Flower Senescence Research Articles

Postharvest transient water deficit limits longevity of cut Dendrobium ‘Khao Sanan’ orchid

A negative water imbalance due to a temporary water deficit (WD) after harvest can stimulate early flower senescence and reduce flower quality and vase life of orchids. To clarify the physiological responses of cut Dendrobium ‘Khao Sanan’ inflorescences under WD stress and early responses during water recovery, relative water content (RWC), water potential, reactive oxygen species (ROS), ethylene production, lipid peroxidation, antioxidant enzymes, and osmolyte were determined. The inflorescences were exposed to WD for 0, 24, 48, and 72 h after harvest, then placed in water for recovery and vase life determination. The results showed that WD significantly reduced RWC in petals, and over 24 h of WD adversely affected postharvest quality including vase life of cut inflorescences by increasing flower abscission, flower bud opening, and decreasing flower quality score. Moreover, ethylene production was induced early by 72 h of WD. Exposure of cut flowers to WD also increased hydrogen peroxide (H2O2) content, malondialdehyde (MDA) content, proline content, and lipoxygenase (LOX) activity. Additionally, ascorbate peroxidase (APX) and catalase (CAT) activities fluctuated with durations of dry and recovery periods. After rewatering, RWC, water potential, MDA content, and LOX activity of all WD periods recovered at non-WD control levels while H2O2 and proline content remained higher than control. On the other hand, ethylene production of the inflorescences exposed to WD over 24 h remarkably increased after rewatering. Our findings suggested that Dendrobium ‘Khao Sanan’ could tolerate transient WD up to 24 h with negligible reduction in longevity, probably corresponding to the lowest ethylene production during the WD period and the accumulation of antioxidant enzymes and osmolytes.

Assessing the efficacy of Thidiazuron, 6- Benzylamino purine and Kinetin in modulating flower senescence in cut spikes of Consolida ajacis (L.) Schur.

The current study assesses the efficacy of thidiazuron and cytokinins (6- benzylamino purine and kinetin) in modulating flower senescence in excised spikes of Consolida ajacis. The spikes harvested at commercial maturity were transported to laboratory and arranged into multiple sets. Each set of spikes was subjected to different treatments of thidiazuron (TDZ), benzylamino purine (BAP) and kinetin (KIN) viz., 25 µM, 50 µM, 75 µM and 100 µM. One set of spikes designated as control was kept in distilled water. Inclusion of these growth regulators significantly improved the postharvest longevity of C. ajacis cut spikes. The enhancement in display life was proportionate with upsurge in the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT). Flowers held in different test solutions of BAP, KIN and TDZ, exhibited higher values of sugars, phenols and proteins. Furthermore, these growth regulators minimized membrane leakiness by reducing lipoxygenase activity (LOX) and improved membrane stability. Among the various growth regulators tested, 50 µM TDZ was found to be highly efficacious in mitigating flower senescence in C. ajacis cut spikes as compared to KIN and BAP.

PlZFP mediates the combinatorial interactions of abscisic acid with gibberellin and ethylene during flower senescence in cut herbaceous peony

Short vase life is a main factor that limits herbaceous peony’s economic value. We found that in cut herbaceous peony, flower senescence was regulated by the combinatorial interactions among plant endogenous hormones. However, the molecular mechanisms underlying these interactive effects are not well understood. In this study, we describe the identification of PlZFP, which influences flower senescence in herbaceous peony. PlZFP was upregulated during herbaceous peony flower senescence and its expression level was influenced by abscisic acid (ABA), ethylene and gibberellin (GA). PlZFP-silenced petal discs had longer lives while PlZFP-overexpressing transgenic tobacco had short flower longevity. Silencing PlZFP in petal discs reduced the transcript abundances of the endogenous hormone biosynthesis-related genes PlACO1, PlACO3, PlACS1, PlNCED2, and PlAAO and increased the transcript abundance of PlGA3ox1. Overexpression of PlZFP in tobacco flowers showed the opposite influences on these genes. Furthermore, PlZFP directly bound to the PlNCED2 promoter, and silencing PlNCED2 delayed senescence in discs. Silencing of PlZFP reduced ethylene production and ABA levels while increased GA levels in peony petal discs. Moreover, exogenous ABA, ethephon and paclobutrazol (PAC, a GA inhibitor), accelerate senescence in PlZFP-silenced discs. Taken together, the PlZFP-PlNCED2 regulatory checkpoint may positively affect the production of ABA and mediates the combinatorial interactions of ABA with GA and ethylene during flower senescence in cut herbaceous peony.

Involvement of a novel NAP member LbNAP in flower senescence and dehydration stress in cut lily

In Arabidopsis thaliana, NAC-like and activated by AP3/PI (NAP) are NAC transcription factors that regulate leaf senescence and environment stress. Gene LbNAP, which has a typical NAC region, was cloned from lily petals. Our results indicated that LbNAP was located in the nucleus, and the gene had transcriptional activation activity. Further studies on LbNAP expression showed that it was lowest in green buds and highest in aging petals during bud development. Silencing of LbNAP in buds using virus-induced gene silencing resulted in a delayed senescence phenotype and less dehydration stress injury, which were related to the increase in catalase and superoxide dismutase activities and expression of their genes. Over-expression of LbNAP in A. thaliana (OE-LbNAP) resulted in slow root growth and decreased fresh weight. When treated with 250 mM mannitol, root length and fresh weight of transgenic seedlings were significantly lower than those of wild type. In addition, flowers of OE-LbNAP showed earlier senescence and weaker dehydration tolerance; when OE-LbNAP plants were subjected to 7 days of drought stress, their survival rate was significantly lower than that of the wild type. These results suggest that LbNAP was positively involved in age-induced flower senescence and dehydration stress.

Identification and Characterization of Circular RNAs Involved in the Flower Development and Senescence of Rhododendron delavayi Franch

Floral development and senescence are a crucial determinant for economic and ornamental value. CircRNAs play an essential role in regulating plant growth and development; however, there is no systematic identification of circRNAs during the lifespan of flowers. This study aims to explore the expression profile and functional role of circRNAs in the full flowering stages of Rhododendron delavayi Franch. We carried out transcriptome sequencing of the six stages of Rhododendron delavayi Franch flowers to identify the circular RNA expression profile. In addition, using bioinformatics methods, we explored the functions of circRNAs, including analysis of the circRNA-miRNA-mRNA network, short time-series expression miner (STEM), and so on. We identified 146 circRNAs, of which 79 were differentially expressed from the budding to fading stages. Furthermore, using STEM analysis, one of the 42 circRNA expression model profiles was significantly upregulated during the senescence stage, including 16 circRNAs. Additionally, 7 circRNA-miRNA-mRNA networks were constructed with 10 differentially expressed circRNAs, in which some target mRNA may regulate the development and senescence of the Rhododendron flowers. Finally, by analyzing the correlation between circRNAs and mRNA, combined with existing reports, we proposed that circRNAs play a regulatory role during flower development and senescence by mediating the jasmonate signaling pathway. Overall, these results provide new clues to the potential mechanism of circRNAs acting as novel post-transcriptional regulators in the development and senescence process of flowers.

Regulation of floral senescence in Arabidopsis by coordinated action of CONSTANS and jasmonate signaling

In Arabidopsis, photoperiodic flowering is controlled by the regulatory hub gene CONSTANS (CO), whereas floral organ senescence is regulated by the jasmonates (JAs). Because these processes are chronologically ordered, it remains unknown whether there are common regulators of both processes. In this study, we discovered that CO protein accumulates in Arabidopsis flowers after floral induction, and it displays a diurnal pattern in floral organs different from that in the leaves. We observed that altered CO expression could affect flower senescence and abscission by interfering with JA response, as shown by petal-specific transcriptomic analysis as well as CO overexpression in JA synthesis and signaling mutants. We found that CO has a ZIM (ZINC-FINGER INFLORESCENCE MERISTEM) like domain that mediates its interaction with the JA response repressor JAZ3 (jasmonate ZIM-domain 3). Their interaction inhibits the repressor activity of JAZ3, resulting in activation of downstream transcription factors involved in promoting flower senescence. Furthermore, we showed that CO, JAZ3, and the E3 ubiquitin ligase COI1 (Coronatine Insensitive 1) could form a protein complex in planta, which promotes the degradation of both CO and JAZ3 in the presence of JAs. Taken together, our results indicate that CO, a key regulator of photoperiodic flowering, is also involved in promoting flower senescence and abscission by augmenting JA signaling and response. We propose that coordinated recruitment of photoperiodic and JA signaling pathways could be an efficient way for plants to chronologically order floral processes and ensure the success of offspring production.

Monitoring Growth Status of Winter Oilseed Rape by NDVI and NDYI Derived from UAV-Based Red–Green–Blue Imagery

The current study aimed to evaluate the potential of the normalized difference vegetation index (NDVI), and the normalized difference yellowness index (NDYI) derived from red–green–blue (RGB) imaging to monitor the growth status of winter oilseed rape from seeding to the ripening stage. Subsequently, collected values were used to evaluate their correlations with the yield of oilseed rape. Field trials with three seed densities and three nitrogen rates were conducted for two years in Salzdahlum, Germany. The images were rapidly taken by an unmanned aerial vehicle carrying a Micasense Altum multi-spectral camera at 25 m altitudes. The NDVI and NDYI values for each plot were calculated from the reflectance at RGB and near-infrared (NIR) bands’ wavelengths pictured in a reconstructed and segmented ortho-mosaic. The findings support the potential of phenotyping data derived from NDVI and NDYI time series for precise oilseed rape phenological monitoring with all growth stages, such as the seedling stage and crop growth before winter, the formation of side shoots and stem elongation after winter, the flowering stage, maturity, ripening, and senescence stages according to the crop calendar. However, in comparing the correlation results between NDVI and NDYI with the final yield, the NDVI values turn out to be more reliable than the NDYI for the real-time remote sensing monitoring of winter oilseed rape growth in the whole season in the study area. In contrast, the correlation between NDYI and the yield revealed that the NDYI value is more suitable for monitoring oilseed rape genotypes during flowering stages.

Abscisic acid: Metabolism, transport, crosstalk with other plant growth regulators, and its role in heavy metal stress mitigation.

Heavy metal (HM) stress is threatening agricultural crops, ecological systems, and human health worldwide. HM toxicity adversely affects plant growth, physiological processes, and crop productivity by disturbing cellular ionic balance, metabolic balance, cell membrane integrity, and protein and enzyme activities. Plants under HM stress intrinsically develop mechanisms to counter the adversities of HM but not prevent them. However, the exogenous application of abscisic acid (ABA) is a strategy for boosting the tolerance capacity of plants against HM toxicity by improving osmolyte accumulation and antioxidant machinery. ABA is an essential plant growth regulator that modulates various plant growth and metabolic processes, including seed development and germination, vegetative growth, stomatal regulation, flowering, and leaf senescence under diverse environmental conditions. This review summarizes ABA biosynthesis, signaling, transport, and catabolism in plant tissues and the adverse effects of HM stress on crop plants. Moreover, we describe the role of ABA in mitigating HM stress and elucidating the interplay of ABA with other plant growth regulators.

Protein Hydrolysates from Animal or Vegetal Sources Affect Morpho-Physiological Traits, Ornamental Quality, Mineral Composition, and Shelf-Life of Chrysanthemum in a Distinctive Manner.

Protein hydrolysates (PHs) are a prominent category of plant biostimulants, mainly constituted of amino acids, oligopeptides and polypeptides, obtained by partial hydrolysis of animal or plant protein sources. Despite scientific evidence supporting the biostimulant action of PHs on vegetables, the morphological, physiological, and shelf-life performances underlying the PH action on cut flowers are still poorly explored. Accordingly, the aim of this research is to assess the effects of three commercial biostimulants, one animal PH (PH A, Hicure®) and two plant PHs (PH V1, Trainer® and PH V2, Vegamin©), on two chrysanthemum (Chrysanthemum morifolium) cultivars (Pinacolada and Radost). In both cultivars, only the plant-derived PH (V1 and V2) treatments recorded significantly higher fresh plant biomass than the control (on average +18%, in both cultivars). The foliar application of the vegetal-derived PHs but not the animal one, particularly in Pinacolada, improved the status of plants, stimulating stem elongation and the apical flower diameter. In Pinacolada, applications with PH V1 resulted in a significant increase in nitrate and P concentration in leaves and Ca content in flowers compared with the control (+43%, +27%, and +28% for nitrate, P, and Ca, respectively). In Radost, PH A and PH V2 applications caused a significant reduction in nitrate concentration in both leaves and flowers compared with the control. One week after harvest, in both cultivars, PH A applications caused flower stems to wilt faster than the control. In contrast, plants treated with PH V1 revealed significantly slower flower stem senescence compared to the control. Flower wilting during vase life was correlated to a decrease in the K-to-Na ratio in flowers due to an inability to transport K to the flowers from the leaves rather than an increase in Na in the flowers themselves.

Differential expression of ethylene biosynthetic and receptor genes in pollination-induced senescence of Dendrobium flowers

Following successful pollination, Dendrobium orchid flowers rapidly undergo senescence. In Dendrobium cv. Khao Chaimongkol, compatible pollination resulted in faster ethylene production and more rapid development of senescence symptoms, such as drooping, epinasty, venation and yellowing, compared with non-pollinated controls or pollination with incompatible pollinia. The DenACS1 and DenACO1 genes in the perianth of florets that had been pollinated with compatible pollinia were expressed more highly than those in non-pollinated open florets. Incompatible pollinia reduced the expression of DenACS1 and DenACO1 genes in the perianth. Transcript levels of the ethylene receptor gene DenERS1 and signaling genes DenEIL1 and DenERF1 showed differential spatial regulation with greater expression in the perianth than in the column plus ovary following compatible pollination. Compatible pollinia increased ethylene production concomitant with premature senescence and the increased expression of the DenACS1 and DenACO1 genes, and suppressed the ethylene receptor gene DenERS1, whereas incompatible pollinia did not stimulate ethylene production nor induce premature senescence but induced higher expression of DenERS1 both in the perianth and in the column plus ovary. These results suggest that the increased ethylene production in open florets pollinated with compatible pollen was partially due to an increase in the expression of DenACS1 and DenACO1 genes. The compatible pollinia induced a negative regulation of DenERS1 which may play an important role in ethylene perception and in modulating ethylene signaling transduction during pollinia-induced flower senescence.

Large flowers can be short‐lived: Insights from a high Andean cactus

AbstractLong‐lived and large flowers signify high floral maintenance costs. Species of arid/semiarid climates with large flowers are expected to have short flower life spans and pollination‐induced flower longevity in order to curb high floral water and other maintenance costs. We explored the context‐dependent large flower/short flower longevity hypothesis in Eriosyce curvispina (Cactaceae), a large‐flowered species of the semiarid central Chilean Andes. We determined breeding system, flower visitation rates, and open‐pollination fruit set and quantified floral water content. In a temperature‐controlled field manipulative experiment, we measured potential flower longevity and tested for the presence of pollination‐induced floral senescence. We measured the time span of the complete flower cycle defined as from when the flowers began to open to when they were totally closed, and the time span of fully open flowers defined as from when they were totally open until they began to close. The potential flower life span averaged 2.8 days (complete flower cycle) to 2.3 days (fully open flower). The complete flower cycle lasted 21.5 h, but flowers were fully open for only 10.1 h across days. Flower longevity in days was far shorter than reported for a large sample of species in the area. No evidence was found for pollination‐induced flower senescence as a complementary means for reducing floral maintenance costs. Eriosyce curvispina is self‐incompatible and abundantly pollinated by two megachilid bees. The level of pollen limitation (L = 0.36) was lower than the average reported for self‐incompatible angiosperms. Thus, the short flower life span in E. curvispina is not an impediment for high fruit set. Flowers contain >5 g of water of which >2 reside in >40 petaloid tepals. The amount of water is far higher than in another large‐flowered, non‐cactus species in the area, but only about 15% of that reported in the giant saguaro cactus which has larger flowers than E. curvispina.

Regulatory network for FOREVER YOUNG FLOWER-like genes in regulating Arabidopsis flower senescence and abscission

FOREVER YOUNG FLOWER (FYF) has been reported to play an important role in regulating flower senescence/abscission. Here, we functionally analyzed five Arabidopsis FYF-like genes, two in the FYF subgroup (FYL1/AGL71 and FYL2/AGL72) and three in the SOC1 subgroup (SOC1/AGL20, AGL19, and AGL14/XAL2), and showed their involvement in the regulation of flower senescence and/or abscission. We demonstrated that in FYF subgroup, FYF has both functions in suppressing flower senescence and abscission, FYL1 only suppresses flower abscission and FYL2 has been converted as an activator to promote flower senescence. In SOC1 subgroup, AGL19/AGL14/SOC1 have only one function in suppressing flower senescence. We also found that FYF-like proteins can form heterotetrameric complexes with different combinations of A/E functional proteins (such as AGL6 and SEP1) and AGL15/18-like proteins to perform their functions. These findings greatly expand the current knowledge behind the multifunctional evolution of FYF-like genes and uncover their regulatory network in plants.

Bioactivities of Phenylpropanoids Extracted from Ephemeral Flowers of Medicinal Woody Species Murraya paniculata (Linn.) Jack

Flowers of Murraya paniculata were assessed for production of phenolic secondary metabolites and were found to yield temporally variable concentrations of total phenolics and flavonoids due to enzymatic regulation by L-phenylalanine ammonia lyase. Maximum yield of phenolics was obtained from partly open flowers, with esterified hydroxycinnamic acids (mainly ferulic acid) forming the major component. Scopoletin-a coumarin product of ferulic acid - was isolated consistently from senescent flowers by High Performance Liquid Chromatography (HPLC). Approximately 200 mg of fresh floral tissue extracted with one millilitre solvent (methanol:water :: 30:70) yielded up to 1.6 mg of ferulic acid and 40 μg of scopoletin from partly open (at 18:00 h) and senescent (at 06:00 h) blooms respectively. Along with other hydroxycinnamic acid and coumarin components of M. paniculata flowers detected by HPLC, o-coumaric acid and isoauraptene were identified by Gas Chromatography-Mass Spectrometry. Various free-radical scavenging assays revealed the ferulic acid fraction to have stronger antioxidant activities than the scopoletin fraction, but no antibiotic activity was detected for ferulic acid. Total antioxidant capacities of ferulic acid and scopoletin fractions were estimated to be 9% and 7.8% of that of ascorbic acid standard, respectively. Scopoletin fraction exhibited Minimum Inhibitory Concentrations at 0.585 mg.mL-1 against Bacillus subtilis and 1.372 mg.mL-1 against Escherichia coli. The high concentrations of these bioactive phenylpropanoids in such a common flower species presents potential application in low-risk crop protection and plant-based nutraceuticals.

Genome-wide analysis of MdABF Subfamily and functional identification of MdABF1 in drought tolerance in apple

Abscisic acid (ABA) is an important hormone involved in plant growth and adaptation to environmental stress. Abscisic acid-responsive elements (ABRE)-binding transcription factors (ABFs) are important transcription factors involved in the ABA signaling pathway that participate in various biological processes in plants. The functions of ABF members are largely unknown in Malus domestica . In this study, sixteen Malus domestica ABF ( MdABF ) family members were identified in the apple ( Malus × domestica ) genome. The phylogenetic tree, chromosomal locations, promoter region cis-acting elements, gene structures, and conserved motifs of these MdABF members were analyzed. Subsequently, gene expression level analysis revealed that MdABFs had differential gene expression patterns in response to multiple abiotic factors, and most MdABF genes were highly expressed in leaves. According to the gene expression pattern analysis, we found that MdABF1 may play an important role in various stress responses. Subsequently, the MdABF1 gene was cloned and transgenic Arabidopsis thaliana material was obtained for further research. Subcellular localization revealed that the transcription factor MdABF1 was localized to the nucleus. Moreover, MdABF1- overexpression in Arabidopsis reduced its resistance to drought, however, there was no observed difference under salt exposure treatment. Meanwhile, expression of MdABF1 promoted early flowering and leaf senescence under drought conditions. These results indicate that MdABF1 may be a pivotal regulator of plant growth under drought conditions. Our findings lay the foundation for further exploration of the functions of MdABF in plant growth and development. • Sixteen ABF family members from apple were analyzed for bioinformatics and expression patterns. • We identified MdABF1 and demonstrated that it was locatized in nucleus. • Expression of MdABF1 in Arabidopsis reduced the drought resistance and promoted flowering and leaf senescence under drought.

Climate warming-driven phenological shifts are species-specific in woody plants: evidence from twig experiment in Kashmir Himalaya.

Experimental evidences in support of climate warming-driven phenological shifts are still scarce, particularly from the developing world. Here, we investigated the effect of experimental warming on flowering phenology of selected woody plants in Kashmir Himalaya. We selected the twigs of four congeneric pairs of temperate woody species (Prunus, Populus, Ulmus, Viburnum)-typical spring-flowering plants in the region. Using randomised block design, we monitored these winter dormant twigs in controlled growth chambers to study the effect of different temperature regimes (9, 17, 20 and 23°C) and species identity on the patterns of phenological shifts. We observed a significant phenological shift in all the species showing preponement in the first flower out and senescence phases ranging from 0.56 to 3.0 and 0.77 to 4.04days per degree increase in temperature, respectively. The duration of flowering phase in all the species showed a corresponding decrease along the gradient of increasing temperature, which was more driven by preponement of the flower senescence than the start of flowering. The patterns of phenological shifts were highly species-specific, and the magnitude of these shifts significantly varied in all the four pairs of congeneric species despite their phylogenetic similarity. Our study provides experimental support to the previous long-term observation and herbarium-based studies showing that the patterns of phenological shifts in response to global climate warming are likely to vary between species, even those belonging to same evolutionary stock. Our findings highlight that a one-size-fits-all strategy to manage the likely impacts of climate warming-induced phenological shifts will seldom succeed, and should instead be designed for the specific phenological responses of species and regions.

Transcriptional Regulation in Leaves of Cut Chrysanthemum (Chrysanthemum morifolium) ‘FenDante’ in Response to Post-Harvest Ethylene Treatment

The early wilting and yellowing of leaves in response to ethylene is the main limitation affecting the vase quality of cut chrysanthemums. Therefore, leaf senescence is the most difficult problem in the post-harvest and production of chrysanthemums. Nevertheless, the molecular mechanism of ethylene on the regulation of post-harvest senescence of cut chrysanthemum leaves is still unclear. In this study, we identified an ethylene-sensitive chrysanthemum ‘FenDante,’ which showed rapid chlorophyll content decrease under ethylene treatment, resulting in leaf yellowing and wilting before flower senescence. A new generation of Illumina sequencing platform was used to identify differentially expressed genes in the leaves in response to ethylene treatment in chrysanthemum. A total of 1.04 Gb of raw reads was obtained, including 753 and 2790 differentially expressed genes at 3 h and 24 h after ethylene treatment, respectively. KEGG analysis revealed that the differentially expressed genes are mainly involved in plant hormone synthesis and signal transduction, chlorophyll metabolism, aquaporins, and reactive oxygen species. The gene expression regulatory networks in the leaves of post-harvest cut chrysanthemums in response to ethylene treatment were studied, which lays the foundation for future research on the molecular mechanisms of ethylene-mediated leaf senescence in cut chrysanthemums.

PlMYB308 Regulates Flower Senescence by Modulating Ethylene Biosynthesis in Herbaceous Peony.

Herbaceous peony is an important cut-flower plant cultivated worldwide, but its short vase life substantially restricts its economic value. It is well established that endogenous hormones regulate the senescence process, but their molecular mechanism in flower senescence remains unclear. Here, we isolated a MYB transcription factor gene, PlMYB308, from herbaceous peony flowers, based on transcriptome data. Quantitative real-time PCR analysis showed that PlMYB308 is strongly up-regulated in senescing petals, and its expression was induced by abscisic acid or ethylene and reduced by gibberellin in petals. Treatment with abscisic acid or ethylene accelerated herbaceous peony petal senescence, and gibberellin delayed the process. PlMYB308 silencing delayed peony flower senescence and dramatically increased gibberellin, but reduced ethylene and abscisic acid levels in petals. PlMYB308 ectopic overexpression in tobacco accelerated flower senescence and reduced gibberellin, but increased ethylene and abscisic acid accumulation. Correspondingly, five endogenous hormone biosynthetic genes showed variable expression levels in petals after PlMYB308 silencing or overexpression. A dual-luciferase assay and yeast one-hybrid analysis showed that PlMYB308 specifically binds the PlACO1 promoter. Moreover, treatment with ethylene and 1-MCP can accelerate PlMYB308 silencing-reduced senescence and delay PlMYB308- overexpression-induced senescence. We also found that PlACO1 silencing delayed senescence in herbaceous peony petals. Taken together, our results suggest that the PlMYB308-PlACO1 regulatory checkpoints positively mediate the production of ethylene, and thus contribute to senescence in herbaceous peony flowers.

Combined Nano Silver, α-Aminoisobutyric Acid, and 1-Methylcyclopropene Treatment Delays the Senescence of Cut Roses with Different Ethylene Sensitivities

Flower senescence varies among cut roses (Rosa hybrida L.), and it is known that the postharvest life of ethylene-sensitive flowers is strongly related to the transcriptional accumulation of ethylene biosynthesis genes, whereas that of ethylene-insensitive flowers is shortened by water stress. These different responses of flowers to hormone and water stresses limit the action of preservatives in inhibiting the postharvest deterioration of cut rose flowers. This study was conducted to investigate the effects of the combined application of antibacterial agents and ethylene biosynthesis and binding inhibitors on the postharvest life and quality of the cut rose cultivars ‘Matador’ (ethylene-sensitive) and ‘Dolcetto’ (ethylene-insensitive). Cut flowers were treated with nano silver (NS), a combination of NS and α-aminoisobutyric acid (NS+A), or a combination of NS+A and 1-methylcyclopropene (NS+AM), and they were subsequently exposed to ethylene for 24 h. Treatment effectiveness was compared with that of control (CON) flowers, which were kept in distilled water and exposed only to ethylene. The results showed that all treatments significantly improved the postharvest quality and vase life of both rose cultivars. However, NS+AM most markedly delayed senescence and prolonged the vase life of cut flowers by 217% in ‘Matador’ and 168.4% in ‘Dolcetto’, compared with those of CON flowers. NS+AM also effectively increased the flower diameter and maintenance time of positive water balance and initial fresh weight by enhancing solution absorption as well as suppressing bacterial growth at the cut stem ends of the cut roses. Furthermore, NS+AM greatly suppressed the ethylene-inducible increase of ethylene biosynthesis genes and the reduction of ethylene receptor genes in petals, which resulted in a reduced flower response to exogenous ethylene in both rose cultivars. These findings show that NS+AM effectively delays flower senescence in both ethylene sensitive and insensitive cultivars by synergistically preventing ethylene response and water stress in cut flowers.

KIL1 terminates fertility in maize by controlling silk senescence.

Plant flowers have a functional life span during which pollination and fertilization occur to ensure seed and fruit development. Once flower senescence is initiated, the potential to set seed or fruit is irrevocably lost. In maize, silk strands are the elongated floral stigmas that emerge from the husk-enveloped inflorescence to intercept airborne pollen. Here we show that KIRA1-LIKE1 (KIL1), an ortholog of the Arabidopsis NAC (NAM (NO APICAL MERISTEM), ATAF1/2 (Arabidopsis thaliana Activation Factor1 and 2) and CUC (CUP-SHAPED COTYLEDON 2)) transcription factor KIRA1, promotes senescence and programmed cell death (PCD) in the silk strand base, ending the window of accessibility for fertilization of the ovary. Loss of KIL1 function extends silk receptivity and thus strongly increases kernel yield following late pollination. This phenotype offers new opportunities for possibly improving yield stability in cereal crops. Moreover, despite diverging flower morphologies and the substantial evolutionary distance between Arabidopsis and maize, our data indicate remarkably similar principles in terminating floral receptivity by PCD, whose modulation offers the potential to be widely used in agriculture.

Isolation and Functional Analysis of EPHEMERAL1-LIKE (EPH1L) Genes Involved in Flower Senescence in Cultivated Japanese Gentians.

The elongation of flower longevity increases the commercial value of ornamental plants, and various genes have been identified as influencing flower senescence. Recently, EPHEMERAL1 (EPH1), encoding a NAC-type transcription factor, was identified in Japanese morning glory as a gene that promotes flower senescence. Here we attempted to identify an EPH1 homolog gene from cultivated Japanese gentians and characterized the same with regard to its flower senescence. Two EPH1-LIKE genes (EPH1La and EPH1Lb), considered as alleles, were isolated from a gentian cultivar (Gentiana scabra × G. triflora). Phylogenetic analyses revealed that EPH1L belongs to the NAM subfamily. The transcript levels of EPH1L increased along with its senescence in the field-grown flowers. Under dark-induced senescence conditions, the gentian-detached flowers showed the peak transcription level of EPH1L earlier than that of SAG12, a senescence marker gene, suggesting the involvement of EPH1L in flower senescence. To reveal the EPH1L function, we produced eph1l-knockout mutant lines using the CRISPR/Cas9 system. When the flower longevity was evaluated using the detached flowers as described above, improved longevity was recorded in all genome-edited lines, with delayed induction of SAG12 transcription. The degradation analysis of genomic DNA matched the elongation of flower longevity, cumulatively indicating the involvement of EPH1L in the regulation of flower senescence in gentians.