Blue Light Acclimation Reduces the Photoinhibition of Phalaenopsis aphrodite (Moth Orchid)

Abstract

The moth orchid is an important ornamental crop. It is very sensitive to high light irradiation due to photoinhibition. In this study, young orchid tissue culture seedlings and 2.5” potted plants pretreated under blue light (BL, λmax = 450 nm) at 100 µmol m−2 s−1 for 12 days (BL acclimation) were found to have an increased tolerance to high light irradiation. After BL acclimation, orchids had an increased anthocyanin accumulation, enhanced chloroplast avoidance, and increased chlorophyll fluorescence capacity whenever they were exposed to high light of 1000 μmol m−2 s−1 for two weeks (HL). They had higher Fv/Fm, electron transport rate (ETR), chlorophyll content, catalase activity and sucrose content when compared to the control without BL acclimation. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) showed that transcript levels of phototropins, D1, RbcS, PEPCK, Catalase and SUT2 were upregulated in the BL-acclimated orchids. Consequently, BL acclimation orchids had better growth when compared to the control under long-term high light stress. In summary, this study provides a solution, i.e., BL acclimation, to reduce moth orchid photoinhibition and enhance growth before transplantation of the young tissue culture seedlings and potted plants into greenhouses, where they usually suffer from a high light fluctuation problem.

Blue Light Mediates Chloroplast Avoidance and Enhances Photoprotection of Vanilla Orchid

“…The reduction of photoinhibition of moth orchid induced by blue light acclimation was recently reported [22]. Similar to moth orchid, vanilla orchid is a shade-loving CAM plant that is sensitive to high light ( Figure 2).…”

“…These findings suggest that vanilla orchid is adapted to the moderately high temperature zone of tropical and subtropical areas through enhanced photosynthesis and thus has better growth. This study shows that similar to moth orchid [22], vanilla orchid is also sensitive to high irradiation. Hence, reduced light intensity is necessary for sustaining a vanilla orchid.…”

“…To date, basic studies on vanilla orchid are scarce. In our previous study, we showed that blue light mediated the photoacclimation of moth orchid [22]. We, therefore, hypothesized that blue light may also induce the photoacclimation of vanilla orchid.…”

“…It has been reported that BL pretreatment induced photoacclimation and thus assisted plants tolerance to excess light photodamage [26][27][28]. Our previous study indicated that BL100 upregulated phototropins, significantly induced chloroplast avoidance movement [12], and induced photoacclimation in Phalaenopsis aphrodite (moth orchid) [22]. Moreover, BL-acclimation improves plant growth due to high BL triggering specific biochemical and physiological processes, causing better acclimation and recovery of plants to light stress [22,29].…”

“…Our previous study indicated that BL100 upregulated phototropins, significantly induced chloroplast avoidance movement [12], and induced photoacclimation in Phalaenopsis aphrodite (moth orchid) [22]. Moreover, BL-acclimation improves plant growth due to high BL triggering specific biochemical and physiological processes, causing better acclimation and recovery of plants to light stress [22,29]. This study showed that BL100 irradiation of vanilla orchid for 8 or 12 days is sufficient to acquire photoacclimation, as shown in the significant increment of ETR, NPQ, and qP capacities after prolonged blue light treatment (Table 1).…”