron transport [8]. Additionally, BL improved protection by decreasing the quantum yield of nonphotochemical loss.…”

“…For example, the application of supplemental high-intensity blue light (HIBL) enhanced the contents of phenolic compounds, flavonoids in the leaves of Hedyotis corymbosa (L.) [8], and carotenoids such as violaxanthin and zeaxanthin involved in the process of dissipating absorbed energy into heat in Lactuca sativa [9]. Additionally, BL induces the synthesis of important pigments, Chls and β-carotene [5].…”