A Possible Regulation of Ethylene Production by the Epidermis in Mung Bean Hypocotyl Sections

IAA-induced and l-aminocyclopropane-l-carboxylic acid (ACC)-dependentethylene production in etiolated mung bean (Vigna radiata [L]Wilczek) hypocotyl sections does not occur in epidermal cells(Todaka and Imaseki 1985). Mung bean hypocotyls contain a proteinwhich inhibits auxin-induced ethylene biosynthesis in hypocotylsections (Sakai and Imaseki 1975a, b). This inhibitory proteinwas also found to inhibit ACC-dependent ethylene productionin hypocotyl sections, but not in hypocotyl sections from whichthe epidermis had been removed. Uptake of ACC by both unpeeledand peeled sections was not inhibited by the protein. Similarly,IAA-induced ethylene production was inhibited by the proteinin unpeeled hypocotyl sections, but not in peeled sections.The protein was not inactivated in peeled sections, as proteinsynthesis by peeled sections was inhibited to the same extentas in unpeeled sections. The protein inhibited incorporationof 3,4-[¹⁴C]-methionine into ACC and ethylene in unpeeled sections,but not in peeled sections, whereas oxidation of the labeledmethionine into CO₂ was inhibited by the protein to a similarextent in both types of hypocotyl sections. KCN, a potent inhibitorof ethylene production, inhibited both IAA-induced and ACC-dependentethylene production in both peeled and unpeeled hypocotyl sections.It is likely that the epidermis plays some role in controllingethylene production which occurs in stem cells other than epidermalcells. (Received July 16, 1985; Accepted October 21, 1985)     

Metabolism of Slices of the Tomato Stem

The rate of respiration of tomato stem slices varied considerably,the highest values (Qo₂, 2–3) being obtained for plantsin a good nutritional state, and the lowest (Qo₂, 1) in starvedplants. The respiratory quotient of 1.0 remained constant. Glucose fermentation was found to follow both glycolytic andalcohol fermentation pathways, the ratio of ethyl alcohol: lacticacid being 6.6:1. Fermentation seems to take place accordingto the Embden-Meyerhof scheme, as shown by the presence of someof these enzymes operative in this scheme and by inhibitionexperiments. In the presence of oxygen there was no formationof alcohol or lactic acid. Pyruvate added to tomato stem slices was metabolized by directoxidation to acetic acid and by dismutation to lactic and aceticacids and CO₂ The metabolism of acetic acid was demonstratedby its condensation with oxaloacetic acid to form citrate, thisbeing the second time that synthesis of citric acid by thismechanism has been found in plants. The presence of aconitase,of isocitric dehydrogenase, of succinic dehydrogenase, and ofmalic dehydrogenase, as well as the inhibition of respirationby malonic acid, favour the hypothesis that oxidation of carbohydratein tomato stem slices proceeds via the citric acid cycle. Thepossibility of an auxiliary route, the malic acid oxidationpathway, also was demonstrated. Tomato stem tissue anaerobicallysplit malic acid into glycolic acid. The further oxidation ofglycolic, glyoxylic, and formic acid was demonstrated. In experiments with C¹⁴-labelled acetate and butyrate a dilutionof the C¹⁴-labelled acids was found after incubation indicatingnew formation of these acids and of active participation offatty acid metabolism in the metabolic activities of the tissue. With the exception of alanine, added amino acids produced adefinite increase in O₂ uptake without extra formation of ammonia. Experimental demonstration of the possibility of electron transportfrom substrate to molecular oxygen in respiration via polyphenoloridase was provided by the attainment in a tomato tissue homogenateof a coupled oxidation-reduction between -ketoglutarate andcatechol with DPN and tyrosinase as the catalysts. The presenceof cytochrome oxidase was also demonstrated. Thus both systemspossibly may take part in the respiration of tomato stem slices.     

Inhibition of Ethylene Production by Fatty Acids in Fruit and Vegetable Tissues

Fatty acids of chain length from C₄ to C₁₂ inhibited ethyleneproduction in wounded albedo tissue of Hassaku (Citrus hassakuHort. ex Tanaka) fruit. Of the fatty acids tested, caprylicacid (C₈) and capric acid (C₁₀) were the most effective. Lauricacid (C₁₂) was less effective, and caproic acid (C₆) and butyricacid (C₄) were the least effective. Caprylic acid at 5 mM markedlyinhibited ethylene production in not only wounded albedo tissueof citrus fruit but also apple (Malus sylvestris Mill.) cortex,tomato (Lycopersicon esculentum Mill.) pericarp, cucumber (Cucumissativus L.) cortex, banana (Musa AAA group Cavendish subgroup)pulp, broccoli (Brassica oleracea L.) floret, spinach (Spinaciaoleracea L.) leaf, lettuce (Lactuca sativa L.) leaf and mungbean (Vigna radiata [L.] Wilczek) hypocotyl. Caprylic acid inhibitedethylene production at the step of conversion of l-aminocyclopropane-l-carboxylicacid to ethylene. The inhibition could be partially relievedby transferring the tissue to caprylic acid-free medium. (Received June 15, 1982; Accepted August 13, 1982)     

Leaf-like Structure in the Photosynthetic, Succulent Stems of Cacti

This research examined the hypothesis that as cacti evolve tothe leafless condition, the stem epidermis and cortex becomemore leaflike and more compatible with a photosynthetic role.All cacti in the relict genus Pereskia have non-succulent stemsand broad, thin leaves. All members of the derived subfamilyCactoideae are ‘leafless’, having an expanded cortexthat is the plant's only photosynthetic tissue. In Pereskia,leaves have a high stomatal density (mean: 50.7 stomata mm^–2in the lower epidermis, 38.1 mm^–2 in the upper epidermis),but stems have low stomatal densities (mean: 11.3 mm ₂, threeof the species have none). Stems of Cactoideae have a high stomataldensity (mean: 31.1 mm^–2, all species have stomata). Theouter cortex cells of stems of Cactoideae occur in columns,forming a palisade cortex similar to a leaf palisade parenchyma.In this palisade cortex, the fraction of tissue volume availablefor gas diffusion has a mean volume of 12.9%, which is identicalto that of Pereskia leaf palisade parenchyma. Pereskia stemcortex is much less aerenchymatous (mean: 5.3% of cortex volume).Cactoideae palisade cortex has a high internal surface density(0.0207 cm₂ cm^–2 which is higher than in Pereskia stemcortex (0.0150 cm₂ cm^–3) but not as high as Pereskia leafpalisade parenchyma (0.0396 cm₂ cm^–3). Pereskia stem cortexhas no cortical bundles, but Cactoideae cortexes have extensivenetworks of collateral vascular bundles that resemble leaf veins. Cactaceae, cactus, intercellular space, stomatal density, internal surface/volume, evolution     

A Protein from Immature Raspberry Fruits which Inhibits Endopolygalacturonases from Botrytis cinerea and other Micro-organisms

A polygalacturonase-inhibiting protein (PGIP) was purified fromimmature raspberry fruits using ion exchange chromatography.The protein was composed of a single polypeptide chain withM_r of 38·5 kDa and a pI residing above pH 10. Kineticstudies suggested that the inhibition was of a non-competitivenature. The PGIP inhibited two endopolygalacturonases (endo-PG)purified from Botrytis cinerea and an endo-PG produced by Aspergillusniger to varying degrees but did not inhibit two exo-PGs purifiedfrom B. cinerea, bacterial endopectate lyases and bacterialendo-PGs. The concentration of PGIP at various stages of flowerand fruit development was determined. The inhibitor was notdetected in the flower, but reached a maximum of 69 units g^–1in the immature green fruit decreasing to 9 units g^–1as fruits matured. The N-terminal amino-acid sequence was determined. Key words: Polygalacturonase-inhibiting protein, Rubus idaeus, red raspberry, Botrytis cinerea, pectinases     

Studies on cutin-esterase I. Preparation of cutin and its fatty acid component from tomato fruit peel

Examination was made of the fatty acid component of tomato cutinvia gas-liquid chromatography and thin layer chromatography.Dihydroxyeicosanoic acid was identified as a major componentof tomato cutinic acid in contrast with the results of BAKERand MARTIN (1) who recognized 10,16-dihydroxyhexadecanoic acidas the dominant acid of cutin in all plants tested. On the thinlayer chromatograms we found more than nine kinds of fatty acidsin the cutin hydrolysate which was saponified with ethanol-potashsolution. The gas-liquid chromatogram for trimethylsilyl etherderivatives of methyl cutinate showed somewhat different results,i.e., unsaturated decanoic, t_R 1.4, unsaturated stearic, t_R4.2 and unsaturated octadecanedioic acid, t_R 16.0 as unsaturatedfatty acids. Two more than C₂₂-hydroxyfatty acids were recognizedas minor components. Beside these components, octanoic, t_R 0.9,hydroxydecanoic, t_R 7.0 and cis-epoxy-hydroxyoctadecanoic acid,t_R 18.7 were identified. The biosynthesis of cutin is positednot to be fulfilled or to be delayed due to less lipoxidaseactivity in tomato fruit. ¹Biological Laboratory, Research Department, Nihon Noyaku Co.Ltd., Kawachinagano, Osaka, Japan (Received December 8, 1969; )     

ISOLATION OF AN INHIBITOR OF GROWTH AND ROOT FORMATION FROM PORTULACA GRANDIFLORA LEAVES

1. From leaves of Portulaca grandiflora, a substance which inhibitedthe IAA-induced elongation of Avena coleoptile sections andthe adventitious root formation of Raphanus hypocotyl cuttingswas separated by means of thin layer chromatography. It wasisolated and crystallized. 2. On paper chromatograms, this substance gave the same R_f valuesas the inhibitor from leaves of Xanthium strumarium and thatfrom leaves of Helianthus tuberosus ("heliangine"), namely,R_f0.9 in ammoniacal isopropanol, R_f 0.85 in methanol-water andR_f 0.0 in n-hexane-water. On thin layer chromatograms, however,these inhibitors were clearly separated from each other. 3. Infra-red absorption spectrum also indicated that this substanceis identical with neither xanthinin nor heliangine. ¹ Contribution No. 8 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Koishikawa, Tokyo     

Homeostatic Regulation of Membrane Potential by an Electrogenic Ion Pump against Change in the K+ Concentration of the Extra- and Intra-Organ Perfusion Solutions

The dependence of membrane potentials on changes in the extra-cellularK⁺ concentration [K⁺]_e was investigated in potato tuber sliceswith dripping perfusion, and in growing Vigna hypocotyl segmentswith pressurized intra-organ perfusion methods. Only under anoxiawere the membrane potential of potato tuber slices and the electricpotential difference between the parenchyma symplast and xylem(V_px) of Vigna hypocotyl segments depolarized markedly (46 mVand 42 mV/log[K⁺]_e unit, respectively) with increasing [K⁺]_eabove the critical values. The electric potential differencebetween the parenchyma symplast and organ surface (V_ps of thehypocotyl segments remained nearly unchanged up to 30 mEq [K⁺]_e.Under highly aerobic conditions the membrane potentials wererelatively independent of [K⁺]_e except at very high K⁺ concentrations.V_ps showed even hyperpolarization with the increasing KCl concentrationin the perfusion solution that is not in direct contact withthe surface membrane of the parenchyma symplast. The respiration-dependentelectrogenic components of the membrane potentials regularlyincreased with the increasing [K⁺]_e. A voltage-dependent homeostaticcontrol of membrane potential is discussed. (Received August 13, 1984; Accepted December 21, 1984)     

Nitric oxide attenuates IGF-I-induced aortic smooth muscle cell motility by decreasing Rac1 activity: essential role of PTP-PEST and p130cas

Recent data support the hypothesis that reactive oxygen species (ROS) play a central role in the initiation and progression of vascular diseases. An important vasoprotective function related to the regulation of ROS levels appears to be the antioxidant capacity of nitric oxide (NO). We previously reported that treatment with NO decreases phosphotyrosine levels of adapter protein p130^cas by increasing protein tyrosine phosphatase-proline, glutamate, serine, and threonine sequence protein (PTP-PEST) activity, which leads to the suppression of agonist-induced H₂O₂ elevation and motility in cultured rat aortic smooth muscle cells (SMCs). The present study was performed to investigate the hypotheses that 1) IGF-I increases the activity of the small GTPase Rac1 as well as H₂O₂ levels and 2) NO suppresses IGF-I-induced H₂O₂ elevation by decreasing Rac1 activity via increased PTP-PEST activity and dephosphorylation of p130^cas. We report that IGF-I induces phosphorylation of p130^cas and activation of Rac1 and that NO attenuates these effects. The effects of NO are mimicked by the overexpression of PTP-PEST or dominant-negative (dn)-p130^cas and antagonized by the expression of dn-PTP-PEST or p130^cas. We conclude that IGF-I induces rat aortic SMC motility by increasing phosphotyrosine levels of p130^cas and activating Rac1 and that NO decreases motility by activating PTP-PEST, inducing dephosphorylating p130^cas, and decreasing Rac1 activity. Decreased Rac1 activity lowers intracellular H₂O₂ levels, thus attenuating cell motility. hydrogen peroxide; protein tyrosine phosphatase-proline, glutamate, serine, and threonine sequence protein; p130^cas     

Growth and Nitrogen Status of Soilless Tomato Plants Following Nitrate Withdrawal from the Nutrient Solution

The effects of withdrawing nitrogen (N) from the nutrient solutionof adult tomato plants growing in rockwool in a greenhouse wereinvestigated over a 6 week period during fruit production. Thetreatment reduced total plant growth after a lag period of about2 weeks. The commercial fruit yield after 6 weeks of N deprivationwas 7.7 kg m^-2compared to 9.3 kg m^-2in control plants. Duringthe experiment, growth of the -N plants was fuelled by N reservescontained in both the substrate (rockwool) and in plant organs.The nitrogen budget calculated for -N plants showed that onlya small amount of organic-N was readily available for internalcycling from organs such as stems. It served mainly to feedgrowing fruits which were the main sinks in the plant. The studyalso established that stores of nitrate-N were fully depletedbut it took 45 d for the -N plants to metabolize completelytheir nitrate reserves. This indicates that internal nitrateis not a readily-accessible store of labile N. An estimationof the critical N concentration (%N_c) in the aerial dry matterwas made from the data. Thus, for a crop yielding about 9.9tons DM ha^-1, %N_cwas close to 2.5%. This result is discussedin light of existing models that describe the ontogenic declinein %N_cin dry biomass of C₃plants. The study indicates that thecurrent regime of N fertilization practised in soilless culturesnot only leads to ineffective nitrogen use but also to largelosses of N to the environment; N concentrations should be decreasedin feeding recipes. The use of N-free nutrient solutions priorto the termination of plant culture may also be a means of limitingthe loss of eutrophying elements, such as nitrate, to the environment.Copyright 2001 Annals of Botany Company Lycopersicon esculentum, tomato, organ dry biomass, critical nitrogen concentration, compartment, rockwool, nitrate interruption, distribution, reserves     

Influence of Sink-Source Interaction on Dry Matter Production in Tomato

Sink-source ratio in tomato was manipulated, in six glasshouseexperiments, by fruit pruning (trusses pruned to two to sevenfruits immediately after fruit set of each truss), truss pruning(removal of every other truss at anthesis) and truss pruningin plants with two shoots. Periodic destructive harvest wereconducted for about 100 d after flowering of the first truss.Dry matter production was not influenced by sink-source ratio,whereas dry matter distribution between fruits and vegetativeparts was greatly affected. The fraction of dry matter distributedto the fruits at the end of the fruit pruning experiments (F_fruits)could be described accurately as a saturation-type functionof number of fruits retained per truss (N_f): F_fruits = 0.660(l-e^-0.341N_f). Specific leaf area and internode length decreasedand plant leaf area increased when sink-source ratio was reduced.Removal of every other truss at anthesis did reduce dry matterpartitioning into the fruits, but it did not influence internodelength. Plant development (number of visible leaves at the endof the experiments) was not influenced by sink-source ratio.In four experiments some plants were pruned to one fruit pertruss. Final dry matter production was 8-24% lower for theseplants, compared with plants with more than one fruit per truss.This was, at least party, the result of less light interceptionby these plants, which had strongly curled leaves pointing downwards. Results indicate that effects of sink demand on dry matter productionper unit of intercepted radiation and probably on leaf photosyntheticrate in commercial tomato production can be ignored.Copyright1995, 1999 Academic Press Dry matter production, feedback control, glasshouse, growth analysis, Lycopersicon esculentum, pruning, sink demand, sink-source ratio, tomato     

Effects and Interactions of Ozone and the Anti-ozonant EDU at Different Stages of Radish {Raphanus sativus L.) Development

The use of the anti-ozonant ethylenediurea (EDU) to assess croplosses due to atmospheric ozone (O₃), is controversial becauseof incomplete knowledge on the optimal dosage, the extent ofprotection provided and potential effects on plant performanceof EDU per se. In a greenhouse experiment, radish (Raphanussativus L.) cv. ‘Cherry Belle’ plants were treatedwith EDU as a soil drench (150 mg1¹, 60 ml plant¹) at threestages of development: early, maximum and late hypocotyl thickening.Two days later the plants were exposed to O₃, mimicking an ambientpattern (70 nl 1¹ O₃, 7 h d¹, 5 d, and up to 120 nl 1¹ O₃ on2 d), or remained in filtered air. Assessment of leaf injury showed complete protection from ozone-inducedleaf damage at all stages of growth due to EDU. EDU did causeslight leaf margin necrosis and hyponastic leaf deformationirrespective of the atmospheric treatment, but biomass and relativegrowth rate (RGR) of the shoot and leaf number duration werenot altered and leaf area duration was increased when comparedto control plants. EDU did not affect dry weight accumulationnor RGR of the hypocotyl. Ozone-induced reductions in growthof below-ground organs (hypocotyl and root), which were mostprominent in the intermediate and early stage of growth, werelargely suppressed by the EDU-treatment. Decreases of hypocotylbiomass due to O₃ were transient and significant increases inRGR of the hypocotyl during the post-exposure period indicateda substantial capability of compensation during the period ofrecovery. Key words: Radish (Raphanus sativus), ozone, anti-ozonant, ethylenediurea (EDU), development, phytotoxicity     

Thyroid hormone inhibits biliary growth in bile duct-ligated rats by PLC/IP(3)/Ca(2+)-dependent downregulation of SRC/ERK1/2

The role of the thyroid hormone agonist 3,3',5 L-tri-iodothyronine (T3) on cholangiocytes is unknown. We evaluated the in vivo and in vitro effects of T3 on cholangiocyte proliferation of bile duct-ligated (BDL) rats. We assessed the expression of ₁-, ₂-, ₁-, and ₂-thyroid hormone receptors (THRs) by immunohistochemistry in liver sections from normal and BDL rats. BDL rats were treated with T3 (38.4 µg/day) or vehicle for 1 wk. We evaluated 1) biliary mass and apoptosis in liver sections and 2) proliferation in cholangiocytes. Serum-free T3 levels were measured by chemiluminescence. Purified BDL cholangiocytes were treated with 0.2% BSA or T3 (1 µM) in the absence/presence of U-73122 (PLC inhibitor) or BAPTA/AM (intracellular Ca²⁺ chelator) before measurement of PCNA protein expression by immunoblots. The in vitro effects of T3 (1 µM) on 1) cAMP, IP₃, and Ca²⁺ levels and 2) the phosphorylation of Src Tyr139 and Tyr530 (that, together, regulate Src activity) and ERK1/2 of BDL cholangiocytes were also evaluated. ₁-, ₂-, ₁-, and ₂-THRs were expressed by bile ducts of normal and BDL rats. In vivo, T3 decreased cholangiocyte proliferation of BDL rats. In vitro, T3 inhibition of PCNA protein expression was blocked by U-73122 and BAPTA/AM. Furthermore, T3 1) increased IP₃ and Ca²⁺ levels and 2) decreased Src and ERK1/2 phosphorylation of BDL cholangiocytes. T3 inhibits cholangiocyte proliferation of BDL rats by PLC/IP₃/Ca²⁺-dependent decreased phosphorylation of Src/ERK1/2. Activation of the intracellular signals triggered by T3 may modulate the excess of cholangiocyte proliferation in liver diseases. cholestasis; cholangiopathies; hyperplasia; intrahepatic biliary epithelium; mitosis     

The Effects of Priming and Ageing on Seed Vigour in Tomato

A comparison was made of the effects of seed priming or ageingtreatments on the performance of tomato (Lycopersicon esculentumMill. cv. UC204C) seeds according to a number of indices ofseed vigour. A single lot of tomato seeds was primed in 120mol m^–3 K2HPO4 + 150 mol m^–3 KNO₃ for 5 d at 20?C, or aged at 13% moisture content (dry weight basis) and 50?C for 6 d. Germination percentage (>98%) was unaffectedby priming and reduced to 85% by ageing. X-ray photographs andlongitudinal sections revealed the formation of free space surroundingthe embryo in dry primed seeds, which was not evident in controlor aged seeds. Priming increased the rate of germination atall temperatures above the base temperature (T_b), while ageingdecreased it. T_b was unaffected by priming and only slightlyincreased by ageing. The variation in individual times to germinationwas approximately doubled in both primed and aged seed comparedto the control, based upon the slopes of probit germinationpercentage versus log thermal time curves. Root growth aftergermination tests and seedling growth in both greenhouse andfield tests were not influenced by either priming or ageing.The conductivity test was found to be unreliable as a vigourtest for tomato seeds. The results identify several indiceswhich can be used to quantify seed vigour in tomato. They alsoillustrate that seed priming can enhance seed performance accordingto some criteria, while having no effect or decreasing qualityaccording to other criteria. Seed vigour can apparently be separatedinto various components which can be independently influencedby seed enhancement treatments. Key words: Tomato, seed germination rate, seed priming, seed vigour     

西双版纳热带季节雨林优势树种树干呼吸特征

 采用红外气体分析法（IRGA）原位监测了西双版纳热带季节雨林11种优势树种树干呼吸速率、1 cm深树干温度以及林内空气变化情况。研究发 现,11种优势树种的树干呼吸具有相同的季节规律,并且雨季均大于干季时的树干呼吸。树种间树干呼吸速率差异显著,在0. 823～2.727 μmol&;#8226;m^-2&;#8226;s^-1。树干1.3 m处所测南北方向树干呼吸无显著性差异。树干呼吸与树干温度显著相关(0.552<0.92),呈良好的自然指数回归关 系,Q₁₀值为1.90～3.03。20 ℃时各树种的RT（总树干呼吸）速率为0.771～2.570μmol&;#8226;m^-2&;#8226;s^-1。     

Inactivation of 1-aminocyclopropane-1-carboxylate (ACC) oxidase

The enzyme 1-aminocyclopropane-1-carboxylate (ACC) oxidase,which catalyses the final step in the biosynthesis of ethylene,showed a non-linear time-course in vitro and activity decayedwith a half-life of around 14 min. This loss of activity wasstudied using tomato ACC oxidase purified from Escherichia coiltransformed with the cDNA clone pTOM13. Inactivation was notdue to end-product inhibition by dehydroascorbic acid or cyanide.Preincubatlon of enzyme in the combined presence of Fe²⁺ ascorbateand ACC, which together allowed catalytic turnover, resultedin almost total loss of ACC oxidase activity. Enzyme Inactivatedby catalysis could not be reactivated by passage through SephadexG-25 or by treating with combina tions of DTT and CO₂ A non-lineartime-course and inactivation in the presence of all substratesand cofactors was also shown for the enzyme assayed in vivowith melon fruit discs. Using the purified tomato enzyme a distinctascorbate-dependent inactivation was also observed, which occurredIn the absence of catalysis and was prevented, although notreversed, by catalase. This ascorbate-dependent inactivationmay thus be due to H₂O₂ attack on ACC oxidase. Key words: 1-aminocyclopropane-1-carboxylate (ACC) oxidase, catalase, catalytic inactivation, ethylene     

Water Import Rate in Tomato Fruit: A Resistance Model

A model of the water import rate in tomato fruit is proposed.It compares the fruit to a hollow sphere (P) with external radiusR and internal radius R_G, corresponding to pericarp, and containingan internal spherical part (G). The pathway limiting water inputrate at any point I at a distance r from the fruit centre wasassumed to be proportional: (a) in P, to the length of the arcwhich has a radius r and which goes from I to the pedicel extension;(b) in G, to r. The water input rate at I was modelled basedon a law similar to Darcy's law which takes into account thedifference between the water potential at entry of fruit andthe water potential at point I. This latter potential was thesum of fruit osmotic potential and pressure potential due toresistance of tissue to deformation. This potential was proportionalto R-r or R_G -r. The model was expressed at fruit level by alaw such that water mass imported per unit time per unit surfacearea of fruit (f_rw) was a linear function of R. The model wascompared to linear regressions of this rate in terms of R whichhad been found during fruit swelling from published results,and which were obtained at different values of nutrient solutionsalinity. The results suggested that water input in tomato fruitis conditioned by passive forces depending on fruit size.Copyright1994, 1999 Academic Press Fruit, growth, model, resistance, salinity, size, tomato, transfer, water     

Auxin-gibberellin relationships in their effects on hypocotyl elongation of light-grown cucumber seedlings VI. Promotive and inhibitory effects of kinetin

The interaction of kinetin with IAA and GA₃ on the elongationof hypocotyl sections of Cucumis sativus L. cv. National Picklingwas studied. Kinetin in the concentration range of 10^–7M to 10^–4 M markedly inhibited IAA-induced elongation,while in a lower range from 10^–10 M to 10^–8 M, itsynergistically enhanced IAA-induced elongation. Kinetin alonein this range had no effect. A 5-to 15-min pulse treatment seemsenough to induce the maximum effect for both inhibition andpromotion. Since the magnitude of the maximum inhibition dependedon the concentration and not on the duration of treatment, thereaction in the cell caused by kinetin seemed to be completedwithin a short period. Washing of the sections with distilledwater after kinetin treatment (30 min) did not significantlyeliminate the kinetin effect. This probably indicates that thebinding of kinetin molecules to a supposed acceptor is not reversible.Interaction of kinetin with GA₃ in their pretreatment effectson IAA-induced elongation shows that in the inhibitory concentrationrange, the kinetin effect was partly overcome by GA₃, and thatin the promotive range, the magnitude of the enhancement wasdetermined by kinetin regardless of the presence of GA₃. Theeffect of kinetin seems to dominate over that of GA₃ indicatingthat the modes of their pretreatment effects differ from oneanother. (Received June 24, 1977; )     

Isolation of the ALG6 locus of Saccharomyces cerevisiae required for glucosylation in the N-linked glycosylation pathway

N-Linked protein glycosylation in most eukaryotic cells initiateswith the transfer of the oligosaccharide Glc₃Man₉GlcNAc₂ fromthe lipid carrier dolichyl pyrophosphate to selected asparagineresidues. In the yeast Saccharomyces cerevisiae, alg mutationswhich affect the assembly of the lipid-linked oligosaccharideat the membrane of the endoplasmic reticulum result in the accumulationof lipid-linked oligosaccharide intermediates and a hypoglycosylationof proteins. Exploiting the synthetic growth defect of alg mutationsin combination with mutations affecting oligosaccharyl transferaseactivity (Stagljar et al., 1994), we have isolated the ALG6locus. alg6 mutants accumulate lipid-linked Man₉GlcNAc₂, suggestingthat this locus encodes an endoplasmic glucosyltransferase.Alg6p has sequence similarity to Alg8p, a protein required forglucosylation of Glc₁Man⁹GlcNAc². Saccharomyces cerevisiae endoplasmic reticulum glycosyltransferase dolichol