This study was designed to investigate the effects of exogenous calcium on the tolerance of Rosa hybrida ‘Carolla’ to high-temperature and the physiological mechanisms underlying this response. Leaves of ‘Carolla’ grown under stress were treated by spraying four different concentrations of calcium chloride (CaCl2; 50, 100, 150, or 200 μM). The photosynthetic responses, antioxidant enzyme activities, and osmotic substance contents were measured under high-temperature stress at the flowering stage. Temperature-stressed ‘Carolla’ with CaCl2 treatment showed significantly increased chlorophyll (Chl) content, net photosynthetic rate (An), transpiration rate (E), stomatal conductance (gs), water use efficiency (WUE), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) activities together with proline (Pro), soluble sugar (SS), and soluble protein (SP) concentrations, while malonaldehyde (MDA) content and relative electrical conductivity (REC) were significantly reduced. The damages caused by high-temperature stress were alleviated by applying CaCl2. Among the CaCl2 treatments, 100 μM CaCl2 best minimized the damage caused by high-temperature to ‘Carolla’. This study showed that exogenous calcium could improve the tolerance of Rosa hybrida ‘Carolla’ to high-temperature stress by regulating photosynthesis, the antioxidant system, and osmotic substances.
The study of the regulatory mechanism of exogenous plant growth regulators (PGRs) on the relevant physiological indicators is essential to maintain the normal growth of Rosa hybrida under high-temperature conditions. The photosynthetic and physiological characteristics of the ornamental cut rose Rosa hybrida ‘Carolla’ under high temperature were studied by spraying leaves with various concentrations of exogenous salicylic acid (SA; 0.5, 1.0, 1.5, or 2.0 mmol·L−1), 6-benzylaminopurine (6-BA; 10, 20, 30, or 50 μmol·L−1), abscisic acid (ABA; 10, 20, 30, or 50 mg·L−1), or distilled water (control). The results indicated that a foliar spray of either SA, 6-BA, or ABA could mitigate the impact of high temperatures. Compared to the control, the application of SA, 6-BA, or ABA increased the net CO2 assimilation rate (An), transpiration rate (E), stomatal conductance (Gs), and water use efficiency (WUE) of ‘Carolla’, while decreasing the leaf relative electrical conductivity (REC) and malondialdehyde (MDA) content. The applications of SA, 6-BA, or ABA increased the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) and altered the proline (Pro), soluble protein, and soluble sugar contents. The results showed that foliar sprays of SA, 6-BA, or ABA could enhance the heat tolerance of ‘Carolla’ by promoting photosynthesis, cell membrane structural stability, antioxidant enzyme activity, and osmoregulation in plants under high-temperature stress. The experiment showed that 1.5 mmol·L−1 SA, 20 μmol·L−1 6-BA, or 20 mg·L−1 ABA could alleviate the damage caused by high temperatures, with 20 μmol·L−1 6-BA having the best effect.
Spathiphyllum floribundum is an important indoor flower species. Thus, optimizing its growth by regulating the light quality under indoor low-light conditions may be critical for generating high-quality flowers. In this study, the effects of the following six light-quality treatments on peroxidase and superoxide dismutase activities in two S. floribundum cultivars (‘Sweet Chico’ and ‘Queen’) were analyzed: monochromatic light comprising 100% red (R, 657 nm) or 100% blue (B, 450 nm) light, a combination of R and B lights [80% R + 20% B (8:2), 70% R + 30% B (7:3), and 60% R + 40% B (6:4)], and white light. The light treatments were performed using light-emitting diodes. The light intensity and photoperiod were set to 45±2 µmol·m-2·s-1 and 14 h·d-1, respectively. The results of this study revealed that an appropriate R:B light ratio may lead to increased pigment contents, thereby increasing the synthesis and accumulation of photosynthetic products, which will result in increased stress resistance and enhanced growth. These findings provide the basis for future investigations on the growth and production of S. floribundum and other indoor ornamental plants.
Tree peony (Paeonia ostii) is an ornamental flowering plant that is generally recalcitrant to establishment of a mature somatic embryo regeneration system in vitro. Glucose-6-phosphate translocator (GPT) plays an important regulatory role in embryogenesis of plants. In this study, PoGPT1 was cloned, and a bioinformatic analysis and functional verification of the gene were performed. The results showed that PoGPT1 encoded a polypeptide of 392 amino acids, which was a basic non-secreted hydrophobic transmembrane protein, and was mainly localized in the plastids. PoGPT1 was highly expressed in tree peony leaves, and its transcript abundance increased with the progression of zygotic embryo development. Overexpression of PoGPT1 caused up-regulation of leafy cotyledon 1 (PoLEC1), somatic embryogenesis receptor-like kinase (PoSERK), and agamous-like15 (PoAGL15) in tree peony callus. In addition, PoGPT1 overexpression promoted the increase in indole-3-acetic acid (IAA), 5-deoxystrigol (5DS), and brassinolide (BL) contents, especially of IAA, but reduced the contents of abscisic acid (ABA), 6-benzyladenosine (BARP), and 1-aminocyclopropanecarboxylic acid (ACC). The present research showed that PoGPT1 synergistically regulated the contents of endogenous hormones and expression levels of embryogenesis-related genes to promote the embryonic development of tree peony. The results provide theoretical and technical support for the establishment of a tree peony embryogenic callus formation and subsequent research on somatic embryogenesis.
Relatively poor in vitro rooting has limited the large-scale commercial production of tree peony. In this study, on the basis of transcriptome sequencing, differentially expressed genes and the associated metabolic pathways were identified in tree peony roots at different stages of root formation under sandy loam cultivation. A total of 31.63 Gb raw data were generated and 120,188 unigenes (mean length of 911.98 bp) were annotated according to six databases (NR, NT, GO, KEGG, COG, and Swiss-Prot). Analyses of the ungerminated root primordium period, induced root primordium period, and root formation period detected 8,232, 6,907, and 10,687 differentially expressed genes related to 133, 132, and 133 metabolic pathways, respectively. Two significantly differentially expressed genes (Unigene13430_All and CL10096.Contig1_All) were associated with the auxin pathway. The full-length Unigene13430_All coding sequence (843 bp) encoded 280 amino acids, whereas the full-length CL10096.Contig1_All coding sequence (1,470 bp) encoded 489 amino acids. Unigene13430_All and CL10096.Con-tig1_All were identified as IAA gene family members and were respectively named PsIAA27 and PsARF19. The qRT-PCR analysis and functional verification indicated that the expressions of PsARF19 and PsIAA27 in tree peony seedlings, cuttings and grafted seedlings were significant different. PsARF19 promoted root development, it might be a regulatory gene related to the formation of tree peony roots, while PsIAA27 inhibited lateral root development, and it might be involved in controlling auxin sensitivity during root formation. The results of this study may form the basis of future investigations on the mechanism mediating peony root formation. The transcriptome data will be an excellent resource for researchers interested in characterizing the rooting-related tree peony genes.
The adventitious rooting−related oxygenase (ARRO−1) gene is specifically expressed in the early rooting stage and is considered a molecular marker of rooting. In this study, a PsARRO−1 gene (GenBank accession number KJ620008) was identified from a pre−constructed transcriptome database of root development of Paeonia suffruticosa under sandy loam cultivation. The expression was verified by RT−qPCR, and it was found that the expression trend was consistent with the expression in the transcriptome database. The PsARRO−1 gene was specifically highly expressed during the root primordium germination phase. In addition, the RT−qPCR analysis indicated that the expression of PsARRO−1 in roots was significantly higher than in stems and leaves, its peak expression in vitro was 5 days earlier than in soil, and its expression was higher than that of tree peony in soil. Subcellular localization analysis showed that PsARRO−1 was localized in the plasma membrane. Moreover, the transient silent expression of the PsARRO−1 gene was found in the roots of peony seedlings grown using VIGS technology. The root activity was significantly reduced after transient silencing of the expression of the PsARRO−1 gene. These results indicate that PsARRO−1 has a positive regulatory effect on tree peony root development.
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