Plants in extreme environments face pronounced seasonal variations in abiotic conditions, influencing their growth and carbon gain. However, our understanding of how plants in cold-arid mountains sustain carbon assimilation during short growing seasons remains limited. Here, we investigate seasonal dynamics and interspecific variability in photochemical performance of 310 individuals, comprising 10 different dicotyledon plant species across 3100-5300 m in the NW Himalayas, spanning semi-deserts to subnival zones. From early June to late September, we measured Fv/Fm and ΦPSII, assessing ΦPSII relationships with leaf traits (N, P, C, C:N ratio, LMA, and LDMC) and environmental factors (temperature, soil moisture content, etc.). Our findings revealed that high-Himalayan plants maintained relatively stable photosynthetic performance (Fv/Fm = 0.7-0.85), indicating optimal function even under potential stress. Contrary to our hypothesis that ΦPSII peaks mid-season in alpine and subnival zones and early season in steppes and semi-deserts, it declined by 33% across species and habitats throughout the season. This decline was closely associated with nutrient depletion, leaf senescence, and energy-water limitations. Species exhibited distinct strategies, with some prioritising structural resilience over photosynthesis, while others optimised photochemical performance despite environmental constraints. Alpine and subnival plant performance was constrained more by soil moisture deficits and high temperatures than cold temperatures, while deep-rooted steppe and semi-desert plants were primarily constrained by high temperatures and evaporative forcing rather than soil moisture deficit. These results provide new insights into how Himalayan plants adapt to extreme environmental conditions, highlighting the crucial interplay between moisture and temperature in shaping their performance within cold-arid mountains.

• Klíčová slova
• Fv/Fm, Himalayas, alpine and subnival ecosystems, chlorophyll fluorescence, cold‐arid mountains, leaf traits, photochemical performance of PSII, seasonal dynamics,
• MeSH
• ekosystém MeSH
• fotosyntéza * fyziologie   MeSH
• listy rostlin fyziologie   MeSH
• nízká teplota MeSH
• půda chemie   MeSH
• roční období MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Himálaj MeSH
• Názvy látek
• půda MeSH

The microalga Scenedesmus sp. (Chlorophyceae) was cultured in a raceway pond (RWP) placed in a greenhouse. The objective of this case study was to monitor the photosynthesis performance and selected physicochemical variables (irradiance, temperature, dissolved oxygen concentration) of microalgae cultures in situ at various depths of RWP. The data of actual photochemical yield Y(II), the electron transport rate monitored by in vivo chlorophyll fluorescence and photosynthetic oxygen production both in situ and ex situ revealed that (i) even in diluted cultures (0.6 g DW L-1), the active photic layer in the culture was only about 1 cm, indicating that most of the culture was "photosynthetically" inactive; (ii) the mechanism of non-photochemical quenching may not be fast enough to respond once the cells move from the surface to the deeper layers; and (iii) even when cells were exposed to a high dissolved oxygen concentration of about 200% sat and higher, the cultures retained a relatively high Y(II) > 0.35 when monitored in situ. The presented work can be used as exemplary data to optimize the growth regime of microalgae cultures in large-scale RWPs by understanding the interplay between photosynthetic activity, culture depth and cell concentration.

• Klíčová slova
• RWP, Scenedesmus, chlorophyll (Chl) fluorescence, electron transport, green microalgae, non-photochemical dissipation, oxygen production, photic layer, photosynthesis,
• Publikační typ
• časopisecké články MeSH

The present paper aims to open discussion on the information content, physical mechanism(s), and measuring protocols to determine the partitioning of the absorbed light energy in oxygenic photosynthetic organisms. Revisiting these questions is incited by recent findings discovering that PSII, in addition to its open and closed state, assumes a light-adapted charge-separated state and that chlorophyll a fluorescence induction (ChlF), besides the photochemical activity of PSII, reflects the structural dynamics of its reaction center complex. Thus, the photochemical quantum yield of PSII cannot be determined from the conventional ChlF-based protocol. Consequently, the codependent quantity - the quantum yield of the so-called nonregulatory constitutive nonphotochemical quenching (npq) - loses its physical meaning. Processes beyond photochemistry and regulatory npq should be identified and characterized by multifaceted studies, including ChlF. Such investigations may shed light on the putative roles of dissipation and other energy-consuming events in the stress physiology of photosynthetic machinery.

• Klíčová slova
• Fv/Fm, chlorophyll a fluorescence, constitutive nonregulatory dissipation, nonphotochemical quenching, quantum yield, structural dynamics,
• Publikační typ
• časopisecké články MeSH

In recent years, cold plasma treatment has emerged as a promising method to positively impact early seed growth. This study aimed to investigate the effects of cold plasma treatment on millet seeds with ambient air plasma discharge at pressures of 100 Pa and power ranging from 40 to 250 W. Results indicated that cold plasma treatment significantly increased radicle length by up to 112.5% (250 W) after 48 h and up to 57% (120 W) after 72 h compared to nontreated plants. The study also found that cold plasma treatment influenced electron transport during the primary phase of photosynthesis, with the effect varying with the power of discharge. However, high levels of discharge resulted in a significantly higher chlorophyll synthesis. These results suggest that cold plasma treatment may be used to reduce plant stress and improve growing properties.

• Klíčová slova
• cold plasma treatment, electron transport, millet, photosynthesis efficiency,
• Publikační typ
• časopisecké články MeSH

Photosynthesis is among the first processes negatively affected by environmental cues and its performance directly determines plant cell fitness and ultimately crop yield. Primarily sites of photosynthesis, chloroplasts are unique sites also for the biosynthesis of precursors of the growth regulator auxin and for sensing environmental stress, but their role in intracellular auxin homeostasis, vital for plant growth and survival in changing environments, remains poorly understood. Here, we identified two ATP-binding cassette (ABC) subfamily B transporters, ABCB28 and ABCB29, which export auxin across the chloroplast envelope to the cytosol in a concerted action in vivo. Moreover, we provide evidence for an auxin biosynthesis pathway in Arabidopsis thaliana chloroplasts. The overexpression of ABCB28 and ABCB29 influenced stomatal regulation and resulted in significantly improved water use efficiency and survival rates during salt and drought stresses. Our results suggest that chloroplast auxin production and transport contribute to stomata regulation for conserving water upon salt stress. ABCB28 and ABCB29 integrate photosynthesis and auxin signals and as such hold great potential to improve the adaptation potential of crops to environmental cues.

• Klíčová slova
• ABC transporter, auxin, drought, hormone transport, photosynthesis, salinity, stress,
• Publikační typ
• časopisecké články MeSH

Haematococcus lacustris is an important species of green algae because it produces the high-value carotenoid astaxanthin. Astaxanthin production is enhanced by various stress conditions causing the transformation of green vegetative cells to red cells with high amounts of astaxanthin, which plays various photoprotective and antioxidant roles. Although intensive research has been conducted to reveal the regulation of astaxanthin production, the photosynthetic capacity of the various cell forms is unresolved at the single-cell level. In this work, we characterized the photosynthetic and morphological changes of Haematococcus cells, using a combination of microfluidic tools and microscopic chlorophyll fluorescence imaging. We found marked but reversible changes in the variable chlorophyll fluorescence signatures upon the transformation of green cells to red cells, and we propose that the photosynthetic activity as revealed by single-cell chlorophyll fluorescence kinetics serves as a useful phenotypic marker of the different cell forms of Haematococcus.

• Klíčová slova
• Haematococcus lacustris, chlorophyll fluorescence, photoprotection, photosynthesis, photosystem II,
• Publikační typ
• časopisecké články MeSH

Microalgae are excellent sources of biomass containing several important compounds for human and animal nutrition-proteins, lipids, polysaccharides, pigments and antioxidants as well as bioactive secondary metabolites. In addition, they have a great biotechnological potential for nutraceuticals, and pharmaceuticals as well as for CO2 sequestration, wastewater treatment, and potentially also biofuel and biopolymer production. In this review, the industrial production of the most frequently used microalgae genera-Arthrospira, Chlorella, Dunaliella, Haematococcus, Nannochloropsis, Phaeodactylum, Porphyridium and several other species is discussed as concerns the applicability of the most widely used large-scale systems, solar bioreactors (SBRs)-open ponds, raceways, cascades, sleeves, columns, flat panels, tubular systems and others. Microalgae culturing is a complex process in which bioreactor operating parameters and physiological variables closely interact. The requirements of the biological system-microalgae culture are crucial to select the suitable type of SBR. When designing a cultivation process, the phototrophic production of microalgae biomass, it is necessary to employ SBRs that are adequately designed, built and operated to satisfy the physiological requirements of the selected microalgae species, considering also local climate. Moreover, scaling up microalgae cultures for commercial production requires qualified staff working out a suitable cultivation regime. KEY POINTS: • Large-scale solar bioreactors designed for microalgae culturing. • Most frequently used microalgae genera for commercial production. • Scale-up requires suitable cultivation conditions and well-elaborated protocols.

• Klíčová slova
• Biomass, Biotechnology, Large-scale production, Microalgae, Solar bioreactor,
• MeSH
• biomasa MeSH
• biopaliva MeSH
• bioreaktory MeSH
• biotechnologie metody   MeSH
• Chlorella * MeSH
• Chlorophyceae * MeSH
• lidé MeSH
• mikrořasy * metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• biopaliva MeSH

Photosystem II (PSII) represents the most vulnerable component of the photosynthetic machinery and its response in plants subjected to abiotic stress has been widely studied over many years. PSII is a thylakoid membrane-located multiprotein pigment complex that catalyses the light-induced electron transfer from water to plastoquinone with the concomitant production of oxygen. PSII is rich in intrinsic (PsbA and PsbD, namely D1 and D2, CP47 or PsbB and CP43 or PsbC) but also extrinsic proteins. The first ones are more largely conserved from cyanobacteria to higher plants while the extrinsic proteins are different among species. It has been found that extrinsic proteins involved in oxygen evolution change dramatically the PSII efficiency and PSII repair systems. However, little information is available on the effects of abiotic stress on their function and structure.

• Klíčová slova
• abiotic stress, extrinsic protein, intrinsic protein, photosynthesis, photosystem II,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

This study investigates how cocoa rootstocks respond to flooding and post-flooding conditions, offering insights for cocoa plantation sustainability in flood-prone areas due to climate change. We studied Theobroma cacao L. rootstocks for 60 d of flooding and 30 d post-flooding, grafting PS-1319 scions onto five rootstocks (TSH-1188, Cepec-2002, Pará, Esfip-02, SJ-02). Photochemical performance remained stable across rootstocks, while flooding progressively reduced electron transport efficiency. Photochemical damage emerged after 7 d, worsening occurred at 19 d. Although post-flooding efficiency improved, recovery time was insufficient for full restoration. Stem diameter increased less in Esfip-02. TSH-1188 had the highest stem dry mass during flooding and the most root and total dry mass during post-flooding. SJ-02 had the lowest stem dry mass and post-flooding total dry mass. Principal component analysis revealed stem and root development as a key for recovery. SJ-02 and Esfip-02 showed lower flooding tolerance and recovery, while TSH-1188 and Pará exhibited higher resilience.

• Klíčová slova
• cocoa, photosynthesis, plasticity, water stress,
• Publikační typ
• časopisecké články MeSH

Photosynthesis, growth and biochemical composition of the biomass of the freshwater microalga Chlamydopodium fusiforme cultures outdoors in a thin-layer cascade were investigated. Gross oxygen production measured off-line in samples taken from the outdoor cultures was correlated with the electron transport rate estimated from chlorophyll a fluorescence measurements. According to photosynthesis measurements, a mean of 38.9 ± 10.3 mol of photons were required to release one mole of O2, which is 4.86 times higher than the theoretical value (8 photons per 1 O2). In contrast, according to the fluorescence measurements, a mean of 11.7 ± 0.74 mol of photons were required to release 1 mol of O2. These findings indicate that fluorescence-based photosynthesis rates may not be fully replace oxygen measurements to evaluate the performance of an outdoor culture. Daily gross biomass productivity was 0.3 g DW L-1 day-1 consistently for 4 days. Biomass productivity was strongly affected by the suboptimal concentration at which the culture was operated and by the respiration rate, as the substantial volume of culture was kept in the dark (about 45% of the total volume). As the cells were exposed to excessive light, the photosynthetic activity was mainly directed to the synthesis of carbohydrates in the biomass. In the morning, carbohydrate content decreased because of the dark respiration. Per contra, protein content in the biomass was lower at the end of the day and higher in the morning due to carbohydrate consumption by respiration. The data gathered in these trials are important for the future exploitation of Chlamydopodium fusiforme as a potential novel species in the field of microalgae for the production of bio-based compounds.

• Klíčová slova
• Biomass composition, Chlamydopodium fusiforme, Chlorophyll fluorescence, Microalgae, Photosynthesis,
• MeSH
• biomasa MeSH
• chlorofyl a MeSH
• Chlorophyta * metabolismus   MeSH
• fotosyntéza MeSH
• kyslík metabolismus   MeSH
• mikrořasy * metabolismus   MeSH
• sacharidy MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a MeSH
• kyslík MeSH
• sacharidy MeSH