Vase life consequences of natural and chemical treatments in foxtail lily (Eremurus spectabilis), as a specialty cut flowers

Eremurus spectabilis is a new, commercially valuable specialty cut flower, but little is known about the applicable treatments to extend the vase-life and maintaining the ornamental quality of this flower. Therefore, the present study was aimed at investigating the impacts of nano-silver, essential oils, and chemical treatments on keeping ornamental quality and vase-life of cut inflorescences of Foxtail lily. The cut inflorescences were placed in different vase solutions containing salicylic acid (100 and 200 mg L-1), methyl jasmonate (25 and 50 mg L-1), silver thiosulfate (0.1 mM) plus isothiazolinone (0.001 and 0.005 mL L-1), nano-silver (5, 10, and 15 mg L-1), thymol (75 and 120 mg L-1), and menthol (75 and 120 mg L-1), which were applied as continuous and pulsing methods. According to the results, all treatments considerably improved the post-harvest performance of Foxtail lily cut flowers. Although there were no significant differences among nano-silver (NS) treatments, the cut inflorescences kept in vase solution containing 10 mg L-1 of NS exhibited the longest vase life (~14 days) and the best ornamental quality. Nano-silver treatment followed by silver-thiosulfate significantly improved solution uptake by flowering inflorescences, thereby delaying the water balance loss and keeping relative fresh weight. Furthermore, 50 mg L-1 methyl jasmonate- and 75 mg L-1 menthol-treated cut inflorescences exhibited significantly higher vase-life longevity by ~ 6 and 4 days, total soluble solutes by 28.38% and 19.12%, and solution uptake rate by 76.46% and 140.6%, respectively, as compared to control. Overall, 10 mg L-1 NS can be recommended as a commercial preservative solution to delay flower senescence and improve the vase life and keeping the quality of foxtail cut inflorescence.

Expression of Ethylene Biosynthetic Genes in the Gynoecium and Receptacle Associated With Sepal Abscission During Senescence in Delphinium Grandiflorum

Delphinium flowers are highly sensitive to ethylene and its sepals abscise during senescence, which is associated with increases in 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) and ACC oxidase (ACO) activities and ethylene production in gynoecium and receptacle. Three ACS genes (DgACS1, DgACS2, and DgACS3) and three ACO genes (DgACO1, DgACO2, and DgACO3) were cloned from Delphinium grandiflorum cv. Super Grand Blue. To investigate the contribution of these genes to ethylene production, their expression was analyzed in these genes in the gynoecium and receptacle during natural senescence and following ethylene exposure and pollination. Ethylene production in the gynoecium and receptacle increased during natural flower senescence. The transcript levels of the ACS and ACO genes in these organs, excluding DgACS2 in the receptacle, increased during senescence. Exposure to ethylene accelerated sepal abscission and more strongly increased ethylene production in the receptacle than in the gynoecium. DgACS1 transcript levels in the gynoecium and DgACS2 and DgACO3 transcript levels in the receptacle were increased by ethylene exposure. Pollination accelerated sepal abscission and increased ethylene production in the gynoecium and receptacle. Pollination slightly affected ACS and ACO transcript levels in the gynoecium, whereas DgACO3 transcript level in the receptacle were markedly increased. These results reveal that ACS and ACO gene expression is differently regulated in the gynoecium and receptacle, and some of these genes are more strongly upregulated by ethylene exposure and pollination in the receptacle than in the gynoecium, suggesting the significance of the receptacle to sepal abscission.

Polyamines accentuate vase life by augmenting antioxidant system in cut spikes of Consolida ajacis (L.) Schur.

Postharvest senescence is one of the crucial challenges limiting the marketability of cut flowers. Pertinently, recent investigations implicate extensive role of polyamines in regulation of flower senescence. The present study was envisaged to test the efficacy of poylamines in preserving the postharvest quality of Consolida ajacis (C. ajacis) cut spikes. The cut spikes of C. ajacis were subjected to various treatments of polyamines viz, 4 mM Spermine (SPM), 6mM Putrescine (PUT) and 6 mM Spermidine (SPD). A separate set of spikes held in distilled water represented the control. Our results authenticate a significant improvement in vase life of cut spikes of C. ajacis as compared to control. The increment in vase life was commensurate with the higher concentration of sugars, proteins and phenols in the tepal tissues. Polyamines amplified the activity of various antioxidant enzymes viz, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) to overcome the deleterious effects of reactive oxygen species (ROS). The membrane outflow of tepal tissues was profoundly reduced due to attenuated lipoxygenase (LOX) activity. These findings reveal conspicuous role of polyamines particularly SPM in modulation of flower senescence in cut spikes of C. ajacis.

Boric acid as a potential substitute for conventional ethylene antagonists in mitigating postharvest flower senescence of Digitalis purpurea

In the floriculture industry, postharvest senescence is one of the glaring challenges restricting the marketability of cut flowers. Hence, maintaining good quality of cut flowers and extending flower longevity are considered to be the most crucial factors in the cut flower trade. Therefore, to gain better understanding of the specific physiological and biochemical aspects of petal senescence we conducted an experiment to evaluate the efficacy of Boric acid (BA) on flower longevity in excised flowers of Digitalis purpurea L. Isolated buds were harvested at stage IV i.e, 1 day before anthesis and divided into 5 sets, with one set of buds held in distilled water (DW) designated as control. The other 4 sets were supplemented with 24h pulse treatment of different concentrations of BA viz., 50, 100, 150 and 200 µM. The application of BA at 150 µM concentration was found to be most effective in increasing flower longevity by about 4 days as compared to control. The enhanced longevity coincided with higher values of floral diameter, fresh mass, dry mass and solution uptake. Flowers with delayed senescence also retained higher soluble proteins, sugars and phenols in addition to lower bacterial density compared to control. Moreover, this ameliorated flower longevity has also been shown to be positively associated with increased activities of various antioxidant enzymes viz., superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) and reduced activity of lipoxygenase (LOX).

Study of Cananga odorata (Lam.) Hook. f. & Thoms. Flower Development: Morphological Variations in an Urban Environment

Cananga odorata is a native plant in the Indonesian archipelago. The flowers are often used to produce essential oils with many uses and a distinct fragrance. This study aims to observe each stage of the Cananga odorata flower development. The flowers were obtained from a home garden in Pasar Minggu, South Jakarta, from November 2020 until January 2021. Further observations of the stamen and pistil developments were conducted using Dino-Lite Edge Digital Microscope AM4115 Series. The results show that Cananga odorata flower development can be categorized into bud, display-petal, initial-flowering, full-flowering, end-flowering, and senescence stages. The flowers require 35 days to develop from bud stage to flower senescence. Stamens and pistils also develop primarily during the bud stages and mature after flower anthesis. Flower mutants were also found and may be caused by a mutation in the flower’s homeotic genes. Each different stages of flower development show a different morphological change in the flower perianth and reproductive organs. A discrepancy of flower morphology within each stage, especially those seen during the anthesis stages, might imply a variation in the flower’s internal factors.

Transcriptome analysis of Rafflesia cantleyi flower stages reveals insights into the regulation of senescence

Rafflesia is a unique plant species existing as a single flower and produces the largest flower in the world. While Rafflesia buds take up to 21 months to develop, its flowers bloom and wither within about a week. In this study, transcriptome analysis was carried out to shed light on the molecular mechanism of senescence in Rafflesia. A total of 53.3 million high quality reads were obtained from two Rafflesia cantleyi flower developmental stages and assembled to generate 64,152 unigenes. Analysis of this dataset showed that 5,166 unigenes were differentially expressed, in which 1,073 unigenes were identified as genes involved in flower senescence. Results revealed that as the flowers progress to senescence, more genes related to flower senescence were significantly over-represented compared to those related to plant growth and development. Senescence of the R. cantleyi flower activates senescence-associated genes in the transcription activity (members of the transcription factor families MYB, bHLH, NAC, and WRKY), nutrient remobilization (autophagy-related protein and transporter genes), and redox regulation (CATALASE). Most of the senescence-related genes were found to be differentially regulated, perhaps for the fine-tuning of various responses in the senescing R. cantleyi flower. Additionally, pathway analysis showed the activation of genes such as ETHYLENE RECEPTOR, ETHYLENE-INSENSITIVE 2, ETHYLENE-INSENSITIVE 3, and ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR, indicating the possible involvement of the ethylene hormone response pathway in the regulation of R. cantleyi senescence. Our results provide a model of the molecular mechanism underlying R. cantleyi flower senescence, and contribute essential information towards further understanding the biology of the Rafflesiaceae family.

Genome and transcriptome-based characterization of high energy carbon-ion beam irradiation induced delayed flower senescence mutant in Lotus japonicus

Background Flower longevity is closely related to pollen dispersal and reproductive success in all plants, as well as the commercial value of ornamental plants. Mutants that display variation in flower longevity are useful tools for understanding the mechanisms underlying this trait. Heavy-ion beam irradiation has great potential to improve flower shapes and colors; however, few studies are available on the mutation of flower senescence in leguminous plants. Results A mutant (C416) exhibiting blossom duration eight times longer than that of the wild type (WT) was isolated in Lotus japonicus derived from carbon ion beam irradiation. Genetic assays supported that the delayed flower senescence of C416 was a dominant trait controlled by a single gene, which was located between 4,616,611 Mb and 5,331,876 Mb on chromosome III. By using a sorting strategy of multi-sample parallel genome sequencing, candidate genes were narrowed to the gene CUFF.40834, which exhibited high identity to ethylene receptor 1 in other model plants. A physiological assay demonstrated that C416 was insensitive to ethylene precursor. Furthermore, the dynamic changes of phytohormone regulatory network in petals at different developmental stages was compared by using RNA-seq. In brief, the ethylene, jasmonic acid (JA), and salicylic acid (SA) signaling pathways were negatively regulated in C416, whereas the brassinosteroid (BR) and cytokinin signaling pathways were positively regulated, and auxin exhibited dual effects on flower senescence in Lotus japonicus. The abscisic acid (ABA) signaling pathway is positively regulated in C416. Conclusion So far, C416 might be the first reported mutant carrying a mutation in an endogenous ethylene-related gene in Lotus japonicus, rather than through the introduction of exogenous genes by transgenic techniques. A schematic of the flower senescence of Lotus japonicus from the perspective of the phytohormone regulatory network was provided based on transcriptome profiling of petals at different developmental stages. This study is informative for elucidating the molecular mechanism of delayed flower senescence in C416, and lays a foundation for candidate flower senescence gene identification in Lotus japonicus. It also provides another perspective for the improvement of flower longevity in legume plants by heavy-ion beam.

Phosphoproteome analysis reveals the involvement of protein dephosphorylation in ethylene-induced corolla senescence in petunia

Background Senescence represents the last stage of flower development. Phosphorylation is the key posttranslational modification that regulates protein functions, and kinases may be more required than phosphatases during plant growth and development. However, little is known about global phosphorylation changes during flower senescence. Results In this work, we quantitatively investigated the petunia phosphoproteome following ethylene or air treatment. In total, 2170 phosphosites in 1184 protein groups were identified, among which 2059 sites in 1124 proteins were quantified. To our surprise, treatment with ethylene resulted in 697 downregulated and only 117 upregulated phosphosites using a 1.5-fold threshold (FDR < 0.05), which showed that ethylene negatively regulates global phosphorylation levels and that phosphorylation of many proteins was not necessary during flower senescence. Phosphoproteome analysis showed that ethylene regulates ethylene and ABA signalling transduction pathways via phosphorylation levels. One of the major targets of ethylene-induced dephosphorylation is the plant mRNA splicing machinery, and ethylene treatment increases the number of alternative splicing events of precursor RNAs in petunia corollas. Conclusions Protein dephosphorylation could play an important role in ethylene-induced senescence, and ethylene treatment increased the number of AS precursor RNAs in petunia corollas.

A MYB transcription factor, PlMYB308, plays an essential role in flower senescence of herbaceous peony

Herbaceous peony is an important cut-flower plant cultivated across the world, but its short vase life substantially restricts the economic value of this crop. It is well established that endogenous hormones regulate the senescing process, but the molecular mechanism of them in flower senescence is still unclear. Here, we isolated a MYB transcription factor gene PlMYB308 from herbaceous peony flowers. Transcript abundance of PlMYB308 was strongly up-regulated in senescing petals. Silencing of PlMYB308 resulted in delayed peony flower senescence, and dramatically increased gibberellin (GA) but reduced ethylene and abscisic acid (ABA) levels in petals. Ectopic overexpression of PlMYB308 in tobacco accelerated flower senescence, and reduced GA but increased ethylene and ABA accumulation. Correspondingly, biosynthetic genes of ethylene, ABA, and GA showed variable expression levels in petals after silencing or overexpression of PlMYB308. A dual-luciferase assay showed that PlMYB308 specifically bound to the PlACO1 promoter. High expression levels of PlMYB308 were accompanied by low petal anthocyanin accumulation in senescing petals. A further bimolecular fluorescence complementation assay revealed an interaction between PlMYB308 and PlbHLH33, which was supposed to inhibit the anthocyanin biosynthesis. Taken together, our results suggest that the PlMYB308-PlACO1 and PlMYB308-PlbHLH33 regulatory checkpoints perhaps positively and negatively operate the production of ethylene and anthocyanin, respectively, and thus contribute to the senescence with impaired pigmentation in herbaceous peony flowers.