Rapid Effects of Abscisic Acid on Ion Uptake in Sunflower Roots

Short-term effects of ABA, ABA + kinetin and kinetin on ion (⁸⁶Rb-potassium and phosphate) and water uptake in sunflower plants (Helianthus annuus var. californicus) were examined with a continuous-recording technique. Ion uptake in the roots and transport to the shoots were also investigated by conventional tracer uptake experiments and by sap bleeding experiments with excised roots. After addition of 5 × 10^?6-4 × 10^?5M ABA to the root medium there was an immediate decrease (30–70%) in the rate of ion uptake which lasted 30–70 min. The rate of water uptake was not significantly affected as measured with this method. Ion transport to the shoots and to the bleeding sap of excised roots was decreased by ABA. ABA-induced inhibition of ion uptake was abolished by the presence of kinetin, and uptake was slightly stimulated by 2 × 10^?5M kinetin alone. We suggest that concentration gradients of ABA or rapid changes in the ABA-kinetin balance in the roots affect ion uptake and transport.     

Effects of Humic Acid on Protein Synthesis and Ion Uptake in Beet Discs

Humic acids stimulate the development of phosphate uptake-capacityin beet discs during ageing under aseptic conditions withoutaffecting phosphate uptake per se. Chloride uptake is inhibitedby humic acids as is the development of chloride uptake capacity.The uptake of proline and leuoine is not influenced by ageingin humic acid. While measurements of the incorporation of theseamino acids into the sub-cellular particles of discs indicatethat humic acid does not affect protein synthesis in general,the stimulation of invertase development during ageing doesshow a definite effect on some aspect of protein synthesis.     

The Effects of 2,4-Dichlorophenoxyacetic Acid on Ion Uptake by Maize Roots

The effects of the synthetic auxin and herbicide 2,4-dichlorophenoxyaceticacid (2,4-D) on K^$ and Cl^– uptake and H^$ release by youngexcised maize roots has been studied. Brief exposure to 2,4-D(0.01 mmol dm^–3) at pH 3.5 causes a large depolarizationof the electrical potential across the root plasma membranesand converts K^$ uptake to K^$ leakage into the bathing solution.These results can be explained by the increased H^$ permeabilityof the membranes induced by the weak acid 2,4-D. The depolarizationresults in a less favourable electrochemical potential gradientfor K^$ uptake across these membranes. These effects are notrelated to the auxin properties of 2,4-D as the nonauxin 3,5-dichlorophenoxyaceticacid (3,5-D) gives rise to similar effects. The relative depolarizationsinduced by a range of weak acids appear to be unrelated to theiroil/water partition coefficients. In contrast, on bathing the roots for longer periods in solutions(pH > 5) containing 2,4-D (0.01 mmol dm^–3) K^$ and Cl^–uptake and H^$ release are inhibited. These effects are not shownwith 3,5-D suggesting an auxin-linked action for 2,4-D. Alsothe electrical potential across the plasma membranes is onlyslightly depolarized so that a change in the electrochemicalpotential gradient cannot be invoked to explain the loweredion fluxes. The evidence is consistent with the removal of anenergy supply to a metabolically linked K^–/H^– exchangemechanism in the plasma membranes. It is likely that both modes of action would operate to lowerion uptake under soil-grown conditions, the former becomingmore manifest in acidic soils.     

Comparative Effects of Benzoic Acid and Water Stress on Wheat Seedlings

In the present study, we compared the effects of allelochemical, water stress (WS) and their combinations on seedling growth, biochemical parameters and responses of antioxidative enzymes in Triticum aestivum L. The wheat seedlings were treated with 0.5, 1.0 and 1.5 mM concentrations of benzoic acid (BA), with and without water stress. Leaf water status, photosynthetic pigments, protein content, amount of proline and activities of nitrate reductase and antioxidant enzymes were examined. Allelopathic stress resulted in reduction of seedling height. Height of water stressed seedlings greatly decreased. The combined treatments, BA + WS further decreased the seedling height. BA treatment with and without water stress caused significant reduction in dry weight of the seedlings. BA and water stress decreased relative water content, pigments and protein content. Total soluble sugar content and nitrate reductase activity were variedly affected under all treatments. Proline content and lipid peroxidation increased in treatments with BA and water stress. Activity of superoxide dismutase increased significantly (P < 0.05) while catalase activity decreased in all treatments. Ascorbate peroxidase and guaiacol peroxidase activities were higher as compared with catalase which seems to protect wheat seedlings from oxidative stress. Water stress elevated the toxic effect of allelochemical.     

Effects of Waterlogging on Water Relations of Actively-growing and Dormant Sitka Spruce Seedlings

Two-year-old Sitka spruce [Picea sitchensis (Bong.) Carr.] seedlings,either actively growing or dormant, were waterlogged in a growthroom at 15 °C. Shoot and root growth, transpiration andleaf water potential were observed. In actively-growing plants shoot extension continued after waterlogging,though at a reduced rate, and shoots of dormant plants brokebud and extended during the waterlogging period. Root growthwas suppressed by waterlogging in both types of plant. The 22day waterlogging treatment eventually killed the actively-growingplants but plants which were dormant at the time of waterloggingwere more tolerant. Changes in plant water relations after waterloggingwere entirely different depending on the condition of the plantswhen the soil was flooded. Dormant plants showed a gradual reductionin transpiration and increased water stress over the waterloggingperiod; after the soil was drained leaf water potential increasedto equal the value of control plants which had been maintainedin a freely drained condition, but transpiration did not increaseuntil root growth began. Actively-growing plants exhibited amore complex behaviour, characterized by a very rapid reductionin transpiration after waterlogging, accompanied by a briefperiod of water stress, followed by a period of increasing transpirationrate in the absence of water stress. Finally a second reductionin transpiration occurred and water stress increased as theseedlings died. The importance of the stage of activity of theroot system to the response of plants to waterlogging is discussed. Picea sitchensis (Bong.) Carr., Sitka spruce, waterlogging, water relations, dormancy, transpiration, water potential     

Rapid Effects on Ion and Water Uptake Induced by Changes of Water Potential in Young Wheat Plants

The effect of rapid changes in the water potential of the root medium or the atmosphere was investigated with particular respect to water and ion uptake in young wheat plants. Either PEG 400 or PEG 6000 were added to the nutrient solution, so that the water potential was decreased from about 0 to –5 bars and –13 bars, respectively. Both water and ion uptake immediately decreased when the water potential of the medium was reduced. By raising the humidity around the shoots from 1400 N m⁻² (60% RH) to about 2300 N m⁻² (100% RH) water uptake decreased, whereas ion uptake transiently increased. If sodium chloride was added to reduce the water potential of the mutrient solution, ion uptake was found to decrease to essentially the same level as when PEG was used. It is suggested that a change in the water potential of the plants has effects on the active-ion-transport mechanism.     

Effects of Ion Activity and Sugar Polyalcohol Osmotica on Ion Uptake

Evangelou, V. P. and Wagner, G. J. 1987. Effects of ion activityand sugar polyalcohol osmotica on ion uptake.—J. exp.Bot. 38: 1637–1651. Theoretical and experimental data are presented here which showthat ion activity—not just ion concentration—canbe an important consideration in interpreting measurements ofion uptake from solution by plant tissues. It is also shownthat sugar polyalcohols often used as osmotica in experimentsusing protoplasts, roots, vacuoles, etc. can greatly influenceion activity. The relationship between element concentrationand ion activity is shown here to be biphasic—the degreebeing dependent on the type of anions and cations involved andion concentration. Generally, the extent of biphasic behaviourincreases with increasing ion valence (i.e. K ⁺ versus Mg^{2 +}or Ca^{2 +} versus Al³⁺) and this character can be prominent inthe concentration range sometimes used to measure ion uptakeby plants (i.e. 1 to 70 mol m³). These observations can affectinterpretation of ion uptake kinetics involving ions with valencegreater than 1. High levels of sugar polyalcohols (i.e. 0·7kmol m ³ sorbitol or mannitol) significantly suppress ion activityand the nature and degree of suppression is dependent on iontype. The implications of this effect should be considered andquantified if ion uptake studies made in the presence of suchosmotica are to be extrapolated to the simpler case of a watersolution containing only inorganic salts. Key words: Kinetics, thermodynamics, solution cultures, ion pairs.     

Effects of Low Root Temperature on Ion Uptake and Ion Translocation in Wheat

Roots of wheat seedlings (Triticum aestivum L. cv. Weibulls Starke) were cooled (+1°C) for 24 h while the shoots were kept at 25°C. The treatment induced an increased water deficit in the leaves. Fresh weight, dry weight, and the uptake and distribution of potassium and calcium were measured before and after cooling. Growth, measured both as fresh weight and dry weight increase, was reduced during the cold treatment. Afterwards (at 20°C), growth recovered to nearly pre-stress rates. Analysis of the potassium fluxes in and out of the roots by ⁸⁶Rb techniques showed that influx, and to a lesser extent efflux, were inhibited at low temperature. The result was a net potassium uptake rate of one-third that of unstressed plants. After the cooling period the potassium influx increased to the rate of control plants. The potassium efflux increased to one and one-half times the rate of unstressed wheat so that net uptake was negative. The increase in potassium efflux was explained by a higher permeability of the root cell membranes after cooling. The net uptake of calcium was reduced to one-third by root cooling. Contrary to potassium uptake, calcium uptake increased under post-stress conditions, partly due to a low efflux rate. During root cooling there was a redistribution of dry matter from the leaves down towards the lower part of the shoot. Afterwards the original distribution of dry matter was reestablished. The net flow of potassium and calcium followed a similar pattern as dry matter, suggesting a growth-regulated flow.     

外源咖啡酸和阿魏酸对黑莓汁中花色苷的辅色研究

为增强黑莓汁中花色苷的稳定,添加适量咖啡酸和阿魏酸到黑莓清汁中,采用可见吸收光谱和高效液相色谱-质谱研究其对黑莓花色苷的辅色作用。研究结果表明:黑莓汁中添加咖啡酸和阿魏酸显著增加了花色苷的最大吸收值(Aλmax),最大吸收波长(λmax)红移,说明咖啡酸和阿魏酸对黑莓汁中花色苷产生了辅色作用,辅色效应随时间的延长和咖啡酸、阿魏酸浓度的增加显著增强。HPLC-DAD-MS分析发现,咖啡酸辅色产生了两种新的花色苷衍生物(矢车菊素-3-O-葡萄糖苷-4-乙烯基儿茶酚和矢车菊-3-O-草酸酐酰葡萄糖苷-4-乙烯基儿茶酚),阿魏酸辅色产生了三种新的花色苷衍生物(矢车菊素-3-O-葡萄糖苷-4-乙烯基愈创木酚、矢车菊-3-O-草酸酐酰葡萄糖苷-4-乙烯基愈创木酚和矢车菊-3-O-阿拉伯糖苷-4-乙烯基愈创木酚),这些衍生物均为羟苯基-吡喃花色苷。     

Differential Inhibition by Ferulic Acid of Nitrate and Ammonium Uptake in Zea mays L

The influence of the allelopathic compound ferulic acid (FA) on nitrogen uptake from solutions containing both NO₃⁻ and NH₄⁺ was examined in 8-day-old nitrogen-depleted corn (Zea mays L.) seedlings. Concurrent effects on uptake of Cl⁻ and K⁺ also were assessed. The presence of 250 micromolar FA inhibited the initial (0-1 hours) rate of NO₃⁻ uptake and also prevented development of the NO₃⁻-inducible accelerated rate. The pattern of recovery when FA was removed was interpreted as indicating a rapid relief of FA-restricted NO₃⁻ uptake activity, followed by a reinitiation of the induction of that activity. No inhibition of NO₃⁻ reduction was detected. Ammonium uptake was less sensitive than NO₃⁻ uptake to inhibition by FA. An inhibition of Cl⁻ uptake occurred as induction of the NO₃⁻ transport system developed in the absence of FA. Alterations of Cl⁻ uptake in the presence of FA were, therefore, a result of a beneficial effect, because NO₃⁻ uptake was restricted, and a direct inhibitory effect. The presence of FA increased the initial net K⁺ loss from the roots during exposure to the low K, ammonium nitrate uptake solution and delayed the recovery to positive net uptake, but it did not alter the general pattern of the response. The implications of the observations are discussed for growth of plants under natural conditions and cultural practices that foster periodic accumulation of allelopathic substances.     

Amelioration of Chilling Injuries in Cucumber Seedlings by Abscisic Acid

Exposure of cucumber seedlings (Cucumis sativus L.) to chilling temperature resulted in injuries such as increased leakage of cellular materials, loss of water and wilting. In addition, the development of the seedlings after the exposure to chilling was impaired. Abscisic acid applied to the seedlings prior to chilling significantly ameliorated these injuries.     

低温胁迫对黄瓜子叶抗坏血酸过氧化物酶活性和谷胱甘肽含量的影响

低温胁迫下黄瓜幼苗子叶抗坏血酸过氧化物酶活性和GSH含量显著下降,下降幅度随低温胁迫程度增加而递增。不同低温胁迫下酶活性和GSH含量变化与子叶电解质泄漏和MDA的增加呈负相关。幼苗用MV和MDA预处理可加剧由低温引起的抗坏血酸过氧化物酶活性和GSH含量降低,而用苯甲酸钠和α-生育酚预处理则可减轻这种降低,显示出过量的活性氧及其引发的膜脂过氧化产物MDA对抗坏血酸过氧化物酶和GSH均有伤害影响。     

Stimulatory Effects of Ferulic Acid on Endurance Exercise Capacity in Mice

Ferulic acid was orally administered to mice in order to investigate its effects on exercise endurance capacity. When a single administration of ferulic acid was given to the mice in an adjustable-current water pool, the duration of exhaustive swimming was longer than that exhibited by the mice in the control group. Also, when the mice were exhaustively exercised for 3 consecutive days, no change in swimming time was found in the ferulic acid-administered group on the final day, and a large decrease in the untreated mice. Administration of ferulic acid efficiently activated the hepatic antioxidative defense system during exercise. The mice that received ferulic acid showed significant increases in the activity of hepatic antioxidant enzymes such as superoxide dismutase, catalase, and glutathione-S-transferase. Furthermore, an increased glutathione level was observed, while the malondialdehyde content was reduced. These results suggest that ferulic acid possesses stimulatory effects that can enhance exercise endurance capacity and reduce fatigue by elevating antioxidative potentials.     

外源甜菜碱对黄瓜幼苗抗冷性的影响

以5 mmol·L-1甜菜碱(GB)根施黄瓜幼苗24h,可缓解低温胁迫[(6±1)℃]5 d后的叶中叶绿素含量的下降,保持相对较高的净光合速率和抗氧化酶活性,削弱丙二醛(MDA)积累,保持细胞膜的相对完整性,提高幼苗存活率.     

Protective Effects of Ferulic Acid on High Glucose-Induced Protein Glycation,Lipid Peroxidation,and Membrane Ion Pump Activity in Human Erythrocytes

Ferulic acid (FA) is the ubiquitous phytochemical phenolic derivative of cinnamic acid. Experimental studies in diabetic models demonstrate that FA possesses multiple mechanisms of action associated with anti-hyperglycemic activity. The mechanism by which FA prevents diabetes-associated vascular damages remains unknown. The aim of study was to investigate the protective effects of FA on protein glycation, lipid peroxidation, membrane ion pump activity, and phosphatidylserine exposure in high glucose-exposed human erythrocytes. Our results demonstrated that FA (10-100 μM) significantly reduced the levels of glycated hemoglobin (HbA1c) whereas 0.1-100 μM concentrations inhibited lipid peroxidation in erythrocytes exposed to 45 mM glucose. This was associated with increased glucose consumption. High glucose treatment also caused a significant reduction in Na⁺/K⁺-ATPase activity in the erythrocyte plasma membrane which could be reversed by FA. Furthermore, we found that FA (0.1-100 μM) prevented high glucose-induced phosphatidylserine exposure. These findings provide insights into a novel mechanism of FA for the prevention of vascular dysfunction associated with diabetes.     

牛蒡寡糖对黄瓜植株生理生化特性的影响

用不同浓度的牛蒡寡糖(BOS)溶液喷施黄瓜幼苗植株,研究牛蒡寡糖对黄瓜正常生长的生理生化特性的影响.结果表明,与对照组相比,施用1、3、5、8和10 g?L-1牛蒡寡糖处理的黄瓜叶片其叶绿素含量、游离脯氨酸含量、可溶性糖含量、可溶性蛋白含量和PSⅡ的光化学效率均有不同程度的升高,而细胞膜相对透性和MDA的含量均有所降低,其中5 g?L-1是最适处理浓度.因此,牛蒡寡糖能够促进植物的生长发育并提高其抗逆性.     

阿魏酸和水杨酸对枣皮红色素理化性质的影响

以枣(Jujube)皮为原料,经酶解和微波超声波处理后提取红色素,研究酰基化剂(Acylating agent)对红色素理化性质的影响.结果显示,枣皮红色素分别与阿魏酸和水杨酸形成的复合物对光和部分金属如Na+、Ca2+和Fe3+稳定;在pH 1～7范围内不稳定,pH 9～14范围内稳定.结果表明,阿魏酸和水杨酸与枣皮红色素复合后产生的酰基化产物有助于红色素分子的稳定.