Acetylcholine and Red-light Influence on Ethylene Evolution from Soyabean Leaf Tissues

Acetylcholine (Ach) and red light inhibited ethylene evolutionfrom excised green soyabean (Glycine max (L.) Merr.) leaf discs.Neostigmine, an Ach-esterase inhibitor, mimicked this effectwhile atropine, an Ach antagonist, increased ethylene evolution.Acetylcholine and red light partially overcame the atropine-inducedresponse. The results were interpreted as an influence of acetylcholineupon the ethylene formation process. Glycine max, ethylene inhibition, leaf discs     

Nitrogenase Activity, Photosynthesis and Nodule Water Potential in Soyabean Plants Experiencing Water Deprivation

The effects of water deprivation on the activity of nodulesof soyabean (Glycine max) have been investigated in controlledenvironments. The water potential of detached nodules was measuredusing a Wescor psychrometer and a specially designed ten chamberpsychrometer; each chamber was capable of holding up to sixnodules which allowed for simultaneous measurements of betweenten and 60 nodules. Nitrogenase activity (acetylene reduction)and respiration of intact, undisturbed nodulated roots was measuredin a flow-through gas system. The equilibration pattern of singlenodules in a Wescor chamber showed a distinct biphasic pattern.Differences between the pseudo- and the true equilibrium valuesof water potential suggest that water potential gradients closeto 01 MPa exist within the nodule tissue. Such gradients probablyreflect histological discontinuities. When detached noduleswere allowed to dry, decreases in water potential and diameterwere accompanied by increases in the resistance to water vapourloss through diffusion. These changes provide evidence for anatomicalmodifications which might provide some regulation of water loss. During a 7 d period of water deprivation there was a close relationshipbetween decreases in leaf and nodule water potential. Nitrogenaseactivity showed a 70% decrease during the first 4 d, whilstphotosynthesis only declined by 5%. It is suggested that waterstress exerts an influence on nitrogenase activity which isindependent of the rate of photosynthesis; it acts directlyon nodule activity through increases in the resistance to oxygendiffusion to the bacteroids. The data suggest that the linearrelationship between oxygen diffusion resistance and water potentialis more important than any reductions in photosynthate supply. Key words: Nitrogen fixation, water potential, photosynthesis     

Influence of Root Oxygen Deficiency on Photosynthesis and Antioxidant Status in Barley Plants1

Roots of barley plants (Hordeum vulgare L., cv. Alfa) were subjected to hypoxia for 120 h. By 72 to 120 h of soil flooding, a noticeable decrease in the rate of CO₂ assimilation and transpiration was observed. A drop in the activities of Rubisco and photorespiratory enzymes was found. We examined the changes in the activities of enzymes involved in the antioxidative system and stress markers related to membrane integrity, namely, lipid peroxidation and electrolyte leakage. Catalase and peroxidase activities were increased during the experiment, whereas superoxide dismutase activity drastically decreased.     

Linear Relations between Carbon Dioxide Concentration and Rate of Development Towards Flowering in Sorghum, Cowpea and Soyabean

Negative linear relations were detected (P < 0·005)between the rate of progress from sowing to panicle initiationand CO₂ concentration (210-720 µmol CO₂ mol^-1 air) fortwo genotypes of sorghum [Sorghum bicolor (L.) Moench]. Relationsbetween CO₂ concentration and the rate of progress from sowingto first flowering were also negative in soyabean [Glycine max(L.) Merrill] (P < 0·025), but positive in cowpea[Vigna unguiculata (L.) Walp.] (P < 0·025), albeitthat in both grain legumes sensitivity was much less than insorghum. Thus CO₂ elevation does not delay flowering in allshort-day species. The considerable effect of CO₂ concentrationon times to panicle initiation resulted in large differencesamong the sorghum plants at this developmental stage; with increasein CO₂ concentration, plants were taller with slightly moreleaves and more pronounced apical extension. At the same timeafter sowing however, sorghum plants were heavier (P < 0·05)at 210 than at 360 µmol CO₂ mol^-1 air. In contrast, relationsbetween the dry masses of the soyabean and cowpea plants andCO₂ concentration were positive and curvilinear (P < 0·05).It is suggested that the impact of global environmental changecould be severe for sorghum production in the semi-arid tropics.Copyright1995, 1999 Academic Press Sorghum bicolor (L.) Moench., sorghum, Glycine max (L.) Merrill, soyabean, Vigna unguiculata (L.) Walp., cowpea, development, flowering, CO₂, dry matter accumulation, environmental change     

High Foliar and Soil Nitrogen Concentrations in Central Appalachian Forests

Regional topography and climate variation yield differences in ecosystem attributes that make spatially scaled estimates of forest productivity challenging. Foliar nitrogen is a primary indicator of forest ecosystem productivity and is used in regional estimates of terrestrial productivity, but this characteristic has not been well described in the Central Appalachian region. Here we describe foliar and soil N variation among species and elevations at two spatial scales in the Central Appalachian region: (1) across the Elklick watershed in the Fernow Experimental Forest and (2) across the state of West Virginia. We found higher foliar N concentrations at both scales than those previously reported for other temperate forest regions. Canopy and soil nitrogen concentrations were also much greater in the Fernow than generally observed across West Virginia. Soil N concentrations in the Fernow were two times greater than those observed across West Virginia. Species-related differences were observed at both spatial scales, but were not always consistent. Canopy N ranges are generally consistent across elevations throughout the state of West Virginia, but should be scaled according to species-related elevation effects for studies that estimate productivity differences in response to harvest or changing species composition. The incongruence of foliar and soil N concentrations at the Fernow Experimental Forest are not explained by elevation or species composition, but are likely a consequence of greater historical N and H⁺ deposition relative to the surrounding West Virginia region.     

The Influence of Applied Nitrogen on Export and Partitioning of Current Assimilate by Field-grown Potato Plants

Field-grown potatoes were subjected to N deficiency (no appliedN) or received high levels of N (240 kg N ha^–1) at planting.The effects of these treatments were monitored at five stagesduring growth in terms of the allocation of photosynthate withinthe leaf, and the export and partitioning of carbon to differentsinks. N deficiency significantly raised the starch concentrationin all organs of the plants, particularly in leaves and stems,and as a consequence the total amount of starch in the canopyof the low N plants remained greater than that of the high Nplants until approx. 100 days after planting (DAP). The totalamounts of carbohydrates, protein and amino acids were calculatedfor each treatment and these values were used to derive a balancesheet for major reserves. Net losses of reserves occurred fromthe canopy in both treatments in the period 97–133 DAP,although these were shown to represent < 3 per cent of thetotal gain in tuber dry weight for the season. Partitioning of ¹⁴C assimilates was examined in whole plantsand also in single leaves. Reduced partitioning to the tubers,seen in high N plants throughout their growth, was shown tobe due to decreased percentage export by the leaf and accumulationof exported ¹⁴C by the stems. Partitioning to the tubers inlow N plants increased prior to senescence when 87 per centof the fixed ¹⁴C was exported within 24 h, 80 per cent of thisto the tubers. The equivalent values for the high N plants were77 and 60 per cent respectively. Increased percentage exportcoincided with decreased allocation to starch in the leaf, anda link between these processes is suggested. N also significantlyaltered the allocation of ¹⁴C within the leaf and may have influencedthe degradation of starch in the dark to a greater degree thanits synthesis in the light. The enzymes sucrose phosphate synthase (SPS), and starch synthasewere measured concurrently with partitioning. High N plantsshowed higher rates of activities of each of the enzymes althoughboth enzymes showed a similar pattern of development over theseason, irrespective of N treatment. The data are discussed in the light of conflicting reports concerningthe influence of N on translocation and partitioning. ¹⁴C assimilates, carbohydrates, nitrogen, potato (Solanum tuberosum L.), protein     

Foliar Nitrogen Dynamics and Nitrogen Resorption of a Sandy Shrub Salix gordejevii in Northern China

Resorption of nitrogen (N) from senescing leaves is an important conservation mechanism that allows plants to use the same N repeatedly. Seasonal variations in leaf nitrogen of mature green and senescing leaves and N resorption in Salix gordejevii Chang, a sandy shrub in northern China, were studied. Our objective was to compare N resorption of this Salix species that successfully occupy different habitats (shifting sandland, fixed sandland and lowland) with differences in soil N availability and moisture. Nitrogen concentrations in green and senescing leaves were higher in June and July. N resorption efficiency (percentage reduction of N between green and senescing leaves) was highest at shifting sandland, intermediate at fixed sandland, and lowest at lowland. There was a clear seasonal variation in N-resorption efficiency, with a lower value at the early growing season and a higher value during summer. N resorption efficiency was lower at the sites with higher soil N availability, suggesting that the efficiency of the resorption process is determined by the availability of the nutrient in the soil. Resorption from senescing leaves may play an important role in the nitrogen dynamics of sandy plants and reduce the nitrogen requirements for plant growth. We conclude that N resorption from senescing leaves in S. gordejevii was correlated to soil characteristics and higher N resorption on poor soils is a phenotypic adjustment by this species to maximize N-use at low availability.     

Studies on Nitrogen Metabolism in Tobacco Plants

Δ¹-Pyrroline-5-carboxylate reductase has been considerably purified from tobacco leaves. This enzyme uses NADPH or NADH for the formation of proline, although the former is better used. This enzyme was found in washed chloroplast extract as well as in cytoplasmic fluid and utilized NADPH, formed by the photosynthetic NADP reduction, for the sythesis of proline in the light.     

Influence of Spectral Range and Carbon and Nitrogen Sources on Oxygen Evolution and Emerson Enhancement in Chlamydomonas reinhardtii

Chlamydomonas reinhardtii was grown in medium with different carbon (acetate, CO₂, or both), and nitrogen (ammonium chloride, peptone, urea) sources and under light of different spectral composition. The light-dark cycles were found more suitable for mixotrophic growth than continuous irradiation. Both blue (BR) and red (RR) radiations decreased photosynthetic capacity of mixotrophic cells compared to “white light” (WL). Effect of RR was associated with photon distribution favouring photosystem 1 (PS1) suggesting increased cyclic phosphorylation. Mixotrophic growth in 10 mM NH₄Cl increased photosynthetic oxygen evolution compared to standard concentration of 5 mM NH₄Cl used for growing C. reinhardtii. Autotrophic growth stimulated the photosynthetic capacity compared to mixotrophic one. However, higher photosynthetic capacity was achieved for mixotrophic cells by growing them at high NH₄ ⁺/K⁺ ratio and high phosphate concentration. This revised version was published online in July 2006 with corrections to the Cover Date.     

对高粱抗蚜植株形态及组织结构的观察

以BTAM428（高抗）和ICS-12B（高感）及二者杂交的F2代为试材,对其形态及组织结构进行研究。结果表明：抗感品种形态及组织结构上均有差异。在抗蚜高粱品系的气孔数目多于感蚜品系;其下表皮的表皮蜡质比感蚜的致密;维管束的直径则小于感性的。     

外来入侵植物的氮代谢及其土壤氮特征

研究了4种外来入侵植物(五爪金龙、南美蟛蜞菊、金腰箭和马缨丹)和1种本地植物鸡矢藤(对照)的氮代谢及其土壤氮特征.结果表明:外来人侵植物的组织硝酸还原酶活性、根际土壤NH4-N、NO3-N含量、蛋白酶活性和脲酶活性均较高,分别为鸡矢藤的1.65～4.34、1.56～2.15、1.72～3.11、1.43～3.23和1.41～3.33倍,而植物组织硝态氮含量则较低,仅为鸡矢藤的17.5%～50.6%.相关分析表明:植物组织硝酸还原酶活性与根际土壤总氮、NH4-N、NO3-N含量呈显著正相关(P<0.05),与蛋白酶活性和脲酶活性呈极显著正相关(P<0.01).这说明,外来植物入侵使土壤氮代谢加快,氮的生物有效性增强,氮同化能力提高,并且较好地将植物体氮素代谢与土壤氮素代谢协调起来.因此,较强的氮素同化能力与加速土壤氮素的转化可能是植物成功入侵的重要机制之一.     

Studies on Nitrogen Metabolism in Tobacco Plants A

The effect of age on non-protein constituents of tobacco leaves (N. tabacum L., var. Bright Yellow) has been studied. For this purpose leaves in three different stalk positions, upper, middle and lower, which represent young, mature and over-mature leaves, respectively, were harvested in the day-time and at night.

The total amino nitrogen content both in the day-time and at night decreases from the upper leaf position downwards. As for the individual groups, the content of both upper and middle leaves increases in the day-time and that of the lower ones increases at night.

In general, the content of the individual amino acids is high in the upper leaves and low in the lower ones. Proline and γ-aminobutyric acid, as a ratio of the total amino acid content, show a marked difference with position, in other words with age of the leaves.

The levels of proline decrease very sharply from the upper leaf position downwards and that of γ-aminobutyric acid exhibits an opposite trend in both samples at night and in the day-time. These trends are very prominent in the case of the midribs.

The contents of other amino acids, regardless of position, show similar trends with time to those reported in the previous paper₁₎, and the aspartic acid content increases at night.     

Effects of Acetylene and External Oxygen Concentration on the Respiratory Quotient (RQ) of Nodulated Roots of Soyabean and White Clover

Carbon dioxide output and oxygen uptake by intact nodulatedroots of soyabean and white clover were determined over a rangeof external oxygen concentrations (10 to 60%) in the presenceand absence of 10% acetylene. The responses of both sets ofroot systems were in agreement with the known characteristicsof the variable oxygen diffusion resistance of the nodules.These measurements were used to calculate the respiratory quotient(RQ, CO2/O2) for both total root respiration and nitrogenase-linkedrespiration values for each external oxygen concentration. Inthe absence of acetylene, the RQ values of soyabean total rootrespiration showed no significant response to external oxygen,with a mean of 1.06, but differences in values for white cloverroots were significant at P=0.05, with a mean of 1.09. The sametrend was shown for RQ values of nitrogenase-linked respiration,with mean values of 1.10 and 1.12 for soyabean and clover, respectively.The addition of acetylene caused a small but significant initialreduction in RQ of total root respiration with both soyabeanand white clover, as did the subsequent reduction of externaloxygen to 10%. For white clover, increases in external oxygenconcentration to 50% and 60% also produced significant increasesin the RQ of total root respiration compared to that in air.These variations were more pronounced for RQ values of nitrogenaselinkedrespiration. Results are discussed in relation to the use ofRQ values of unity in calculations of nodular oxygen diffusionresistance and the involvement of physical and biochemical processesin the regulation of oxygen supply to bacteroids. Key words: Respiratory quotient, nodules, oxygen, diffusion resistance     

Macroscale Variation in Red Maple (Acer rubrum) Foliar Carbon,Nitrogen, and Nitrogen Resorption

Ecosystems - Many tree species grow across large climatic and geographical gradients, but there is a lack of information related to intraspecific variation in leaf traits for some of the most...     

Effects of Leghaemoglobin Components on Nitrogen Fixation and Oxygen Consumption

The effects of purified oxyleghaemoglobin components added toa suspension of bacteroids from soybean and pea root noduleprepared anaerobically were studied in terms of nitrogen fixationand oxygen consumption. Soybean leghaemoglobin components (Lba and Lb c) and pea leghaemoglobin components (Lb I and Lb IV)have different O₂-binding affinities. Lb a and Lb IV showedhigher O₂-binding affinities than Lb c and Lb I. When anaerobicallyprepared bacteroids were incubated with these leghaemoglobincomponents separately under low oxygen tension and in the presenceof a reduction system, Lb a and Lb IV were more effective forboth nitrogen fixation and oxygen consumption than Lb c andLb I. These results suggest that leghaemoglobin components participatein more effective nitrogen fixation by controlling oxygen transportto bacteroids. (Received July 7, 1981; Accepted November 2, 1981)     

Influence of Potassium Bromate on Some Malting Properties of Nigerian Sorghum (Sorghum bicolor)

The effect of various concentrations of potassium bromate (a malting additive) was studied on malting sorghum. Potassium bromate at concentrations of 50-125 mg/litre sprinkled on germinating sorghum (28°C ± 1°C) at steep out increased the filtration rate and cold and hot extract values after four days of germination. There was no significant decrease in malting loss at the low concentrations (50-125 mg/litre) of the additive. A higher dose, of 150 mg/litre, decreased the malting loss, while at a concentration of 125 mg/litre a significant increase was observed for the diastatic power after four days of germination.     

植物来源抗虫基因的研究进展

植物抗虫基因工程为农林业生产中的害虫防治提供了新的途径,随着研究的不断深入,已经获得了很多抗虫基因。本文综述了目前源于植物的抗虫基因的种类,归纳了研究较多的抗虫基因的作用机制及其在转基因植物中的应用,提出了植物抗虫基因在虫害防治中面临的问题及相应的解决策略,展望了植物抗虫基因工程研究发展的方向和前景。     

营养动脉结扎和液氮冷冻对股骨头内局部氧分压的影响

目的：观察营养动脉结扎和液氮冷冻对股骨头内局部氧分压的影响,为后期制作极度低氧股骨头缺血坏死模型打下基础。方法：9只雄性大耳白兔随机平均分为对照组、液氮冷冻组和动脉结扎＋液氮冷冻组,对照组动物不做任何处理,液氮冷冻组动物行股骨头液氮冷冻使其发生缺血坏死,动脉结扎＋液氮冷冻组动物先结扎旋股内外侧动脉,再对股骨头进行液氮冷冻。造模后立刻活体观察股骨头内氧分压变化。结果：液氮冷冻组股骨头内氧分压较对照组下降一半左右,2组比较有显著性差异（P〈0．05）;动脉结扎＋液氮冷冻组动物股骨头内氧分压进一步下降到对照组的1／8左右,与其他2组相比有显著性差异（P〈0．05）。结论：液氮冷冻和旋股内、外侧动脉结扎均可明显降低股骨头内氧分压,两者合用具有重叠效应,可共同促使股骨头内氧分压下降。