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Begonia semperflorens, or wax begonias, are popular ornamental plants often challenged by heat and high light stress in subtropical and tropical regions. This study examined the responses of two stress-tolerant genotypes (FB08-059 and OPGC 5104) and two stress-susceptible genotypes (Cocktail Vodka and Sprint White) under elevated temperature and light conditions. The results revealed significant genotype-dependent differences in stress responses. Stress-tolerant genotypes demonstrated distinct adaptive traits, including thicker cuticles, acute leaf folding, and elevated anthocyanin accumulation, which collectively contributed to enhanced photoprotection and mitigation of cellular damage. Notably, FB08-059 exhibited the most robust stress-adaptive responses, characterized by a 25.83% increase in cuticle thickness and a threefold increase in anthocyanin content under stress conditions. These adaptations effectively limited ROS accumulation and maintained higher Fv/Fm values, thereby sustaining photosynthetic efficiency relative to the other genotypes. In contrast, stress-susceptible genotypes exhibited increased ion leakage, reduced chlorophyll content, and impaired gas exchange rates, reflecting greater oxidative stress and cellular damage. These findings highlight cuticle thickness, anthocyanin accumulation, and leaf folding as key indicators of heat and light stress resilience. This research provides critical insights for breeding programs focused on improving the resilience of wax begonias, supporting the development of heat- and light-tolerant cultivars for sustainable production in stress-prone environments.

• Background and Aims Foliar variegation is recognized as arising from two major mechanisms: leaf structure and pigment-related variegation. Begonia has species with a variety of natural foliar variegation patterns, providing diverse examples of this phenomenon. The aims of this work are to elucidate the mechanisms underlying different foliar variegation patterns in Begonia and to determine their physiological consequences. • Methods Six species and one cultivar of Begonia were investigated. Light and electron microscopy revealed the leaf structure and ultrastructure of chloroplasts in green and light areas of variegated leaves. Maximum quantum yields of photosystem II were measured by chlorophyll fluorescence. Comparison with a cultivar of Ficus revealed key features distinguishing variegation mechanisms. • Key Results Intercellular space above the chlorenchyma is the mechanism of variegation in these Begonia. This intercellular space can be located (a) below the adaxial epidermis or (b) below the adaxial water storage tissue (the first report for any taxa), creating light areas on a leaf. In addition, chlorenchyma cell shape and chloroplast distribution within chlorenchyma cells differ between light and green areas. Chloroplasts from both areas showed dense stacking of grana and stroma thylakoid membranes. The maximum quantum yield did not differ significantly between these areas, suggesting minimal loss of function with variegation. However, the absence of chloroplasts in light areas of leaves in the Ficus cultivar led to an extremely low quantum yield. • Conclusions Variegation in these Begonia is structural, where light areas are created by internal reflection between air spaces and cells in a leaf. Two forms of air space structural variegation occur, distinguished by the location of the air spaces. Both forms may have a common origin in development where dermal tissue becomes loosely connected to mesophyll. Photosynthetic functioning is retained in light areas, and these areas do not include primary veins, potentially limiting the costs of variegation.

Begonia is an important horticultural plant group, as well as one of the most speciose Angiosperm genera, with over 2000 described species. Genus wide studies of genome size have shown that Begonia has a highly variable genome size, and analysis of paralog pairs has previously suggested that Begonia underwent a whole genome duplication. We address the contribution of gene duplication to the generation of diversity in Begonia using a multi-tissue RNA-seq approach. We chose to focus on chalcone synthase (CHS), a gene family having been shown to be involved in biotic and abiotic stress responses in other plant species, in particular its importance in maximising the use of variable light levels in tropical plants. We used RNA-seq to sample six tissues across two closely related but ecologically and morphologically divergent species, Begonia conchifolia and B. plebeja , yielding 17,012 and 19,969 annotated unigenes respectively. We identified the chalcone synthase gene family members in our Begonia study species, as well as in Hillebrandia sandwicensis , the monotypic sister genus to Begonia , Cucumis sativus , Arabidopsis thaliana , and Zea mays . Phylogenetic analysis suggested the CHS gene family has high duplicate turnover, all members of CHS identified in Begonia arising recently, after the divergence of Begonia and Cucumis . Expression profiles were similar within orthologous pairs, but we saw high inter-ortholog expression variation. Sequence analysis showed relaxed selective constraints on some ortholog pairs, with substitutions at conserved sites. Evidence of pseudogenisation and species specific duplication indicate that lineage specific differences are already beginning to accumulate since the divergence of our study species. We conclude that there is evidence for a role of gene duplication in generating diversity through sequence and expression divergence in Begonia .

Arrays of blue (B, 400-500 nm) and red (R, 600-700 nm) light-emitting diodes (LEDs) used for plant growth applications make visual assessment of plants difficult compared to a broad (white, W) spectrum. Although W LEDs are sometimes used in horticultural lighting fixtures, little research has been published using them for sole-source lighting. We grew seedlings of begonia (Begonia ×semperflorens), geranium (Pelargonium ×horturum), petunia (Petunia ×hybrida), and snapdragon (Antirrhinum majus) at 20°C under six sole-source LED lighting treatments with a photosynthetic photon flux density (PPFD) of 160 μmol∙m-2∙s-1 using B (peak = 447 nm), green (G, peak = 531 nm), R (peak = 660 nm), and/or mint W (MW, peak = 558 nm) LEDs that emitted 15% B, 59% G, and 26% R plus 6 μmol∙m-2∙s-1 of far-red radiation. The lighting treatments (with percentage from each LED in subscript) were MW100, MW75R25, MW45R55, MW25R75, B15R85, and B20G40R40. At the transplant stage, total leaf area, and fresh and dry weight were similar among treatments in all species. Surprisingly, when petunia seedlings were grown longer (beyond the transplant stage) under sole-source lighting treatments, the primary stem elongated and had flower buds earlier under MW100 and MW75R25 compared to under B15R85. The color rendering index of MW75R25 and MW45R55 were 72, and 77, respectively, which was higher than those of other treatments, which were ≤64. While photosynthetic photon efficacy of B15R85 (2.25 μmol∙J-1) was higher than the W light treatments (1.51-2.13 μmol∙J-1), the dry weight gain per unit electric energy consumption (in g∙kWh-1) of B15R85 was similar to those of MW25R75, MW45R55, and MW75R25 in three species. We conclude that compared to B+R radiation, W radiation had generally similar effects on seedling growth at the same PPFD with similar electric energy consumption, and improved the visual color quality of sole-source lighting.

The previously reported begonias in a limestone forest of Guangxi mainly belong to Begoniasect.Coelocentrum Irmscher. In this article, we described and illustrated a new species in sect. Platycentrum (Klotzsch) A.DC., X.X.Feng, R.K.Li & Z.X.Liu, which was discovered in a karst forest of south-western Guangxi. The begonia shows high morphological similarity to S.H. Huang and Irmscher, but differs from the latter two in its narrower oblique-ovate asymmetric leaf blade, 4 (occasionally 6) tepals of pistillate flower and smaller membranous inflorescence bracts. Molecular phylogenetic analysis, based on ITS sequence data, supports the new species as monophyletic and distinct from and . Considering its narrow distribution and the disturbance of human activities, the conservation status of new taxon is evaluated as \"Vulnerable\" (VU B1, B2 ab (i, iv, v), D2) according to the IUCN Red List Categories and Criteria.

Iridoplasts (modified plastids in adaxial epidermal cells) reported from Begonia were originally hypothesized to cause iridescence, which was broadly accepted for decades. However, several species of Begonia with iridoplasts are not iridescent causing confusion. Here chloroplast ultrastructure was observed in 40 taxa of Begoniaceae to explore the phenomenon of iridescence. However, 22 Begonias and Hillebrandia were found to have iridoplasts, but only nine display visually iridescent blue to blue-green leaves. Unexpectedly, a new type of plastid, a ‘minichloroplast,’ was found in the abaxial epidermal cells of all taxa, but was present in adaxial epidermal cells only if iridoplasts were absent. Comparative ultrastructural study of iridoplasts and a shading experiment of selected taxa show that a taxon with iridoplasts does not inevitably have visual iridescence, but iridescence is greatly affected by the spacing between thylakoid lamellae (stoma spacing). Thus, we propose instead the name ‘lamelloplast’ for plastids filled entirely with regular lamellae to avoid prejudging their function. To evaluate photosynthetic performance, chlorophyll fluorescence (Fv/Fm) was measured separately from the chloroplasts in the adaxial epidermis and lower leaf tissues by using leaf dermal peels. Lamelloplasts and minichloroplasts have much lower photosynthetic efficiency than mesophyll chloroplasts. Nevertheless, photosynthetic proteins (psbA protein of PSII, RuBisCo and ATPase) were detected in both plastids as well as mesophyll chloroplasts in an immunogold labeling. Spectrometry revealed additional blue to blue-green peaks in visually iridescent leaves. Micro-spectrometry detected a blue peak from single blue spots in adaxial epidermal cells confirming that the color is derived from lamelloplasts. Presence of lamelloplasts or minichloroplasts is species specific and exclusive. High prevalence of lamelloplasts in Begoniaceae, including the basal clade Hillebrandia, highlights a unique evolutionary development. These new findings clarify the association between iridescence and lamelloplasts, and with implications for new directions in the study of plastid morphogenesis.

Recent, rapid radiations make species-level phylogenetics difficult to resolve. We used a multiplexed, high-throughput sequencing approach to identify informative genomic regions to resolve phylogenetic relationships at low taxonomic levels in Begonia from a survey of sixteen species. A long-range PCR method was used to generate draft plastid genomes to provide a strong phylogenetic backbone, identify fast evolving regions and provide informative molecular markers for species-level phylogenetic studies in Begonia.

Begonia fimbristipula Hance (Begoniaceae) is a valuable medicinal herb that is classified as a protected species in Guangdong Province, China. In this study, we present a chromosome-level genome assembly of B . fimbristipula , aiming to facilitate its conservation and utilization. The genome was assembled using a combination of Oxford Nanopore long-read data and Illumina short-read data. The assembled genome size of B . fimbristipula is 462.11 Mb, with a scaffold N50 of 38.22 Mb. A total of 91.96% (424.94 Mb) of the sequences were anchored to 11 pseudochromosomes using Hi-C technology. The genome assembly exhibits a BUSCO completeness of 90.3% and an LTR Assembly Index (LAI) of 17.73. Genome annotation revealed 25,563 protein-coding genes and 274 tRNA genes. The high-quality chromosome-level assembly and annotation provide valuable insights into the genomic characteristics of B . fimbristipula , thereby offering essential resources for its conservation and economic utilization.

Begonia semperflorens (B. semperflorens), belonging to the family Begoniaceae, has now been widely cultivated worldwide and is famous for its ornamental plants with colourful flowers and distinctive leaves. The selection of appropriate internal reference genes is very important to accurately determine target gene expression via quantitative real-time PCR. However, internal reference gene selection has never been conducted in B. semperflorens. In this study, seven candidate reference genes of B. semperflorens, including 18S ribosomal RNA (Bs18S), pentatricopeptide repeat-containing protein (BsPPR), actin-related protein 5 isoform X2 (BsACT), DNAJ homologue subfamily C member 17 (BsDNAJ), glyceraldehyde-3-phosphate dehydrogenase (BsGAPDH), NAD-dependent malic enzyme 59 kDa isoform, mitochondria (BsNAD-ME), and peptidyl-prolyl cis–trans isomerase CYP26-2, chloroplast (BsCYP), which were obtained from our previous studies, were selected. The stabilities of these genes under stress conditions were analysed using geNorm and NormFinder. Validation of target gene expressions, including phenylalanine ammonia-lyase (BsPAL) and respiratory burst oxidase homologue D (BsRBOHD) under biotic and abiotic conditions, phenylalanine ammonia-lyase (BsPAL), anthocyanidin synthase (BsANS), chalcone synthase (BsCHS), and flavanone-3-hydroxylase (BsF3H) under low temperature, using these seven internal reference genes for normalisation further confirmed the stabilities of the selected genes and indicated the need for reference gene selection for normalising gene expressions in B. semperflorens. Of the seven candidate reference genes, the combination of BsACT, BsDNAJ, and BsNAD-ME was the ideal reference gene set for normalising gene expression in samples under biotic conditions. BsCYP combined with BsACT or BsGAPDH was the best reference gene pair under abiotic conditions. BsACT and BsPPR could be combined to normalise gene expression under low temperature. Our results will benefit future studies on gene expression in plants of Begoniaceae.

Species conservation assessments using the criteria outlined by the International Union for the Conservation of Nature Red List can be compromised by limited data availability. Species-rich tropical plant taxa with numerous microendemics are particularly problematic. This study focusses on the Begonia flora of the Indonesian island of Sulawesi, comprised of 65 herbaceous species mainly found in rainforest habitats. Sixty-two species are Sulawesi endemics, including 20 species restricted to limestone karst landscapes. Forty-eight species are represented by fewer than 10 herbarium collections. Here, we outline and discuss an approach that, despite these data limitations, allows meaningful conservation assessments by integrating analyses of occurrences, data primarily based on remote sensing approaches, including forest landscape integrity, forest cover loss, and land cover, and extent of suitable habitat estimation. The results indicate that most Sulawesi Begonia species are narrow endemics whose rainforest habitats have substantially deteriorated in the last two decades: 27 species are assessed as Critically Endangered, 24 as Endangered, six as Vulnerable, five as Least Concern, and three species are Data Deficient. Conservation action, including extension of the protected area network in Sulawesi with emphasis on areas of old-growth forest and limestone karst landscapes, and strengthening of ex-situ living collections, is recommended.