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Cell Division and Expansion in Petals during Flower Development and Opening in Eustoma grandiflorum
Abstract
We investigated morphological changes in petal cells during flower development and opening in Eustoma grandiflorum. The morphology of petal epidermal cells was observed by scanning electron microscopy, and their number was determined. The numbers of adaxial and abaxial epidermal cells increased during flower development. Increase in these numbers terminated before flower opening earlier in abaxial than in adaxial epidermal cells. Measurements of cell number and area showed that the petal growing stage during flower development and opening can be divided into four phases: cell division and expansion, cell division, cell division and expansion, and cell expansion. Adaxial epidermal cells in the petal blade showed a conical-papillate shape whereas adaxial epidermal cells in the petal claw were longitudinally elongated in shape. Abaxial epidermal cells were longitudinally elongated in both petal blade and claw. The ultrastructure of petal cells at the bud stage and the open stage was observed by transmission electron microscopy. In the petal cells at the bud stage, nuclei and several plastids were observed, although the cells were mainly occupied with vacuoles. Relatively large spherical electron-dense bodies were observed only in the vacuoles of adaxial epidermal cells at the bud stage. The petal cells were largely occupied with enlarged vacuoles at the open stage. We conclude that petal growth in Eustoma is divided into four phases, based on the activities of cell division and expansion, and that petal growth in the final phase is mainly due to cell expansion with marked enlargement of vacuoles.
... Similarly, flower opening in the rose (Yamada et al., 2009b) and Tweedia caerulea (Norikoshi et al., 2013) is mainly due to cell expansion. Also, the final stage of petal growth associated with flower opening is due to cell expansion in Eustoma (Norikoshi et al., 2016). Cell expansion requires accumulation of osmotically active compounds, which facilitate water influx to the cell. ...
... However, in our study, petal FW and DW increased during flower opening, but the FW/DW ratio decreased between stages 4 and 5 (Fig. 1). This result is consistent with that reported previously (Norikoshi et al., 2016). We observed that the basal parts of petals at stage 5 secreted an unknown sticky substance, which may be responsible for the marked increase in dry weight. ...
... Petal growth associated with flower opening has been found to be due mainly to cell expansion in many plants including G. grandiflora (Koning, 1984), the rose (Yamada et al., 2009a), and T. caerulea (Norikoshi , 2013). Similarly, petal growth during flower opening was dependent on cell expansion in Eustoma (Norikoshi et al., 2016). Osmotic potential was lower in the symplast than in the apoplast in the petals at stage 2 (Fig. 5), facilitating water influx to petal cells. ...
Petal growth associated with flower opening is due to cell expansion. To elucidate the role of soluble carbohydrates in expansion of petal cells in Eustoma grandiflorum, its soluble carbohydrates were identified, and changes in their subcellular concentrations during flower opening were investigated. In addition to glucose, fructose, sucrose, and myo-inositol, d-bornesitol was identified using 1H-NMR. d-Bornesitol was the major soluble carbohydrate in leaves and stems. Given that cyclitols are known to be the translocated carbohydrates in alfalfa, phloem exudate was analyzed. However, the translocated carbohydrate was suggested to be sucrose, and not d-bornesitol. In the petals, glucose and sucrose content increased whereas d-bornesitol and myo-inositol contents were almost constant during flower opening. The fructose content in petals was very low. Glucose, sucrose, myo-inositol, and d-bornesitol were found mainly in the vacuole, although sucrose was also found in the cytoplasm. In the petals of open flowers, glucose and sucrose concentrations in the vacuole increased to 60 and 53 mM. Inorganic ion concentrations in the symplast and apoplast did not increase during flower opening. The osmotic potential of the symplast and apoplast in the petals was lower at the open stage than the potential of those at the bud stage, and this difference was mainly attributed to increases in glucose and sucrose concentrations. The results suggest that the accumulation of glucose and sucrose in the vacuole reduces the symplastic osmotic potential, which appears to be involved in the cell expansion associated with flower opening, but that the contribution of d-bornesitol as an osmoticum to cell expansion is limited in Eustoma.
... Flower weight of ground cover rose (Rosa x hybrida) increased during flower development due to higher water content of petals (Schmitzer et al., 2010). Petal cell expansion and cell division increase with flower development (Norikoshi et al., 2015), therefore it is likely that petal area, flower width and length increases are closely related to cell division, expansion and water content during flower development. Results also show that cessation of sepal area enlargement may be related to decline of cell division and expansion after stage II. ...
... Results also show that cessation of sepal area enlargement may be related to decline of cell division and expansion after stage II. Petal area expansion during flower development has also been observed in other plant species (Norikoshi et al., 2015). In addition, increased relative water content of petals might also be an important factor for petal growth in oil-bearing rose. ...
Oil-bearing rose is a very valuable member of the Rosa genus. Despite the importance of oil-bearing rose, metabolic changes during flower development are not well understood. Thus, the objective of this study was to investigate the changes in phenological, primary and secondary metabolites and their interactions at five developmental stages of oil-bearing rose. Flower width, flower and petal fresh weights, petal area and petal relative water content increased from bud stage to blooming stage, while flower length and sepal area increased only at early stages. Thirty-seven essential oil components were identified at different stages of petal development and nonadecane, β-citronellol and n-heneicosane were the prevalent essential oil components regardless of stage. Sixteen fatty acids were identified and the amount of saturated fatty acids was higher than the mono and polyunsaturated fatty acids in all developmental stages. Eight organic acids were detected in petals and four of them (tartaric, malic, citric and succinic acids) showed significant changes, and total organic acids content decreased during flower development. Catechin and epicatechin were the most abundant phenolic compounds in petals. While total phenolic, flavonoid and free amino acids contents decreased during flower development, total free fatty acids content increased, but was not significant between the developmental stages. Correlation analysis between phenological traits and some metablolites revealed 20 significant correlations and 11 of which were positive. Results showed that flower development stages had significant effects on metabolite content and quality of products obtained, and significant shifts in metabolite type and content occurred at flower development stages III and IV.
... These results were coincident with results in Gaillardia grandiflora [23], carnation [24] and T. caerulea [16], indicating that the cell division ceased and cell expansion occurred during floral opening process. However, in rose [25] and E. grandiflorum [26] cell division and cell expansion simultaneously appeared during this process. What's more, based on TEM observation, it was found that vacuole occupied most area of adaxial petal epidermal cells in O. fragrans (Fig. 1c, Table S1). ...
... What's more, based on TEM observation, it was found that vacuole occupied most area of adaxial petal epidermal cells in O. fragrans (Fig. 1c, Table S1). The same situation occurred in E. grandiflorum [26]. These results indicated that the petal cell expansion was accompanied by the enlargement of vacuole. ...
Background:
Sweet osmanthus (Osmanthus fragrans Lour.) is one of the top ten traditional ornamental flowers in China. The flowering time of once-flowering cultivars in O. fragrans is greatly affected by the relatively low temperature, but there are few reports on its molecular mechanism to date. A hypothesis had been raised that genes related with flower opening might be up-regulated in response to relatively low temperature in O. fragrans. Thus, our work was aimed to explore the underlying molecular mechanism of flower opening regulated by relatively low temperature in O. fragrans.
Results:
The cell size of adaxial and abaxial petal epidermal cells and ultrastructural morphology of petal cells at different developmental stages were observed. The cell size of adaxial and abaxial petal epidermal cells increased gradually with the process of flower opening. Then the transcriptomic sequencing was employed to analyze the differentially expressed genes (DEGs) under different number of days' treatments with relatively low temperatures (19 °C) or 23 °C. Analysis of DEGs in Gene Ontology analysis showed that "metabolic process", "cellular process", "binding", "catalytic activity", "cell", "cell part", "membrane", "membrane part", "single-organism process", and "organelle" were highly enriched. In KEGG analysis, "metabolic pathways", "biosynthesis of secondary metabolites", "plant-pathogen interaction", "starch and sucrose metabolism", and "plant hormone signal transduction" were the top five pathways containing the greatest number of DEGs. The DEGs involved in cell wall metabolism, phytohormone signal transduction pathways, and eight kinds of transcription factors were analyzed in depth.
Conclusions:
Several unigenes involved in cell wall metabolism, phytohormone signal transduction pathway, and transcription factors with highly variable expression levels between different temperature treatments may be involved in petal cell expansion during flower opening process in response to the relatively low temperature. These results could improve our understanding of the molecular mechanism of relatively-low-temperature-regulated flower opening of O. fragrans, provide practical information for the prediction and regulation of flowering time in O. fragrans, and ultimately pave the way for genetic modification in O. fragrans.
... These results were coincident with results in Gaillardia grandi ora [23], carnation [24] and T. caerulea [16], indicating that the cell division ceased and cell expansion occurred during oral opening process. However, in rose [25] and E. grandi orum [26] cell division and cell expansion simultaneously appeared during this process. What's more, based on TEM observation, it was found that vacuole occupied most area of adaxial petal epidermal cells in O. fragrans (Fig. 1c, Table S1). ...
... What's more, based on TEM observation, it was found that vacuole occupied most area of adaxial petal epidermal cells in O. fragrans (Fig. 1c, Table S1). The same situation occurred in E. grandi orum [26]. These results indicated that the petal cell expansion was accompanied by the enlargement of vacuole. ...
Background: Sweet osmanthus ( Osmanthus fragrans Lour.) is one of the top ten traditional ornamental flowers in China. The flowering time of once-flowering cultivars in O . fragrans is greatly affected by the relatively low temperature, but there are few reports on its molecular mechanism to date. A hypothesis had been raised that genes related with flower opening might be up-regulated in response to relatively low temperature in O . fragrans . Thus, our work was aimed to explore the underlying molecular mechanism of flower opening regulated by relatively low temperature in O . fragrans .
Results: The cell size of adaxial and abaxial petal epidermal cells and ultrastructural morphology of petal cells at different developmental stages were observed. The cell size of adaxial and abaxial petal epidermal cells increased gradually with the process of flower opening. Then the transcriptomic sequencing was employed to analyze the differentially expressed genes (DEGs) under different number of days’ treatments with relatively low temperatures (19°C) or 23°C. Analysis of DEGs in Gene Ontology analysis showed that “metabolic process”, “cellular process”, “binding”, “catalytic activity”, “cell”, “cell part”, “membrane”, “membrane part”, “single-organism process”, and “organelle” were highly enriched. In KEGG analysis, “metabolic pathways”, “biosynthesis of secondary metabolites”, “plant-pathogen interaction”, “starch and sucrose metabolism”, and “plant hormone signal transduction” were the top five pathways containing the greatest number of DEGs. The DEGs involved in cell wall metabolism, phytohormone signal transduction pathways, and eight kinds of transcription factors were analyzed in depth.
Conclusions: Several unigenes involved in cell wall metabolism, phytohormone signal transduction pathway, and transcription factors with highly variable expression levels between different temperature treatments may be involved in petal cell expansion during flower opening process in response to the relatively low temperature. These results could improve our understanding of the molecular mechanism of relatively-low-temperature-regulated flower opening of O. fragrans , provide practical information for the prediction and regulation of flowering time in O . fragrans , and ultimately pave the way for genetic modification in O . fragrans .
... This results was coincident with Gaillardia grandiflora [29], carnation [30] and T. caerulea [16], the cell division ceased and cell expansion occurred during floral opening process. However, in rose [31] and E. grandiflorum [32] cell division and cell expansion simultaneously appeared during this process. The vacuole occupied most area of petal cells in O. fragrans according to the results of TEM (Fig. 1c). ...
... The vacuole occupied most area of petal cells in O. fragrans according to the results of TEM (Fig. 1c). The same condition was occurred in E. grandiflorum [32]. These results indicated that the petal cell expansion was accompanied by the enlargement of vacuole. ...
Background: Osmanthus fragrans Lour. is one of the top ten traditional ornamental flower in China. The flower time of once-flowering cultivars in O. fragrans is greatly affected by the relatively low temperature, but there is few reports on its molecular mechanism to date.
Results: In this study, the cell size of adaxial and abaxial petal epidermal cells and ultrastructural morphology of petal cells at different developmental stages were observed. The cell size of adaxial and abaxial petal epidermal cells increased gradually with the process of flower opening. Then the transcriptomic sequencing was employed to analyze the differentially expressed genes (DEGs) under different days’ treatments with relatively low temperatures (19°C) or 23°C. Analysis of DEGs in GO analysis showed that “metabolic process”, “cellular process”, “binding”, “catalytic activity”, “cell”, “cell part”, “membrane”, “membrane part”, “single-organism process”, and “organelle” were highly enriched. In KEGG analysis, “metabolic pathways”, “biosynthesis of secondary metabolites”, “plant-pathogen interaction”, “starch and sucrose metabolism”, and “plant hormone signal transduction” were the top five pathways containing the greatest number of DEGs. DEGs involved in cell wall metabolism, phytohormone signal transduction pathways, and eight kinds of transcription factors were analyzed in depth.
Conclusions: Several unigenes involved in cell wall metabolism, phytohormone signal transduction pathway, and TFs with highly variable expression levels between different temperature treatments may be involved in petal cell expansion during flower opening process in response to the relatively low temperature. These results could improve our understanding of the molecular mechanism of relatively low temperature regulating flower opening of O. fragrans and provide theoretical reference for the prediction and regulation of flowering time and genetic modification in O. fragrans.
... Shinner) là loài hoa kiểng được người Á Đông xem là biểu tượng của sự viên mãn, an lành. Cây Cát Tường đa dạng về màu sắc, kiểu dáng và được phân thành hai loại là Cát Tường đơn và Cát Tường kép [1,2]. Cát Tường đơn có số cánh hoa khoảng từ 10 đến 15 cánh, kích thước hoa nhỏ với bốn màu sắc cơ bản là: tím, hồng, trắng và vàng. ...
... Cát Tường đơn có số cánh hoa khoảng từ 10 đến 15 cánh, kích thước hoa nhỏ với bốn màu sắc cơ bản là: tím, hồng, trắng và vàng. Cát Tường kép số cánh hoa khoảng từ 17 đến 22 cánh, kích thước hoa lớn, màu nhạt ở vùng gần cuống và đậm dần ở vùng rìa cánh hoa, nhưng vẫn thuộc các màu cơ bản tương tự như Cát Tường đơn [1]. Tuy nhiên, cây Cát Tường có phát hoa tương đối ngắn dẫn đến chất lượng hoa không đồng đều. ...
In this paper, plant growth regulators including 6-benzylaminopurine (BA), kinetin, indole-3-acetic acid (IAA), gibberellic acid (GA3) and ethrel, at different concentrations were used individually or in combination to induce adventitious shoots from the explants, which contain shoot apical meristem and young leaves. Histological and physiological changes during shoot development were analysed. The highest shoot initiation was achieved on Murashige and Skoog (MS) medium supplemented with 0.5 mg/L BA and 1.0 mg/L GA3. Regenerated shoots were rooted on MS medium with 0.25 or 0.5 mg/L IAA. Shoot development from in vitro shoot explants initiated from the axil and cortex of stem. The shoot regeneration from shoot apical explants was effected by the meristem integrity or auxin from shoot apical meristem. Roles of plant growth regulators, especially polar auxin transport, and the ablation on the shoot initiation were discussed.
... The phenomenon of flower opening consists of both petal cell division and cell expansion, and they greatly affect petal growth and development. Many research studies indicate that petal growth associated with flower opening is mainly attributable to cell expansion, and the accumulation of osmosis is required [54][55][56]. Soluble carbohydrates, which act as osmotica and substrates for both respiration and cell wall synthesis for cell expansion, accumulate in the petal cells of many flowers, including roses [57]. The sugar accumulation in petal cells is pivotal for reducing petal water potential promotion of water influx, which is vital for cell enlargement and flower opening [51,58,59]. ...
Kutno is a picturesque city in central Poland, known for extensive rose breeding worldwide. Soil samples and rose petals were collected from 13 locations in the city and characterized by diverse environments. This allowed determining the response of plants to changing cultivation conditions. Rose petals have found a wide range of applications. They are used in the food, pharmaceutical and cosmetic industries. The aim of the research was to assess the contents of Cu, Zn, Cd, Ni, Pb and Cr in soils and their accumulation in rose petals. Samples were subjected to the microwave mineralization process using a mixture of concentrated HCl and HNO3. The metal contents in the soil and roses were determined by HR-CS-AAS and ICP-OES, respectively. Roses are usually cultivated in soils with a limited mobile fraction of heavy metals. In these unfavorable conditions, flower petals can absorb heavy metals substantially. Petals of roses cultivated for cosmetic, pharmaceutical or food purposes should be tested for heavy metal content. This study indicates that toxic metals are blocked at the root zone, and their transport to the above-ground parts is severely hampered. Nevertheless, metals related to the photo-synthesis process (Zn, Cu) are more intensively taken up by roses, while the uptake of toxic metals is partially inhibited.
... Following the methodology outlined by Norikoshi et al. 24 , fresh petals were carefully cleaned with distilled water to remove any impurities. Subsequently, 5 mm × 5 mm samples were extracted and immersed in glutaraldehyde fixative for preservation. ...
Pink-flowered Prunus sibirica, of the genus Prunus, is an exceptional germplasm resource with high ornamental value. Understanding the mechanism behind petal coloration is crucial for cultivating ornamental P. sibirica varieties. This study utilized pink-flowered and white-flowered P. sibirica petals at different stages of flowering to explore the relationship between various physiological indicators, anatomical structures of petals, and flower coloration during flowering. Results indicated that anthocyanins, key pigment indicators in pink-flowered P. sibirica, directly influenced the a* values (redness). Increased activity of phenylalanine deaminase (4.43–29.69 U/g), chalcone isomerase (9.80–46.67 U/g), and soluble sugar content (29.25–35.28 mg/g) promoted anthocyanin synthesis and accumulation. These substances indirectly affected flower color by influencing anthocyanin content through physiological processes related to petal coloration. Structural changes in epidermal cells of pink and white flower petals during flowering were similar, with differences in pigment content and distribution impacting petal light absorption. Correlation analysis revealed that a* values were significantly and positively correlated with five factors, one of which was anthocyanin content, and significant negative correlations with soluble protein content and cytosol pH. This study examined the factors influencing petal coloration in pink-flowered P. sibirica from both physiological and anatomical perspectives, providing a theoretical foundation for breeding new varieties of ornamental flowering plants.
... Flower size is mainly influenced by petal cell division and expansion, and it represents one of the most vital determinants of the economic value of ornamental plants [17]. The Dof proteins are plant-specific TFs containing a C 2 -C 2 single zinc finger structural domain that is highly conserved, and are widely participated in plant development [11]. ...
Petal size is a key indicator of the ornamental value of plants, such as Petunia hybrida L., which is a popular ornamental species worldwide. Our previous study identified a flower-specific expression pattern of a DNA-binding one finger (Dof)-type transcription factor (TF) PhDof28, in the semi-flowering and full-flowering stages of petunia. In this study, subcellular localization and activation assays showed that PhDof28 was localized in the cell nucleus and could undergo in vitro self-activation. The expression levels of PhDof28 tended to be significantly up-regulated at the top parts of petals during petunia flower opening. Transgenic petunia ‘W115’ and tobacco plants overexpressing PhDof28 showed similar larger petal phenotypes. The cell sizes at the middle and top parts of transgenic petunia petals were significantly increased, along with higher levels of endogenous indole-3-acetic acid (IAA) hormone. Interestingly, the expression levels of two TFs, PhNAC100 and PhBPEp, which were reported as negative regulators for flower development, were dramatically increased, while the accumulation of jasmonic acid (JA), which induces PhBPEp expression, was also significantly enhanced in the transgenic petals. These results indicated that PhDof28 overexpression could increase petal size by enhancing the synthesis of endogenous IAA in petunias. Moreover, a JA-related feedback regulation mechanism was potentially activated to prevent overgrowth of petals in transgenic plants. This study will not only enhance our knowledge of the Dof TF family, but also provide crucial genetic resources for future improvements of plant ornamental traits.
... In addition, the dry weight of the stems was considerably higher for G. intraradices (3.73 g plant -1 ) compared to 1.62 g plant -1 of the control treatment, which indicates a higher carbohydrate reserve -a determining factor in the development of the bud and flower opening ( Figure 5). Cavasini et al. (2018) recorded a >50% reduction in carbohydrate reserves in lisianthus buds, from 20.74 mg 100 g -1 (harvest) to 9.85 mg 100 g -1 (day 17), which decrease during the harvest and postharvest stage, so bigger and wider stems represent more reserves for postharvest (Norikoshi et al., 2016). ...
Lisianthus (Eustoma grandiflorum) is an ornamental species used as a potted plant or cut flower, its popularity is due to the diversity of colors, number of flower buds, and shelf life. Nevertheless, during the first phases of development, problems such as foliar chlorosis and root diseases affects most cultivars, causing poor growth, thin stems, and few flowers. The use of plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) improved plant growth as these microbes colonize the plant system root. Therefore, in order to provide better conditions for the stem development, the aim of this work was to evaluate the individual and combined effect of Bacillus subtilis (PGPR) and Glomus intraradices (AMF) on the growth and postharvest quality of the stems of lisianthus cv. Mariachi. Then commercial product Alubión-X (Bacillus subtilis (PGPR) and mycorrhizal fungus (Glomus intraradices) were used. The variables evaluated were stem height and diameter, foliar area, leaves number and in postharvest, buds number, open and diameter of flowers and stem dry weight. The results showed a significant effect of the inoculation of G. intraradices on the size (66.92 cm) of the stem, as well as the combination of B. subtilis + G. intraradices (65.51 cm) compared to the control (36.9 cm). The number of buds and open flowers of the stems treated with G. intraradices were 33.35 and 23.9 respectively significantly higher than the control. G. intraradices alone is the best option for applying to lisianthus, when compared to applying with B. Subtilis.
... In rose (Rosa hybrida), flower opening driven by both cell division and cell expansion involves irreversible petal movement that is manifested in a transition from an entangled position to a horizontally expanded position (Yamada et al. 2009). In contrast, E. grandiflorum flower opening results from reversible asymmetric expansion of cells on the abaxial and adaxial side of petals (Ryo et al. 2016). Flower organ growth begins after formation of the flower primordium and all cells enter the stage of continuous division. ...
Flowers are key organs in many ornamental plants, and various phases of flower development impact their economic value. The final stage of petal development is associated with flower senescence, which is an irreversible process involving programmed cell death, and premature senescence of cut flowers often results in major losses in quality during postharvest handling. Flower opening and senescence are two sequential processes. As flowers open, the stamens are exposed to attract pollinators. Once pollination occurs, flower senescence is initiated. Both the opening and senescence processes are regulated by a range of endogenous phytohormones and environmental factors. Ethylene acts as a central regulator for the ethylene-sensitive flowers. Other phytohormones, including auxin, gibberellin, cytokinin, jasmonic acid and abscisic acid, are also involved in the control of petal expansion and senescence. Water status also directly influences postharvest flower opening, while pollination is a key event in initiating the onset flower senescence. Here, we review the current understanding of flower opening and senescence, and propose future research directions, such as the study of interactions between hormonal and environmental signals, the application of new technology, and interdisciplinary research.
... more steeply conical and the base diameter is narrower than for abaxial cells (Figures 1b-g and S1). This type of dorsoventral epidermal variation has been previously observed in corollas of other petunia cultivars and plant species (Baumann et al., 2007;Bergougnoux et al., 2007;Glover and Martin, 1998;Norikoshi et al., 2016;Reale et al., 2002). Moreover, in petunia P720, a distinct adaxial, but not abaxial, acropetal gradient of decreasing cell density was revealed by SEM (Figure 1h). ...
Floral guides are patterned cues that direct the pollinator to the plant reproductive organs. The spatial distribution of showy visual and olfactory traits allows efficient plant–pollinator interactions. Data on the mechanisms underlying floral volatile patterns or their interactions with pollinators are lacking. Here we characterize the spatial emission patterns of volatiles from the corolla of the model plant Petunia × hybrida and reveal the ability of honeybees to distinguish these patterns. Along the adaxial epidermis, in correlation with cell density, the petal base adjacent to reproductive organs emitted significantly higher levels of volatiles than the distal petal rim. Volatile emission could also be differentiated between the two epidermal surfaces: emission from the adaxial side was significantly higher than that from the abaxial side. Similar emission patterns were also observed in other petunias, Dianthus caryophyllus (carnation) and Argyranthemum frutescens (Marguerite daisy). Analyses of transcripts involved in volatile production/emission revealed lower levels of the plasma‐membrane transporter ABCG1 in the abaxial versus adaxial epidermis. Transient overexpression of ABCG1 enhanced emission from the abaxial epidermis to the level of the adaxial epidermis, suggesting its involvement in spatial emission patterns in the epidermal layers. Proboscis extension response experiments showed that differences in emission levels along the adaxial epidermis, that is, petal base versus rim, detected by GC‐MS are also discernible by honeybees.
... The accumulation of starch accompanied by little or no change in the contents of reducing sugars and sucrose, along with induced CWIN activity in elongated flower buds, are indicative of substantial import of carbohydrates via accelerated phloem unloading (Ruan, 2014). The subsequent consumption of starch concomitant with a reduction in CWIN activity reflects the predominant usage of carbohydrate that promotes floral organ development, including the pronounced enlargement of petals associated with flower opening (Norikoshi et al., 2016b). This is consistent with observations made for several other ornamental plants, thereby highlighting the importance of starch synthesis and degradation in flower opening (van Doorn and van Meeteren, 2003;Horibe and Yamada, 2017), and an increase in CWIN activity during the intermediate stage of rose petal opening (Yamada et al., 2007). ...
In this study, we examined sucrose metabolism and expression of invertase, a sucrolytic enzyme, during vegetative and floral development in Eustoma grandiflorum, a widely cultivated ornamental plant. During vegetative growth, sucrose content was relatively lower in roots and unexpanded leaves than in expanded leaves. The activities of cell-wall invertase (CWIN) and vacuolar invertase (VIN) were higher in roots and unexpanded leaves, respectively, whereas the activity of cytoplasmic invertase (CIN) was higher in both organs. During flower development, although the contents of reducing sugars and sucrose were relatively unchanged, starch content was higher in elongated flower buds (stage 2), and we also detected a significant increase in CWIN activity. VIN and CIN showed contrasting changes in enzymatic activity, with the former being higher, and the latter lower in opened flowers (stage 3). Furthermore, we cloned two putative CWIN genes (EgCWIN1 and EgCWIN2), one putative VIN gene (EgVIN1), and one putative CIN gene (EgCIN1), and examined the transcript levels of these four genes. Although we detected no clear correlations between invertase activities and the transcript levels of invertase genes in vegetative organs, we observed changes in the transcript levels of EgCWIN1, EgVIN1, and EgCIN1 corresponding to changes in activities of the respective invertase during flower development. These results indicate that carbon partitioning during vegetative and floral development in E. grandiflorum is controlled by three invertase isoforms, and that differential gene expression underlies the successive induction of these invertase isoforms during flower opening.
... Soluble carbohydrates also play an important role in flower opening and may work as an osmotica (Norikoshi et al. 2016). After chilling, carbohydrates of Citrus unshiu Marc. ...
As biennial recretohalophytes, Limonium bicolor plants need 2 years to complete their life cycle. A growth habit mutant Vernalization Requirement Loss 15 (vrl15) was obtained by ion implantation. However, the biological characteristics of the mutant were unclear. In the current study, the related traits of vrl15 and some possible reasons for these traits were examined. Compared with wild type (WT), vrl15 can bolt and flower in approximately four months without vernalization. Moreover, vrl15 needed much less time to bolting and flowering than wild-type L. bicolor under different vernalization treatments. After 20 days’ vernalization, bolting vrl15 plants had 24 rosette leaves and bolting WT had 31 rosette leaves. Moreover, the pollen number per anther, the proportion of active pollen, the seed setting rate and the 1000 seed weight of vrl15 were all lower than those of WT. The soluble sugar content and soluble protein content in leaves of the vrl15 were much higher than those of WT sowed at the same time. In addition, the GA content in the leaves of bolting vrl15 was higher than that of the non-bolting WT sowed at the same time and non-bolting vrl15, whereas the contents of ABA and BR were much lower than that of the non-bolting WT. These results indicate that to some extent the increase of GA and decrease of ABA and BR content may be involved in the growth habit and male fertility alteration of mutant vrl15 of L. bicolor.
Corolla elongation and the roles of plant hormones in this process in Gaillardia grandiflora Van Houtte ray flowers were examined. The sterile ray flowers elongated during a 2-day period, and corolla growth was accompanied by fresh and dry weight increases and epidermal cell elongation (greatest near the base of the corolla) but not by cell division. Corollas excised from young ray flowers were measured during treatment in vitro with solutions of plant growth regulators. They elongated in response to gibberellins and fusicoccin but did not respond to auxins, cytokinins, abscisic acid, ethylene, or inhibitors of ethylene biosynthesis. Sequential and simultaneous hormone applications indicated no additive or synergistic effects between hormones, but auxin did reduce gibberellin-promoted growth. Analyses of endogenous auxins showed no significant variation, and ethylene production decreased prior to elongation, while a 20-fold increase in endogenous gibberellin activity was observed just prior to rapid corolla elongation. It appears that corolla growth in Gaillardia is accomplished by an increase in gibberellin activity alone, that multiple hormone interactions are not important in the control of corolla growth, and that part of the mode of action of gibberellin is acid-induced growth.
Rhythmic pulses of irreversible petal expansion in rose ( Rosa hybrida L. ‘Sonia’) petals cause diurnal changes in the rate of flower opening. Time-lapse cinematography revealed a transient increase in the rate of rose flower opening that commenced shortly before the onset of a light period and lasted for a few hours. Petal expansion, which occurred sequentially from the outer to the innermost whorl, involved rhythmic increases in fresh and dry weights. The amount of expansion was greatest in the distal portion of each petal and least near the petal base. Periods of rapid expansion were accompanied by decreases in starch and increases in soluble sugars in the petals, but the total carbohydrate content of the petals remained constant during a light–dark cycle. During expansion, the osmotic potential of the outer petal increased from −790 to −690 kPa. Starch hydrolysis during petal growth appears to be important for maintenance of cell size, but it is not the factor controlling cell expansion.
The petals of a number of flowers are shown to contain similar intensely coloured intravacuolar bodies referred to herein as anthocyanic vacuolar inclusions (AVIs). The AVIs in a blue-grey carnation and in purple lisianthus have been studied in detail. AVIs occur predominantly in the adaxial epidermal cells and their presence is shown to have a major influence on flower colour by enhancing both intensity and blueness. The latter effect is especially dramatic in the carnation where the normally pink pelargonidin pigments produce a blue-grey colouration. In lisianthus, the presence of large AVIs produces marked colour intensification in the inner zone of the petal by concentrating anthocyanins above levels that would be possible in vacuolar solution. Electron microscopy studies on lisianthus epidermal tissue failed to detect a membrane boundary in AVI bodies. AVIs isolated from lisianthus cells are shown to have a protein matrix. Bound to this matrix are four cyanidin and delphinidin acylated 3,5-diglycosides (three, new to lisianthus), which are relatively minor anthocyanins in whole petal extracts where acylated delphinidin triglycosides predominate. Flavonol glycosides were not bound. A high level of anthocyanin structural specificity in this association is thus implied. The specificity and effectiveness of this anthocyanin “trapping” is confirmed by the presence in the surrounding vacuolar solution of only delphinidin triglycosides, accompanied by the full range of flavonol glycosides. “Trapped” anthocyanins are shown to differ from solution anthocyanins only in that they lack a terminal rhamnose on the 3-linked galactose. The results of this study define for the first time the substantial effect AVIs have on flower colour, and provide insights into their nature and their specificity as vacuolar anthocyanin traps.
We have identified a family of expansin transcripts that include seven α-expansins (MjExp1 through MjExp7) and three β-expansins (MjExpB1 through MjExpB3) from Mirabilis jalapa (Nyctaginaceae) that show dramatic changes in transcript abundance during the rapid expansion and subsequent senescence of the ephemeral flowers. In general, α-expansin expression was low in small buds, high during maximal elongation of the floral tube, reduced during floral display, and upregulated during calyx infolding and collapse. Transcripts encoding auxin responsive proteins (Aux/IAA) showed a similar pattern of expression. Northern analysis using a set of overlapping probes designed to the MjExp2 transcript demonstrated a gradient of sequence conservation along its length (high to low, from the 5′ to the 3′ end of the coding region), and identified the presence of floral senescence-specific expansins. Beta expansin transcripts were found to be preferentially expressed during early floral development and sharply downregulated coincident with rapid growth. All three β-expansin transcripts are highly related, and ψMjExpB2 is an intronless pseudogene derived from MjExpB1. MjExpB3 appears to have derived from MjExpB1 in a separate gene duplication event, and is predicted to encode a truncated protein.
Growth of petal cells is a basis for expansion and morphogenesis (outward bending) of petals during opening of carnation flowers
(Dianthus caryophyllus L.). Petal growth progressed through elongation in the early stage, expansion with outward bending in the middle stage, and
expansion of the whole area in the late stage of flower opening. In the present study, four cDNAs encoding xyloglucan endotransglucosylase/hydrolase
(XTH) (DcXTH1–DcXTH4) and three cDNAs encoding expansin (DcEXPA1–DcEXPA3) were cloned from petals of opening carnation flowers and characterized. Real-time reverse transcription-PCR analyses showed
that transcript levels of XTH and expansin genes accumulated differently in floral and vegetative tissues of carnation plants
with opening flowers, indicating regulated expression of these genes. DcXTH2 and DcXTH3 transcripts were detected in large quantities in petals as compared with other tissues. DcEXPA1 and DcEXPA2 transcripts were markedly accumulated in petals of opening flowers. The action of XTH in growing petal tissues was confirmed
by in situ staining of xyloglucan endotransglucosylase (XET) activity using a rhodamine-labelled xyloglucan nonasaccharide as a substrate.
Based on the present findings, it is suggested that two XTH genes (DcXTH2 and DcXTH3) and two expansin genes (DcEXPA1 and DcEXPA2) are associated with petal growth and development during carnation flower opening.
The definition of the patterns of cell division and expansion in plant development is of fundamental importance in understanding the mechanics of morphogenesis. By studying cell division and expansion patterns, we have assembled a developmental map of Petunia hybrida petals. Cycling cells were labelled with in situ markers of the cell cycle, whereas cell expansion was followed by assessing cell size in representative regions of developing petals. The outlined cell division and expansion patterns were related to organ asymmetry. Initially, cell divisions are uniformly distributed throughout the petal and decline gradually, starting from the basal part, to form a striking gradient of acropetal polarity. Cell areas, in contrast, increased first in the basal portion and then gradually towards the petal tip. This growth strategy highlighted a cell size control model based on cell-cycle departure time. The dorso-ventral asymmetry can be explained in terms of differential regulation of cell expansion. Cells of the abaxial epidermis enlarged earlier to a higher final extent than those of the adaxial epidermis. Epidermal appendage differentiation contributed to the remaining asymmetry. On the whole our study provides a sound basis for mutant analyses and to investigate the impact of specific (environmental) factors on petal growth.
Imaging of chlorophyll autofluorescence by confocal microscopy in intact whole petals of Arabidopsis thaliana has been used to analyze chloroplast development and redifferentiation during petal development. Young petals dissected from unopened buds contained green chloroplasts throughout their structure, but as the upper part of the petal lamina developed and expanded, plastids lost their chlorophyll and redifferentiated into leukoplasts, resulting in a white petal blade. Normal green chloroplasts remained in the stalk of the mature petal. In epidermal cells the chloroplasts were normal and green, in stark contrast with leaf epidermal cell plastids. In addition, the majority of these chloroplasts had dumbbell shapes, typical of dividing chloroplasts, and we suggest that the rapid expansion of petal epidermal cells may be a trigger for the initiation of chloroplast division. In petals of the Arabidopsis plastid division mutant arc6, the conversion of chloroplasts into leukoplasts was unaffected in spite of the greatly enlarged size and reduced number of arc6 chloroplasts in cells in the petal base, resulting in few enlarged leukoplasts in cells from the white lamina of arc6 petals.
Visual symptoms of the onset of senescence in Sandersonia aurantiaca flowers begin with fading of flower colour and wilting of the tissue. When fully senescent, the flowers form a papery shell
that remains attached to the plant. The cell walls of these flowers have been examined to determine whether there are wall
modifications associated with the late stages of expansion and subsequent senescence‐related wilting. Changes in the average
molecular size of pectin were limited through flower opening and senescence, although there was a loss of neutral sugar‐containing
side‐branches from pectins in opening flowers, and the total amounts of pectin and cellulose continued to rise in cell walls
of fully senescent sandersonia flowers. Xyloglucan endotransglycosylase activity increased in opening and mature flowers,
but declined sharply as flowers wilted. Concomitantly, the proportion of hemicellulose polymers of increasing molecular weight
increased from flower expansion up to the point at which wilting occurred. Approximately 50% of the non‐cellulosic neutral
sugar in mature flower cell walls was galactose, primarily located in an insoluble cell wall fraction. Total galactose in
this fraction increased per flower with maturity, then declined at the onset of wilting. β‐Galactosidase activity was low
in expanding tepals, but increased as flowers matured and wilted.
The expansins comprise a family of proteins that appear to be involved in the disruption of the noncovalent bonds between cellulose microfibrils and cross-linking glycans, thereby promoting wall creep. To understand better the expansion process in Petunia hybrida (petunia) flowers, we isolated a cDNA corresponding to the PhEXP1 alpha-expansin gene of P. hybrida. Evaluation of the tissue specificity and temporal expression pattern demonstrated that PhEXP1 is preferentially expressed in petal limbs during development. To determine the function of PhEXP1, we used a transgenic antisense approach, which was found to cause a decrease in petal limb size, a reduction in the epidermal cell area, and alterations in cell wall morphology and composition. The diminished cell wall thickness accompanied by a reduction in crystalline cellulose indicates that the activity of PhEXP1 is associated with cellulose metabolism. Our results suggest that expansins play a role in the assembly of the cell wall by affecting either cellulose synthesis or deposition.
Senescence of carnation petals progresses gradually, even when climacteric ethylene production is blocked. The most distinct visible changes in the later stages of petal senescence are a fading of flower colour and a change in appearance ("freshness"). Cut carnation cv. Excerea flowers treated with silver thiosulphate were kept in vase solutions with or without 1% (w/v) sucrose under high-temperature conditions (32°C). Changes in pigment content and the micro- morphology of epidermal cells in petals were monitored. The main pigment in 'Excerea' carnation petals was pelargonidin-3-malylglucoside (Pg3MG). A 48-70% reduction in Pg3MG occurred between day-5 and day-15 in petals kept under high-temperature conditions. Petal colour changes, as determined by lower C* and h° values using a colourimeter, were consistent with the reduction in Pg3MG content. Sucrose [1% (w/v)] in the vase water was effective at inhibiting the reduction in pigment content in petals kept under high-temperature conditions. An enlargement of epidermal cells occurred on both the abaxial and adaxial surfaces of petals between day-5 and day-15, irrespective of petal position, temperature conditions, or the composition of the vase solution. This enlargement in epidermal cells could cause the change in appearance of the flowers.
The number of epidermal cells, osmotic potential, and carbohydrate and inorganic ion concentrations in petals during development and opening of Tweedia caerulea D. Don flowers was studied. The number of adaxial epidermal cells was greater than that of abaxial epidermal cells at all stages. The increase in cell number stopped at the stage just before flower opening. The size of adaxial and abaxial epidermal cells increased during flower development and opening. The results indicate that petal growth before flower opening depended on cell division and expansion, and petal growth during flower opening was attributable to petal cell expansion. Osmotic potential decreased and fructose, glucose and sucrose concentrations in the petals gradually increased during flower opening. Starch content and total inorganic ion concentration were almost constant during flower opening. Decreased osmotic potential is mainly attributed to increased glucose, fructose and sucrose concentrations. It is concluded that an increase in these sugar concentrations largely contributes to the decrease in osmotic potential. This decrease may facilitate water influx to cells, thereby maintaining pressure potential, which is apparently involved in petal cell expansion associated with flower opening.
The dry matter and carbohydrate contents of intact growing ‘Sonia’ rose corollas were measured from an immature bud to full expansion of the petals. Reducing sugars and starch, but not sucrose, accumulated throughout most of the corolla development. These findings were compared with the carbohydrate changes in the corollas of flowers cut at different stages and allowed to age with their stems either in water or in a sucrose-containing solution. For a few days after cutting the carbohydrate metabolism of the cut flower roughly paralleled that of the intact flower until starch hydrolysed to maintain the soluble carbohydrate pool. Feeding with the sucrose solution maintained the soluble carbohydrate levels and retarded the hydrolysis of starch.
The cut flowers were fed with ¹⁴C-sucrose and the labelled metabolites in the leaves and flowers were analysed. Active incorporation of ¹⁴C into ethanol-soluble carbohydrates, starch and ethanol-insoluble material was found indicating that an active anabolic phase precedes the catabolic phase during the senescence of the cut flower. The findings are discussed in relation to the source-sink hypothesis of flower development, with regard to the senescence and growth of the corollas of cut and intact flowers respectively.
Ultrastructural changes associated with carnation petal senescence were investigated using ethylene levels of individual petals as a physiological monitor of the senescence process. Limited vacuolar and cytoplasmic vesiculation was observed in pre-senescent petals which became more extensive in pre-climacteric tissues, along with dilation of the outer mitochondrial membrane. Climacteric mesophyll tissue was characterized by widespread cytolysis. Intact cells possessed a highly reduced cytoplasm and vacuoles with electron-dense deposits. Degenerative changes became evident in the vasculature at this stage. These included occlusion of the sieve plate, and membrane abnormalities in the companion cells. Post-climacteric tissue was characterized by loosening of wall fibrillar structure in the vasculature, the appearance of intracellular cytoplasmic debris and cells completely devoid of contents. These changes are discussed in relation to developmental regulation on the one hand, and increasing levels of membrane disorganisation on the other, leading to a possible 'error catastrophe' and final senescence.
Application of forchlorfenuron (CPPU) to flower buds induces morphologically different paracorollas, i.e., wide and narrow type, in torenia (Torenia fournieri L.). We investigated the morphological properties and the role of floral homeotic genes in the formation of these two types of paracorolla. The morphology of epidermal cells and distribution pattern of vascular bundles in the wide paracorolla was the same as in the petal; however, in the narrow paracorolla, the morphology of epidermal cells was either petal-like or stamen-like, and the distribution pattern of vascular bundles was stamen-like. In situ hybridization analysis of the floral homeotic genes showed that a class A gene, T. fournieri SQUAMOSA (TfSQUA), and class B genes, TfDEFICIENS (TfDEF) and TfGLOBOSA (TfGLO), were expressed in the broad part of the primordia of the wide paracorolla, as in the petal. Class C genes, TfPLENA1 (TfPLE1) and TfFARINELLI (TfFAR), were only expressed at the margin of the primordia. However, in the primordia of the narrow paracorolla, TfSQUA was only expressed at the margin, but the class B genes and one of the class C genes (TfPLE1) were expressed in a broad section, as in the primordia of the wide paracorolla. This expression pattern in the narrow paracorolla was intermediate between that of the petal and the stamen. In later developmental stages, quantitative real-time PCR analyses showed that, in the wide paracorolla, TfSQUA and class B genes were highly expressed but the expression of class C genes, as in the petal, was low. In the narrow paracorolla, class B genes were also highly expressed as in the petal; however, the expression of both TfSQUA and the class C genes was low, as in the stamen and the petal, respectively. This expression pattern probably reflects the unstable floral organ identity of the narrow paracorolla, and the expression pattern in paracorollas is determined by the site where the paracorolla is formed.
Flower opening is important for floricultural crops. The mechanisms flower opening associated with the expansion of petal cells were investigated in Eustoma grandiflorum (Raf.) Shinn. Eustoma petals showed marked changes in their fresh weight, shape, and color during flower opening. Concurrently, petal cell-wall extensibility increased. This suggests that petal growth through flower opening is mainly caused by cell expansion. Expansin and xyloglucan endotransglycosylase/hydrolase (XTH) are known as representative proteins that loosen cell walls in plants. Three expansins and one XTH gene were isolated from opening Eustoma petals. We monitored for the first changes in their protein abundance in growing petals by Western blot analysis using antibodies to specifically detect expansin or XTH. The accumulation of these proteins marked the highest amount in petals when the flower was blooming and the petals were bending outwards. Thus, we showed that expansins participate in continuous petal growth from bud to opening flower and XTH plays a role in rapid petal growth accompanied by dynamic changes in petal fresh weight and petal shape.
Vegetative apices, floral apices and flower petals of five Solanaceae (potato, tomato, tobacco, petunia and nightshade) and of corn and Nigella were examined with an electron microscope for the presence of protein bodies in the cell vacuoles. Electron-dense bodies were found in vacuoles of all plants investigated but not in every tissue examined. The bodies observed in the apices are similar to the protein bodies previously found in tomato leaves where they appear to be related to the presence of chymotrypsin inhibitor I protein (Shumway et al., 1970). The bodies appeared in very young cells in small vacuoles, disappearing as the cell matured. They are apparently related to the growth and development of the new cells. The results suggest that plants may regulate specific proteins within the apical region through selective synthesis and degradation of proteins accompanied by compartmentalization in the vacuole.
A new guillotine thermocouple psychrometer was used to make continuous measurements of water potential before and after the excision of elongating and mature regions of darkgrown soybean (Glycine max L. Merr.) stems. Transpiration could not occur, but growth took place during the measurement if the tissue was intact. Tests showed that the instrument measured the average water potential of the sampled tissue and responded rapidly to changes in water potential. By measuring tissue osmotic potential (Ψ s ), turgor pressure (Ψ p ) could be calculated. In the intact plant, Ψ s and Ψ p were essentially constant for the entire 22 h measurement, but Ψ s was lower and Ψ p higher in the elongating region than in the mature region. This caused the water potential in the elongating region to be lower than in the mature region. The mature tissue equilibrated with the water potential of the xylem. Therefore, the difference in water potential between mature and elongating tissue represented a difference between the xylem and the elongating region, reflecting a water potential gradient from the xylem to the epidermis that was involved in supplying water for elongation. When mature tissue was excised with the guillotine, Ψ s and Ψ p did not change. However, when elongating tissue was excised, water was absorbed from the xylem, whose water potential decreased. This collapsed the gradient and prevented further water uptake. Tissue Ψ p then decreased rapidly (5 min) by about 0.1 MPa in the elongating tissue. The Ψ p decreased because the cell walls relaxed as extension, caused by Ψ p , continued briefly without water uptake. The Ψ p decreased until the minimum for wall extension (Y) was reached, whereupon elongation ceased. This was followed by a slow further decrease in Y but no additional elongation. In elongating tissue excised with mature tissue attached, there was almost no effect on water potential or Ψ p for several hours. Nevertheless, growth was reduced immediately and continued at a decreasing rate. In this case, the mature tissue supplied water to the elongating tissue and the cell walls did not relax. Based on these measurements, a theory is presented for simultaneously evaluating the effects of water supply and water demand associated with growth. Because wall relaxation measured with the psychrometer provided a new method for determining Y and wall extensibility, all the factors required by the theory could be evaluated for the first time in a single sample. The analysis showed that water uptake and wall extension co-limited elongation in soybean stems under our conditions. This co-limitation explains why elongation responded immediately to a decrease in the water potential of the xylem and why excision with attached mature tissue caused an immediate decrease in growth rate without an immediate change in Ψ p.
Establishing the technique for controlling the rate of cut flower opening is important to maintain appropriate cut flower supplies to meet consumer demand. Cut flowers of Eustoma grandiflorum (Raf.) Shinn. were held in a vase solution containing (±)-abscisic acid (ABA), 6-benzylaminopurine (BA), gibberellic acid-3 (GA), methyl jasmonate (MeJA) or 1-naphthaleneacetic acid (NAA) at 100 μM. MeJA accelerated flower opening. Only the timing of flowering was earlier, and there was no change in maximum flower diameter at the fully open stage. Expansin and xyloglucan endotransglycosylase/hydrolase (XTH), regarded as cell wall loosing proteins, participate in petal growth from bud stage to the fully open stage in Eustoma. MeJA also accelerated the expression of EgEXPA2, EgEXPA3 and EgXTH1 mRNA and the accumulation of expansin and XTH protein in petals. Meanwhile, the acceleration of both flower opening and expression of these genes was not observed by ABA, BA or GA treatment. It was proposed that early flower opening by JA treatment resulted from petal cell wall loosening by accelerated expression of expansin and XTH.
An unknown sugar-like compound other than glucose, fructose, sucrose and myo-inositol was detected in the ethanol extract of carnation (Dianthus caryophyllus L.) leaves and isolated using high performance liquid chromatography. The isolated compound was identified as D-(+)-chiro-inositol monomethylether (pinitol) by 1H-NMR and 1C-NMR spectra. Pinitol was the most abundant sugar in the leaf and also was present in stem, petal and the remaining part of flower in large amounts in 4 cultivars tested. In petals, the pinitol content remained constant during flower bud development on a fresh weight basis, but the organ pinitol content increased markedly. The pinitol content was also high in the other parts of the flower. These findings suggest that pinitol, a major sugar constituent, contributes to the bud growth and subsequent petal opening in the carnation together with other metabolic sugars, such as glucose and sucrose.
Associations between petal growth patterns and the formation of three-dimensional corolla shapes were investigated using five cultivars of Eustoma grandiflorum with different corolla shapes. The cultivars showing outward curvature in the distal regions of petals exhibited rapid distal petal widening during the later stages of flower opening, whereas the cup-shaped cultivars exhibited rapid widening in the basal to middle regions of petals during earlier stages of flower development. In a funnel-shaped cultivar showing no apparent curvature, no regional differences in petal expansion were found. Distal petal widening was not due to cell widening but was the result of the rapid expansion both in width and length of petal cells, whereas basal expansion was partly due to cell widening. The data obtained suggested that non-uniform cell expansion within a petal resulted in petal distortion, and this played a central role in corolla curvature of E. grandiflorum.
Changes in water relations, carbohydrate contents, and acid invertase activity in expanding gladiolus perianths on cut stems were studied.1. The specific rate of elongation of the perianth was fastest just before anthesis, but slowed down while the floral organs unfolded; it approached zero as the perianth became fully expanded.2. Pressure potential of tissue water was high while the perianth was growing rapidly.3. Fructose and glucose were the predominant soluble sugars in the perianth. These solutes were considered to contribute to the low osmotic potential of perianth tissues during their elongation process.4. Acid invertase activity of perianth tissue was correlated to the specific rate of elongation. There was no correlation between the enzyme activity and the growth rate when the perianth was wilting.5. Starch in florets was considered to be the primary source of soluble carbohydrates which contribute to the early stages of flower expansion. 6. At the wilting stage, soluble sugars were probably translocated from the perianth to other organs.
Effects of pulse treatment with silver thiosulfate complex (STS), sucrose and their combination on the quality and vase life of cut Eustoma grandiflorum flowers were investigated. Cut Eustoma flowers with two open florets and four buds were treated with 0.2 mM STS, 4% sucrose and 0.2 mM STS combined with 4% sucrose and kept at 23°C, 70% relative humidity in the dark for 20 h. The vase life of cut flowers is considered to be from harvest to when less than two open florets are subtended with erect pedicels. Treatment with STS plus sucrose and sucrose alone extended vase life, advanced bud opening, and increased anthocyanin concentration in the colored parts of petals more than did STS alone. These results indicate that pulse treatments including sucrose are more effective than STS alone to improve the quality of cut, floret-bearing Eustoma flowers which are not highly sensitive to ethylene.
There have been few reports on the morphology of flower opening, despite its horticultural significance. It is not clear when cell division stops during rose petal development or what changes occur in cell morphology. This study aims to clarify the details of cell morphological changes during rose petal development. Rose (Rosa hybrida L. 'Sonia') petals were sampled in six flower bud stages. Cell morphological changes were observed by light microscopy, transmission and scanning electron microscopy using cross sections of the petals, and the number of epidermal cells was measured using Nomarski differential interference contrast microscopy. The number of epidermal cells increased with flower opening, but the rate of increase in the number of abaxial epidermal cells slowed down at an earlier stage than in adaxial epidermal cells. The increase in the epidermal cell area was much more rapid in later stages compared with the increase in cell number, suggesting that petal growth in later stages is mainly due to cell expansion. During flower opening, the unique expansion of spongy parenchyma cells produced large air spaces. Epidermal cells of the upper part showed obvious lateral expansion. In particular, marked expansion of adaxial epidermal cells with enlargement of the central vacuole was observed. Differences in the patterns of cell expansion among cell types and locations would contribute to the reflex of petals during rose flower opening. JSHS
Rhododendron flower development occurs in three easily defined stages: a pre-rest stage, during which petal growth is mainly by cell elongation; an indeterminate rest period; and an after-rest stage, that begins when the flowers resume growth and ends at anthesis.
Early in the pre-rest stage of development, protein bodies and amyloplasts accumulate in the petals. The epidermal cells accumulate only protein bodies and the mesophyll cells accumulate amyloplasts that have a few small protein bodies around the periphery. The subepidermal cells and the cells around the vascular bundles accumulate both large protein bodies and amyloplasts. During the rest period there is a cessation of cell elongation and the reserve protein bodies and amyloplasts remain intact.
The protein bodies in all of the cells including those around the amyloplasts are proteolized early in the after-rest stage of development. Digestion of the starch granules occurs when the petals are about one-half their final size.
Epidermal-cell expansion during after-rest is relatively uniform; the walls between adjacent epidermal cells remain attached to each other. The mesophyll cells elongate irregularly and the walls of adjacent cells separate giving rise to large intercellular spaces.
At anthesis the petal cells consist of a cell wall, a parietal cytoplasm, and a large central vacuole.
The co-ordination of expression of anthocyanin biosynthetic genes was studied in developing flowers. Four genes encoding enzymes operating late in the anthocyanin biosynthetic pathway are induced together during flower development but the early steps appear to be induced more rapidly. Co-ordination of expression could imply a common regulatory mechanism controlling the expression of metabolically related genes. The data presented here show that while four genes may share such a mechanism for the control of their expression during flower development, different control processes regulate the early steps of the pathway. Spatially, gene expression is patterned across the flower and appears to be very similar for all the biosynthetic genes. However, the observed influence of the regulatory gene Delila shows that the spatial co-ordination of gene expression must involve more than one regulatory system. Delila itself appears to have a dual function, being required for activation of expression of the later genes in the flower tube but repressing chalcone synthase gene expression in the mesophyll of the corolla lobes. It is postulated that common signals induce the expression of genes in the pathway during flower development. The data presented here suggest that the same regulatory mechanism interprets these signals for four of the genes encoding the later biosynthetic enzymes, but that different or modified mechanisms interpret the signals to control expression of chalcone synthase and chalcone isomerase genes in Antirrhinum flowers.
Nitrogen metabolism including nitrate reductase (EC 1.6.6.1), glutamate dehydroge-nase (EC 1.4.1.2) and glutamate-oxalacetate aminotransferase (EC 2.6.1.1) activities were studied during growth of petals taken from carnation flowers (Dianthus caryophyllus L. cv. Sir Arthur) together with senescence parameters (lipid hydroper-oxides, soluble amino acids and permeability). A slight decline in nitrogen percentage on a dry weight basis was found together with a sharp decrease in nitrate reduct-ase, glutamate-oxalacetate aminotransferase and glutamate dehydrogenase activities during the maximum growth phase, which was characterized by increase in respiration, dry weight, length, organic nitrogen and DNA per petal. Changes generally associated with senescence, like lipid hydroperoxide and soluble ammo nitrogen accumulation and increases in permeability began to appear already during early growth. The results indicate that permeability and proteolysis may be closely related. The possible significance of the decrease in nitrogen percentage and enzyme activities during growth of petals is discussed.
We found that the corolla of petunia (Petunia hybrida Vilm.) could be conspicuously enlarged by the separate application of three cytokinins: forchlorfenuron (CPPU), N 6 -benzylaminopurine (BA), and zeatin. To obtain the same enlargement as that achieved by CPPU, approximately 30 and 900 times the concentration of BA and zeatin, respectively, were required. CPPU at 3.2 mmol/L increased the limb area of the corollas of 15 cultivars to between 1.3 and 2.4 times (1.8 times on average) the size of the control area. The increase was negatively correlated (R = 0.58) with the ''genetic'' limb area (i.e., that of the untreated plant). The enlargement of the corolla caused by cytokinin application was mainly attributed to an increase in cell number in most cultivars. This increase resulted from a high rate of cell proliferation and from prolongation of the cell proliferation phase during corolla development. This anatomical change caused by cytokinin application was similar to the anatomical difference among cultivars because genetic differences in limb area resulted mainly from differences in cell number.
Petal growth associated with flower opening depends on cell expansion. To understand the role of soluble carbohydrates in petal cell expansion during flower opening, changes in soluble carbohydrate concentrations in vacuole, cytoplasm and apoplast of petal cells during flower opening in rose (Rosa hybrida L.) were investigated. We determined the subcellular distribution of soluble carbohydrates by combining nonaqueous fractionation method and infiltration-centrifugation method. During petal growth, fructose and glucose rapidly accumulated in the vacuole, reaching a maximum when petals almost reflected. Transmission electron microscopy showed that the volume of vacuole and air space drastically increased with petal growth. Carbohydrate concentration was calculated for each compartment of the petal cells and in petals that almost reflected, glucose and fructose concentrations increased to higher than 100 mM in the vacuole. Osmotic pressure increased in apoplast and symplast during flower opening, and this increase was mainly attributed to increases in fructose and glucose concentrations. No large difference in osmotic pressure due to soluble carbohydrates was observed between the apoplast and symplast before flower opening, but total osmotic pressure was much higher in the symplast than in the apoplast, a difference that was partially attributed to inorganic ions. An increase in osmotic pressure due to the continued accumulation of glucose and fructose in the symplast may facilitate water influx into cells, contributing to cell expansion associated with flower opening under conditions where osmotic pressure is higher in the symplast than in the apoplast.
An ultrastructural study of petal cells of wallflower (Erysimum cheirii) of the family Brassicaceae shows that the adaxial epidermal cells are of the conical papillate type whereas the cells of
the abaxial epidermis are lenticular in shape. The abaxial epidermis contains stomata, which are solitary and lack any obvious
subsidiary cells. Pigmentation is apparent in both epidermal and internal mesophyll cells and results from the presence of
both chromoplasts and large cytoplasmic vesicles containing pigment. These pigmented vesicles are very obvious in preparations
of fixed isolated petal cells. Chromoplasts are of the globular type and are present in significant numbers in both epidermal
and mesophyll cells. Division of chloroplasts in young petals prior to bud break appears to give rise to the populations of
chromoplasts observed in mature petals since there was no evidence of chromoplast division itself. The development of wallflower
petals and their chromoplasts is discussed in relation to development of petals in the related species Arabidopsis thaliana. Copyright 1999 Annals of Botany Company
We modified Sato's lead stain in order to obtain a more stable staining solution. The staining solution formed no lead carbonate film on the surface for periods up to 3 hr after exposure to the air. No precipitates were formed in the solution kept at room temperature for over 1 year. The best results were obtained when Epon sections were stained with the new stain for 2 min.
The plant cell wall is a strong fibrillar network that gives each cell its stable shape. To enlarge, cells selectively loosen this network, enabling it to yield to the expansive forces generated by cell turgor pressure. Twenty-five years ago, cell wall loosening was mostly explored within the context of rapid auxininduced growth, particularly in terms of the acidgrowth hypothesis (19) proposed independently by Hager in Germany and by Cleland and Rayle in the USA. Discussion of cell wall structure centered on the influential “Albersheim model” first presented by Keegstra et al. (10) (Fig. 1A), and extension growth was widely conceived of as the result of enzymatic hydrolysis of matrix polysaccharides (12). Today, some new characters such as expansin, xyloglucan endotransglycosylase, and membranebound endoglucanases have made an entrance into this scene, forcing a re-evaluation of how wall enlargement is controlled. This brief history summarizes key concepts of cell wall loosening, a topic that inevitably is linked to our view of cell wall structure. EVOLVING MODELS OF CELL WALL STRUCTURE Based on selective enzymatic degradation of sycamore suspension cell walls, Keegstra et al. (10) proposed that matrix polymers, consisting of xyloglucan, pectic polysaccharides, and structural proteins, were covalently linked to form a giant macromolecular network, illustrated in Figure 1A. In this model cellulose is bonded to the matrix via H-bonding to xyloglucans. This scheme presented several possible sites for wall loosening. For instance, scission of any of the matrix linkages could plausibly to lead to wall extension, since they are arranged in a chain-link series. Keegstra et al. also proposed that low pH might directly weaken the H-bonding between xyloglucan and cellulose, thereby allowing microfibril slippage, but subsequent work from the same laboratory later made this idea untenable. When later work could not confirm the pectinxyloglucan linkage, an alternative model gained fa
Dry weight, water content, soluble carbohydrate content, and carbohydrate composition of daylily (Hemerocallis hybrid cv Cradle Song) flower petals were monitored in the 3 d leading up to full opening and in the first day of senescence. Timing of events was related to the time (hour 0) when flower expansion was 60% complete. Petal dry weight increased linearly from hour -62 (tight bud) to hour 10 (fully developed flower), then fell rapidly to hour 34 as senescence advanced. Increase in water content was proportional to dry weight increase from hour -62 to hour -14, but was more rapid as the bud cracked and the flower opened, giving an increase in fresh weight/dry weight ratio. Soluble carbohydrate was 50% of petal dry weight up to hour 10, then decreased during senescence to reach 4% by hour 34. Up until hour -14, fructan accounted for 80% of the soluble carbohydrate in the petals, whereas hexose accounted for only 2%. Fructan hydrolysis started just prior to bud crack at hour -14, reaching completion by hour 10 when no detectable fructan remained, and fructose plus glucose accounted for more than 80% of the total soluble carbohydrate. The proportion of sucrose remained constant throughout development. Osmolality of petal cell sap increased significantly during fructan hydrolysis, from 0.300 to 0.340 osmolal. Cycloheximide applied to excised buds between hour -38 and hour -14 halted both fructan hydrolysis and flower expansion. The findings suggest that onset of fructan hydrolysis, with the concomitant large increase in osmoticum, is an important event driving flower expansion in daylily.
The mechanism of dusky reddish-brown "kaki" color development of morning glory, Ipomoea nil cv. Danjuro, was studied. Three major known anthocyanins were isolated as glucosylated pelargonidin derivatives. Measurement of the vacuolar pH with proton-selective microelectrodes revealed the vacuolar pH of the colored cell of open flowers to be 6.8, while that of buds was 5.8. Mixing of the three anthocyanins according to the composition ratio in petals at pH 6.8 allowed the identical color to that of petals to be reproduced. The typical "kaki" color development was mostly caused by 5-OH free acylated anthocyanins, which have two lambdamax around 435 and 535 nm in the visible region.
Lisianthus (Eustoma)
- N Katsutani
Katsutani, N. 2006. Lisianthus (Eustoma). p. 230-236. In: Japan.
Soc. Hort. Sci. (ed.). Horticulture in Japan 2006. Nakanishi
Printing. Kyoto.