栽培甜菜花粉发育过程的超微结构

利用透射电镜技术对栽培甜菜(Beta vulgaris)花粉发育过程进行了超微结构观察。结果表明, 在小孢子母细胞减数分裂期间, 细胞内发生了“细胞质改组”, 主要表现在核糖体减少, 质体和线粒体结构发生了规律性变化。末期I 不形成细胞板,而是在2个子核间形成“细胞器带”。“细胞器带”的存在起到类似细胞板的作用, 暂时将细胞质分隔成两部分。四分体呈四面体型, 被胼胝质壁包围。小孢子外壁的沉积始于四分体晚期, 至小孢子晚期外壁已基本发育完全。单核小孢子时期, 细胞核大, 细胞器丰富。二细胞花粉发育主要表现在生殖细胞壁的变化上, 生殖细胞壁上不具有胞间连丝。成熟花粉为三细胞型, 含有1个营养细胞和2个精细胞。精细胞具有短尾突, 无壁, 为裸细胞, 每个精细胞通过2层质膜与营养细胞的细胞质分开。生殖细胞与精细胞里缺乏质体。     

pH-mediated release of betalains from transformed root cultures of Beta vulgaris L.

Brief exposure of Beta vulgaris root cultures to acidic medium resulted in release of betalain pigments while the capability for regrowth and continued pigment accumulation was retained. A 10-min exposure to pH 2 followed by return to standard growth medium (pH 5.5, 1.1 mM PO₄) resulted in release of 0.59 mg pigment/g dry weight over the subsequent 24-h period. The released pigment corresponds to 36.8% of the total pigments. Further improvement in culture productivity was achieved through phosphate limitation. Specific pigment productivity increased fivefold for cultures grown in phosphate-free medium as compared to cultures grown in control medium (1.1 mM PO₄). A maximum total pigment production of 25.2 mg/l was observed at an initial medium phosphate level 0.3 mM. When combined with phosphate limitation, low pH facilitated the release of 3.03 mg pigment/g dry weight, which corresponds to 50% of the total pigment. The permeabilized roots were capable of regrowth and continued pigment accumulation. A cytochemical assay for respiratory activity revealed that the basis of regrowth was lateral root initials that were unaffected during the acidic pH treatment. Received: 16 December 1997 / Received revision: 7 May 1998 / Accepted: 16 May 1998     

The actin cytoskeletal characteristics of the root meristem cells in Beta vulgaris L. at different mitotic stages

For the first time the actin cytoskeleton in meristem cells of B. vulgaris root has been studied. It was established that all discovered earlier patterns of microfilament arrangement were also specific for meristem of present species. Specific rearrangements of actin in the sites of spindle (prophase) and phragmoplast formation (telophase) were revealed. It is supposed, that actin cytoskeleton determines certain position of spindle in cells and takes part in the cell plate formation.     

The location of acid invertase activity and sucrose in the vacuoles of storage roots of beetroot (Beta vulgaris).

Vacuoles were isolated from freshly cut slices of the storage roots of beetroot (Beta vulgaris), and from slices that had been washed in aerated water for 1-3 days. The unique vacuolar location of betanin permitted the use of a correlative method to determine whether sucrose and acid invertase were located in the vacuoles. The specific content (the activity of the enzyme or amount of substrate per mg of protein) and the percentage recoveries for betanin, sucrose and acid invertase were determined for the different fractions obtained during the isolation of the vacuoles. For each fraction the specific content of betanin was plotted against those of sucrose and acid invertase. Similar correlative plots were drawn for the percentage recoveries. For both specific contents and percentage recoveries for correlation coefficients for sucrose and for acid invertase versus betanin were close to unity, and the lines passed near the origins. It is concluded that, in beetroot, most of the sucrose and much of the acid invertase are in the vacuoles. Measurements of vacuolar sucrose and acid invertase in beetroot slices washed for 1-3 days demonstrated an inverse relationship between sucrose content and acid invertase activity.     

Spectrophotometric and cytochemical analyses of phosphatase activity in Beta vulgaris L

Spectrophotometric and cytochemical methods were used to investigate the localization and/or the sensitivity of phosphatase activities in aldehyde-fixed beet leaves and membrane fractions. The nonspecific acid phosphatase substrates, p-nitrophenyl phosphate and beta-glycerol phosphate, each exhibited unique spectrophotometric patterns of hydrolysis as a function of pH. Additionally, beta-glycerol phosphatase activity was primarily present on the tonoplast, whereas p-nitrophenyl phosphatase was present on the plasma membrane. Because of the unique pH response of each enzyme and their different localization, we conclude that they cannot be entirely "nonspecific." The spectrophotometric pattern of ATP hydrolysis differed from that of p-nitrophenol phosphate in that it decreased at pH 5.0-5.5 and was greatly inhibited by 10 mM sodium fluoride; however, both activities were on the plasma membrane. Therefore, we conclude that these activities represent either two enzymes or only one enzyme that differs in its ability to hydrolyze these two substrates. Generally, enzymatically produced lead deposits on the plasma membrane of non-vascular cells were as frequent and large as those on phloem cells; frequently, deposits on sieve element plasma membranes were relatively small. We therefore conclude that there is no evidence for the presence of relatively intense ATPase activity on the plasma membrane of phloem cells in beet leaf, in contrast to other species. Studies with membrane fractions indicated that formaldehyde could completely inhibit the inhibitor-sensitive phosphatase activities in mitochondrial and vacuolar fractions while preserving significant activity in the plasma membrane fraction.     

Structure of the mitochondrial genome of Beta vulgaris L.

Summary The structure of mitochondrial DNA (mt-DNA) from sugarbeet (Beta vulgaris L.) has been studied by biochemical methods and electron microscopy. It was found to be complex multipartite consisting of two main classes of molecules: high molecules weight (HMW) mtDNA and low molecular weight (LMW) mtDNA. The HMW mtDNA consists of rosette-like structures and globules resembling chromomeres (150–200nm). A typical rosette has a protein core and radially stemming closed DNA loops (from 0.6-1.5 m). The number of loops in a rosette varies from 16–30. The bulk of HMW mtDNAs are represented by interconnected rosettes (total contour length about 130–160 m, 403–496 kbp). Such large circular DNAs may be evidence of the master chromosome arrangement of the sugarbeet genome. Globules and rosettes are interconnected by thick and thin DNA fibrils, along which nucleosome- and nucleomere-like structures are distributed. The LWM mtDNA is composed of two groups of supercoiled circular molecules, 0,2–1.5 m and 0.02–0.05 m in size. Electrophoretic analysis demonstrated that LWM mtDNA is represented by minicircle plasmid-like DNA molecules of 1.3, 1.4 and 1.6 kbp.     

Reproduction of the beet cyst nematode Heterodera schachtii Schm. on transformed root cultures of Beta vulgaris L.

Transformed hairy root cultures of Beta vulgaris L., grown in petri-dishes, were inoculated with a suspension of surface-sterilized larvae of the beet cyst nematode Heterodera schachtii Schm. Larvae developed into both male and female adults. Juvenile larvae were hatched from the newly-formed cysts, indicating that fertilization had occurred. Results of a glasshouse test showed that H. schachtii did not lose its pathogenicity after being cultured on transformed roots. This technique can be developed further for the mass-propagation of sedentary nematodes and for the in vitro storage of isclates.     

Origin of gynogenetic embryos of Beta vulgaris L.

Haploid plants of Beta vulgaris were obtained by gynogenesis from ovules isolated from male-fertile and annual and biennial male-sterile plants. We show that on a N6 basal medium, supplemented with 2.85 M IAA and 0.94 M Kinetin or 0.88 M BAP, haploids originate directly through embryogenesis. In order to determine the optimal developmental stage of the ovule of Beta vulgaris for gynogenesis, we carried out a histological study of whole ovules from open male-sterile flowers (collected 1 to 5 days after flowering) and unopened male-fertile flowers (collected 1 to 3 days before anthesis). In all cases, the gametophyte appeared completely differentiated. These results suggest that maturity of the gametophyte is reached a few days before anthesis and therefore ovules from unopened flowers are already suitable for plating. A developmental study of the haploid cells of the sugarbeet embryo sac during the first week of in vitro culture showed that the viable gynogenetic embryo originated only from the egg cell.     

Promotion of elongation and acid invertase activity in Phaseolus vulgaris L. internode segments by phenylacetic acid

Phenylacetic acid (PAA) significantly stimulated the elongation of isolated Phaseolus vulgaris internodal segments and prevented the decline in acid invertase specific activity observed in segments incubated in the absence of growth substances. Unlike IAA, which stimulated both elongation and invertase activity over a very wide range of concentrations (<10^-4 - 1 mol.m^-3; optimum 10^-2 mol.m^-3), the response to PAA was restricted to a much narrower range of concentrations (3 × 10^-2 - 1 mol.m^-3; optimum ca. 1–2 × 10^-1mol.m^-3). At the optimum concentration of PAA, the stimulation of both responses was about 63–75% of that induced by the optimum concentration of IAA. The differences in the concentration range and magnitude of the responses to IAA and PAA were not due to differences in uptake of the two compounds. The stimulation of elongation by both compounds was prevented by 3.6 × 10^-2mol.m^-3 cycloheximide (CH), and acid invertase activites were greatly reduced compared with samples treated with growth substances alone. A saturating concentration of the specific auxin efflux carrier inhibitor N-1-naphthylphthalamic acid (NPA) slightly promoted the growth of control segments, probably by reducing the loss of residual endogenous auxin to the incubation medium. The elongation induced by PAA at its optimum concentration was considerably greater than the elongation induced by NPA, indicating that PAA did not cause growth by preventing the loss of endogenous auxin from the segments. Elongation responses to combinations of IAA and PAA suggested that the compounds were acting additively and that they were affecting growth by the same mechanism.     

Effects of 5-aminolevulinic acid on Swiss chard (Beta vulgaris L. subsp. cicla) seedling growth under saline conditions

Salinity is a widespread adverse environmental problem globally, and significantly limits crop production. In this study, the possibility of enhancing salinity stress tolerance of Swiss chard (Beta vulgaris L. var. cicla) by 5-aminolevulinic acid (ALA) foliar application was investigated. The Swiss chard plants were grown in hydroponic culture. Twelve-week-old uniform seedlings were treated by 0 and 40 mM saline regimes generated by the mixture of sodium chloride and sodium sulfate (molar ratio NaCl:Na₂SO₄ = 9:1), and were foliar-sprayed with 0 and 60 μM L^?1 ALA (every 3 days) for 6 days; then the plants were treated for another 7 days (every 3 day) with increased concentration of salinity and ALA, 80 mM and 120 μM L^?1. Salinity without ALA application significantly decreased plant growth [43 % in shoot dry weight (DW), 21 % in root DW, 24 % in relative growth rate (RGR), 43 % in leaf area (LA)], water uptake [20.8 % in relative water content (RWC), 47.9 % in osmotic potential (OP)], chlorophyll (Chl) a content (10 %), P_n (36 %), G_s (72 %) and T_r (59 %) compared with those in control plants; however, under saline conditions, ALA foliar application improved plant growth (49.7 % in shoot DW, 27 % in root DW, 42.3 % in RGR, 72.1 % in LA) and increased RWC (12 %), Chl a content (10 %) and photosynthetic parameters (27 % in P_n, 28 % in G_s, 14 % in T_r) compared with those in untreated plants. Salinity significantly increased Na⁺ content, resulting in the reduction of Mg²⁺ and K⁺ contents. ALA foliar application alleviated ionic toxicity through the reduction of Na⁺ content and Na⁺/K⁺ ratio. On the other hand, it increased total nitrogen and glycine betaine (GB) content. ALA foliar application slightly reduced malondialdehyde (MDA) content, indicating that ALA has the potential to alleviate oxidative stress in salinity-stressed Swiss chard.     

The influence of atmospheric humidity on leaf expansion in Beta vulgaris L.

Humidity effects on leaf expansion in sugar beets (Beta vulgaris L.) were explored using linear variable differential transducers. In continuous light, an increase in relative humidity (RH) from 35 to 61 or 75% resulted in a rapid increase in leaf extension which was maintained for 10–15 min before slowing down. Increasing RH from 35 to 85% increased leaf-extension rate (LER) in light and in dark and substantially diminished the ratio of dark LER to light LER, showing that high humidity can offset the reduction in LER which occurs on illumination. Episodes of irradiance with visible or infrared radiation resulted in diminished LER, indicating that increases in transpiration may reduce the flux of water available for leaf cell expansion. The hypothesis that leaf area expansion in sugarbeet may be controlled by the expansion of the leaf epidermis is discussed.Abbreviations IR infrared - LER leaf extension rate - LVDT linear variable differential transformer - RH relative humidity     

In wounded sugar beet (Beta vulgaris L.) tap-root, hexose accumulation correlates with the induction of a vacuolar invertase isoform.

Wounding of sugar beet tap-root causes an induction of invertase activity, which contributes to post-harvest sucrose losses. In this first comprehensive monitoring of wound-induced invertase mRNAs, proteins, enzyme activities, and tissue hexose concentrations, the VI isoform responsible for wound-induced hexose accumulation in mature tap-root could be identified.     

Tonoplast of Beta vulgaris L. contains detergent-resistant membrane microdomains

The experiments conducted on tonoplast of Beta vulgaris L. roots were performed to identify detergent-resistant lipid–protein microdomains (DRMs, interpreted as lipid rafts).The presence of DRMs can be found when dynamic clustering of sphingolipids, sterols, saturated fatty acids is registered, and the insolubility of these microdomains in nonionic detergents at low temperatures is proven. The elucidation of tonoplast microdomains has been based on results obtained with the aid of high-speed centrifuging in the sucrose gradient. The experiments have shown that tonoplast microdomains are rich in sphingolipids, free sterols and saturated fatty acids (such a lipid content is also typical of lipid–protein microdomains of other membranes), while only few phospholipids are present in tonoplast microdomains. The presence of microdomains has been confirmed by fluorescence and confocal microscopy using filipin and Laurdan as fluorescent probes. The experiments with Laurdan have shown that tonoplast microdomains are characterized by a high order compared to characteristics of the rest of the tonoplast. Thus, the presence of detergent-resistant lipid–protein microdomains in the tonoplast has been demonstrated.     

Sieve Elements of Minor Veins in the Leaves of Beta vulgaris L.

End walls of sieve elements of minor veins of the leaves ofBeta vulgaris L. do not contain the multi-perforate sieve plateswhich typically occur on the end walls of sieve-tube membersof major veins. Instead, both end and side walls of the sieveelements of minor veins contain scattered pores which may occursingly or in small numbers. These pores are similar to thosewhich are grouped in sieve plates of major veins in size, possessionof callose and plugs of filaments. In addition to these pores,there are tubular connections 0.1 µ in diameter throughcharacteristically thickened parts of the cell wall betweensieve cells and companion cells. Sieve elements of minor veinsdiffer from those of major veins in structure as well as infunction.     

Compensation among root classes in Phaseolus vulgaris L.

The activity of soil pathogens, competition for assimilates, and the changing availability of below-ground resources make root systems subject to a continuous and dynamic process of formation and loss of both fine and coarse roots. As hypocotyl borne roots appear later than other root classes, they may serve to functionally replace basal and primary roots lost to biotic and abiotic stress. Using common bean (Phaseolus vulgaris L.), we conducted experiments in solution and solid media culture with treatments involving the removal of part of the root system (basal, hypocotyl borne or primary roots), phosphorus availability, and depth of seeding to test the hypothesis that there are compensation mechanisms among basal, hypocotyl borne and primary roots to cope with the loss of part of the root system. The root system was highly plastic in response to root excision, which resulted in the maintenance of below-ground biomass accumulation. In most cases, this compensation among root classes was enough to maintain plant performance in both phosphorus sufficient and phosphorus stressed plants. Removal of a specific root class induced an increase in the growth of the remaining root classes. All root classes, but especially the primary root, contributed to the compensation mechanism in some way. Primary roots represented around 10% of the root system in control plants and this proportion increased dramatically (up to 50%) when other root classes were removed. In contrast, negligible compensatory re-growth was observed following removal of the primary root. Greater planting depth increased the production of hypocotyl borne roots at the expense of basal roots. The proportion of hypocotyl borne roots increased from 25% of the whole root system when seeds were placed at a depth of 2 cm to 30% when they were placed at 5 cm and to 38% when placed at 8 cm, with corresponding decreases in the proportion represented by basal roots. The common feature of our observations is the innate ability of the root system for its own regeneration. Total root biomass maintained strict allometric relationships with total shoot biomass in all treatments. Re-stabilization of root to shoot balance after partial root loss is governed by overall plant size following allometric relationships similar to undisturbed plants. However, the pattern of this root regeneration was not uniform since the way the three root classes compensated each other after the removal of any one of them varied among the different growth media and phosphorus supply conditions. The resulting changes in root architecture could have functional significance for soil resource acquisition.     

A Model for the Simulation of the Growth of Beta vulgaris L.

A simple explanatory model for the simulation of the growthof Beta is described. It takes account of photosynthesis, respiration,and the light-intercepting properties of the foliage, but usesthe observed distribution pattern of dry matter. A crop of Beta was grown and, by periodic sampling of plants,growth curves were obtained.These are compared with simulatedgrowth curves and the reasons for the discrepancies are discussed. From simulations with different values of the constants of themodel, the effects on yield of variations in these constantsare predicted     

Abundance and length polymorphism of microsatellite repeats in Beta vulgaris L.

Simple sequence repeats (SSRs) are known to exhibit high degrees of variability even among closely related individuals. Their usage as nuclear genetic markers requires their conversion into sequence-tagged sites (STSs). In this paper we present the development of simple sequences as STSs for Beta vulgaris. This species comprises wild, cultivated, and weedy forms; the latter are thought to originate from accidental hybridisation between the other two. Two partial genomic libraries were screened with simple sequence motifs (AT, CA, CT, ATT, GTG, and CA, CT, respectively). Clones of 22 CA, nine CT, eight ATT, and one GTG sequence were obtained. AT micro satellites were present in compound motifs, not recognised by the probe. Sequence comparisons revealed that 20 CA clones containing short motifs (<16 bp) were variants of a previously described approximately 320-bp satellite DNA (Schmidt et al. 1991), and hence did not correspond to unique loci. Polymorphism of one (ATT)₁₅ and three (CT)_n, with n=15, 17 and 26, was detected by PCR on a sample of 64 plants from the different forms of B. vulgaris. 13 (ATT), 13 (CT), nine (CT) alleles and one (CT) allele were detected. One of the ATT alleles was much larger than the others (>800 bp). Genetic variability was high among wild beets, lower among cultivated beets, and intermediate among weed beets. One allele of each locus was found at high frequencies in cultivated beets and, to a lower extent, in weed beets. The combination of three polymorphic loci allowed the individual identification of 17/17 wild and 15/15 weed beets, and 21/32, mostly homozygous, cultivated beets.