Initial water deficit effects on Lupinus albus photosynthetic performance, carbon metabolism, and hormonal balance: metabolic reorganization prior to early stress responses

The early (2-4 d) effects of slowly imposed soil water deficit on Lupinus albus photosynthetic performance, carbon metabolism, and hormonal balance in different organs (leaf blade, stem stele, stem cortex, and root) were evaluated on 23-d-old plants (growth chamber assay). Our work shows that several metabolic adjustments occurred prior to alteration of the plant water status, implying that water deficit is perceived before the change in plant water status. The slow, progressive decline in soil water content started to be visible 3 d after withholding water (3 DAW). The earliest plant changes were associated with organ-specific metabolic responses (particularly in the leaves) and with leaf conductance and only later with plant water status and photosynthetic rate (4 DAW) or photosynthetic capacity (according to the Farquhar model; 6 DAW). Principal component analysis (PCA) of the physiological parameters, the carbohydrate and the hormone levels and their relative values, as well as leaf water-soluble metabolites full scan data (LC-MS/MS), showed separation of the different sampling dates. At 6 DAW classically described stress responses are observed, with plant water status, ABA level, and root hormonal balance contributing to the separation of these samples. Discrimination of earlier stress stages (3 and 4 DAW) is only achieved when the relative levels of indole-3-acetic acid (IAA), cytokinins (Cks), and carbon metabolism (glucose, sucrose, raffinose, and starch levels) are taken into account. Our working hypothesis is that, in addition to single responses (e.g. ABA increase), the combined alterations in hormone and carbohydrate levels play an important role in the stress response mechanism. Response to more advanced stress appears to be associated with a combination of cumulative changes, occurring in several plant organs. The carbohydrate and hormonal balance in the leaf (IAA to bioactive-Cks; soluble sugars to IAA and starch to IAA; relative abundances of the different soluble sugars) flag the initial responses to the slight decrease in soil water availability (10-15% decrease). Further alterations in sucrose to ABA and in raffinose to ABA relative values (in all organs) indicate that soil water availability continues to decrease. Such alterations when associated with changes in the root hormone balance indicate that the stress response is initiated. It is concluded that metabolic balance (e.g. IAA/bioactive Cks, carbohydrates/IAA, sucrose/ABA, raffinose/ABA, ABA/IAA) is relevant in triggering adjustment mechanisms.     

Acid invertase confers heat tolerance in rice plants by maintaining energy homoeostasis of spikelets

Heat stress impairs both pollen germination and pollen tube elongation, resulting in pollination failure caused by energy imbalance. Invertase plays a critical role in the maintenance of energy homoeostasis; however, few studies investigated this during heat stress. Two rice cultivars with different heat tolerance, namely, TLY83 (heat tolerant) and LLY722 (heat susceptible), were subjected to heat stress. At anthesis, heat stress significantly decreased spikelet fertility, accompanied by notable reductions in pollen germination on stigma and pollen tube elongation in ovule, especially in LLY722. Acid invertase (INV), rather than sucrose synthase, contributed to sucrose metabolism, which explains the different tolerances of both cultivars. Under heat stress, larger enhancements in NAD(H), ATP, and antioxidant capacity were found in TLY83 compared with LLY722, whereas a sharp reduction in poly(ADP-ribose) polymerase (PARP) activity was found in the former compared with the latter. Importantly, exogenous INV, 3-aminobenzamide (a PARP inhibitor), sucrose, glucose, and fructose significantly increased spikelet fertility under heat stress, where INV activity was enhanced and PARP activity was inhibited. Therefore, INV can balance the energy production and consumption to provide sufficient energy for pollen germination and pollen tube growth under heat stress.     

Genome-wide analysis of invertase gene family in wheat (Triticum aestivum L.) indicates involvement of TaCWINVs in pollen development

Plant Growth Regulation - Invertase (INV, EC3.2.1.26) is involved in carbohydrate partitioning by irreversibly hydrolyzing sucrose into fructose and glucose. INV genes that are specifically...     

菊芋蔗糖代谢相关产物与关键酶基因对高温的响应

蔗糖是一类重要的碳水化合物,其代谢与植物生长发育及抵抗胁迫等有密切的关系。蔗糖合成酶(SUS)、蔗糖磷酸合成酶(SPS)与蔗糖转化酶(INV)是参与蔗糖代谢的三类关键酶。本研究依据转录组测序数据,从能源植物菊芋中鉴定了2个SUS、2个SPS和7个INV基因(GenBank No:MK386943-53)。生物信息学分析表明,菊芋SUS、SPS和INV的氨基酸序列与其他物种具有较高的相似性,均属于亲水性蛋白。在25、30°C处理10、15、20 d的菊芋幼苗叶片中,这三种基因家族成员呈现不同的表达模式;除可溶性总糖含量减少外,果糖、蔗糖、蔗果三糖等含量没有发生明显变化。表明高温下幼苗蔗糖代谢关键酶基因发生了响应,蔗糖代谢处于平衡状态,显示了菊芋对高温的良好耐受性。     

<Emphasis Type="Italic">Lyso</Emphasis>-phosphatidylethanolamine-enhanced phenylalanine ammonia-lyase and insoluble acid invertase in isolated radish cotyledons

Application of lyso-phosphatidylethanolamine (LPE) is purported to suppress fruit ripening and delay foliar senescence. However, the endogenous LPE response of plants is more typically associated with propagation of wound and stress signals. Experiments were therefore carried out to determine whether exogenous LPE could elicit defense responses in plants by determining the effect of this lyso-phospholipid on activity of two key metabolic enzymes and pathogenesis-related proteins viz phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) and insoluble acid invertase (Ac INV; EC 3.2.1.26) in expanding cotyledons of Raphanus sativus L. cv. Cherry Belle (radish). Activity of both enzymes was increased following exposure of tissue to 18:0-LPE and the response was dose dependent. Soluble Ac INV activity was not enhanced by exogenous 18:0-LPE. Increased PAL activity appeared to coincide with a decline in phenolic acid content and a rise in sinapine and lignin. An increase in insoluble Ac INV by 18:0-LPE was associated with a reduction in sucrose concentration. However, levels of glucose and fructose were unaffected. In view of these findings it is proposed that applied LPE acts to co-ordinate carbohydrate partitioning locally to fulfill anabolic respiratory requirements associated with the propagation of systemic wound and stress responses. Furthermore, the impact of exogenous 18:0-LPE on insoluble Ac INV activity is discussed in relation to the proposed role of this enzyme in cytokinin-mediated senescence delay.     

温度胁迫对二化螟滞育幼虫生理指标的影响

为从生理生化水平上探讨二化螟滞育幼虫应对温度胁迫的生理机制,分别对系列温度胁迫(STS)和梯度温度胁迫(GTS)处理后的幼虫水、脂质、总糖、小分子碳水化合物含量及超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性进行了测定.结果表明:随着温度的降低,两种处理二化螟滞育幼虫虫体含水量趋于减少,且0℃以下时GTS处理下降幅度较STS处理显著;两种处理脂质含量均逐步下降且二者间无显著差异;两种处理总糖含量分别先减后增和持续下降,均检测出4种小分子碳水化合物,其中STS处理葡萄糖、甘油和果糖含量先增后减,海藻糖含量变化与此相反,而GTS处理海藻糖含量先减后增,葡萄糖和甘油含量呈相反变化,果糖含量无变化;14～-14℃范围内STS处理SOD和POD活性较GTS处理低,CAT活性相反.二化螟滞育幼虫生理指标的变化反映了其应对不同温度胁迫的生理响应.     

Purification and partial characterization of fructosyltransferase and invertase from Aspergillus niger AS0023

Fructosyltransferase (EC.2.4.1.9) and invertase (EC.3.2.1.26) have been purified from the crude extract of Aspergillus niger AS0023 by successive chromatographies on DEAE-sephadex A-25, sepharose 6B, sephacryl S-200, and concanavalin A-Sepharose 4B columns. On acrylamide electrophoresis the two enzymes, in native and denatured forms, gave diffused glycoprotein bands with different electrophoretic mobility. On native-PAGE and SDS-PAGE, both enzymes migrated as polydisperse aggregates yielding broad and diffused bands. This result is typical of heterogeneous glycoproteins and the two enzymes have proved their glycoprotein nature by their adsorption on concanavalin A lectin. Fructosyltransferase (FTS) on native PAGE migrated as two enzymatically active bands with different electrophoretic mobility, one around 600 kDa and the other from 193 to 425 kDa. On SDS-PAGE, these two fractions yielded one band corresponding to a molecular weight range from 81 to 168 kDa. FTS seems to undergo association-dissociation of its glycoprotein subunits to form oligomers with different degrees of polymerization. Invertase (INV) showed higher mobility corresponding to a molecular range from 82 to 251 kDa, on native PAGE, and from 71 to 111 kDa on SDS-PAGE. The two enzymes exhibited distinctly different pH and temperature profiles. The optimum pH and temperature for FTS were found to be 5.8 and 50 degrees C, respectively, while INV showed optimum activity at pH 4.4 and 55 degrees C. Metal ions and other inhibitors had different effects on the two enzyme activities. FTS was completely abolished with 1 mM Hg(2+) and Ag(2+), while INV maintained 72 and 66% of its original activity, respectively. Furthermore, the two enzymes exhibited distinctly different kinetic constants confirming their different nature. The K(m) and V(m) values for each enzyme were calculated to be 44.38 mM and 1030 micromol ml(-1)min(-1) for FTS and 35.67 mM and 398 micromol ml(-1) min(-1) for INV, respectively. FTS and INV catalytic activity was dependent on sucrose concentration. FTS activity increased with increasing sucrose concentrations, while INV activity decreased markedly with increasing sucrose concentration. Furthermore, INV exhibited only hydrolytic activity producing exclusively fructose and glucose from sucrose, while FTS catalyzed exclusively fructosyltransfer reaction producing glucose, 1-kestose, nystose and fructofuranosyl nystose. In addition, at 50% sucrose concentration FTS produced fructooligosaccharides at the yield of 62% against 54% with the crude extract.     

Mobilization of fructan reserves and changes in enzyme activities in wheat stems correlate with water stress during kernel filling

Triticum aestivum (wheat) plants grown at a daynight temperature of 1813 °C from anthesis were held as well watered controls, or subject to either a mild (large pot volume) or a more severe (small pot volume) water stress by withholding water from the time of anthesis. Extracts from the peduncle (enclosed by the flag leaf sheath) and the penultimate internode were prepared to determine the activities of fructan exohydrolase and acid invertase and to assess the level of hexose sugars, sucrose and fructans. Measurements were made of ear and individual grain weights and stem fresh weight and dry weight. Plant water relations at the time of each sampling were determined as the flag leaf water potential and the water content of individual organs. Water stress resulted in a shorter duration of kernel filling, smaller kernels at maturity and an earlier loss of stem weight. There was an increase in stem fructose and a fall in fructan level that preceded the loss of dry matter associated with water stress. Coincident with the early fall in fructan content under water stress there was a rise in both fructan exohydrolase and acid invertase in the internodes of stressed plants. This correlation suggests that the conversion of fructans to fructose might have resulted from enzyme induction associated with water stress, but as this conversion occurs before the major export of reserves from the stem it might be only indirectly related to changes in the demand for reserves.     

Carbohydrate metabolism in Nerine sarniensis bulbs developing in liquid culture

Anatomical and physiological changes accompanying enhanced Nerine sarniensis cv. Salmon Supreme bulb growth in vitro were examined. Small bulbs, 2–3 mm in diameter, grown in vitro on a semi-solid medium were subcultured to liquid medium with elevated levels of sucrose (Suc) and inorganic phosphate. Bulbs' fresh and dry weights, carbohydrate contents and the activities of enzymes related to carbohydrate metabolism were determined at different stages of bulb development. Starch was the dominant storage carbohydrate in these bulbs, and the leaf bases parenchyma cells were the principal storage tissue. During the first month of bulb growth, only small changes in starch content were detected. However, an increase in starch level was observed at later stages of development. The activity of ADP-glucose pyrophosphorylase (EC 2.7.7.27), a key enzyme of starch synthesis, increased just before the increase in starch accumulation. Sucrose was the dominant soluble sugar in the bulbs, only traces of glucose and fructose were detected. The activity of alkaline invertase (INV, EC 3.2.1.26) was higher than that of acid INV during the growth period. Sucrose synthase (EC 2.4.1.13) exhibited the highest Suc-degrading activity during bulb growth. Suc was hydrolyzed in the medium by the cell wall bound acid INV during the growing period. The results are discussed in relation to enhanced nerine bulb growth and development in vitro.     

Soluble carbohydrates in Delphinium and their influence on sepal abscission in cut flowers

A carbohydrate other than sucrose, glucose, fructose and myo -inositol was detected in sepal extracts of Delphinium . This compound was identified as mannitol by ¹H-NMR. Mannitol was the major carbohydrate in all examined organs: the sepal, the other parts of the flower, the stem and leaves. Mannitol as well as glucose (both at 0.55 M ), fed to cut Delphinium flowers, similarly delayed the abscission of sepals. 3- O -methyl glucose (3-OMG) and polyethylene glycol 200 at the same molar concentrations had no such effect. The treatment with glucose markedly increased the concentrations of glucose and fructose in the sepals without changing the concentrations of sucrose and mannitol. On the other hand, the treatment with mannitol increased the concentrations of glucose and fructose in addition to mannitol in the sepals, suggesting that mannitol is metabolized in Delphinium flowers. The treatment with 3-OMG increased the concentration of 3-OMG but not other carbohydrates. Mannitol and glucose similarly delayed the increase in ethylene production in flowers, but 3-OMG did not. The sensitivity to ethylene was similarly reduced by the treatment with glucose and mannitol, but not by 3-OMG. These results suggest that the treatment with mannitol, a major carbohydrate in Delphinium , delayed the abscission of sepals by reducing the sensitivity to ethylene. Mannitol further acted, not merely as an osmolyte, but as an apparent source for carbohydrate metabolism in the flower.     

甘草叶片渗透调节物质及蔗糖代谢相关酶对干旱胁迫的响应特性

该研究以甘草幼苗为试材,采用盆栽自然干旱方法,设计对照(CK)、轻度(LS)、中度(MS)、重度(SS)干旱胁迫处理,测定分析甘草叶片的渗透调节物质及蔗糖代谢相关酶[蔗糖磷酸合成酶(SPS)、蔗糖合成酶合成方向(Ss+)、蔗糖合成酶分解方向(Ss-)、中性转化酶(NI)、酸性转化酶(AI)、淀粉磷酸化酶(SP)]活性的变化,以探讨甘草的渗透调节特性以及糖分调节的酶学机制,揭示甘草对干旱胁迫的响应机理。结果显示:(1)随着干旱胁迫程度的加剧,甘草叶片可溶性糖、可溶性蛋白和脯氨酸含量呈逐渐增加的趋势,束缚水/自由水的比值呈先增加后降低的趋势。(2)随着干旱胁迫程度的加剧,甘草叶片蔗糖、葡萄糖、果糖含量均呈先升高后降低的趋势,但不同胁迫强度出现峰值的时间不同;其中在CK和LS干旱胁迫时蔗糖含量淀粉含量葡萄糖含量果糖含量,在MS和SS干旱胁迫时淀粉含量葡萄糖含量蔗糖含量果糖含量,表明随着干旱程度的增加,甘草叶片中蔗糖转化成了淀粉。(3)随着干旱胁迫程度的加重,甘草叶片的SPS活性呈先升高后降低的趋势,Ss活性和Inv(蔗糖转化酶)活性呈逐渐升高的趋势,SP活性呈逐渐降低的趋势;各胁迫处理的Ss+活性与CK差异不显著,而Ss-活性与CK差异显著,并且Ss-活性在各胁迫处理下远大于Ss+活性,表明甘草叶片Ss-活性在蔗糖代谢过程中占主导作用。(4)相关分析结果显示,在LS中,NI与蔗糖呈负相关关系,Ss-与淀粉呈显著正相关关系、与蔗糖呈负相关关系;在MS中,蔗糖和葡萄糖与SPS、Ss+、Ss-、NI和AI均呈正相关关系,与SP呈负相关关系;在SS中,SP和NI与蔗糖呈正相关关系,而与淀粉呈负相关关系;表明在轻度干旱处理下,Ss参加了蔗糖的分解,继而合成淀粉;在中度和重度干旱条件下,SP主要催化淀粉的分解来增加蔗糖含量以此平衡蔗糖代谢。     

Fructose as a factor of Carbonyl and oxidative stress development and accelerated aging in the yeast Saccharomyces

Excessive and prolonged consumption of fructose may lead to the development of metabolic disorders. However, the mechanisms of disturbances are still discussed. In the present work, the budding yeast Saccharomyces cerevisiae has been used as a model to compare the effects of prolonged consumption of different concentrations of glucose and fructose on certain physiology-biochemical parameters of eukaryotes. It has been shown that the yeast growth, their metabolic activity, intracellular level of glycogen and oxidized proteins were higher in cells grown on fructose. The observation is consistent with the data on a higher in vitro ability of fructose than glucose to initiate glycation which products of which are highly reactive a-dicarbonyl compounds and activated oxygen forms. Thus the intensity of carbonyl and oxidative stress is higher in cells grown on fructose. This can explain a higher rate of aging of yeast consuming fructose as a source of carbon and energy as compared to cells growing on glucose. However, carbohydrate restriction used in this study ham- pered the accumulation of glycogen and oxidized proteins and did not reveal any difference between markers of aging and carbonyl and oxidative stress in yeast grown on glucose and fructose.     

Study of developmental changes on hexoses metabolism in rat cerebral cortex

We have studied the developmental changes of glucose, mannose, fructose and galactose metabolism in rat cerebral cortex. As the animals aged, glucose, mannose and fructose oxidation to CO₂ increased, whereas galactose oxidation decreased. Lipid synthesis from glucose and fructose also increased with age, that from mannose decreased and galactose did not change. Cytochalasin B, a potent non-competitive inhibitor of sodium-independent glucose transport, significantly impaired glucose, mannose and galactose metabolism, but had no effect on fructose metabolism. Both galactose or fructose did not change, whereas mannose declined the glucose metabolism. Glucose decreased fructose, galactose and mannose metabolism. Our results show that besides glucose, the metabolism of mannose, galactose and fructose present developmental changes from fetal to adult age, and reinforce the literature data indicating that mannose and galactose are transported by glucose carriers, while fructose is not.     

Fructose triggers DNA modification and damage in an Escherichia coli plasmid

The nonenzymatic reaction between reducing sugars and amino groups of long-lived macromolecules results in an array of chemical modifications that may account for several physiological complications. The characteristics of the reaction are directly related to the type of the reducing sugars involved, whether aldoses or ketoses, phosphorylated or non-phosphorylated, and these in turn determine the consequences of the induced modifications. So far, most studies have been focused on the nonenzymatic reaction between glucose and proteins, while the reaction with fructose, a faster glycating agent, attracted only a minor attention. We have recently demonstrated that long-term fructose consumption induces age-related changes in collagen from skin and cortical bones faster than glucose. In the present study we provide evidence that fructose and its phosphate metabolites can modify DNA faster than glucose and its phosphate metabolites under in vitro conditions. Incubating the plasmid pBR322 with fructose and glucose phosphate metabolites induced DNA modifications and damage that were verified by gel electrophoresis and transformation capacity of the plasmid into an Escherichia coli host. The intensity of the tested sugars to modified and damage DNA after incubation for 15 days increased significantly in the following order: glucose 1-phosphate < glucose < glucose 6-phosphate < fructose 1-phosphate < fructose < fructose 6-phosphate. The data suggest that fructose should deserve more attention as a factor that may influence glycation and induce physiological complications.     

Sympathetic overactivity precedes metabolic dysfunction in a fructose model of glucose intolerance in mice

Consumption of high levels of fructose in humans and animals leads to metabolic and cardiovascular dysfunction. There are questions as to the role of the autonomic changes in the time course of fructose-induced dysfunction. C57/BL male mice were given tap water or fructose water (100 g/l) to drink for up to 2 mo. Groups were control (C), 15-day fructose (F15), and 60-day fructose (F60). Light-dark patterns of arterial pressure (AP) and heart rate (HR), and their respective variabilities were measured. Plasma glucose, lipids, insulin, leptin, resistin, adiponectin, and glucose tolerance were quantified. Fructose increased systolic AP (SAP) at 15 and 60 days during both light (F15: 123 ± 2 and F60: 118 ± 2 mmHg) and dark periods (F15: 136 ± 4 and F60: 136 ± 5 mmHg) compared with controls (light: 111 ± 2 and dark: 117 ± 2 mmHg). SAP variance (VAR) and the low-frequency component (LF) were increased in F15 (>60% and >80%) and F60 (>170% and >140%) compared with C. Cardiac sympatho-vagal balance was enhanced, while baroreflex function was attenuated in fructose groups. Metabolic parameters were unchanged in F15. However, F60 showed significant increases in plasma glucose (26%), cholesterol (44%), triglycerides (22%), insulin (95%), and leptin (63%), as well as glucose intolerance. LF of SAP was positively correlated with SAP. Plasma leptin was correlated with triglycerides, insulin, and glucose tolerance. Results show that increased sympathetic modulation of vessels and heart preceded metabolic dysfunction in fructose-consuming mice. Data suggest that changes in autonomic modulation may be an initiating mechanism underlying the cluster of symptoms associated with cardiometabolic disease.     

Glucose and fructose feeding lead to alterations in structure and function of very low density lipoproteins

Young male rats were fed regular lab chow, or a diet containing 66% of total calories as either glucose or fructose. Both experimental diets led to hypertriglyceridemia, with fasting TG concentrations after one week of 195 +/- 20 and 296 +/- 44 mg/dl for rats fed glucose and fructose, respectively, compared to 94 +/- 10 mg/dl in the control rats. Moderate changes in VLDL composition were observed with both test diets, characterized by slight increases in TG: protein ratio, and increased total cholesterol and phospholipid content. In addition, VLDL isolated from rats fed high carbohydrate diets were increased in size, with a mean VLDL particle diameter of 666 A and 720 A in glucose-fed and fructose-fed rats, as compared to 536 A in control rats. The changes in lipid composition and size of VLDL particles isolated from glucose and fructose-fed donor rats were associated with an increase in their rate of removal from the circulation following their injection into normal recipient rats (half-life time 2.4 +/- 0.2 and 3.2 +/- 0.3 min respectively) as compared to VLDL-TG derived from chow fed donors (4.1 +/- 0.2 min). These data indicate that diets high in either glucose or fructose can lead to both structural and functional changes in VLDL, and provide additional evidence that the ability of fructose to induce profound hypertriglyceridemia is not secondary to a defect in VLDL-TG catabolism.     

Glucose and Fructose Have Sugar-Specific Effects in Both Liver and Skeletal Muscle In Vivo: A Role for Liver Fructokinase

We examined glucose and fructose effects on serine phosphorylation levels of a range of proteins in rat liver and muscle cells. For this, healthy adult rats were subjected to either oral glucose or fructose loads. A mini-array system was utilized to determine serine phosphorylation levels of liver and skeletal muscle proteins. A glucose oral load of 125 mg/100 g body weight (G 1/2) did not induce changes in phosphorylated serines of the proteins studied. Loading with 250 mg/100 g body weight of fructose (Fr), which induced similar glycemia levels as G 1/2, significantly increased serine phosphorylation of liver cyclin D3, PI3 kinase/p85, ERK-2, PTP2 and clusterin. The G 1/2 increased serine levels of the skeletal muscle proteins cyclin H, Cdk2, IRAK, total PKC, PTP1B, c-Raf 1, Ras and the β-subunit of the insulin receptor. The Fr induced a significant increase only in muscle serine phosphorylation of PI3 kinase/p85. The incubation of isolated rat hepatocytes with 10 mM glucose for 5 min significantly increased serine phosphorylation of 31 proteins. In contrast, incubation with 10 mM fructose produced less intense effects. Incubation with 10 mM glucose plus 75 µM fructose counteracted the effects of the incubation with glucose alone, except those on Raf-1 and Ras. Less marked effects were detected in cultured muscle cells incubated with 10 mM glucose or 10 mM glucose plus 75 µM fructose. Our results suggest that glucose and fructose act as specific functional modulators through a general mechanism that involves liver-generated signals, like micromolar fructosemia, which would inform peripheral tissues of the presence of either glucose- or fructose-derived metabolites.     

干旱胁迫对宁夏枸杞生长及果实糖分积累的影响

文章研究不同干旱胁迫下宁夏枸杞生长及果实糖分积累的变化规律,为宁夏枸杞在干旱地区高产栽培提供参考依据。采用盆栽控水试验,设置正常灌水、轻度干旱、中度干旱和重度干旱处理,研究了干旱胁迫对宁夏枸杞植株生长、生物量分配以及果实糖分积累的影响。结果表明：干旱抑制宁夏枸杞新稍、果实、株高和地径的生长：随着干旱程度加剧,根和茎中干物质分配率逐渐升高,而枝条、叶和果实中干物质分配率大幅降低;轻度干旱有利于果实发育过程中果糖的积累,中度和重度干旱胁迫则不利于成熟期果糖和蔗糖积累;干旱胁迫明显降低成熟期转化酶、蔗糖磷酸合成酶（SPS）和蔗糖合成酶（SS）的活性;果实发育过程中果糖的含量与SPS和转化酶活性存在极显著相关。可见,在果实发育期,土壤含水量为田间持水量55％以上,能促进宁夏枸杞果实中糖分积累,有效提高果实品质。     

Effect of sugar level on phleinase induction in stem base of orchardgrass after defoliation

Yamamoto, S. and Mino, Y. 1987. Effect of sugar level on phleinase induction in stem base of orchardgrass after defoliation.
The induction of phleinase (β-D-fructan fructohydrolase, EC 3.2.1.80) in stem base of orchardgrass ( Dactylis glomerata L. clone N-377) after defoliation was studied in relation to the concomitant changes in sugar and protein levels. Phleinase activity in the stubble increased accompanied by a decrease in sucrose and glucose levels. This activity also increased under shading conditions without cutting. The induction of phleinase in excised stem base was suppressed by exogenously supplied glucose, fructose or sucrose. The suppression increased with increasing concentrations of glucose and it was not overcome by cyclic adenosine 3',5'-monophosphate. Protein level in the stem base decreased after defoliation and the decrease was reversed by exogenous glucose. Some hypotheses concerning the induction mechanism of phleinase are discussed.     

外源水杨酸对氯化钠胁迫下番茄幼苗糖代谢的影响

采用营养液水培法,用100、300和500 mg·L^-1不同浓度的水杨酸（SA）处理‘辽园多丽’番茄幼苗,测定在NaCl胁迫下番茄幼苗叶片果糖、葡萄糖、蔗糖含量和蔗谢代谢相关酶活性（酸性转化酶AI、中性转化酶NI、蔗糖磷酸合成酶SPS、蔗糖合成酶活性SS）的变化.结果表明：SA处理叶片可以维持或提高NaCl胁迫条件下番茄幼苗叶片果糖、葡萄糖含量及AI、NI、SPS和SS活性,其最高值分别比单纯NaCl处理植株增加30.0%、31.1%、24.7%、27.9%、22.0%和24.5%;但对NaCl胁迫条件下番茄幼苗叶片蔗糖含量的影响不大.表明水杨酸可以通过提高NaCl胁迫下番茄叶片转化酶活性来提高番茄叶片果糖和葡萄糖含量,从而缓解NaCl胁迫对番茄的伤害,其中以500 mg·L^-1的SA处理效果较理想.