As a secondary messenger, calcium participates in various physiological and biochemical reactions in plants. Photosynthesis is the most extensive biosynthesis process on Earth. To date, researchers have found that some chloroplast proteins have Ca²⁺-binding sites, and the structure and function of some of these proteins have been discussed in detail. Although the roles of Ca²⁺ signal transduction related to photosynthesis have been discussed, the relationship between calcium and photosynthesis is seldom systematically summarized. In this review, we provide an overview of current knowledge of calcium’s role in photosynthesis.

This study identified 45 calcium-dependent protein kinase (CDPK) genes in cultivated peanut (Arachis hypogaea L.), which are integral in plant growth, development, and stress responses. These genes, classified into four subgroups based on phylogenetic relationships, are unevenly distributed across all twenty peanut chromosomes. The analysis of the genetic structure of AhCDPKs revealed significant similarity within subgroups, with their expansion primarily driven by whole-genome duplications. The upstream promoter sequences of AhCDPK genes contained 46 cis-acting regulatory elements, associated with various plant responses. Additionally, 13 microRNAs were identified that target 21 AhCDPK genes, suggesting potential post-transcriptional regulation. AhCDPK proteins interacted with respiratory burst oxidase homologs, suggesting their involvement in redox signaling. Gene ontology and KEGG enrichment analyses affirmed AhCDPK genes’ roles in calcium ion binding, protein kinase activity, and environmental adaptation. RNA-seq data revealed diverse expression patterns under different stress conditions. Importantly, 26 AhCDPK genes were significantly induced when exposed to Ca deficiency during the pod stage. During the seedling stage, four AhCDPKs (AhCDPK2/-25/-28/-45) in roots peaked after three hours, suggesting early signaling roles in pod Ca nutrition. These findings provide insights into the roles of CDPK genes in plant development and stress responses, offering potential candidates for predicting calcium levels in peanut seeds.

Excessive nitrogen and insufficient calcium could significantly impact peanut yields. This study investigated the effects of nitrogen and calcium fertilizers on nutrient absorption, utilization, and yield; experiments were conducted using the peanut cultivar from Xianghua 2008 in a split-plot arrangement with two calcium fertilizer levels (Ca₀: 0 and Ca₁: 568 kg CaO ha⁻¹) in the main plots and six nitrogen fertilizer gradients (N₀: 0, N_45.0: 45.0, N_90.0: 90.0, N_112.5: 112.5, N_135.0: 135.0, and N_157.5: 157.5 kg N ha⁻¹) in subplots between 2015 and 2016 in Changsha, China. We examined the impact of different rates of calcium and nitrogen fertilizers on the net photosynthetic rate (Pn), agronomic traits, dry matter quality, yield and yield composition, nutrient accumulation, and distribution. The combined application of calcium and nitrogen fertilizers significantly affected the yield and yield components, Pn, main stem height, dry matter, and nutrient accumulation. Under the same calcium level, nitrogen application significantly increased the main stem height and Pn and promoted the accumulation of dry matter and nutrients in the plant, particularly in the kernel. Under the same nitrogen treatment, calcium significantly increased Pn and promoted the accumulation of dry matter, calcium, and magnesium. The pod yield increased gradually with an increasing nitrogen application rate (0–112.5 kg ha⁻¹) and peaked at N_112.5, increasing by 52.3–138.0% compared with N₀. However, excessive nitrogen application (N > 112.5 kg ha⁻¹) decreased the pod yield. Under different nitrogen fertilizer levels, calcium application increased pod yields by 11.5–29.6% by promoting Pn, nutrient uptake, accumulation in the individual plant, and nutrient accumulation in the kernel. Therefore, this study suggested that adjusting the calcium (568 kg ha⁻¹) and nitrogen (112.5 kg ha⁻¹) fertilizer rates significantly improved peanut growth and productivity by enhancing photosynthetic efficiency and nutrient accumulation in calcium-deficient acidic red soil.

Photo-oxidative stress, resulting from an imbalance between light absorption and photosynthetic carbon utilization, poses a fundamental challenge to plant survival and productivity. This review synthesizes recent advances to present an integrated framework connecting reactive oxygen species (ROS) signaling, damage propagation, and systems-level resilience. We move beyond describing ROS as mere toxic byproducts to position them as central hubs in a complex, interconnected network. We integrate the specific sites of ROS generation, particularly ¹O₂ at PSII and H₂O₂ at PSI, with their distinct retrograde signaling pathways (e.g., EXECUTER, β-cyclocitral, and RES/RCS pathways) that reprogram nuclear gene expression. A systems perspective is then applied to reveal how initial photochemical damage propagates through a self-amplifying “vicious cycle” of impaired photosystem repair, lipid peroxidation, and protein oxidation, ultimately threatening cellular integrity. Counteracting this cycle is a multi-layered photoprotective arsenal including NPQ, alternative electron sinks (CEF, WWC), and an integrated antioxidant network, which we re-evaluate not as independent modules but as a coordinated, evolutionary-tuned defense system. We synthesize this knowledge to highlight a central paradigm for crop improvement: the pervasive growth–defense trade-off. Investment in photoprotection, while crucial for survival, diverts resources from yield, explaining why single-gene modifications often fail in the field. Therefore, we argue that future strategies must move beyond simply enhancing single components and instead focus on “optimizing the network”. We conclude by outlining how synthetic biology, multi-omics integration, and genomics-assisted breeding can be leveraged to fine-tune this integrated system, aiming to develop climate-resilient crops that balance productivity with survival in an increasingly volatile climate.

Background: During active infections, plants prevent further spread of pathogenic microorganisms by inducing the rapid programmed death of cells around the infection point. This phenomenon is called the hypersensitive response and is a common feature of plant immune responses. Plants recognize conserved structures of pathogenic microorganisms, called pathogen-associated molecular patterns (PAMPs), e.g., flagellin 22 (flg22) and chitohexose, which bind to receptors on plant cells to induce various immune-response pathways. Although abiotic stresses are known to alter photosynthesis, the different effects of flg22 and chitohexose, which are involved into PAMP-induced signaling, on photosynthesis needs further study. Methods: In the present study, we assessed the role of PAMPs in peanut (Arachis hypogaea) photosynthesis, particularly, the interaction between PAMPs and Ca²⁺ signal transduction pathway. Results: Both flg22 and chitohexose significantly promoted the expression of the pathogenesis-related genes PR-4 and PR-10, as did Ca²⁺. We found that Ca²⁺ is involved in downregulating the photosystem II (PSII) reaction center activity induced by the flg22 immune response, but the role of chitohexose is not obvious. Additionally, Ca²⁺ significantly reduced the non-photochemical energy dissipation in the flg22- and chitohexose-induced immune response. Conclusion: These results indicated that flg22 and chitohexose can trigger peanut immune pathways through the Ca²⁺ signaling pathway, but they differ in their regulation of the activity of the PSII reaction center.