Development of potato minitubers in microgravity

Stem segments of aseptically grown potato (Solanum tuberosum L. cv. Zarevo) were cultivated for 4 weeks under laboratory conditions and were then grown for 8 d on board the "Mir" orbital space station. Timing was such that minitubers initiated and developed during the 8 d on the "Mir". Under space flight and stationary conditions, spherical minitubers were formed with no statistically significant differences in either the frequency of tuber formation or tuber size. These observations are the first to document the formation of vegetative reproductive organs and of well developed amylogenic storage tissue during the microgravity conditions of orbital space flight. In these minitubers, a majority of the starch was stored in parenchyma, with numerous amyloplasts per cell. In space flight tissue, however, grain size of starch was decreased and lamellae within the amyloplasts was locally enlarged. Furthermore, mitochondria of these tissues were characterized by increased matrix density and well developed cristae.     

A role of phosphorylase in the potato minituber function under altered gravity

The goal of our work was a role of phosphorylase (EC. 2.4.1.1) in starch accumulation in plastids of storage parenchyma cells in potato minitubers forming under clinorotation. An increased enzyme activity under the influence of simulated microgravity has been revealed by using the biochemical and electron cytochemical methods. The obtained results suggest the correlation between an increase in phosphorylase activity and acceleration growth rate and senescence of plant storage organs in microgravity.     

Clinorotation [correction of Clinoratation] effects on the structural-functional response in potato minitubers

It is established that high plant growth and development in microgravity occurred normal. However, the change of plant growth rate is accompanied by the change of carbohydrate metabolism in photosynthesized cells (Kordyum, 1997). The decrease of starch grain size in chloroplasts and the decrease of content cellulose in cell wall were revealed (Sytnik et al., 1984; Nedukha, 1996). The change carbohydrate metabolism in photosynthesized organs could influence on the growth of underground organs and content of storage carbohydrates in these organs. Therefore, the aim of our study was to investigate the long-term clinorotation influence on the formation, structure of potato minitubers and content of starch and sugars in minitubers.     

Plasmalemmasomes in cotyledon leaves of germinating Vigna radiata L. (mung beans)

Abstract. Storage parenchyma, vascular parenchyma and phloem companion cells are found adjacent to sieve tubes in the vascular bundles of cotyledon leaves of mung bean ( Vigna radiata L.) seedlings. The paramural bodies of storage parenchyma cells are characterized by flask shaped invaginations of the plasmalemma whereas the plasmalemmasomes of the adjacent vascular parenchyma and companion cells consist of numerous finger-like evaginations which are not enclosed in plasmalemma pockets. Phloem associated transfer cells are not present and it is suggested that the fine tubular plasmalemmasomes may act as the interface between apoplast and symplast in the transport of rapidly mobilized reserves during germination. Tubular structures observed within the protoplasts of storage cells close to vascular tissue were also observed in vascular parenchyma and companion cells between the plasmalemmae and cell walls.     

Intracellular localization of lipoxygenases-1 and -2 in germinating soybean seeds by indirect labeling with protein a-colloidal gold complexes

Soybean lipoxygenases-1 and -2 were localized intracellularly in seeds at various stages of germination by indirect labeling of cryosections with protein A-colloidal gold complexes. Two sizes of gold particles (Au⁵ and Au¹⁶) were used in single- and double-labeling experiments. In primary leaves, lipoxygenases are demonstrated to occur in vacuolating parenchyma cells but not in massive, nondifferentiated cells. In cotyledons, both isoenzymes are localized in the cytoplasm of storage parenchyma cells and in an aberrant type of protein bodies, occurring in hypodermis and vascular bundle sheath cells. No association has been found with either protein bodies in storage parenchyma cells or lipid bodies, mitochondria, and other organelles in any type of cell. The possible significance of lipoxygenase in the metabolism of storage lipids and its possible function as a regulatory enzyme are discussed on the basis of the random distribution throughout the cytoplasm of storage parenchyma cells and the course of biochemical processes during seed germination.     

Ultrastructure of Jincheng Juice Sac of Citrus sinensis

Ultrastructure of Jincheng juice sac of Citrus sinensis (L.) Osb. was continuously investigated from the initial cell to the stalk-bearing sac. The initial cell and cells formed globularstructure, as well as the uper cells of the column-structure were typical meristem cells with mitochondria, plastids, rough endoplasmic reticulum, rich ribosome without Golgi body in their dense cytoplasm. These meristem cells would differentiate into parenchyma ceils pro2 viding storage function. At the beginning of differentiation of the meristem cells, the number of small vacuoles increased and some Golgi bodies appeared. Small vacuoles gradually fused into a central vacuole. During the fusion of small vacuoles, the cytoplasm became thinned, but still contained mitochondria, plastids, Golgi bodies, end0plasmic reticulum and some chromplasts with lipid drops. Almost no organelle were ever observed in the parenchyma cells of juice sac from mature fruit.     

锦橙汁囊的超微结构

用常规电镜方法观察了锦橙［Ｃｉｔｒｕｓｓｉｎｅｎｓｉｓ （Ｌ．） Ｏｓｂ．］汁囊从原始细胞到发育为一个具柄的成熟汁囊的过程中,汁囊构成细胞超微结构的变化。锦橙汁囊原始细胞及发育为球状体时的构成细胞以及柱状结构顶端的细胞都是一种典型的分生组织细胞。在细胞质中有包括线粒体、质体、内质网、核糖体等丰富的细胞器,但没有观察到高尔基体。这些分生细胞分裂一段时期后就停止活动,逐渐分化为适应贮藏功能的液泡化薄壁细胞。分生细胞开始分化时,在细胞中出现许多小液泡和高尔基体。这些小液泡逐渐地融合,同时细胞质变少,最后形成一个有中央大液泡的薄壁细胞,在紧贴细胞膜的薄薄的一层细胞质中有线粒体、质体、高尔基体以及含有许多脂滴的杂色体。但成熟果实中汁囊的薄壁细胞中几乎没有任何细胞器。     

Expression patterns and subcellular localization of a 52 kDa sucrose-binding protein homologue of Vicia faba (VfSBPL) suggest different functions during development

A cDNA coding for a 54 kDa signal sequence containing protein has been isolated from a faba bean cotyledonary library and characterized. The deduced protein is designated Vicia faba SBP-like protein (VfSBPL) since it shares 58% homology to a 62 kDa soybean (Glycine max) protein (GmSBP) which has been described as a sucrose-binding and sucrose-transporting protein (SBP). VfSBPL as well as GmSBP are outgroup members of the large vicilin storage protein family. We were unable to measure any sucrose transport activity in mutant yeast cells expressing VfSBPL. During seed maturation in late (stage VII) cotyledons mRNA was localized by in situ hybridization in the storage parenchyma cells. At the subcellular level, immunolocalization studies proved VfSBPL accumulation in storage protein vacuoles. However, mRNA localization in stage VI cotyledons during the pre-storage/storage transition phase was untypical for a storage protein in that, in addition to storage parenchyma cell labelling, strong labelling was found over seed coat vascular strands and the embryo epidermal transfer cell layer reminiscent of sucrose transporter localization. The VfSBPL gene is composed of 6 exons and 5 introns with introns located at the same sites as in a Vicia faba 50 kDa vicilin storage protein gene. The time pattern of expression as revealed by northern blotting and the GUS accumulation pattern caused by a VfSBPL-promoter/GUS construct in transgenic tobacco seeds was similar to a seed protein gene with increasing expression during seed maturation. Our data suggest different functions of VfSBPL during seed development.     

Phloem unloading in the potato tuber. Pathways and sites of ATPase

Summary Potential pathways for sucrose unloading in the potato tuber were examined by light and electron microscopy. Abundant plasmodesmata connected sieve elements with surrounding parenchyma elements and also sieve elements with companion cells. Plasmodesmata were rarer, however, between companion cells and parenchyma elements. These observations suggest that sucrose may leave the sieve elements and enter the storage parenchyma cells directly via the symplast and that transport through the companion cell may not be a prerequisite for unloading. Plasmodesmata, grouped together in primary pit fields, were also abundant between storage cells, and isolated storage cells, separated enzymically, showed considerable variation in plasmodesmatal distribution between cells and also on different faces of a single cell. Deposition of starch was found to occur in the tuber cortex while an endodermis with Casparian strip was present external to the phloem, suggesting that assimilates initially enter the cortical storage cells by an entirely symplastic pathway. The possible involvement of ATPase in the unloading process was examined cytochemically, using a lead-salt precipitation method. By contrast with previous findings for phloem no evidence was found for ATPase activity that was unique to the sieve element-companion cell complex. The present observations favour the view that phloem unloading in the potato tuber is a symplastic and passive process.     

Developmental Changes in the Anatomy of the Sugarcane Stem in Relation to Phloem Unloading and Sucrose Storage

Transverse sections of immature and mature sugarcane internodes were investigated anatomically with white and fluorescence light microscopy. The pattern of lignification and suberization was tested histo-chemically. Lignification began in the xylem of vascular bundles and progressed through the sclerenchymatic bundle sheath into the storage parenchyma. Suberization began in parenchyma cells adjacent to vascular bundle sheaths and spread to the storage parenchyma and outer sheath cells. In mature internodes most of the storage parenchyma was lignified and suberized to a significant degree, except in portions of walls of isolated cells. The pattern of increasing lignification and suberization in maturing internodes more or less paralleled an increase of sucrose in stem tissue. In mature internodes having a high sucrose concentration, the vascular tissue was surrounded by thick-walled, lignified and suberized sclerenchyma cells. The apoplastic tracer dyes triso-dium 3-hydroxy-5,8,10-pyrenetrisulfonate (PTS) and amido black 10 B, fed into cut ends of the stalk, wereconfined to the vascular bundles in all internodes above the one that was cut — with no dye apparently in storage parenchyma tissue. Thus both structural and experimental evidence is consistent with vascular tissue being increasingly isolated from the storage parenchyma as maturation of the tissue proceeds. We conclude that in mature internodes the pathway for sugars from the phloem to the storage parenchyma is symplastic. The data suggest that an increasingly greater role for a symplastic pathway of sugar transfer occurs as the tissue undergoes lignification/suberization.     

In vitro induction of minitubers in yam (<Emphasis Type="Italic">Dioscorea cayenensis</Emphasis>- <Emphasis Type="Italic">D. rotundata</Emphasis> complex)

Two methods were used to produce yam minitubers from two different yam cultivars (cv. Krengle and cv. Kponan) using in vitro culture techniques. Method 1: Yam microtubers were first initiated in vitro and then transplanted to soil to generate plants from which minitubers were produced. Yam plants were obtained either by directly planting the microtubers to soil, or by inducing the germination of the microtubers using various chemical and physical treatments, before their transfer to soil. Method 2: Yam plantlets were first produced in vitro and then transplanted to soil for further development and tuber production. In both methods, the presence of jasmonic acid (JA) in the culture medium was found to be essential for yam tuberization, as well as for the germination of yam microtubers. In vitro production of yam microtubers was variety dependant. Compared to cv. Krengle, cv. Kponan responded better to microtuberization, and 2.5 μM JA was the optimum concentration resulting in 70 and 90% explants producing microtubers in the MS medium and the Tuberization medium (T-medium), respectively. Germination of the microtubers required treatment of JA at concentrations ranging from 1.0 to 2.5 μM. The overall length of the process to produce minitubers from microtubers took 32 weeks. In contrast, minitubers were obtained within 20 weeks when plantlets were directly transferred to soil. In this case, plantlets were first grown for 8 weeks on medium containing JA (0.1–1.0 μM) and 8% sucrose to initiate plant growth and rooting.     

Cell structure and mobilization of lipids and proteins from cotyledon under microgravity influence

The structural-functional organization of cotyledon parenchyma cells of 6-day soybean (Glycine max L.) seedlings that were grown on board the space Shuttle Columbia (STS-87) have been studied. The purafil (KMnO4) was used in the experiment for the removing of some part of ethylene that secretes out from seedlings. There were four variants of the experiment: ground control (+purafil), ground control (-purafil), microgravity (+purafil) and microgravity (-purafil). The electron microscopy, srereological, and pyroantimonate cytochemical methods have been used. It is established the some indices of changes of storage substances in cotyledon parenchyma cells under influence of microgravity. It is displayed in the change of cell ultrastructure, the decrease of relative volume of storage cytoplasmic lipid bodies, a disappearance of storage protein body into vacuole and the redistribution of ionized calcium in cell. It was supposed that microgravity is influenced on the acceleration of storage substances catabolism.     

Wood anatomical correlates with theoretical conductivity and wood density across China: evolutionary evidence of the functional differentiation of axial and radial parenchyma

Background and Aims

In recent years considerable effort has focused on linking wood anatomy and key ecological traits. Studies analysing large databases have described how these ecological traits vary as a function of wood anatomical traits related to conduction and support, but have not considered how these functions interact with cells involved in storage of water and carbohydrates (i.e. parenchyma cells).

Methods

We analyzed, in a phylogenetic context, the functional relationship between cell types performing each of the three xylem functions (conduction, support and storage) and wood density and theoretical conductivity using a sample of approx. 800 tree species from China.

Key Results

Axial parenchyma and rays had distinct evolutionary correlation patterns. An evolutionary link was found between high conduction capacity and larger amounts of axial parenchyma that is probably related to water storage capacity and embolism repair, while larger amounts of ray tissue have evolved with increased mechanical support and reduced hydraulic capacity. In a phylogenetic principal component analysis this association of axial parenchyma with increased conduction capacity and rays with wood density represented orthogonal axes of variation. In multivariate space, however, the proportion of rays might be positively associated with conductance and negatively with wood density, indicating flexibility in these axes in species with wide rays.

Conclusions

The findings suggest that parenchyma types may differ in function. The functional axes represented by different cell types were conserved across lineages, suggesting a significant role in the ecological strategies of the angiosperms.     

蒜鳞片薄壁细胞衰退过程中酶的细胞化学定位及DNA生化分析

蒜在储藏过程中。鳞茎薄壁细胞衰退。其营养物质供给幼芽萌发生长。采用细胞化学方法,对蒜休眠进程中的鳞茎薄壁细胞进行了ATPase以及APase的细胞化学定位,结果显示在薄壁细胞的质膜、细胞壁和胞间连丝上的酶活性随着蒜自休眠至萌发的不同发育进程而呈现增强的趋势,且在萌芽期酶活性表现最为强烈。表明细胞内物质的降解、转化与输出的加强有助于细胞内含物向新生芽的彻底转移。配合采用琼脂糖凝胶电泳对衰退薄壁细胞的DNA进行了分析,实验结果表现出典型的DNA Ladder．为蒜鳞茎薄壁细胞的衰退属于受基因控制的程序性死亡范畴补充了生化证据。     

Occurrence of Localized Intense Cation Uptake Sites in the Vascular Rings of Red Beet Storage Tissue 2

Development and decline of cation uptake capacity in discs takenfrom the vascular and parenchyma rings of storage tissue ofred table beet (Beta vulgaris L.) were observed during 12 dof ageing. Uptake capacity for Na⁺ and Rb⁺ showed a steady risereaching maximums by the fourth to fifth days of ageing. Thereafter,there was a steady decline in the uptake rates. Vascular ringtissues were able to develop a greater uptake capacity for bothNa⁺ and Rb⁺ than the tissues of parenchyma rings. This difference,which was more pronounced for Rb⁺ than for Na⁺ uptake, is attributedto a combination of variations in cell density and differencesin the acquisition and retention of the cation uptake capacity.Respiration of tissue discs showed no significant rise duringageing, nor were there significant differences in the respirationof vascular and parenchyma tissues. Vascular tissues containedsignificantly more betacyanin than parenchyma tissues; and theyretained their pigment, as well as their acquired cation uptakecapacity, for a longer period during the ageing process. Key words: Cation uptake, Red beet, Vascular rings, Ageing     

Living cells in wood. 1. Absence,scarcity and histology of axial parenchyma as keys to function

The diversity of expression in axial parenchyma (or lack of it) in woods is reviewed and synthesized with recent work in wood physiology, and questions and hypotheses relative to axial parenchyma anatomy are offered. Cell shape, location, abundance, size, wall characteristics and contents are all characteristics for the assessment of the physiological functions of axial parenchyma, a tissue that has been neglected in the consideration of how wood histology has evolved. Axial parenchyma occurrence should be considered with respect to mechanisms for the prevention and reversal of embolisms in tracheary elements. This mechanism complements cohesion–tension‐based water movement and root pressure as a way of maintaining flow in xylem. Septate fibres can substitute for axial parenchyma (‘axial parenchyma absent’) and account for water movement in xylem and for the supply of carbohydrate abundance underlying massive and sudden events of foliation, flowering and fruiting, as can fibre dimorphism and the co‐occurrence of septate fibres and axial parenchyma. Rayless woods may or may not contain axial parenchyma and are informative when analysing parenchyma function. Interconnections between ray and axial parenchyma are common, and so axial and radial parenchyma must be considered as complementary parts of a network, with distinctive but interactive functions. Upright ray cells and more numerous rays per millimetre enhance interconnection and are more often found in woods that contain tracheids. Vesselless woods in both gymnosperms and angiosperms have axial parenchyma, the distribution of which suggests a function in osmotic water shifting. Water and photosynthate storage in axial parenchyma may be associated with seasonal changes and with succulent or subsucculent modes of construction. Apotracheal axial parenchyma distribution often demonstrates storage functions that can be read independently of osmotic water shifting capabilities. Axial parenchyma may serve to both enhance mechanical strength or, when parenchyma is thin‐walled, as a tissue that adapts to volume change with a change in water content. Other functions of axial parenchyma (contributing resistance to pathogens; a site for the recovery of physical damage) are considered. The diagnostic features of axial parenchyma and septate fibres are reviewed in order to clarify distinctions and to aid in cell type identification. Systematic listings are given for particular axial parenchyma conditions (e.g. axial parenchyma ‘absent’ with septate fibres substituting). A knowledge of the axial parenchyma information presented here is desirable for a full understanding of xylem function. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 291–321.     

Distribution of pectic epitopes in cell walls of the sugar beet root

Immunolabelling techniques with antibodies specific to partially methyl-esterified homogalacturonan (JIM5: unesterified residues flanked by methylesterified residues. JIM7: methyl-esterified residues flanked by unesterified residues), a blockwise de-esterified homogalacturonan (2F4), 1,4-galactan (LM5) and 1,5-arabinan (LM6) were used to map the distribution of pectin motifs in cell walls of sugar beet root (Beta vulgaris). PME and alkali treatments of sections were used in conjunction with JIM5-7 and 2F4. The JIM7 epitope was abundant and equally distributed in all cells. In storage parenchyma, the JIM5 epitope was restricted to some cell junctions and the lining of intercellular spaces while in vascular tissues it occurred at cell junctions in some phloem walls and in xylem derivatives. After secondary wall formation, the JIM5 epitope was restricted to inner cell wall regions between secondary thickenings. The 2F4 epitope was not detected without de-esterification treatment. PME treatments prior to the use of 2F4 indicated that HG at cell corners was not acetylated. The LM5 epitope was mainly present in the cambial zone and when present in storage parenchyma, it was restricted to the wall region closest to the plasma membrane. The LM6 epitope was widely distributed throughout primary walls but was more abundant in bundles than in medullar ray tissue and storage parenchyma. These data show that the occurrence of oligosaccharide motifs of pectic polysaccharides are spatially regulated in sugar beet root cell walls and that the spatial patterns vary between cell types suggesting that structural variants of pectic polymers are involved in the modulation of cell wall properties.     

Developmental Changes in Cell and Tissue Water Relations Parameters in Storage Parenchyma of Sugarcane

The osmotic pressure of the cell sap of stalk storage parenchyma of sugarcane (Saccharum spp. hybrids) increases by an order of magnitude during ontogeny to reach molar concentrations of sucrose at maturity. Stalk parenchyma cells must either experience very high turgor at maturation or have an ability to regulate turgor. We tested this hypothesis by using pressure probe techniques to quantify parameters of cell and tissue water relations of sugarcane storage parenchyma during ontogeny. The largest developmental change was in the volumetric elastic modulus, which increased from 6 bars in immature tissue to 43 bars in mature tissue. Turgor was maintained relatively low during sucrose accumulation by the partitioning of solutes between the cell and wall compartments. Membrane hydraulic conductivity decreased from about 12 × 10⁻⁷ centimeters per second per bar down to 4.4 × 10⁻⁷ centimeters per second per bar. The 2.7-fold decrease in membrane hydraulic conductivity during tissue maturation was accompanied by a 7.8-fold increase in wall elasticity. Integration of the cell wall and membrane properties appears to be by the opposing effects of turgor on hydraulic conductivity and elastic modulus. The changes in these properties during development of sugarcane stalk tissue may be a way for parenchyma cells to develop a capacity for expansive growth and still serve as a strong sink for storing high concentrations of sucrose.     

Functional Specialization of Vacuoles in Sugarcane Leaf and Stem

Plant vacuoles are frequently targeted as a storage site for novel products. We have used environment-sensitive fluorescent dyes and the expression of vacuolar marker proteins to characterize the vacuoles in different organs and cell types of sugarcane. The results demonstrated that the lumen of the vacuole in the parenchyma cells of the stem is acidic (<pH 5) and contains active proteases, characteristic of lytic vacuoles. Western blots and tissue labelling with antibodies to vacuolar H⁺-ATPase suggest that this proton pump is involved in acidification of the vacuolar lumen. Quantitative real-time PCR was used to show that the expression of vacuolar proteases and a vacuolar sorting receptor is also coordinately regulated. In contrast to the stem parenchyma cells, the cells of sugarcane leaves contain diverse types of vacuoles. The pH of these vacuoles and their capacity to hydrolyze protease substrates varies according to cell type and developmental stage. Sugarcane suspension-cultures contain cells with vacuoles that resemble those of stem parenchyma cells and are thus a useful model system for investigating the properties of the vacuole. Understanding the growth and development of storage capacity will be useful in designing strategies to maximize the production of sucrose or alternative bioproducts.