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Chlorophylls (Chls) are the most abundant plant pigments on Earth. Chls are located in the membrane of thylakoids where they constitute the two photosystems (PSII and PSI) of terrestrial plants, responsible for both light absorption and transduction of chemical energy via photosynthesis. The high efficiency of photosystems in terms of light absorpt...
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... harvesting complexes have evolved many adaptive mechanisms that permit photosynthetic organisms to thrive in different environments. The spectral distribution of sunlight that reaches our planet largely covers the absorption spectra of photosynthetic pigments utilized in light harvesting antennas (Figure 2). In a general way, light harvesting antennas have developed the ability to optimize light capture under both low-and high-intensity light conditions [1]. ...
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... However, variety Ken Yu 90 exhibited an increase in carotenoid content at 60 mM compared to the control. This increase may be due to the carotenoids' capacity to scavenge oxygen free radicals generated in photosynthetic pigments under stress, thus enhancing carotenoid levels at 60 mM to shield them from oxidative damage (Guidi, Tattini, and Landi 2017). The antioxidant enzyme system, including SOD, CAT and POD, is crucial for scavenging ROS and plays a vital role in maintaining metabolic homeostasis in plants (Neto et al. 2006). ...
1) Soil alkalinization and salinization represent a growing global challenge. Maize (Zea mays L.), with its relatively low tolerance to salt and alkali, is increasingly vulnerable to saline‐alkali stress. Identifying maize genotypes that can withstand salinity and alkalinity is crucial to broaden the base of salt‐alkali‐tolerant maize germplasm. (2) In this study, we screened 65 maize germplasm resources for alkali stress using a 60 mM NaHCO3 solution. We measured fifteen morphological and physiological indices, including seedling height, stem thickness, and leaf area. Various analytical methods—correlation analysis, principal component analysis, subordinate function analysis, cluster analysis, stepwise discriminant analysis, and ridge regression analysis—were used to assess the seedling alkali tolerance of these maize germplasm resources. The physiological indices of six tested maize varieties were analyzed in greater detail. (3) The findings revealed complex correlations among traits, particularly strong negative associations between conductivity and root traits such as length, volume, surface area, diameter, and number of branches. The 15 evaluation indices were reduced to 7 principal components, explaining 77.89% of the variance. By applying affiliation functions and weights, we derived a comprehensive evaluation of maize seedling alkali tolerance. Notably, three germplasms—Liang Yu 99, Bi Xiang 638, and Gan Xin 2818—demonstrated significant comprehensive seedling alkali tolerance. Cluster analysis grouped the 65 maize germplasm resources into four distinct categories (I, II, III, and IV). The results of the cluster analysis were confirmed by multiclass stepwise discriminant analysis, which achieved a correct classification rate of 92.3% for 60 maize genotypes regarding alkalinity tolerance. Using principal component and ridge regression analyses, we formulated a regression equation for alkali tolerance: D‐value = −1.369 + 0.002 * relative root volume + 0.003 * relative number of root forks + 0.006 * relative chlorophyll SPAD + 0.005 * relative stem thickness + 0.005 * relative plant height + 0.001 * relative conductivity + 0.002 * relative dry weight of underground parts. Under sodium bicarbonate stress, morphological indices and germination rates were significantly reduced, germination was inhibited, photosynthetic pigment levels in maize leaves decreased to varying degrees, and the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) significantly increased. Alkali stress markedly enhanced the antioxidant enzyme activities in maize varieties, with alkali‐resistant varieties exhibiting a greater increase in antioxidant enzyme activities than alkali‐sensitive varieties under such stress. (4) By screening for alkali tolerance in maize seedlings, the identified alkali‐tolerant genotypes can be further utilized as suitable donor parents, thereby enhancing the use of alkali‐tolerant germplasm resources and providing theoretical guidance for maize cultivation in saline‐alkaline environments.
... While our approach may not perfectly mirror real-world conditions, it allows us to isolate and study the effects of the two radiation regimes on plant physiology in a controlled setting. Previous studies have indicated that both shortwave and longwave radiation are necessary for the ideal growth of garden cress, which absorbs primarily in both the red (around 665-680 nm) and blue (around 430-450 nm) regions of the electromagnetic spectrum (Okamoto et al., 1996;Ménard et al., 2006;Guidi et al., 2017;Ajdanian et al., 2019). Our results, which demonstrate slightly higher dry masses for garden cress under Solar light, align with the biochemical parameters of the plant. ...
Stars with about 45 to 80% the mass of the Sun, so-called K dwarf stars, have previously been proposed as optimal host stars in the search for habitable extrasolar worlds. These stars are abundant, have stable luminosities over billions of years longer than Sun-like stars, and offer favourable space environmental conditions. So far, the theoretical and experimental focus on exoplanet habitability has been on even less massive, though potentially less hospitable red dwarf stars. Here we present the first experimental data on the responses of photosynthetic organisms to a simulated K dwarf spectrum. We find that garden cress Lepidium sativum under K-dwarf radiation exhibits comparable growth and photosynthetic efficiency as under Solar illumination on Earth. The cyanobacterium Chroococcidiopsis sp. CCMEE 029 exhibits significantly higher photosynthetic efficiency and culture growth under K dwarf radiation compared to Solar conditions. Our findings of the affirmative responses of these two photosynthetic organisms to K dwarf radiation suggest that exoplanets in the habitable zones around such stars deserve high priority in the search for extrasolar life.
... Increasing the amount of energy flow by engineering the LHC is done to improve the efficiency of light reactions. The state of the antenna pigments is essential in a reaction to light since the pigments absorb and transfer protons to PSII and PSI [24]. During microalgal culture, photo-inhibition is amplified as cell density increases. ...
Most of the industrially produced energy materials and chemicals are derived from fossil fuel-based resources, which attribute adverse environmental impacts. Biomass resources have been identified as an alternative to shrink the reliance on fossil fuels. Also, sensible food/feed supplies, ecological alarms, climate discrepancy, and geopolitical concerns endorse to explore of 3G feedstocks in renewable energies and platform chemicals. This chapter provides an insight for the potential and sustainable transformation of abundant renewable resources to produce wide-ranging biofuels, platform chemicals, and high-value materials in 3G biorefinery. Algal feedstocks are the key component of the 3G biorefinery that strengthens the bio-renewables industry. It has perceived considerable success in research laboratories, leading to advanced technical progresses in microalgal biomass transformation. Thus, this chapter signifies a conceivable picture of microalgal-based 3G biorefinery and future research directions to explore biomass resources in biofuels and platform chemicals in sustainability aspects via multidisciplinary technology routes.
... Overall, Mohammed et al. (2023) highlighted the role of Bi in affecting the oxidative status and antioxidant processes in plants, suggesting a species-specific response to counteract the oxidative burst induced by Bi exposure. In garden cress plants exposed to different Bi nitrate concentrations, Pietrini et al. (2023) observed that damage at the growth level was accompanied by a reduction in the carotenoid content, which, in addition to their role as photosynthetic pigments, are also involved in the antioxidant response in plants, namely by scavenging the oxygen free radicals in chloroplasts and protecting chlorophylls from photooxidative damage (Guidi et al., 2017). In contrast, Bi-treated plants showed a slight increase in the level of flavonoids, whose involvement in the defence against oxidative stress has been well reported (Ferdinando et al., 2012). ...
... This was discussed in the context of the different responses observed in regulated (ΦNPQ) and non-regulated (ΦNO) energy dissipation at the PSII level. In bean and wheat plants grown in soil supplied with 500 mg kg − 1 Bi nitrate, Mohammed et al. (2023) attributed a protective response against oxidative attack to photosystems to an increase in the content of carotenoids, a well-known antioxidant molecule that protects photosynthetic machinery from excess light, which generates ROS (Guidi et al., 2017). Furthermore, an increase in flavonoid levels was observed by Pietrini et al. (2023) in plantlets of L. sativum exposed to Bi nitrate in soil. ...
... Chl-c is characterized by a strong blue absorption band and a weaker band in the red region (more pronounced in Chl-a, which also absorbs in the violet-blue spectral range). 62,63 . Carotenoids exhibit intense absorption between 400 and 500 nm, with exception of fucoxanthin whose broad absorption between 460 and 570 nm covers the gap left by Chl-a and Chl-c in the www.nature.com/scientificreports/ ...
Ordered, quasi-ordered, and even disordered nanostructures can be identified as constituent components of several protists, plants and animals, making possible an efficient manipulation of light for intra- and inter- species communication, camouflage, or for the enhancement of primary production. Diatoms are ubiquitous unicellular microalgae inhabiting all the aquatic environments on Earth. They developed, through tens of millions of years of evolution, ultrastructured silica cell walls, the frustules, able to handle optical radiation through multiple diffractive, refractive, and wave-guiding processes, possibly at the basis of their high photosynthetic efficiency. In this study, we employed a range of imaging, spectroscopic and numerical techniques (including transmission imaging, digital holography, photoluminescence spectroscopy, and numerical simulations based on wide-angle beam propagation method) to identify and describe different mechanisms by which Pleurosigma strigosum frustules can modulate optical radiation of different spectral content. Finally, we correlated the optical response of the frustule to the interaction with light in living, individual cells within their aquatic environment following various irradiation treatments. The obtained results demonstrate the favorable transmission of photosynthetic active radiation inside the cell compared to potentially detrimental ultraviolet radiation.
... A certain level of light is required by plants for growth; light levels that are too high or too low may prevent photosynthesis (Shafiq et al. 2021). Furthermore, chlorophyll fluorescence provides useful information about leaf photosynthetic performance of plants under drought stress (Banks 2018) and indicates the extent to which PSII is using the energy absorbed by chlorophyll and how far it is being damaged by excessive light (Guidi et al. 2017). The use of stable carbon and nitrogen isotope ratios (δ 13 C and δ 15 N, respectively) to study the acquisition and use of resources by plants has become a basic tool for terrestrial ecologists (Dawson et al. 2002). ...
... Anthocyanin-rich leaves exhibit shade properties and are less prone to dynamic photoinhibition in many crops [3]. The major protective role of anthocyanin depends on photosystem protection from light damage by absorbing more photons that would otherwise excite chlorophyll pigments [19], thus protecting chloroplasts from photoinhibition by diminishing energy flux through chlorophylls [20,21]. ...
Anthocyanins are a class of natural pigments that accumulate transiently or permanently in plant tissues, often in response to abiotic and biotic stresses. They play a photoprotective role by attenuating the irradiance incident on the photochemical apparatus and quenching oxyradicals through their powerful anti-oxidative function. The objective of the current study is to understand the impact of introducing Vitis vinifera mybA1 (VvmybA1) in ‘Hamlin’ sweet orange trees on various aspects, including photosynthetic performance, pigment composition, and gene expression related to photosynthesis and light harvesting. We describe the relationship between anthocyanin accumulation and photosynthetic measurements in genetically modified ‘Hamlin’ sweet orange trees expressing the grapevine-derived Vitis vinifera mybA1 (VvmybA1). The juvenile leaves of transgenic plants displayed an intense purple color compared to the mature leaves, and microscopic visualization showed anthocyanin accumulation primarily in the leaf epidermal cells. Under optimal growth conditions, there were no significant differences in leaf gas exchange variables, suggesting normal photosynthetic performance. The chlorophyll fluorescence maximum quantum yield of PSII was slightly reduced in VvmybA1 transgenic leaves compared to the performance of the control leaves, while the total performance index per absorbance remained unaffected. Comparison of the chlorophyll and carotenoid pigment contents revealed that chlorophyllide a and carotenoid pigments, including trans-neoxanthin, trans-violaxanthin, cis-violaxanthin, zeaxanthin, antheraxanthin, and total xanthophylls were enhanced in VvmybA1 transgenic leaves. Although there were no significant changes in the rates of the gas exchange parameters, we recorded a high relative expression of the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (RuBP) and rubisco activase (RCA) in the mature leaves of transgenic plants, indicating activation of Rubisco. Our findings confirm an efficient photoacclimation of the photosynthetic apparatus, allowing the transgenic line to maintain a photosynthetic performance similar to that of the wild type.
... Additionally, reactive oxygen species (ROS) production sets up oxidative damage in thylakoids. Chlorophyll and carotenoids in plants are affected, and the core complexes of photosystems I (PSI) and II (PSII) degrade as a result and inhibit crucial photochemical activities (Shahid et al. 2014;Guidi et al. 2017). Heat stress occurs at multiple time scales and with varying levels of severity and duration (Ishimaru et al. 2016). ...
Climate change is the major cause of environmental stresses, which badly affect agricultural crops. Abiotic stresses such as heat, drought, and soil salinization, among this soil salinity, are the main problem that is very dangerous to global food security and environmental sustainability. Soil salinity causes osmotic stress, led to an imbalance of nutrient uptake, and disturbs plant growth. It is necessary to overcome this problem through different approaches like the use of compost, UV radiations, nanotechnology, integrated agro-farming systems, salty farming combined with subsurface drainage, tolerant bacteria combined with cultivars of tolerant plants, and other emerging reclamation strategies. This chapter focuses on the strategies in order to restore agricultural sustainability and ensure global food security in the face of climate change leading to an increase in soil salinity.
... The Optical Density at λ = 680 nm (OD680) of the culture samples was measured using a Biochrom Ultrospec ® III UV/Visible spectrophotometer. The chosen wavelength (680 nm) corresponds to a typical absorbance peak of Chlorophyll a [26], which provides a reading proportional to the concentration of suspended cells. ...
Microalgae, renowned for their high photosynthetic efficiency and minimal competition with land-based crops, hold great promise in the biofixation of CO2 from waste sources, making them valuable for diverse applications, including biofuels, food production, and biomaterials. An innovative technology, the integrated carbonate-based carbon capture and algae biofixation system is emerging as an alternative to traditional carbon capture and sequestration (CCS) methods. This closed-loop system utilizes bicarbonates as inorganic carbon sources, which can directly enter microalgae photosynthesis, subsequently regenerating carbonates for another cycle of carbon capture. This system offers significant advantages, including cost savings in carbon supply, simplified photobioreactor development, and reduced labor and energy requirements. Nevertheless, further research is essential to evaluate the suitability of various microorganisms and search for optimal growth conditions. In this study, we assessed the performance of two strains of Spirulina within the integrated system. Employing a Design of Experiments approach, we simultaneously varied temperature, bicarbonate concentration, and light irradiation while operating within a lab-scale photobioreactor. We achieved remarkable results, with a biomass productivity of 875 mg/L·d and an impressive CO2 utilization efficiency of 58%. These findings indicate a genuine opportunity for further exploration and scaling of this approach in industrial settings.
... As extensively reported (Sun et al., 2022), carotenoids are not only photosynthetic pigments but also important antioxidants. In Bi-treated plants, the reduction in carotenoid content can be ascribed to a damaging effect exerted by the presence of the metal, likely hampering the plants to eliminate oxygen free radicals in chloroplasts and, thereby, protect chlorophylls from photooxidative damage (Guidi et al., 2017). ...
Environmental pollution caused by heavy metals has long been considered a relevant threat to ecosystem survival and human health. The use of safer substitutes for the most toxic heavy metals in many industrial applications is discussed as a potential way to face this issue. In this regard, Bi has been proposed for replacing Pb in several production processes. However, few literature records reported on the effects of Bi on living organisms, particularly on plants. In this study, garden cress (Lepidium sativum L.) plants were exposed to different concentrations of Bi nitrate added to soil in growth chambers for 21 days. Results evidenced the toxic effect of Bi on shoot growth, regardless of the Bi nitrate concentration in the soil, paralleled by a similar reduction in the chlorophyll and carotenoid content, a decrease in the nitrogen balance index values, and an impairment of the photosynthetic machinery evaluated by chlorophyll fluorescence image analysis. The presence of Bi in the soil was shown to affect element accumulation in roots and translocation to shoots, with micronutrient content particularly reduced in the leaves of Bi-treated plants. A dose-dependent plant accumulation of Bi to metal concentration in the soil was observed, even if very low metal bioconcentration ability was highlighted. The reduced Bi translocation from roots to shoots in plants exposed to increasing Bi concentrations in the soil is discussed as a possible defense mechanism likely associated with the observed increase of anthocyan and flavonol contents and the activation of photoprotection mechanisms preventing higher damages to the photosynthetic apparatus.
