Bud Structure Research Articles

Investigating properties of sweet cherry (Prunus avium) flower buds that help promote freezing avoidance by supercooling.

Mechanisms involved in the supercooling of plant tissues as a means of low temperature survival are still not fully understood. We investigated properties that may promote supercooling in overwintering sweet cherry (Prunus avium) flower buds. We conducted experiments on sweet cherry flower buds using differential thermal analysis (DTA) and observed locations of ice formation in the bud structure. We also used anatomical development and water-soluble dye uptake throughout the overwintering period to identify changes that correlate with gain and loss of supercooling capacity. Our results revealed barriers to ice propagation are likely unique to each primordium, as inferred from exotherms produced from buds subjected to DTA, although multiple primordia may freeze simultaneously. Ice is accommodated between the bud scales and within the bud axis; however, full expression of supercooling was not dependent on the presence of scales. Anatomical and DTA studies revealed a correlation between vascular differentiation in primordia and loss of supercooling in the spring; these observations were at a higher temporal resolution than previously described for Prunus. Furthermore, disturbing tissues subtending the primordia interfered with typical patterns of supercooling, indicated more erratic and numerous exotherms produced during DTA. In summary, sweet cherry flower buds undergo extra-organ freezing. In winter, a barrier to ice propagation in the region directly subtending primordia protects the flower from freezing damage, but in the spring xylem differentiation in primordia provides a conduit for ice propagation that compromises supercooling.

CT image-based 3D inflorescence estimation of Chrysanthemum seticuspe.

To study plant organs, it is necessary to investigate the three-dimensional (3D) structures of plants. In recent years, non-destructive measurements through computed tomography (CT) have been used to understand the 3D structures of plants. In this study, we use the Chrysanthemum seticuspe capitulum inflorescence as an example and focus on contact points between the receptacles and florets within the 3D capitulum inflorescence bud structure to investigate the 3D arrangement of the florets on the receptacle. To determine the 3D order of the contact points, we constructed slice images from the CT volume data and detected the receptacles and florets in the image. However, because each CT sample comprises hundreds of slice images to be processed and each C. seticuspe capitulum inflorescence comprises several florets, manually detecting the receptacles and florets is labor-intensive. Therefore, we propose an automatic contact point detection method based on CT slice images using image recognition techniques. The proposed method improves the accuracy of contact point detection using prior knowledge that contact points exist only around the receptacle. In addition, the integration of the detection results enables the estimation of the 3D position of the contact points. According to the experimental results, we confirmed that the proposed method can detect contacts on slice images with high accuracy and estimate their 3D positions through clustering. Additionally, the sample-independent experiments showed that the proposed method achieved the same detection accuracy as sample-dependent experiments.

The role of p63 in embryonic external genitalia outgrowth in mice.

Embryonic external genitalia (genital tubercle [GT]) protrude from the cloaca and outgrow as cloacal development progresses. Individual gene functions and knockout phenotypes in GT development have been extensively analyzed; however, the interactions between these genes are not fully understood. In this study, we investigated the role of p63, focusing on its interaction with the Shh-Wnt/Ctnnb1-Fgf8 pathway, a signaling network that is known to play a role in GT outgrowth. p63 was expressed in the epithelial tissues of the GT at E11.5, and the distal tip of the GT predominantly expressed the ΔNp63α isoform. The GTs in p63 knockout embryos had normal Shh expression, but CTNNB1 protein and Fgf8 gene expression in the distal urethral epithelium was decreased or lost. Constitutive expression of CTNNB1 in p63-null embryos restored Fgf8 expression, accompanied by small bud structure development; however, such bud structures could not be maintained by E13.5, at which point mutant GTs exhibited severe abnormalities showing a split shape with a hemorrhagic cloaca. Therefore, p63 is a key component of the signaling pathway that triggers Fgf8 expression in the distal urethral epithelium and contributes to GT outgrowth by ensuring the structural integrity of the cloacal epithelia. Altogether, we propose that p63 plays an essential role in the signaling network for the development of external genitalia.

Are scale leaves essencial in temperate-cold climates? An evaluation in tree species from temperate rainforests of South America

The development of scaly buds (= cataphylls) has been traditionally associated with seasonally cold climates, although only few species from the southern hemisphere were investigated in this regard. The present work focuses on apical and axillary buds of seven tree species native to the South-American Temperate Rainforests (STR). Due to differences in the lineages from which these species derived, high levels of inter-specific variation in bud structure were expected. Apical and axillary buds were dissected under stereomicroscope, and the sizes of their parent shoots were evaluated. Cataphylls and leaf primordia were counted, and the presence of colleters and/or trichomes registered. Both intra- and inter-specific variations in bud structure were found. The apical buds were scaly in two out of seven species, and naked in the other species. Axillary buds were scaly in all but one species. In general terms, larger shoots developed buds with more organs. The presence of colleters (in four species) was not restricted to those buds lacking an outer cover of cataphylls. Further studies should focus on the relevance at a broader scale of colleters and trichomes as protective structures in tree buds.

Boiling heat transfer characteristics of bionic flower bud structure microchannels

Boiling heat transfer characteristics of bionic flower bud structure microchannels

Three‐dimensional virtual flower bud of walnut tree based on micro‐computed tomography

AbstractWalnut (Juglans regia L.) is one of the most widely cultivated and high‐yielding tree nut in temperate areas. In‐depth study of walnut flower bud structure has important practical applications for early determination of flower bud's quality and to promote scientific production guidance. The flower buds of walnut tree were scanned by micro‐computed tomography (Micro‐CT) and the three‐dimensional (3D) virtual flower buds of the same were reconstructed based on the scanned images. The reconstructed flower buds exhibited the shape, size, exterior characteristics, and internal structure clearly as that of real walnut flower buds, including scales, leaf primordia, bracts, and female floral primordia from out‐ to inward. The results showed that the female flower bud had nine scales, seven leaf primordia and two female floral primordia. The male flower buds are pinecone‐shaped and contain multiple male flowers. Each male flower is divided into bracts, calyx, and stamens from outside to inside. Our study showed that the Micro‐CT could achieve the 3D visualization of walnut flower buds, and could also create videos of the virtual observation of fruit tree flower buds, providing an effective way for digital flower bud construction.

Bud structure and development in trees of a neotropical savanna differing by leaf persistence

AbstractThe climatic seasonality affects markedly plant organs' development in the neotropical savannas. Essential understandings about bud structure and its development in deciduous, semi‐deciduous and evergreen trees are unknown in Cerrado vegetation, the largest neotropical savanna. We aimed to determine the bud development, structure and the relationship between budburst and dry and wet seasons for 15 tree species distributed in leaf phenological groups. We labelled five buds in each of the five adult individuals in tree species of each phenological group at the dry season's peak in July 2016. The labelled buds were monitored every week since their opening up to branch development and leaf production in April 2017. Another group of buds was collected at the dry–wet season transition to determine the bud structure. Deciduous tree species showed preformed leaves in buds, the evergreen trees had neoformed leaves, and semi‐deciduous trees had buds with preformed and neoformed leaves. Cataphylls were protecting the buds in all deciduous trees and the semi‐deciduous species Eriotheca gracilipes. Budburst in the deciduous species and semi‐deciduous except for Guapira noxia and Xylopia aromatica occurred at the dry season's peak. In the evergreen trees, buds developed only after the wet season start. While deciduous and evergreen tree species presented different bud structures and development, the semi‐deciduous trees shared the bud traits with phenological groups. We captured distinct growth strategies in groups of trees according to leaf persistence and bud structural and developmental traits.

Determination of the Characteristic Structures of Low Temperature Exotherm in Grapevine Buds and Their Relationship with the Bud Structure

Determination of the Characteristic Structures of Low Temperature Exotherm in Grapevine Buds and Their Relationship with the Bud Structure

Naked resting bud morphologies and their taxonomic and geographic distributions in temperate, woody floras.

Resting bud cataphylls are often assumed to play an essential protective role in winter due to their widespread presence among temperate, woody plants. This view is challenged by our documentation of significant numbers of temperate woody angiosperm taxa with naked buds that overwinter without cataphyll protection. We inventoried temperate, woody angiosperm taxa reported to have resting buds without cataphyll protection in winter and for the first time characterised the morphological and functional diversity of naked buds. Using this new classification of bud types, the taxonomic and geographic distributions of taxa with naked buds were summarised and relationships between plant functional traits and bud type were investigated. Naked buds are not, as long presumed, markedly rare in temperate, woody floras. They occur in at least 87 genera in 42 families throughout the angiosperm phylogeny in various morphologically distinct manifestations. The geographic distribution of species with naked buds in temperate areas was found to be associated with summer precipitation, but not with winter climatic variables. Resting bud structure is not necessarily a trait optimised solely for winter survival. A taxon's bud composition may be influenced by factors such as biogeographic history and ontogenetic pattern of leaf formation over the growing season.

Freezing stress damage and growth viability in Vaccinium macrocarpon Ait. bud structures.

After a freezing event, it can be challenging to extrapolate levels of freezing damage to plant growth viability based on the presence or absence of symptoms in specific bud tissues. This study investigated the relationship between freezing damage in terminal buds during ecodormancy and their viability during the subsequent growing season. We identified the bud structure that best explained this relationship, and developed a model to explain the changes in bud cold hardiness. Vertical shoots (uprights) of Vaccinium macrocarpon Ait. were sampled in central Wisconsin during Spring of 2018 and 2019. Sets of uprights with terminal buds were subjected to controlled freezing tests, followed by either visual freeze damage evaluation or assessment of shoot viability by growth assays. We determined the Browning Lethal‐Temperature50 (BLT50), as temperature for 50% damage (tissue browning) at each bud structure, and Growth Lethal‐Temperature50 (GLT50) temperature where 50% reduction in growth viability occurred. Two models were constructed to explain: (1) bud structure damage and growth viability, and (2) GLT50's seasonal changes, representing the cold hardiness variations, and environmental factors. The correlation between the BLT50 and GLT50 values was closest for the bud scales and bud axis, indicating the better correspondence between levels of freezing damage with the impact on the growth potential. In addition, the latter was also the most suitable candidate for modeling due to easier damage evaluation. The freezing stress damage of the bud axis explained comparatively best the resulting growth viability. Seasonal changes in GLT50 were best explained by temperature indices based on daily minimum and on maximum temperatures over 10‐day periods. However, among the model components, daily maximum temperatures had the greatest influence on V. macrocarpon cold hardiness changes during ecodormancy.

The Relationship Between Bud Size and Exotherm Formation in Dormant Buds of Grapevine

This study was conducted to determine the relationship between bud size and low temperature exotherm (LTE) formation in dormant period of grapevines. For this purpose, primary and secondary buds of Karaerik (Vitis vinifera L.) and 53 Pazar 01 (Vitis labrusca) genotypes which are known to have differences between the bud structure and size, were examined separately. In the study carried out in 2016-2017 and 2017-2018 dormant periods, low temperature exotherms were determined by Differential Thermal Analysis (DTA) method in order to determine the freezing point of the buds. Dormant buds of grapevine size were determined by microscopic imaging of the sections taken after histological procedures. It was demonstrated by the DTA test that the buds with different histological structures had different character and number of LTE. In this study, it was determined that bud samples belonging to Vitis vinifera L. form exotherm at lower temperatures than bud samples belonging to Vitis labrusca species. For both genotypes, it was determined by the histological determinations that the primary buds had a larger structure than the secondary buds. In the study, it was found that the buds with an area less than 0.010 mm2 did not produce LTE. As a result of the study, it was found that the bud structure and size were effective on LTE formation of grapevine dormant buds.

Freezing stress survival mechanisms in Vaccinium macrocarpon Ait. terminal buds.

Plants' mechanisms for surviving freezing stresses are essential adaptations that allow their existence in environments with extreme winter temperatures. Although it is known that Vaccinium macrocarpon Ait. buds can acclimate in fall and survive very cold temperatures during the winter, the mechanism for survival of these buds is not known. The main objective of this study was to determine which of the two major mechanisms of freezing stress survival, namely, deep supercooling or freeze-induced dehydration, are employed by V. macrocarpon terminal buds. In the present study, no low-temperature exotherms (LTEs) were detected by differential thermal analysis. Furthermore, a gradual reduction of relative liquid water content in the inner portions of buds during magnetic resonance imaging (MRI) scans performed between 0 and -20°C (where no damage was detected in controlled freezing tests (CFT)) indicates these buds may not deep supercool. The higher ice nucleation activity of outer bud scales and the appearance of large voids in this structure in early winter, in conjunction with the MRI observations, are evidence supportive of a freeze-induced dehydration process. In addition, the presence of tissue browning in acclimated buds as a result of freezing stress was only observed in CFT at temperatures below -20°C, and this damage gradually increased as test temperatures decreased and at different rates depending on the bud structure. Ours is the first study to collect multiple lines of evidence to suggest that V. macrocarpon terminal buds survive long periods of freezing stress by freeze-induced dehydration. Our results provide a framework for future studies of cold hardiness dynamics for V. macrocarpon and other woody perennial species and for the screening of breeding populations for freezing stress tolerance traits.

The growth of flower bud, life history, and population structure of Rafflesia arnoldii (Rafflesiaceae) in Bengkulu, Sumatra, Indonesia

Abstract. Susatya A. 2020. The growth of flower bud, life history, and population structure of Rafflesia arnoldii (Rafflesiaceae) in Bengkulu, Sumatra, Indonesia. Biodiversitas 21: 792-798. The life history of Rafflesia arnoldii R.Br. is the reflection of the complex interaction between flower bud development and the external environments in order to reach its optimal survivorship. The objectives of the study were to determine the growth of flower buds at various development stages, to reconstruct the life history, and to know the population structure of R. arnoldii. The study was carried out at Taba Penanjung, Bengkulu Province, Indonesia. Two populations consisting of 17 individual buds of R. arnoldii were selected for the research. All buds were categorized into six visible stages, mapped, measured their diameters, and recorded their fates every two weeks for six months. The exponential model of growth development was applied to reconstruct the life history. The results showed that buds from the perigone stage respectively grew 3.5 and 12 times faster than those from the bract and cupule stages. The exponential growth of flower bud was confirmed, and explained by Y = 0.785 e0.0052 X, where Y and X were respectively diameter and age of flower bud. The complete life history of R. arnoldii required 3.5 to 5 years, where a female flower needed a longer time than a male flower. The population structure of R. arnoldii was not constant, but changed dynamically over time. The dynamics of population structure was mainly caused by the high mortality of small buds and the low flower bud recruitment.

Bmp4 is an essential growth factor for the initiation of genital tubercle (GT) outgrowth.

The external genitalia are appendage organs outgrowing from the posterior body trunk. Murine genital tubercle (GT), anlage of external genitalia, initiates its outgrowth from embryonic day (E) 10.5 as a bud structure. Several growth factors such as fibroblast growth factor (FGF), Wnt and Sonic hedgehog (Shh) are essential for the GT outgrowth. However, the mechanisms of initiation of GT outgrowth are poorly understood. We previously identified bone morphogenetic protein (Bmp) signaling as a negative regulator for GT outgrowth. We show here novel aspects of Bmp4 functions for GT outgrowth. We identified the Bmp4 was already expressed in cloaca region at E9.5, before GT outgrowth. To analyze the function of Bmp4 at early stage for the initiation of GT outgrowth, we utilized the Hoxa3-Cre driver and Bmp4 flox/flox mouse lines. Hoxa3 Cre/+ ; Bmp4 flox/flox mutant mice showed the hypoplasia of GT with reduced expression of outgrowth promoting genes such as Wnt5a, Hoxd13 and p63, whereas Shh expression was not affected. Formation of distal urethral epithelium (DUE) marked by the Fgf8 expression is essential for controlling mesenchymal genes expression in GT and subsequent its outgrowth. Furthermore, Fgf8 expression was dramatically reduced in such mutant mice indicating the defective DUE formation. Hence, current results indicate that Bmp4 is an essential growth factor for the initiation of GT outgrowth independent of Shh signaling. Thus, Bmp4 positively regulates for the formation of DUE. The current study provides new insights into the function of Bmp signaling at early stage for the initiation of GT outgrowth.

Bud structure of linseed (Linum usitatissimum L.) in relation to incidence of bud fly (Dasyneura lini Barnes) in Central Uttar Pradesh

A field experiment conducted for screened 288 elite gen pool of linseed against bud fly infestation at Kanpur, India during rabi 2012-13 to study the bud structure of resistance of linseed against bud fly. The results indicated that the bud length and width showed significant positive correlation coefficient relationship (r=0.1559 and 0.0761) bud infestation. The resistant germplasm line minimum (GS-234) minimum bud length and width (7.93 ×3.26 mm) had relative minimum bud infestation (6.88%) and was statically at par other resistant germplasm lines viz. A-95B, CI-1385, EC-1392, EC-1424, GS-234, IC-15888 and JRF-5. While susceptible germplasm line (Arny) exhibited maximum bud length and width (8.25 ×3. 23 mm) maximum bud infestation(65.11%) which was statically at par with other susceptible lines viz. Ajgan-3-1, Ajgan-20M, Alipur (Hamirpur), Anand, GS-148, GS-440, Gunawal Local, NP(RR)193, RAULD-7810, RLC-28(PM), MS-14, SJKO-2, SJKO-45.

AP1 transcription factors are required to maintain the peripheral taste system.

The sense of taste is used by organisms to achieve the optimal nutritional requirement and avoid potentially toxic compounds. In the oral cavity, taste receptor cells are grouped together in taste buds that are present in specialized taste papillae in the tongue. Taste receptor cells are the cells that detect chemicals in potential food items and transmit that information to gustatory nerves that convey the taste information to the brain. As taste cells are in contact with the external environment, they can be damaged and are routinely replaced throughout an organism's lifetime to maintain functionality. However, this taste cell turnover loses efficiency over time resulting in a reduction in taste ability. Currently, very little is known about the mechanisms that regulate the renewal and maintenance of taste cells. We therefore performed RNA-sequencing analysis on isolated taste cells from 2 and 6-month-old mice to determine how alterations in the taste cell-transcriptome regulate taste cell maintenance and function in adults. We found that the activator protein-1 (AP1) transcription factors (c-Fos, Fosb and c-Jun) and genes associated with this pathway were significantly downregulated in taste cells by 6 months and further declined at 12 months. We generated conditional c-Fos-knockout mice to target K14-expressing cells, including differentiating taste cells. c-Fos deletion caused a severe perturbation in taste bud structure and resulted in a significant reduction in the taste bud size. c-Fos deletion also affected taste cell turnover as evident by a decrease in proliferative marker, and upregulation of the apoptotic marker cleaved-PARP. Thus, AP1 factors are important regulators of adult taste cell renewal and their downregulation negatively impacts taste maintenance.

Insulin-Like Growth Factors Are Expressed in the Taste System, but Do Not Maintain Adult Taste Buds.

Growth factors regulate cell growth and differentiation in many tissues. In the taste system, as yet unknown growth factors are produced by neurons to maintain taste buds. A number of growth factor receptors are expressed at greater levels in taste buds than in the surrounding epithelium and may be receptors for candidate factors involved in taste bud maintenance. We determined that the ligands of eight of these receptors were expressed in the E14.5 geniculate ganglion and that four of these ligands were expressed in the adult geniculate ganglion. Of these, the insulin-like growth factors (IGF1, IGF2) were expressed in the ganglion and their receptor, insulin-like growth factor receptor 1 (IGF1R), were expressed at the highest levels in taste buds. To determine whether IGF1R regulates taste bud number or structure, we conditionally eliminated IGF1R from the lingual epithelium of mice using the keratin 14 (K14) promoter (K14-Cre::Igf1rlox/lox). While K14-Cre::Igf1rlox/lox mice had significantly fewer taste buds at P30 compared with control mice (Igf1rlox/lox), this difference was not observed by P80. IGF1R removal did not affect taste bud size or cell number, and the number of phospholipase C β2- (PLCβ2) and carbonic anhydrase 4- (Car4) positive taste receptor cells did not differ between genotypes. Taste buds at the back of the tongue fungiform taste field were larger and contained more cells than those at the tongue tip, and these differences were diminished in K14-Cre::Igf1rlox/lox mice. The epithelium was thicker at the back versus the tip of the tongue, and this difference was also attenuated in K14-Cre::Igf1rlox/lox mice. We conclude that, although IGFs are expressed at high levels in the taste system, they likely play little or no role in maintaining adult taste bud structure. IGFs have a potential role in establishing the initial number of taste buds, and there may be limits on epithelial thickness in the absence of IGF1R signaling.

Bud structure, position and fate generate various branching patterns along shoots of closely related Rosaceae species: a review.

Branching in temperate plants is closely linked to bud fates, either floral or vegetative. Here, we review how the fate of meristematic tissues contained in buds and their position along a shoot imprint specific branching patterns which differ among species. Through examples chosen in closely related species in different genera of the Rosaceae family, a panorama of patterns is apparent. Patterns depend on whether vegetative and floral buds are borne individually or together in mixed buds, develop as the shoot grows or after a rest period, and are located in axillary or terminal positions along the parent shoot. The resulting branching patterns are conserved among varieties in a given species but progressively change with the parent shoot length during plant ontogeny. They can also be modulated by agronomic and environmental conditions. The existence of various organizations in the topology and fate of meristematic tissues and their appendages in closely related species questions the between-species conservation of physiological and molecular mechanisms leading to bud outgrowth vs. quiescence and to floral induction vs. vegetative development.

A chloroplast tree for Viburnum (Adoxaceae) and its implications for phylogenetic classification and character evolution.

• Premise of the study: Despite recent progress, significant uncertainties remain concerning relationships among early-branching lineages within Viburnum (Adoxaceae), prohibiting a new classification and hindering studies of character evolution and the increasing use of Viburnum in addressing a wide range of ecological and evolutionary questions. We hoped to resolve these issues by sequencing whole plastid genomes for representative species and combining these with molecular data previously obtained from an expanded taxon sample.• Methods: We performed paired-end Illumina sequencing of plastid genomes of 22 Viburnum species and combined these data with a 10-gene data set to infer phylogenetic relationships for 113 species. We used the results to devise a comprehensive phylogenetic classification and to analyze the evolution of eight morphological characters that vary among early-branching lineages.• Key results: With greatly increased levels of confidence in most of the early branches, we propose a phylogenetic classification of Viburnum, providing formal phylogenetic definitions for 30 clades, including 13 with names recognized under the International Code of Nomenclature for Algae, Fungi, and Plants, eight with previously proposed informal names, and nine newly proposed names for major branches. Our parsimony reconstructions of bud structure, leaf margins, inflorescence form, ruminate endosperm, extrafloral nectaries, glandular trichomes, palisade anatomy, and pollen exine showed varying levels of homoplasy, but collectively provided morphological support for some, though not all, of the major clades.• Conclusions: Our study demonstrates the value of next-generation plastid sequencing, the ease of creating a formal phylogenetic classification, and the utility of such a system in describing patterns of character evolution.

Meristem temperature substantially deviates from air temperature even in moderate environments: is the magnitude of this deviation species‐specific?

Meristem temperature (Tmeristem ) drives plant development but is hardly ever quantified. Instead, air temperature (Tair ) is usually used as its approximation. Meristems are enclosed within apical buds. Bud structure and function may differ across species. Therefore, Tmeristem may deviate from Tair in a species-specific way. Environmental variables (air temperature, vapour pressure deficit, radiation, and wind speed) were systematically varied to quantify the response of Tmeristem . This response was related to observations of bud structure and transpiration. Tomato and cucumber plants were used as model plants as they are morphologically distinct and usually growing in similar environments. Tmeristem substantially deviated from Tair in a species-specific manner under moderate environments. This deviation ranged between -2.6 and 3.8 °C in tomato and between -4.1 and 3.0 °C in cucumber. The lower Tmeristem observed in cucumber was linked with the higher transpiration of the bud foliage sheltering the meristem when compared with tomato plants. We here indicate that for properly linking growth and development of plants to temperature in future applications, for instance in climate change scenarios studies, Tmeristem should be used instead of Tair , as a species-specific trait highly reliant on various environmental factors.