Histological analysis of the maturation of native and wound periderm in potato (Solanum tuberosum L.) Tuber

Maturation of potato (Solanum tuberosum L.) tuber native and wound periderm and development of resistance to periderm abrasion were investigated utilizing cytological and histochemical techniques. Both native and wound periderm consist of three different tissues: phellem, phellogen and phelloderm. It was previously determined that the phellogen walls of immature native periderm are thin and prone to fracture during harvest, leading to periderm abrasion (excoriation). Phellogen walls thicken and become less susceptible to fracture upon maturation of the periderm, leading to resistance to excoriation. We now demonstrate that phellogen cells of immature wound periderm also have thin radial walls and that wound periderm abrasion is due to fracture of these walls. Maturation of the wound periderm is also associated with an increase in the thickness of the phellogen radial walls. Histological analysis with ruthenium red and hydroxylamine-FeCI2, which stain unesterified and highly methyl-esterified pectins, respectively, indicates that the phellogen cell walls of native and wound periderm differ significantly regardless of the stage of maturity. Results obtained by staining with ruthenium red and hydroxylamine-FeCI2 imply that phellogen cell walls of immature native periderm contain methyl-esterified pectin, but are lacking in unesterified (acidic) pectins. Maturation of native periderm is accompanied by an apparent increase in unesterified pectins in the walls of phellogen cells, which may allow for the strengthening of phellogen cell walls via calcium pectate formation. Histological staining of the phellogen walls of wound periderm, on the other hand, implies that these walls are deficient in pectins. Moreover, maturation of wound periderm is not accompanied by an increase in unesterified pectins in these walls. Since peroxidase is known to catalyse the cross-linking of cell wall polymers, we stained native and wound periderm for the presence of peroxidase utilizing guaiacol as a substrate. Peroxidase staining was strong in the phellogen walls of both immature and mature native periderm and we could not detect any differences in staining between them. Peroxidase staining was weak in the phellogen walls of immature wound periderm and was not detectably different in mature wound periderm. Peroxidase data imply that there are distinct differences between native and wound periderm, though our data do not indicate that changes in peroxidase activity are involved in the development of resistance to periderm abrasion that occurs upon maturation of the periderm. However, we cannot rule out the involvement in this process of peroxidase isozymes that have low affinity for the substrates utilized here.     

转BADH基因马铃薯无性繁殖二代耐盐性检测

在0%、0.3%、0.6%NaCl胁迫下,检测转BADH基因马铃薯及其受体亲本‘甘农薯2号’的盆栽植株耐盐性的结果表明:BADH基因的遗传性稳定且转基因植株的耐盐性比非转基因的强。     

Free Air CO2 Enrichment of potato (Solanum tuberosum L.): development, growth and yield

A FACE (Free Air CO₂ Enrichment) experiment was carried out on Potato (Solanum tuberosum L., cv. Primura) in 1995 in Italy. Three FACE rings were used to fumigate circular field plots of 8 m diameter while two rings were used as controls at ambient CO₂ concentrations. Four CO₂ exposure levels were used in the rings (ambient, 460, 560 and 660 μmol mol^–1). Phenology and crop development, canopy surface temperature, above- and below-ground biomass were monitored during the growing season. Crop phenology was affected by elevated CO₂, as the date of flowering was progressively anticipated in the 660, 560, 460 μmol mol^–1 treatments. Crop development was not affected significantly as plant height, leaf area and the number of leaves per plant were the same in the four treatments. Elevated atmospheric CO₂ levels had, instead, a significant effect on the accumulation of total nonstructural carbohydrates (TNC = soluble sugars + starch) in the leaves during a sunny day. Specific leaf area was decreased under elevated CO₂ with a response that paralleled that of TNC concentrations. This reflected the occurrence of a progressive increase of photosynthetic rates and carbon assimilation in plants exposed to increasingly higher levels of atmospheric CO₂. Tuber growth and final tuber yield were also stimulated by rising CO₂ levels. When calculated by regression of tuber yield vs. the imposed levels of CO₂concentration, yield stimulation was as large as 10% every 100 μmol mol^–1 increase, which translated into over 40% enhancement in yield under 660 μmol mol^–1. This was related to a higher number of tubers rather than greater mean tuber mass or size. Leaf senescence was accelerated under elevated CO₂ and a linear relationship was found between atmospheric CO₂ levels and leaf reflectance measured at 0.55 μm wavelength. We conclude that significant CO₂ stimulation of yield has to be expected for potato under future climate scenarios, and that crop phenology will be affected as well.     

Carbon isotope discrimination in irrigated and droughted potato (Solanum tuberosum L.)

Carbon isotope discrimination (Δ) was measured in irrigated and droughted potato. Under irrigation, Δ in leaflets at given nodes increased (P < 0.001) between 21 and 63 d after emergence (DAE), which was attributed to increasing stomatal conductance (g_s) during leaf expansion. The effect of leaf position on Δ was non-significant in mature leaves. Under drought, Δ decreased (P < 0.001) in successive leaves up the stem, reflecting changes in g_s and water stress. At each node Δ remained constant or decreased, suggesting that effects of water stress were greater than changes with leaf expansion. There were significant differences in Δ between cultivars in both treatments, and in the progressive decrease in Δ up the stem under drought. Differences in Δ between cultivars were consistent with differences in stomatal control of leaf water status following water stress. Values for Δ in tubers were consistently lower than in stem and leaf, and decreased more rapidly. Differences in Δ between cultivars did not reflect dry matter production in either treatment, and differences in water use were non-significant between cultivars under drought. So, plants can achieve similar dry matter production through different growth strategies when irrigated or droughted, and Δ does not provide a simple, indirect method of selecting for dry matter production under water stress.     

Exchange diffusion of alkali ions through the apoplast of the potato (Soianum tuberosum L.) storage parenchyma

Interdiffusion coefficients of K and Na for tangential transport through cell walls were found to be independent of ion strength and only moderately (c. 50%) lower than values known for diffusion in water. Although at low salt concentrations alkali ion exchange diffusion on the cell wall pathway is facilitated by accumulation of diffusing species in the Donnan space, at all concentrations the resistance of the whole tissue for apoplastic cation exchange diffusion remained significantly higher than that of unstirred liquid of equal thickness, as the area fraction of the cell wall pathway in the parenchyma is small.     

The role of ethylene and reducing agents on anther culture response of tetraploid potato (Solanum tuberosum L.)

Summary The role of ethylene in embryogenesis of cultured potato anthers was studied indirectly by testing various substances known to affect ethylene formation. The reducing agents ascorbic acid and L-cysteine prevented browning of anther cultures and significantly stimulated embryogenesis. Embryogenesis was also promoted by the use of the ethylene inhibitors AgNO₃ and n-propyl-gallate and by the polyamines spermidine and putrescine. The use of the ethylene releasing compound ethrel significantly inhibited embryogenesis.Abbreviations MS Murashige & Skoog - PVP polyvinylpyrrolidone - MW molecular weight - ACC 1-aminocyclopropane-1-carboxylic acid - ethrel 2-chloroethylphosphonic acid (ethephon)     

Inheritance of three electrophoretically determined protein bands in potato (Solanum tuberosum L.)

Summary A modified polyacrylamide gel electrophoresis technique is employed to resolve proteins for use as biochemical gene markers in potato. Dominant, duplicate dominant and complementary gene action are three modes of inheritance that adequately explain the segregation of three respective protein bands in two generations of crossing within diploid Phureja X haploid Tuberosum families.Scientific Journal Seires Article 10,171 of the Minnesota Agricultural Experiment Station     

Energy Metabolism in Rhizomes of Acorus calamus (L.) and in Tubers of Solanum tuberosum (L.) With Regard to their Anoxia Tolerance

Rhizomes of the marsh plant Acorus calamus (L.) and tubers of the flooding-intolerant Solanum tuberosum (L.) var. Bintje, both kept under strict anoxia, differ markedly in their fermentation properties. The fermentation capacities as measured by ADH and LDH activities and their respective product concentrations were estimated. While rhizomes of Acorus calamus, having high ADH and low LDH activities, accumulate mainly ethanol, tubers of Solanum tuberosum tend towards lactic acid fermentation. The total amount of adenine nucleotides is quite stable in Acorus calamus, whereas they show a sharp decline in S. tuberosum during the first 6h of anoxia. The adenylate energy charge of A. calamus recovers after a short initial drop (AEC > 0.8). AEC values of S. tuberosum decrease rapidly and remain at very low values (AEC ～ 0.3). Tuber tissues became soft and lost viability after about 48–72 h of anoxia at 25 °C. This might be due to tissue acidification and impaired energy metabolism, but not to the lack of energy reserves. Energy metabolism of A. calamus is well adapted to anoxia.     

Biochemical and molecular determinance of resistance and susceptibility in Solanum tuberosum (potato) plants challenged with Phytopthora infestans

Determinance of resistance was studied in four different varieties of Solanum tuberosum using biochemical and molecular parameters. It was clearly evident that due to infection of P. infestans, the total protein, total phenol and lignin were induced in all four verities; however, the induction was found more in resistant varieties compared to susceptible varieties. Induction of proteins was also determined by SDS-PAGE analysis. Deposition of lignin was showed by histological comparison using Phloroglucinol HCl staining. Higher deposition of lignin in resistant varieties could be considered as reliable characters related to disease resistance and could be used as biochemical markers for late blight resistance. The RAPD profile generated using eight different decameric primers showed both, polymorphic as well as monomorphic bands. There were many unique bands found only in resistant varieties. These polymorphic bands could also be served as molecular markers for screening of LB resistance potato varieties.     

马铃薯'转心乌'块茎色素的组成和含量

马铃薯转心乌块茎的内、外韧皮部和髓为淡黄色,周皮和木质部为紫色;木质部的紫色形成一个不规则的环",并向内韧皮部蔓延.系列特征颜色反应和紫外可见光谱分析表明:‘转心乌’块茎紫色素属于黄酮类化合物,可能含有酚性邻位二羟基,并被肉桂酸酰化,不含类胡萝卜素、查耳酮、噢哢、异黄酮、儿茶素;花色苷和/或其苷元花色素奠定了‘转心乌’块茎着色的基础,其它的非红色的黄酮类化合物发挥共色素的作用.块茎的皮"紫色最浓","环"其次,"肉"最淡,这与"皮"、"环"和"肉"的色价、花色苷含量和总黄酮类化合物含量的变化趋势呈正相关.     

Sucrose and jasmonic acid interact in photosynthetic pigment metabolism and development of potato (Solanum tuberosum L. cv. Sante) grown in vitro

Potato (Solanum tuberosum L., cv. Sante) plantlets grown from stem node culture on medium supplemented with 90 mM sucrose accumulated lower amounts of photosynthetic pigments per mg dry weight in comparison to those grown on 30 mM sucrose. Addition of 0.1, 1 or 10 µM jasmonic acid (JA) to the medium resulted in a decrease of chlorophylls and carotenoids in the plantlets grown on either sucrose concentration. JA treatment induced de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin only in those plantlets grown on a higher amount of sucrose in which hyperhydric symptoms were observed. The synergistic effect of JA and sucrose was clearly demonstrated in the plantlets grown on 90 mM sucrose and 1 µM JA. This was possibly due to overaccumulation of sucrose, the consequence of the most developed root system, and/or to stimulated water and solute transport by other mechanisms.     

Organ-specific distribution and subcellular localisation of ascorbate peroxidase isoenzymes in potato (Solanum tuberosum L.) plants

Summary. Ascorbate peroxidase (EC 1.11.1.11), a heme-containing homodimeric protein, is a hydrogen peroxide-scavenging enzyme, playing an important role in plants in order to protect them from oxidative stress, thus adverting cellular damage. Several ascorbate peroxidase isoenzymes have been reported but the understanding of their physiological role still depends on a better knowledge of their precise localisation within plant organs. Immunocytochemistry techniques were performed in order to elucidate the peroxisomal and cytosolic ascorbate peroxidase distribution within tissues of leaves and sprouts of potato plants. The peroxisomal isoenzyme was found to have a broad distribution in sprouts, but a differential one in leaves, being restricted to the spongy parenchyma. This differential expression may be associated to the mesophyll asymmetry and the diverse physiological processes that occur in it. The cytosolic isoenzyme was not detected in leaves under the used conditions, probably because it is present in low amounts in these tissues. The results obtained in sprouts were at least curious: cytosolic ascorbate was found to be adjacent to the amyloplasts. Given these results, it is possible to state that apart from their similarity, these two isoenzymes reside in different organelles and seem to take part in different physiological processes as suggested by their organ- and tissue-specific distribution. Correspondence and reprints: Plant Functional Biology Department, Institute for Cell and Molecular Biology, University of Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.     

Biochemical and bioassay analysis of resistance of potato (Solanum tuberosum L.) cultivars to attack by the slug Deroceras reticulatum (Muller)

A method is described for using young field slugs Deroceras reticulatum (Muller) in a bioassay study of biochemical resistance of potato (Solanum tuberosum L.) cultivars to slugs. Tuber parts or an artificial diet were provided as food sources. Comparisons were made of feeding, survival and weight gain between the susceptible cultivar Maris Piper and the resistant cultivar Pentland Dell. Biochemical analyses were made of these two cultivars and the resistant cultivars Stormont Enterprise and Majestic. Comparisons of tuber sections and peelings as food sources indicated factors affecting growth were located in the surface layers of the tubers. Phenolics and glycoalkaloids were concentrated in the surface layers but the amounts were similar in the susceptible and resistant cultivars and the bioassays indicated that neither acting alone could explain resistance. The amounts and distribution of free amino acids also did not correlate with resistance although when supplied in the artificial diet they partly inhibited feeding. Proteinaceous inhibitors of slug gut proteolytic enzymes were present throughout the tubers but were not concentrated in the surface layers and the amounts were similar in the different cultivars thus they too did not explain the difference in susceptibility between the cultivars. Bioassays using acetone extracts (low molecular weight substances) and acetone powders (high molecular weight substances) either alone or in combination indicated that the resistant cultivar Pentland Dell contained a high molecular weight substance which together with a low molecular weight substance from either the same cultivar or the susceptible Maris Piper could confer resistance. Bioassays using protein extracts supplied in the presence or absence of chlorogenic acid indicated that this mechanism could comprise enzymic oxidation of phenolics. Assays of phenolase confirmed this since activity was highest in the outer layers of the tubers and was highest in the three resistant cultivars. Thus the chief resistance factor identified was high phenolase activity acting rapidly on phenolics when the slug first bites the tuber surface. The quantity of phenolics per se did not control the resistance. Thus while phenolics must be available, resistance is compatible with low blackening on cutting the tuber.     

Expression of bacterial cellulase genes in transgenic alfalfa (Medicago sativa L.), potato (Solanum tuberosum L.) and tobacco (Nicotiana tabacum L.)

The genes encoding thermostable cellulases E2 and E3 of Thermomonospora fusca were expressed in plants under the control of the constitutive, hybrid Mac promoter. For both E2 and E3, the genes were modified so as to remove the sequence encoding the bacterial leader peptide. Western blot analysis indicated that expression levels of recombinant cellulase in tobacco lines ranged up to about 0.1% (E2) and 0.02% of soluble protein (E3). No phenotypic effect of cellulase expression was noted. Recombinant E2 expressed in either tobacco or alfalfa was active and retained heat stability. These findings are an important first step in the development of crop plants as a production system for cellulases.     

Changes in jasmonate and gibberellin levels during development of potato plants (Solanum tuberosum)

Among the multiple environmental signals and hormonal factors regulatingpotato plant morphogenesis and controlling tuber induction, jasmonates (JAs)andgibberellins (GAs) are important components of the signalling pathways in theseprocesses. In the present study, with Solanum tuberosum L.cv. Spunta, we followed the endogenous changes of JAs and GAs during thedevelopmental stages of soil-grown potato plants. Foliage at initial growthshowed the highest jasmonic acid (JA) concentration, while in roots the highestcontent was observed in the stage of tuber set. In stolons at the developmentalstage of tuber set an important increase of JA was found; however, in tubersthere was no change in this compound during tuber set and subsequent growth.Methyl jasmonate (Me-JA) in foliage did not show the same pattern as JA; Me-JAdecreased during the developmental stages in which it was monitored, meanwhileJA increased during those stages. The highest total amount of JAs expressed asJA+Me-JA was found at tuber set. A very important peak ofJA in roots was coincident with that observed in stolons at tuber set. Also, aprogressive increase of this compound in roots was shown during the transitionof stolons to tubers. Of the two GAs monitored, gibberellic acid(GA₃) was the most abundant in all the organs. While GA₁and GA₃ were also found in stolons at the time of tuber set, noothermeasurements of GAs were obtained for stolons at previous stages of plantdevelopment. Our results indicate that high levels of JA and GAs are found indifferent tissues, especially during stolon growth and tuber set.     

Abscisic acid and mefluidide in the regulation of cold hardiness development in Solanum tuberosum L. potato

Plants of Solanum tuberosum L. potato do not cold acclimate when exposed to low temperature such as 5°C, day/night. When ABA (45 M) was added to the culture medium, stem-cultured plantlets of S. tuberosum, cv. Red Pontiac, either grown at 20°C/15°C, day/night, or at 5°C, increased in cold hardiness from –2°C (killing temperature) to –4.5°C. The increase in cold hardiness could be inhibited in both temperature regimes if cycloheximide (70 M) was added to the culture medium at the inception of ABA treatment. Cycloheximide did not inhibit cold hardiness development, however, when it was added to the culture medium 3 days after ABA treatment.When pot-grown plants were foliar sprayed with mefluidide (50 M), ABA content increased from 10 nmol to 30 nmol g^–1 dry weight and plants increased in cold hardiness from –2°C to about –3.5°C. The increases in free ABA and cold hardiness occurred only in plants grown at 20°C/15°C; neither ABA nor cold hardiness increased in plants grown at 5°C.The results suggest that an increase in ABA and a subsequent de novo synthesis of proteins are required for the development of cold hardiness in S. tuberosum regardless of temperature regime, and that the inability to synthesize ABA at low temperature, rather than protein synthesis, appears to be the reason why S. tuberosum does not cold acclimate.     

Changes in the location of polyphenol oxidase in potato (Solanum tuberosum L.) tuber during cell death in response to impact injury: comparison with wound tissue

In order to elucidate the nature of the response of potato to impact injury at the biochemical level, changes in the location of the enzyme responsible for the discoloration, polyphenol oxidase, were determined using immunogold location with an antibody specific for potato tuber polyphenol oxidase. Tissue printing revealed that the enzyme was distributed throughout the tuber. Following impact injury, both tissue printing and quantitative electron microscopy indicated that there was no increase in the level of the enzyme although there was subcellular redistribution of polyphenol oxidase. This redistribution was first apparent at 12 h after impact, as determined by the use of confocal immunolocation, and coincided with loss of membrane integrity. These changes were examined in parallel with a number of stress-related parameters in both impact and wound responses. Wounding was accompanied by active gene expression and protein synthesis, leading to metabolic activity and tissue repair. In contrast, the bruising response was characterised by a limited active response and vital-staining methods indicated that after 16 h the tissue undergoes cell death. Received: 4 June 1998 / Accepted: 18 September 1998     

The most abundant soluble basic protein of the stylar transmitting tract in potato (Solanum tuberosum L.) is an endochitinase

An abundant, pistil-specific basic protein has been purified and characterized from potato (Solanum tuberosum L.). A polymerase chain reaction (PCR) probe was generated for the corresponding gene using oligonucleotides based on internal peptide sequences of the protein, and the PCR probe was further employed to isolate cDNA and genomic clones. The sequence of the gene exhibits up to 70% similarity to previously described endochitinase class 1a protein sequences, and the purified protein possesses chitinase {poly[1, 4-(N-acetyl--D-glucosaminide)] glucanohydrolase, EC 3.2.1.14} activity. The protein, termed SK2, has been located by immunocytochemistry to the intercellular matrix of the stylar transmitting tract. Immunoblot analysis has shown SK2 to be distinct from the wound-induced chitinases of potato. The SK2-class of chitinase is restricted in its distribution within the Solanaceae to the sub-family Solanoidae, which includes cultivated tomato and potato species. It was absent from the Cestroidae species tested (Petunia hybrida, Nicotiana tabacum). A role for SK2 endochitinase in protecting the ovary against pollen-tubemediated pathogen ingress is proposed.Abbreviations FPLC fast protein liquid chromatography - IEF isoelectric focussing - PCR polymerase chain reaction We are indebted to Drs. E. Kombrink, J. Logemann, J. Schmidt and Mr. G. Jach (MPI für Züchtungsforschung, Köln, Germany) for advice on chitinase assays. The technical assistance of Ms. U. Seul and Mrs. B. Piegeler is gratefully acknowledged. Electron microscopy was carried out under the supervision of Drs. Brian Wells and Keith Roberts, (John Innes Centre for Plant Science Research, Norwich, UK). This research was supported by the Deutsche Forschungsgemeinschaft SPP Mechanisms of Hybrid Breeding, and the EC BRIDGE programme.