Growth and development of Arabidopsis thaliana under single-wavelength red and blue laser light

Effects of pulsed Nd:YAG laser kernel irradiation on maize (Zea mays L.): Insights into germination, gas exchange, photosynthetic pigments, and morphological modifications

Energy has always been the most concerned topic worldwide due to its large consumption. Among various types of energies, light has amazing characteristics and have interesting effects on living organisms. Interest is increasing in the use of laser kernel treatment as an environment friendly physical technique for better results in agronomic crops, but the work is still in progress. The present study was conducted with the aim to examine the application of range of Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) pulsed laser exposures (200, 400, 600, 800, 1000, 1200, 1400 J/cm2) as pre-sowing kernel treatment on seedling survival rate, leaf photosynthetic activity in relation with photosynthetic pigments and visual morphological effects at seedling to maturity stage. Results showed that the low laser exposure (200, 400 and 600 J/cm2) improved the photosynthetic activity in parallel with improvement in chlorophyll a, chlorophyll b, total chlorophyll, carotenoids as well as morphological traits. Kernel treatments with higher laser fluences (800, 1000, 1200 and 1400 J/cm2) showed irregular responses in studied attributes examined at the individual plant level. At 800 and 1000 J/cm2 improvements were found in some plants but at higher doses clear negative impacts were recorded on studied attributes. In conclusion, the lower doses of Nd:YAG pulsed laser fluences are found beneficial for induction of improvement in maize plants for better growth but higher doses were found toxic ones. In future further studies are needed to check the impacts of low laser doses on yield related attributes under field conditions and the high doses might also be used to create variants with beneficial characteristics if possible.

Light spectra manipulation stimulates growth, specialized metabolites and nutritional quality in Anethum graveolens

Light-Emitting Diodes (LED) play a major role in manipulating light spectra that helps in regulating the growth and specialized metabolite synthesis relevant to the plant defence system. In this study, we assessed photosynthetic performance, phytonutrients, and anatomical variations of an aromatic herb Anethum graveolens (also known as dill), grown under various combinations of LED lights viz. red (100R:0B), red:blue (50R:50B); blue (0R:100B) and warm white (WW, served as control). Exposure to 0R:100B LED lights led to the tallest stem height, whereas, the number of leaves were highest under 50R:50B LED lights. The photosynthetic performance was observed to be highest under 50R:50B LED lights. HPLC analysis revealed chlorogenic acid and rosmarinic acid as the major phenolic compounds accumulated under different spectral irradiations. The highest chlorogenic acid content was observed in 50R:50B LED treated dill plants, while 100R:0B light showed the highest accumulation of rosmarinic acid. Dill plants grown under 50R:50B light displayed a relatively higher content of volatile compounds including, myristicin (phenylpropene), psi-limonene, and α-phellandrene (monoterpenoids). Expression analyses of candidate genes of phenylpropanoid and monoterpenoid biosynthetic pathways showed good correlations with the enhanced phenolic compounds and monoterpenes detected under appropriate light treatments. Further, the stem anatomy revealed higher vascularization under the influence of 0R:100B LED lights, whereas, intense histochemical localization of specialized metabolites could be correlated with enhanced accumulation of phenolic compounds and terpenoids observed in this study. Taken together, these studies suggest that proper combinations of blue and red spectra of light could play important role to augment the growth and phytochemical characteristics of dill, thus improving its value addition in the food industry.

Response of photomorphogenesis and photosynthetic properties of sweet pepper seedlings exposed to mixed red and blue light

Various light spectra, especially red (RL) and blue light (BL), have great effects on physiological processes and growth of plants. Previously, we revealed that the plant photomorphogenesis and photosynthesis of sweet pepper was significantly altered under BL or mixed RL and BL. The present study aimed to elucidate how mixed RL and BL influences plant photosynthesis during photomorphogenesis. We examined the growth, plant morphology, photosynthetic response of sweet pepper seedlings under monochromatic RL, BL, different ratios of mixed RL and BL (9R1B, 6R1B, 3R1B, 1R1B, 1R3B) with the same photosynthetic photon flux density of 300 μmol·m^-2·s^-1. White light (WL) were used as a control. The findings showed that the elongation of hypocotyl and first internode as well as leaf expansion were all stimulated by RL, while significantly restrained by BL compared with WL. Conversely, the leaf development, biomass accumulation and photosynthetic properties were inhibited by RL but promoted by BL. Additionally, compared with WL and other treatments, 3R1B could significantly improve the net photosynthetic rate, gas exchange, photosynthetic electron transport capacity, photochemical efficiency, shoot and root biomass accumulation. Furthermore, seedlings grew robustly and exhibited the greatest value of seedling index when exposed to this treatment. Overall, these results suggested that pepper seedlings grown under 3R1B performed better, possibly due to the more balanced light spectrum. It was more conducive to improve the plant photomorphogenesis and photosynthesis of sweet pepper, and a higher biomass accumulation and energy utilization efficiency could be achieved simultaneously under this mixed light spectrum.

Illumination uniformity of an LD and LED hybrid lighting system applied to plant growth

To develop a current plant lighting source with both a suitable illumination area and high illumination uniformity, we propose a lighting system for plant growth based on the combination of laser diode and LED lighting modes. We added a triangular-prism-shaped base plate element to the previous array type optical structure to increase the light coupling degree and expand the illumination area. The Taguchi method was used in our design and experiment, and the influence of different factors on the illumination uniformity was studied and compared to the lighting effect of a traditional array floor structure. Finally, a plant lighting source with an illumination uniformity of 88.54% and color-mixing uniformity of 84.75% was obtained. Compared to the commonly adopted array structure, this plant lighting source expands the illumination area by 31.03%, which verifies the effectiveness of the scheme.

Engineered magnetic nanoparticles enhance chlorophyll content and growth of barley through the induction of photosystem genes

This study investigates the impact of an engineered magnetic nanoparticle (MNP) on a crop plant. For this purpose, a sonochemical synthetic approach was utilized in order to dope magnetic elements (Co and Nd) into technologically important iron oxide NPs. After being characterized by using TEM, SEM, and XRD instruments, the MNPs were hydroponically applied to barley plants with varying doses (from 125 to 1000 mg/L) both in germination (4 days) and early growing stages (3 weeks). Physiological responses, as well as expression of photosystem marker genes, were assessed. Compared to the untreated control, MNP treatment enhanced germination rate (~ 31%), tissue growth (8% in roots, 16% in shoots), biomass (~ 21%), and chlorophyll (a, b) (~ 20%), and carotenoids (~ 22%) pigments. In general, plants showed the highest growth enhancement at 125 or 250 mg/L treatment. However, higher doses diminished the growth indices. Compared to the control, the catalase activity was significantly reduced in the leaves (~ 33%, p < 0.005) but stimulated in the roots (~ 46%, p < 0.005). All tested photosystem marker genes (BCA, psbA, and psaA) were overexpressed in MNP-treated leaves than non-treated control. Moreover, the gene expressions were found to be proportionally increased with increasing MNP doses, indicating a positive correlation between MNPs and the photosynthetic machinery, which could contribute to the enhancement of plant growth.

Effects of red and blue light on leaf anatomy, CO2 assimilation and the photosynthetic electron transport capacity of sweet pepper (Capsicum annuum L.) seedlings

BACKGROUND

The red (R) and blue (B) light wavelengths are known to influence many plant physiological processes during growth and development, particularly photosynthesis. To understand how R and B light influences plant photomorphogenesis and photosynthesis, we investigated changes in leaf anatomy, chlorophyll fluorescence and photosynthetic parameters, and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and Calvin cycle-related enzymes expression and their activities in sweet pepper (Capsicum annuum L.) seedlings exposed to four light qualities: monochromatic white (W, control), R, B and mixed R and B (RB) light with the same photosynthetic photon flux density (PPFD) of 300 μmol/m2·s.

RESULTS

The results revealed that seedlings grown under R light had lower biomass accumulation, CO2 assimilation and photosystem II (PSII) electron transportation compared to plants grown under other treatments. These changes are probably due to inactivation of the photosystem (PS). Biomass accumulation and CO2 assimilation were significantly enriched in B- and RB-grown plants, especially the latter treatment. Their leaves were also thicker, and photosynthetic electron transport capacity, as well as the photosynthetic rate were enhanced. The up-regulation of the expression and activities of Rubisco, fructose-1, 6-bisphosphatase (FBPase) and glyceraldehyde-phosphate dehydrogenase (GAPDH), which involved in the Calvin cycle and are probably the main enzymatic factors contributing to RuBP (ribulose-1, 5-bisphosphate) synthesis, were also increased.

CONCLUSIONS

Mixed R and B light altered plant photomorphogenesis and photosynthesis, mainly through its effects on leaf anatomy, photosynthetic electron transportation and the expression and activities of key Calvin cycle enzymes.

Involvement of Photoprotective Compounds of a Phenolic Nature in the Response of Arabidopsis Thaliana Leaf Tissues to Low-Intensity Laser Radiation

The influence of low-intensity laser radiation (LILR) on the changes in the content of anthocyanins, kaempferol, quercetin and their glycosides in the leaves of 5-week-old plants of Arabidopsis thaliana L. was studied by means of methods of high-performance liquid chromatography and gas chromatography mass spectrometry (GC-MS). It was found that in the leaves subjected to a stimulating He-Ne laser radiation dose (3.6 J cm^-2 , continuous wave radiation, wavelength-632.8 nm, exposure time-5 min), the radiation induced an increase in the content of such compounds, the most significant one being in the case of anthocyanins (9 times). The present study also revealed an increase in the antioxidant potential of kaempferol, quercetin and their glycosides as a result of laser exposure. This increase was due to the preferential synthesis of compounds with a larger number of OH-groups on the phenyl ring. Thus, the content of quercetin, which has five OH-groups in its structure, increased almost by three times as compared to the control.

Uptake and translocation of magnetite (Fe3O4) nanoparticles and its impact on photosynthetic genes in barley (Hordeum vulgare L.)

This study investigates the fate and impact of iron oxide or magnetite (Fe₃O₄, ∼13 nm in size) nanoparticles (NPs) in barley (Hordeum vulgare L.), a common crop cultivated around the world. Barley seedlings were grown in hydroponic culture for three weeks to include NPs (125, 250, 500, and 1000 mg/L). Transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) techniques were used to assess their uptake and translocation. Photosynthesis marker genes were quantified by RT-qPCR. Results revealed that increasing doses of Fe₃O₄ NPs were gradually enhanced the plant growth up to 500 mg/L, which promoted the fresh weight (FW) respectively ∼19% and ∼88% for leaf and root tissues than the ones for control. No phytotoxic effect was recorded even at high NPs doses. NPs inclusion increased some phenological parameters such as chlorophyll, total soluble protein, number of chloroplasts, and dry weight. High NPs doses dramatically reduced the catalase activity and hydrogen peroxide content, suggesting a possible function of NPs as nanozyme in vivo. TEM observations showed that Fe₃O₄ NPs penetrated and internalized in the root cells. In leaves, they were mostly existed at the surrounding cell wall, suggesting their translocation from root to shoot without cellular penetration. Further analysis by using VSM confirmed the existence of Fe₃O₄ NPs in leaves which result in dramatic alterations of the photosystem genes (PetA, psaA, BCA and psbA). In conclusion, barley plants uptake and translocate Fe₃O₄ NPs, which promoted the plant growth probably due to the promoted gene expression and efficient photosynthetic activity.

Towards a tailored indoor horticulture: a functional genomics guided phenotypic approach

As indoor horticulture gathers momentum, electric (also termed artificial) lighting systems with the ability to generate specific and tunable wavelengths have been developed and applied. While the effects of light quality on plant growth and development have been studied, authoritative and reliable sets of light formulae tailored for the cultivation of economically important plants and plant traits are lacking as light qualities employed across laboratories are inconsistent. This is due, at least in part, to the lack of molecular data for plants examined under electric lights in indoor environments. It has hampered progress in the field of indoor horticulture, in particular, the transition from small-scale indoor farming to commercial plant factories. Here, we review the effects of light quality on model and crop plants studied from a physiological, physical and biochemical perspective, and explain how functional genomics can be employed in tandem to generate a wealth of molecular data specific for plants cultivated under indoor lighting. We also review the current state of lighting technologies in indoor horticulture specifically discussing how recent narrow-bandwidth lighting technologies can be tailored to cultivate economically valuable plant species and traits. Knowledge gained from a complementary phenotypic and functional genomics approach can be harvested not only for economical gains but also for sustainable food production. We believe that this review serves as a platform that guides future light-related plant research.

Micropropagation in the Twenty-First Century

Despite more than a century of research on effective biotechnological methods, micropropagation continues to be an important tool for the large-scale production of clonal plantlets of several important plant species that retain genetic fidelity and are pest-free. In some cases, micropropagation is the only technique that supports the maintenance and promotes the economic value of specific agricultural species. The micropropagation of plants solved many phytosanitary problems and allowed both the expansion and access to high-quality plants for growers from different countries and economic backgrounds, thereby effectively contributing to an agricultural expansion in this and the last century. The challenges for micropropagation in the twenty-first century include cost reduction, enhanced efficiency, developing new technologies, and combining micropropagation with other systems/propagation techniques such as microcuttings, hydroponics, and aeroponics. In this chapter, we discuss the actual uses of micropropagation in this century, its importance and limitations, and some possible techniques that can effectively increase its wider application by replacing certain conventional techniques and technologies.

Plant Growth and Photosynthetic Characteristics of Mesembryanthemum crystallinum Grown Aeroponically under Different Blue- and Red-LEDs

Mesembryanthemum crystallinum is a succulent, facultative crassulacean acid metabolism (CAM) plant. Plant growth and photosynthetic characteristics were studied when M. crystallinum plants were grown indoor under light emitting diodes (LED)-lighting with adequate water supply. Plants were cultured aeroponically for a 16-h photoperiod at an equal photosynthetic photon flux density of 350 μmol m-2 s-1 under different red:blue LED ratios: (1) 100:0 (0B); (2) 90:10 (10B); (3) 80:20 (20B); (4) 70:30 (30B); (5) 50:50 (50B); and (6)100:0 (100B). M. crystallinum grown under 10B condition had the highest shoot and root biomass and shoot/root ratio while those grown under 0B condition exhibited the lowest values. Compared to plants grown under 0B condition, all other plants had similar but higher total chlorophyll (Chl) and carotenoids (Car) contents and higher Chl a/b ratios. However, there were no significant differences in Chl/Car ratio among all plants grown under different red- and blue-LEDs. Photosynthetic light use efficiency measured by photochemical quenching, non-photochemical quenching, and electron transport rate, demonstrated that plants grown under high blue-LED utilized more light energy and had more effective heat dissipation mechanism compared to plants grown under 0B or lower blue-LED. Statistically, there were no differences in photosynthetic O2 evolution rate, light-saturated CO2 assimilation rate (Asat), and light-saturated stomatal conductance (gssat) among plants grown under different combined red- and blue-LEDs but they were significantly higher than those of 0B plants. No statistically differences in total reduced nitrogen content were found among all plants. For the total soluble protein, all plants grown under different combined red- and blue-LEDs had similar values but they were significantly higher than that of plants grown under 0B condition. However, plants grown under higher blue-LEDs had significant higher ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) protein than those plants grown under lower blue-LED. High Asat and gssat but very low CAM acidity of all M. crystallinum plants during light period, imply that this facultative CAM plant performed C3 photosynthesis when supplied with adequate water. Results of this study suggest that compared to red- or blue-LED alone, appropriate combination of red- and blue-LED lighting enhanced plant growth and photosynthetic capacities of M. crystallinum.