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Heterosis is a crucial factor in enhancing crop yield, particularly in sorghum (Sorghum bicolor). This research utilised six sorghum restorer lines, six sorghum sterile lines, and 36 hybrid combinations created through the NCII incomplete double-row hybridisation method. We evaluated the performance of F1 generation hybrids for leaf photosynthesis-related parameters, carbon metabolism-related enzymes, and their correlation with yield traits during the flowering stage. Results showed that hybrid sorghum exhibited significant high-parent heterosis in net photosynthetic rate (P n), transpiration rate (T r), stomatal conductance (G s), apparent leaf meat conductance (AMC), ribulose-1,5-bisphosphate (RuBP) carboxylase, phosphoenolpyruvate (PEP) carboxylase, and sucrose phosphate synthase (SPS). Conversely, inter-cellular carbon dioxide concentration (C i), instantaneous water uses efficiency (WUE), and sucrose synthase (SuSy) displayed mostly negative heterosis. Traits such as 1000-grain weight (TGW), grain weight per spike (GWPS), and dry matter content (DMC) exhibited significant high-parent heterosis, with TGW reaching the highest value of 82.54%. P n demonstrated positive correlations with T r, C i, G s, RuBP carboxylase, PEP carboxylase, GWPS, TGW, and DMC, suggesting that T r, C i, and G s could aid in identifying high-photosynthesis sorghum varieties. Concurrently, P n could help select carbon-efficient sorghum varieties due to its close relationship with yield. Overall, the F1 generation of sorghum hybrids displayed notable heterosis during anthesis. Combined with field performance, P n at athesis can serve as a valuable indicator for early prediction of the yield potential of the F1 generation of sorghum hybrids and for screening carbon-efficient sorghum varieties. There is limited information on the hybridisation of enzymes linked to these characteristics. Understanding hybrid dominance of photosynthetic traits and their associated enzymes in sorghum is crucial for identifying sorghum hybrids with highly dominant combinations and selecting suitable parents. This study utilised 36 sorghum hybrid F1 generations and their respective parents to assess hybrid dominance in leaf photosynthetic parameters, key enzyme activities during photosynthesis, yield formation, and other relevant factors, while also examining their correlation with yield in field conditions. This article belongs to the Collection Machine Learning for Plant Stress Phenotyping. [ABSTRACT FROM AUTHOR]

This study reveals a new acclimation mechanism of the eukaryotic unicellular green alga Chlorella vulgaris in terms of the effect of varying atmospheric pressures on the structure and function of its photosynthetic apparatus using fluorescence induction measurements (JIP-test). The results indicate that low (400 mbar) and extreme low (<10 mbar) atmospheric pressure decreases the density and thus increases the fluidity of the thylakoid membrane, possibly facilitating plastoquinone (PQ) movement within the membrane and resulting in enhanced photosynthetic electron flow and photochemical quenching. Molecular dynamic simulations of different light harvesting complexes within thylakoid membrane models confirm this mechanism and reveal the associated atomic scale details. The exposure of microalga to an extremely low pressure (<10 mbar) in a 100% CO2 atmosphere (simulating the Mars atmosphere), reveals that the impact of extremely low atmospheric pressure on PQ mobility within the photosynthetic membrane, coupled with the low density of an almost 100% CO2 Mars-like atmosphere, results to a similar photosynthetic efficiency to that on Earth. These findings pave the way for the identification of novel functional acclimation mechanisms of microalgae to extreme environments that are vastly distinct from those found on Earth. This study reveals a new acclimation mechanism of microalgae in low atmospheric pressure. Experimental results and molecular dynamic simulations indicate that low atmospheric pressure reduces the density and enhances the fluidity of photosynthetic thylakoid membranes, leading to enhanced photochemical quenching. Particularly, extremely low pressure (<10 mbar) in a 100% CO2 atmosphere (Mars-like atmosphere) yields a photosynthetic efficiency comparable to that of Earth, shedding light on new astrobiological perspectives. [ABSTRACT FROM AUTHOR]

Heliotropium thermophilum (Boraginaceae) plants have strong antioxidant properties. This study investigated the effectiveness of the antioxidant system in protecting the photosynthetic machinery of H. thermophilum. Plants were obtained from Kızıldere geothermal area in Buharkent district, Aydın, Turkey. Plants in the geothermal area that grew at 25–35°C were regarded as the low temperature group, while those that grew at 55–65°C were regarded as the high temperature group. We analysed the physiological changes of these plants at the two temperature conditions at stage pre-flowering and flowering. We meaured the effect of high soil temperature on water potential, malondialdehyde, cell membrane stability, and hydrogen peroxide analysis to determine stress levels on leaves and roots. Changes in antioxidant enzyme activities, ascorbate and chlorophyll content, chlorophyll fluorescence, photosynthetic gas exchange parameters, and photosynthetic enzymes (Rubisco and invertase) activities were also determined. Our results showed minimal changes to stress levels, indicating that plants were tolerant to high soil temperatures. In general, an increase in antioxidant enzyme activities, ascorbat levels, and all chlorophyll fluorescence parameters except for non-photochemical quenching (NPQ) and F v/ F m were observed. The pre-flowering and flowering stages were both characterised by decreased NPQ, despite F v/ F m not changing. Additionally, there was a rise in the levels of photosynthetic gas exchange parameters, Rubisco, and invertase activities. High temperature did not affect photosynthetic yield because H. thermophilum was found to stimulate antioxidant capacity, which reduces oxidative damage and maintains its photosynthetic machinery in high temperature conditions and therefore, it is tolerant to high soil temperature. Heliotropium thermophilum did not exhibit significant stress parameters under high soil temperature conditions, and it was a highly tolerant plant to high temperature. In the measurements taken at pre-flowering and flowering, plants in the pre-flowering stage were slightly more tolerant to high temperatures. The protection of PSII function in plants at higher temperatures could be linked to an increase in antioxidant activities. [ABSTRACT FROM AUTHOR]

Transgenic Arabidopsis thaliana (ecotype Columbia) was successfully transformed with the gene fructose-1,6-bisphosphatase (FBPase) and named as AtFBPase plants. Transgenic plants exhibited stable transformation, integration and significantly higher expressions for the transformed gene. Morphological evaluation of transgenic plants showed increased plant height (35 cm), number of leaves 25), chlorophyll contents (28%), water use efficiency (increased from 1.5 to 2.6 µmol CO2 µmol-1 H2O) and stomatal conductance (20%), which all resulted in an enhanced photosynthetic rate 2.7 µmol m-2 s-1) compared to wild type plants. This study suggests the vital role of FBPase gene in the modification of regulatory pathways to enhance the photosynthetic rate, which can also be utilised for economic crops in future. [ABSTRACT FROM AUTHOR]

Continuous increasing leaf photosynthesis may enhance plant yield. As an evolutionary property, plants use less photosynthetic capacity than is theoretically possible. Plant nanobionics is a bioengineering field that improves plant functions using nanoparticles. We applied orange carbon dots (o-CDs) onto the foliage of green beans (Phaseolus vulgaris) grown in hydroponics to improve their photosynthetic performance and CO2 assimilation. Photosynthesis parameters, photosynthetic pigments content, total phenolic content (TPC) and antioxidative activity (TAA) were measured. Results show that photosynthetic pigments remained unchanged, while photosynthesis was improved. Both o-CDs concentrations decreased TPC and TAA. The light response curve showed higher CO2 assimilation at both o-CDs concentrations, particularly at lower light intensity. Correlation analysis confirmed increased CO2 binding and assimilation at 1 mg L−1. This study demonstrated the potential of using o-CDs as a safe biostimulator through photosynthesis increase and CO2 assimilation without toxic effects on plants. This may stimulate yield increase that paves the way for their agricultural application. [ABSTRACT FROM AUTHOR]

Orchids (Phalaenopsis spp.) growing in tropical and subtropical regions are epiphytes. As such, they grow on trees with the root system utilised to anchor themselves to tree branches. These roots are highly specialised, display a large diameter and are often green, suggesting the ability to carry out photosynthesis. However, the role of photosynthesis in orchid roots is controversial. Orchids that are leafless can photosynthesise in their roots, thus indicating that some orchid roots carry out photosynthesis in a similar manner to leaves. However, the primary site of photosynthesis in orchids are in their leaves, and the roots of epiphytic orchids may mostly conduct internal refixation of respiratory CO2. Besides contributing to the overall carbon metabolism of orchid plants, oxygen produced through root photosynthesis may also be important by alleviating potential root hypoxia. The bulky tissue of most epiphytic orchid roots suggests that oxygen diffusion in these roots can be limited. Here, we demonstrate that the bulky roots of a widely commercially cultivated orchid belonging to the genus Phalaenopsis are hypoxic in the dark. These roots are photosynthetically active and produce oxygen when exposed to light, thus mitigating root hypoxia. Orchid (Phalaenopsis spp.) is a most popular flowering potted plant. However, it has been poorly studied at the physiological and molecular level. The bulky aerial roots of Phalaenopsis have a large diameter and are possibly photosynthetically active. Here, we present evidence demonstrating that root photosynthesis prevents hypoxia in the root tissue. Our results support the existence of hypoxic niches in plant roots and highlight the existence of mechanisms to modulate the intensity of hypoxia. This article belongs to the Collection Flooding Stress and Hypoxic Responses in Plants. [ABSTRACT FROM AUTHOR]

Plant growth and development is adversely affected by environmental constraints, particularly salinity and drought. Climate change has escalated the effect of salinity and drought on crops in varying ways, affecting agriculture and most importantly crop productivity. These stressors influence plants across a wide range of levels, including their morphology and physiological, biochemical, and molecular processes. Plant responses to salinity and drought stress have been the subject of intense research being explored globally. Considering the importance of the impact that these stresses can have on agriculture in the short term, novel strategies are being sought and adopted in breeding programs. Better understanding of the molecular, biochemical, and physiological responses of agriculturally important plants will ultimately help promote global food security. Moreover, considering the present challenges for agriculture, it is critical to consider how we can effectively transfer the knowledge generated with these approaches in the laboratory to the field, so as to mitigate these adversities. The present collection discusses how drought and salinity exert effects on plants. Environmental constraints like salinity and drought hinder plant growth by affecting plant morphology, physiology, biochemistry, and molecular processes, final crop productivity and threat to global food security. Researches on plant responses to salinity and drought stress is ongoing worldwide. Novel breeding strategies are being adopted due to their short-term impact on agriculture. Given agriculture's current challenges, we must consider how to effectively transfer laboratory knowledge to the field to mitigate these challenges. This collection discusses plant responses to drought and salinity. This article belongs to the Collection Understanding the Mechanistic Basis of Plant Adaptation to Salinity and Drought. [ABSTRACT FROM AUTHOR]

Water stress (drought and waterlogging) leads to an imbalance in plant water distribution, disrupts cell homeostasis, and severely inhibits plant growth. Melatonin is a growth hormone that plants synthesise and has been shown to resist adversity in many plants. This review discusses the biosynthesis and metabolism of melatonin, as well as the changes in plant morphology and physiological mechanisms caused by the molecular defence process. Melatonin induces the expression of related genes in the process of plant photosynthesis under stress and protects the structural integrity of chloroplasts. Exogenous melatonin can maintain the dynamic balance of root ion exchange under waterlogging stress. Melatonin can repair mitochondria and alleviate damage caused by reactive oxygen species and reactive nitrogen species; and has a wide range of uses in the regulation of stress-specific genes and the activation of antioxidant enzyme genes. Melatonin improves the stability of membrane lipids in plant cells and maintains osmotic balance by regulating water channels. There is crosstalk between melatonin and other hormones, which jointly improve the ability of the root system to absorb water and breathe and promote plant growth. Briefly, as a multifunctional molecule, melatonin improves the tolerance of plants under water stress and promotes plant growth and development. Melatonin, as an exogenous hormone, has been widely used in improving plant stress resistance. This paper systematically describes how melatonin improves the ability of plants to resist water stress (drought and waterlogging) in the processes of photosynthesis, antioxidation and osmosis at the physiological and genetic levels. Melatonin can also improve plant stress resistance with other hormone crosstalk, which has high application value. [ABSTRACT FROM AUTHOR]

In this study, we investigated the importance of one of the intramembrane proteases, EGY2, for the proper functioning of PSII under short-term high light stress conditions. EGY2 is a chloroplast intramembrane protease of the S2P family, whose absence in Arabidopsis thaliana affects PSII protein composition. The egy2 mutants exhibited a slower degradation of PsbA and decreased content of PsbC and PsbD. During exposure to high light stress, these stoichiometric changes affect the functional state of PSII, leading to its higher sensitivity to photoinhibition of the PSII reaction centre and increased heat dissipation. Furthermore, we explored the relationship between EGY2 and the pTAC16 transcription factor, which is a potential EGY2 substrate. Under light stress, WT plants showed decreased levels of pTAC16, while it remained unchanged in the egy2 mutants. This finding suggests that EGY2 may release pTAC16 from thylakoid membranes through proteolytic cleavage. We also confirmed the physical interaction between EGY2 and pTAC16 using the yeast two-hybrid system, providing evidence of EGY2's involvement in the regulation of PsbA and PsbC/PsbD operons by releasing pTAC16 from the thylakoid membrane. [ABSTRACT FROM AUTHOR]

Viscum schimperi is an evergreen hemiparasitic plant that can grow on stems and branches of several tree species. It penetrates the host tissues and forms a vascular bridge (haustorium) to withdraw the nutritive resources. Its relationships with hosts remain unknown. This study aimed to investigate the physiological and biochemical attributes of the host-hemiparasite association Acacia gerrardii-Viscum schimperi. The hemiparasite exhibited 2.4- and 3.0-fold lower photosynthetic activity and water use efficiency, and 1.2- and 4.1-fold higher transpiration rate and stomatal conductance. Equally, it displayed 4.9- and 2.6-fold greater water potential and osmotic potential, and in least 3.0 times more accumulated 39K, 85Rb and 51V, compared to the host. Nevertheless, it had no detrimental effect on photosynthetic activity, water status and multi-element accumulations in the host. Based on metabolome profiling, V. schimperi could use xanthurenic acid and propylparaben to acquire potassium from the host, and N-1-naphthylacetamide and N-Boc-hydroxylamine to weaken or kill the distal part of the infected branch and to receive the total xylem contents. In contrast, A. gerrardii could used N-acetylserotonin, arecoline, acetophenone and 6-methoxymellein to defend against V. schimperi infection. [ABSTRACT FROM AUTHOR]

Solanaceous crops act as a source of food, nutrition and medicine for humans. Soil salinity is a damaging environmental stress, causing significant reductions in cultivated land area, crop productivity and quality, especially under climate change. Solanaceous crops are extremely vulnerable to salinity stress due to high water requirements during the reproductive stage and the succulent nature of fruits and tubers. Salinity stress impedes morphological and anatomical development, which ultimately affect the production and productivity of the economic part of these crops. The morpho-physiological parameters such as root-to-shoot ratio, leaf area, biomass production, photosynthesis, hormonal balance, leaf water content are disturbed under salinity stress in Solanaceous crops. Moreover, the synthesis and signalling of reactive oxygen species, reactive nitrogen species, accumulation of compatible solutes, and osmoprotectant are significant under salinity stress which might be responsible for providing tolerance in these crops. The regulation at the molecular level is mediated by different genes, transcription factors, and proteins, which are vital in the tolerance mechanism. The present review aims to redraw the attention of the researchers to explore the mechanistic understanding and potential mitigation strategies against salinity stress in Solanaceous crops, which is an often-neglected commodity. [ABSTRACT FROM AUTHOR]