China has the richest germplasm resources of Rhododendron, but most species thrive in high-altitude cool areas. Currently, only a limited number of these species are utilized in landscaping, and their summer performance is generally poor. With the exacerbation of the global greenhouse effect, it has become imperative to research on the heat response of Rhododendron germplasm resources, to screen for heat-tolerant germplasms, and to develop heat-tolerant cultivars. In this paper, we elucidated the heat response mechanisms of Rhododendron under heat stress from four aspects: initial response and heat signal transduction, gene expression and regulation, physiological metabolic adjustment, and morphological structural changes. Additionally, we reviewed the current research on heat resistance evaluation indicators and methods for Rhododendron, as well as strategies for improving heat resistance. Furthermore, we compiled a catalog of Rhododendron germplasm resources with heat resistance potential distributed in low-altitude warm areas worldwide. Finally, we provided a perspective on future research directions in the molecular mechanisms of heat resistance and the genetics of domestication, aiming to offer a reference for the study and breeding of heat-tolerant Rhododendron germplasm resources.

The underground-bud plants, namely, the geophytes, constitute an important category in bud classification of plants. These plants include a significant number of ornamental flowers. These plants adapt to cold and other unfavorable environments through the dormancy of buds (including persistent organs) that are partially or fully covered beneath the surface of the growth substrate. Therefore, the regulatory mechanism of underground-bud dormancy is a crucial aspect in the research field of ornamental flowers. In this paper, we systematically reviewed the research findings on the physiological and molecular regulatory mechanisms involved in the induction, maintenance, and release of endodormancy in underground-bud ornamental flowers over the past decade or more. They covered external environmental factors such as light and temperature, as well as internal factors such as hormone metabolism, carbohydrate conversion, reactive oxygen species clearance, secondary metabolism, epigenetics, and intercellular communication via symplast. Subsequently, a comparison of various research findings and experimental methods was conducted between underground-bud ornamental flowers and Poplar spp., which is the model plant for bud dormancy research. Finally, we analyzed the bud-dormancy research characteristics of two important categories in underground-bud ornamental flowers (perennial flowers and bulbous flowers). This review helps to comprehensively understand the latest research progress of the underground-bud dormancy research in landscape plant and ornamental horticulture field and can provide systematic theoretical support for flower cultivation and production.

The PIN protein family is an auxin efflux carrier responsible for transporting auxin from intracellular to extracellular space, a process that is essential for the distribution of auxin and the establishment of concentration gradients in plants. In this study, 113 members of the PIN gene family were identified in five species of chrysanthemum plants by bioinformatics methods, and their physicochemical properties were analyzed in depth, revealing the diversity of physical and chemical properties of these members. By constructing a phylogenetic tree, we found that these PIN genes were divided into six distinct branches, and the closely related members presented similar conserved motifs and conserved domains, suggesting that they may have similar or related functions. Chromosome localization and collinearity analysis further demonstrated the distribution patterns of PIN genes in chrysanthemum plants, as well as their replication and rearrangement events in the genome. In addition, promoter cis-acting element analysis showed that the promoter region of the PIN gene was rich in regulatory elements related to growth and development, hormone signal transduction and stress response, suggesting that the PIN gene may be regulated by multiple signals in plant growth and development and environmental adaptation. Gene expression analysis showed that the PIN gene presented specific expression patterns in different organs of chrysanthemum plants. The above results provide a theoretical basis for the subsequent study of the function of the PIN gene in chrysanthemum plants.

In this study, evolutionary and expression analyses of the P450 gene family in Rosa chinensis were conducted using bioinformatics analysis methods, and the mechanism by which these genes are involved in the synthesis of rose fragrance was explored. A total of 448 P450 genes were identified in the rose genome. A phylogenetic tree of P450 genes with 4 849 P450 genes from 14 species, including Rosa chinensis, Rosa rugosa, Rosa wichurana, Pyrus bretschneideri,and Prunus persica was constructed and could be divided into 38 families. Among them, CYP71, CYP76, CYP81, CYP82, CYP706, CYP72, CYP714, CYP90, CYP86 and CYP94 underwent specific expansion within the Rosaceae. The results of transcriptome analysis showed that the expression patterns of rose P450 genes were tissue-specific. There were four genes highly expressed in petals. Most of the highly expressed P450 genes were related to the synthesis of terpenoids. Combined with metabolic data, 21 P450 genes potentially involved in rose fragrance synthesis were identified through weighted gene coexpression network analysis (WGCNA), such as RcHm_v2.0_Chr1g0351001_CYP86, RcHm_v2.0_Chr2g0115981_CYP71, RcHm_v2.0_Chr1g0359661_CYP82, etc. Most of these genes belonged to the significantly expanded CYP71 clan. This study reveals that multiple families expand in the Rosaceae and identified multiple P450 genes involve in fragrance synthesis, most of which are derived from the expanded CYP71 clan, indicating that P450 expansion may have promoted the diversity of rose fragrance.

Protoplasts are important receptors for genetic transformation and gene function verification. Lily is an important ornamental, edible, and medicinal plant worldwide. The isolation and cultivation system for lily protoplasts is still incomplete. In this study, taking Lilium pumilum and Lilium formosanum×Lilium longiflorum var. scabrum as materials, the isolation, cultivation, and transient transformation of lily protoplasts were studied. The results revealed that lily leaves and embryogenic callus tissues were both excellent materials for isolating protoplasts. The optimal solution for isolating protoplasts from sterile plantlet leaves was cell protoplast wash medium (CPW)＋1.0%-2.0% cellulase RS＋0.5% macerozyme R-10＋0.10% pectinase Y-23＋12-14 g/L D-mannitol. The optimal solution for isolating protoplasts from embryogenic callus tissues was CPW＋2.0% cellulase RS＋0.60% pectinase Y-23＋12-14 g/L D-mannitol. Protoplasts isolated from leaves were excellent receptors for transient transformation, with a transformation efficiency of 34.0%-36.7%. Protoplasts isolated from embryogenic callus tissues of Lilium formosanum×Lilium longiflorum var. scabrum had strong division ability. In a solid-liquid double-layer culture medium with MS (Murashige-Skoog, containing 206.25 mg/L NH₄NO₃)＋60 g/L glucose and a cultivation density of 2×10⁵ cells/mL, callus tissues were formed after 70 days of cultivation. This study lays the foundation for lily cell engineering and molecular breeding.

Protoplast isolation and purification are influenced by plant genotype and extraction conditions. Establishing a system for the isolation, purification, and transient transformation of tulip (Tulipa gesneriana)protoplasts is an effective way to explore the mechanism of tulip growth and development and conduct studies of somatic cell fusion. In the present study, we established a polyethylene glycol-calcium ion (PEG-Ca^2＋) mediated transient transformation system for tulip protoplasts by the leaves of the tulip variety ‘Dow Jones’, which depended upon comparisons of different pre-treatments of leaves, osmotic pressures, and enzymatic hydrolysis durations. The results showed that the most suitable material for protoplast extraction was 3-week-old leaves. The middle part of each leaf was cut into 1.0 cm×2.0 cm pieces and then the upper and lower epidermis of the leaf pieces were peeled off. The enzymatic mixture was composed of 1.5% cellulase R-10, 0.75% macerozyme R-10, 10 mmol/L 2-morpholinoethanesulphonic acid (pH=5.7), 0.4 mol/L D-mannitol, 20 mmol/L KCl, 10 mmol/L CaCl₂, 0.1% bovine serum albumin and 1.5 mmol/L β-mercaptoethanol. The optimal enzymatic hydrolysis duration was 6 h. Under the optimal extraction conditions, there ware certain differences in protoplast yield among different varieties. The protoplast yield of ‘Dow Jones’ was greater than that of ‘Verandi’ and ‘World’s Favorite’, with 8.05×10⁵ protoplasts per gram of fresh leaves. The p35S::GFP vector was transfected into ‘Dow Jones’ protoplasts using PEG-Ca^2＋ mediated transient transformation, and the expression of green fluorescent protein was observed using confocal laser scanning microscope, with a transformation efficiency of 33.2%. This study provides new technical support for the functional research on tulip genes and the cultivation of new varieties.

In this study, we explored the construction of a homologous gene silencing system for Lycoris insularis, which is a rich wild resource in Zhejiang Province with bulbs as explants, and through this system, the biological functions of Lycoris insularis bulb genes were verified. The 1 706 bp fragment of LiCWIN gene was cloned from the bulb by using specifically designed primers. After double enzyme digestion, the virus-induced gene silencing (VIGS) recombinant vector was constructed by connection with tobacco rattle virus (TRV) vector TRV2-GFP. After the transformation of Agrobacterium tumefaciens, the damaged and stimulated bulbs were infected with the bacterial solution. After 2 d of infection, the green fluorescence was observed in the vascular tissues of bulbs, and the expression level of LiCWIN gene was significantly decreased in the silenced group, as determined by real time fluorogenic quantitative polymerase chain reaction (qRT-PCR). After 40 d of infection, compared with the empty vector control group, the number of bulblets in LiCWIN gene silencing group decreased, and their formation was delayed. The above results showed that VIGS system successfully silenced functional genes in the bulbous tissues of Lycoris insularis and had a lasting effect on the later development of bulblets. After silencing of LiCWIN gene, the formation of bulblets was blocked. This study can lay a foundation for the study of key gene functions of Lycoris bulb formation and development.

MYC2 (myelocytomatosis protein 2) transcription factor is a member of the basic helix-loop-helix (bHLH) transcription factor family and is a key regulator of the jasmonate signaling pathway, which is involved in plant growth, development, and defense processes. In this study, the LlMYC2 gene of Lilium lancifolium was cloned, and the function and expression of this gene were analyzed to preliminarily explore the mechanism by which the LlMYC2 gene regulates the expansion ofthe microbulbs (bulblets and bulbils) in Lilium lancifolium. The results showed that the LlMYC2 gene is 2 148 bp in length, encodes 715 amino acids, has a molecular mass of 77.745 kDa, contains a typical MYC domain, and lacks the transmembrane domain. Phylogenetic tree analysis revealed that the LlMYC2 protein was the most closely related to the MYC2 proteins of Lilium regale and Lilium hybrid division Ⅶ. Subcellular localization results showed that LlMYC2 was a nucleus localized protein. Real time fluorogenic quantitative polymerase chain reaction (qRT-PCR) results showed that LlMYC2 was expressed in different tissues of Lilium lancifolium, with the highest expression level in the leaves, followed by the ovary, mature bulbils and mature bulblets. The expression level of LlMYC2 showed two distinct upregulation trends in the growth and development of microbulbs. Gene function verification results showed that after silencing LlMYC2 in Lilium lancifolium microbulbs, the expansion of bulblets and bulbils was inhibited. Treatment of mature bulbils with methyl jasmonate (MeJA) and its biosynthesis inhibitor salicylic acid hydroxamic acid (SHAM) affected the expression of LlMYC2. In summary, LlMYC2 is involved in the development of Lilium lancifolium microbulbs and the expansion of Lilium lancifolium microbulbs.

The dihydroflavonol 4-reductase (DFR) gene plays a crucial role in the formation of flower color. In this study, two DFR genes were isolated from Tulipa gesneriana ‘Strong Fire’. Sequence analysis showed that TgDFR1 and TgDFR2 encode putative proteins of 365 and 422 amino acids, respectively. The expression levels of these genes at different developmental stages of the flower were examined, revealing that TgDFR1 and TgDFR2 were significantly upregulated at the second stage of flower development (coloring). While the expression level of TgDFR1 declined at the third (early flowering) and fourth (full flowering) stages, TgDFR2 maintained high expression levels, showing a positive correlation with the accumulation of anthocyanins. Overexpression of TgDFR1 and TgDFR2 in tobacco showed that the expression levels of TgDFR1 and TgDFR2 and anthocyanin content were significantly increased in transgenic lines. Further analysis of the expression of the flower color related genes indicated significant upregulation of NtDFR and significant downregulation of genes encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavonol synthase (FLS)andflavanone 3-hydroxylase (F3H)in transgenic tobacco plants compared with the empty vector control plants. In summary, TgDFR1 and TgDFR2 play key roles in the accumulation of anthocyanins in tulips.

This study primarily utilized stem segments of two wild species of Paeonia anomala and Paeonia intermedia as experimental materials. Plant growth regulators such as 6-benzylaminopurine (6-BA), naphthalene acetic acid (NAA), thidiazuron (TDZ), and 2, 4-dichlorophenoxyacetic acid (2, 4-D) were added to 1/2 MS (Murashige & Skoog ) media to investigate the main factors affecting the induction and proliferation of callus of stem segments in peony. The results showed that there were differences in the induction effects of callus between different peony species, with Paeonia anomala exhibiting the most significant induction effect and the highest induction rate of callus. The optimum media for callus induction were 1/2 MS＋6-BA 1.0 mg/L＋NAA 0.5 mg/L for Paeonia anomala and 1/2 MS＋TDZ 0.5 mg/L＋2, 4-D 0.5 mg/L for Paeonia intermedia. The optimum media for callus proliferation were 1/2 MS＋2, 4-D 0.5 mg/L＋NAA 0.2 mg/L^{for Paeonia anomala and 1/2 MS＋TDZ 1.0 mg/L＋2, 4-D 0.5 mg/L＋NAA 0.2 mg/L for Paeonia intermedia. This study not only provides a theoretical reference for future research, but also offers possibilities for finding new pathways for the propagation and conservation of wild peony.}

Receptacle browning issues arise during the storage and transportation of cut chrysanthemums, leading to a decline in both ornamental and commercial values. Given the recurring nature of this issue in batches, it is hypothesized to be caused by pathogenic bacteria infection. To investigate the causes of this problem and find solutions, we analyzed the receptacle browning phenotype in ‘Jinshan’ summer chrysanthemums, isolated and identified the pathogenic bacteria following Koch’s postulates, determined the species through whole-genome sequencing analysis, screened high-efficiency inhibitors through agar plate inhibition assays, and validated their efficacy using cut chrysanthemum treatment experiments. The results indicated that receptacle browning led to an annual loss of approximately 10% in summer chrysanthemum production. The identified pathogenic bacterium was Bacillus altitudinis, which optimally grew at pH=7.0 and 42 ℃. Among the 15 commonly used ecofriendly and low-toxicity antibacterial agents evaluated, 80% ethylicin emerged as the most effective, with a 1 000-time dilution significantly inhibiting receptacle browning in two other chrysanthemum cultivars. In conclusion, this study successfully isolates and identifies the pathogenic bacteria responsible for receptacle browning in cut chrysanthemums, and screens ecofriendly, low-toxicity, and high-efficiency antibacterial agents, thereby providing a theoretical basis and technical support for addressing receptacle browning issues in cut chrysanthemums.

Paenonia lactiflora Pall. is a renowned traditional Chinese flower, and it is of great significance to study its cold tolerance mechanism for breeding new varieties and expanding its popularization. In this study, we compared ‘Hang Baishao’, a low-altitude southern variety with concentrated industrial cultivation, with ‘Hongling Chijin’, a northern variety with superior performance in Harbin, both of which are grown in open fields of Harbin during the winter. We investigated the physiological and molecular responses of their rhizomes to cold stress under freezing conditions through physiological observations, transcriptome sequencing, and gene expression analysis. The results showed that as winter temperature decreased, the levels of soluble sugars, abscisic acid, auxins, and cytokinins in ‘Hongling Chijin’ increased more markedly than those in ‘Hang Baishao’, while gibberellin levels decreased. The omics analysis showed that genes related to starch and sucrose metabolism, plant-pathogen interaction, and hormone signaling were significantly differentially expressed between two varieties. Co-expression analysis showed that, genes such as dehydration-responsive element-binding protein 2A gene (DREB2A),cysteine-rich receptor-like kinase 8 gene (CRK8),and heat shock protein 90.1 gene (HSP90.1) may regulate herbaceous peony’s cold stress response. This study can preliminarily reveal the key genes of herbaceous peony’s response to cold stress in extremely cold weather, lay a foundation for the subsequent study of gene function and gene interaction, and contribute to the cultivation of new varieties of herbaceous peony that can be widely cultivated and bred at China’s highest latitudes.

In order to investigate the physiological changes of double petaled Echinacea purpurea (L.) Moench under different soil moisture contents and the suitable soil moisture content for medicinal cultivation, the water-controlled pot experiment method was used, and five soil moisture treatments including a control group [(70±5)% of saturated water content], mild drought [(55±5)% of saturated water content], severe drought [(40±5)% of saturated water content], mild waterlogging [(85±5)% of saturated water content], and waterlogging (continuous soaking of pots) were set up in this study. The growth, physiology, and chicory acid content changes of Echinacea purpurea under different water conditions were compared. The results showed that water stress could inhibit the growth of Echinacea purpurea, leading to significant decreases in plant height, crown width, relative water content of leaves, and accumulation of photosynthetic pigments. Although 30 d of waterlogging stress caused severe plant damage, it did not lead to death. Under severe drought and waterlogging treatment, Echinacea purpurea could increase the activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and contents of osmoregulatory substances (soluble sugar, soluble protein, and proline) in leaves to reduce water stress damage. Although water stress inhibited the growth of Echinacea purpurea, it increased the accumulation of chicory acid in the leaves. On the 30th day of water stress, the content of chicory acid in leaves under severe drought and waterlogging treatments was 1.389 and 1.650 times of the control, respectively. Correlation analysis showed that the content of chicory acid was significantly positively correlated with physiological indicators related to multiple stress responses, such as peroxidase activity, and proline and malondialdehyde contents, indicating that the accumulation of chicory acid was related to stress resistance. In summary, double petaled Echinacea purpurea has strong drought and waterlogging resistance. In the medicinal cultivation, the content of chicory acid in leaves could be increased through short-term water stress, with severe drought being the best. This study can provide a theoretical basis for the standardized cultivation of double petaled Echinacea purpurea for medicinal and ornamental purposes, as well as for improving the content of chicory acid in leaves through water control methods.