Changes in Phosphorus Fractions and Phytase Activity of Rice Seeds during Germination

The present experiment provides information on the phosphorus compounds in rice seeds and elucidates the changes they undergo during germination. In ungerminated seeds, the bulk of total-P appears in phytin (about 76 per cent). It is then dephosphorylated in course of germination with a simultaneous accumulation of large amounts of inorganic-P. Lipid-P increases very rapidly from 0 to 24 hours. The increase up to 72 hours is gradual, after which it drops at 96 hours and again rises to a maximum after 120 hours. The ester-P and RNA-P, fractions increase in concentration with time of germination (except 120 hours). Protein-P begins to fall after 48 hours, while DNA-P remains more or less constant throughout the experiment. The two pH optima recorded for phytase activity at 4.0 and 9.0, suggests that there exist two phytases, one acidic and the other alkaline. Both behave similarly during germination with a continuous increase throughout the course of the experiment. The enzyme with an optimal pH at 4 hydrolyses phytin more actively than the other with the pH optimum at 9.0. Phytase shows maximum activity at a stage when most of the phytin has disappeared; the metabolic significance is uncertain.     

Changes in Enzyme Levels During Germination of Seeds of Triticum durum

The changes in level of activity during the germination of wheat seedling (Triticum durum) in the dark have been investigated with 4 enzymes of glycolysis, 2 enzymes of the pentose phosphate shunt, 2 of the tricarboxylic acid cycle, 2 of amino acid metabolism and acid phosphatase. For some enzymes, which function in photosynthesis (fructose diphosphate aldolase, glyceraldehyde phosphate dehydrogenase NADP dependent), the level of activity was influenced by the presence of light.     

31P NMR studies of spinach leaves and their chloroplasts

An experimental arrangement is described which enables high quality 31P NMR spectra of compressed spinach leaf pieces to be continuously recorded in which all the resonances observed (cytoplasmic and vacuolar Pi, glycerate-3-P, nucleotides) were sharp and well resolved. 31P NMR spectra obtained from intact chloroplasts showed a distinct peak of stromal Pi. An upfield shift of the stromal Pi resonance was associated with a decrease in the external Pi and vice versa. Nucleotides were largely invisible to NMR in intact chloroplasts, whereas the same nucleotides reappeared in a typical 31P NMR spectrum of an acid extract of intact chloroplasts. Perfusion of compressed spinach leaf pieces with a medium containing Pi triggered a dramatic increase in the vacuolar Pi over 12 h. Addition of choline to the Pi-free perfusate of compressed leaf pieces resulted in a steady accumulation of phosphorylcholine in the cytoplasmic compartment at the expense of cytoplasmic Pi. When a threshold of cytoplasmic Pi concentration was attained, Pi was drawn from the vacuole to sustain choline phosphorylation. In spinach leaves, the vacuole represents a potentially large Pi reservoir, and cycling of Pi through vacuolar influx (energy dependent) and efflux pathways is an efficient system that may provide for control over the cytosolic-free Pi and phosphorylated intermediate concentrations. 31P NMR spectra of neutralized perchloric acid extracts of spinach leaves showed well defined multipeak resonances (quadruplet) of intracellular phytate. The question of cytosolic Pi concentration in green cells is discussed.     

水稻种子萌发期间谷氨酰胺合成酶和NADH-谷氨酸合酶的变化

测定了水稻种子不同萌发时期胚乳、胚芽鞘和幼根的谷氨酰胺合成酶（GS）和依赖于NADH的谷氨酸合酶（NADH－GOGAT）活性变化。胚乳和胚芽鞘的GS活性在萌发过程中升高,幼根的GS活性则有所降低。NADH－GOGAT的活性变化趋势与GS相同。Native-PAGE活性染色表明,在萌发阶段的水稻种子胚乳和幼根里,始终只观察到一种GS活性带。但是,在水稻种子萌发3d后,在胚芽鞘中除继续检测到GS1的活性外,还可以观察到GS2的活性。蛋白质印迹显示,水稻种子胚乳中的GS（GSe)和GS1和GSra一样是一种胞质型GS。实验结果提示,这些不同组织中的GS与NADH－GOGAT构成的循环途径也许是水稻种子萌发时氨同化的主要途径。     

胡杨种子萌发过程中几种相关酶的活性变化

在室温条件下,胡杨种子保留冠毛贮藏可适当延长其生命力;室温贮藏带冠毛的胡杨种子,前20 d萌发率降低幅度不大.随着种子贮藏时间的延长,过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均先上升后下降,峰值出现时间与种子室温贮藏20 d相对应;脱氢酶活性先上升后下降再回升,峰值出现时间也与种子室温贮藏20 d相对应;酸性磷酸酯酶(ACP)活性与种子萌发率同步下降.室温贮藏40 d的带冠毛胡杨种子仍有22.3%的萌发率.     

Potassium Release and Uptake in Germinating Legume Seeds in Relation to Seed Condition and Germination Environment

The levels of K^$ and total electrolyte leakage into leachingsolution from imbibed seeds of Pisum sativum L. and Phaseolusvulgaris L. have been followed to determine the relationshipof K^$ loss to the level of total electrolyte loss, and its relationto the physiological condition of the seed. The extent and rate of loss of both K^$ and total electrolytesvaried with both seed condition and the conditions imposed bythe experiment. K^$ accounted for between 25 and 50% of the totalelectrolyte leakage. The relationship was at all times significantlycorrelated, but changed with time and with experimental conditions. The effect of immersion, which increased electrolyte leakagedue to soaking injury, masked differences in seeds of varyingfield performance. Imbibition at either 5 °C or 40 °C before leaching wasshown to increase both K^$ and total electrolyte loss in comparisonto seeds imbibed at 25 °C. These results suggest that the ‘conductivity test’,which is used as a measure of seed deterioration, may need tobe re-examined in terms of experimental procedure and interpretation.     

小麦种子成熟和萌发过程中的假萌发素活性

用SDS-PAGE方法研究了假萌发素(ψG)在小麦种子成熟和萌发过程中活性的变化.结果表明:在种子成熟过程中只有ψG表达,扬花后10 d,在颖壳、内外桴、种皮和果皮中皆可检测到ψG的草酸氧化酶活性,随着发育进程的推进,ψG的活性增大.在种子萌发过程中,在小麦品种中育5号的维管束过渡区中除了萌发素G和G'外,还可检测到ψG的草酸氧化酶活性.由于ψG在种子成熟过程中主要存在于颖壳、内外桴、果皮及种皮这些保护组织中,且开始大量表达的时间正是生长接近停止时,于是推测ψG很可能通过降解草酸产生H2O2而推动这些组织细胞壁的木质化.     

On the Germination and Changes in Chemical Composition During Seedling Emergence and Development of Cotton Seeds

Seeds from two cotton varieties attained similar maximum germinationpercentages at 30°C. Failure of germination occurred at15 and 45°C. At lower and higher temperatures than 30°Cmaximum germination percentages were lower and the periods beforegermination was intiated longer. Fumigation of seeds with methylbromide decreased their maximum emergence percentages in thefield, but dressing seeds with mercuric compounds had no effecton emergence. During the first 20 days of seed development theaccumulation of total dry-matter and oil was rapid and thenit continued at a steady and slower rate till day 52. A linearrelationship existed between the oil and residual dry-mattercontent of developing seeds. The disappearance of oil from thecotyledons of germinating seeds was gradual over the periodof 5 days of germination while that of starch was very rapidduring the first day, thereafter very little starch was mobilizedfrom the cotyledons to the embryo.     

Application of 13C and 31P NMR to the study of hepatic metabolism

Alternate scan 13C and 31P NMR has been used to follow the metabolism of 13C-labeled substrates, in the presence and absence of insulin, in isolated perfused liver from fasted rats. Because both 31P and 13C NMR spectra are recorded almost simultaneously with this method, both phosphate metabolites and 13C-labeled metabolites are measured, noninvasively and repetitively, to give an immediate, broad survey of the hepatic response to a variety of stimuli. During the metabolism of [2-13C]pyruvate, [1,2-13C]ethanol, and NH4+, 13C-labeled glycogen increases synchronously with, and at the same rate as, the synthesis of 13C-labeled glucose; thus, glycogenesis was essentially a gluconeogenic process under our conditions and was unaltered by the presence of insulin. From the position of the 13C-labeled citrate peak observed in liver, the measurement of KD for the citrate-magnesium complex under our conditions, and the expression relating these quantities to the concentration of free Mg2+, the intracellular level of free Mg2+ is estimated to be 0.46 +/- 0.05 mM. Later administration of glucagon led to a rapid decrease in glycogen and citrate and a 44% increase in glycero-3-phosphocholine (GPC); increase in GPC is consistent with stimulation of liver phospholipase activity by glucagon. Simultaneous administration of two different 13C-labeled substrates, or one doubly labeled substrate, introduced multiplet structure arising from spin-spin interaction between labeled adjacent carbons into the peaks of several key metabolites. The 13C NMR intensity distributions within the several multiplets are used, within the context of a first-order model for fluxes into the Krebs cycle, to estimate relative fluxes under the conditions of the experiment.     

31P NMR Measurements of Cytoplasmic pH Changes in Maize Root Tips

³¹P nuclear magnetic resonance (NMR) spectroscopy has been usedto measure the changes caused by sodium azide and anaerobiosisin the cytoplasmic pH of maize (Zea mays L.) root tips. Measurementsof H⁺ influx, lactate accumulation and ATP hydrolysis, togetherwith estimates of the cytoplasmic volume and the cytoplasmicbuffering capacity, were used to calculate the expected pH changesunder the same conditions. In the case of azide inhibition,where there was a large H⁺ influx, there was good agreementbetween the calculated and measured pH changes. In contrastduring anoxia, where the accumulation of lactate was the mostimportant source of protons, the predicted cytoplasmic pH changewas greater than the observed change. It was concluded thatin the absence of a compensating H⁺ efflux, the excess H⁺ productionwas offset by the production of H⁺-consuming metabolites suchas -aminobutyrate. Key words: Cytoplasmic pH, ³¹P NMR, Membrane H⁺ fluxes.     

Water Status Changes During Development in Relation to the Germination and Desiccation Tolerance of Aesculus hippocastanum L. Seeds

Seed growth characteristics of Aesculus hippocastanum were examinedin detail during development from about 70 to 140 d after anthesis(DAA), mainly in 1988 and 1989. Mean fresh and dry weights increasedfor both the axis and the whole seed up to the time of peakseed fall at 135 DAA with no cessation before fruit abscission.Water per seed increased up to 100 DAA, after which no furtherincrease occurred; moisture content declined for the embryonicaxis and whole seed respectively from above 75 and 65% at 95DAA to 65 and 50% at 130 DAA. At fruit shedding in 1990 waterpotential values of -1·2, -2·6 and -1·1MPa were observed for the testa, cotyledon and axis tissuesrespectively; relevant sorption isotherms are presented. Decreases in seed moisture content during development were accompaniedby increases in desiccation tolerance and in germinability,both reaching their maximum at the time of peak seed fall. Atmaturity, only about 10% viability was retained on drying seedto 20% moisture content; it is confirmed that the seeds are'recalcitrant'. The exact relationship between moisture contentand germination during development was dependent on the deptof dormancy, as judged by the period of chilling required; eachduration of chilling at 2°C within the range 3-12 weeksyields a curve of sigmoid shape. No germination occurred at26°C without chilling, but nearly full germination can beobserved for samples collected at 6 weeks before maximum seedfall with 12 weeks chilling. The rate of moisture loss duringdesiccation at 15°C and 15% rh becomes reduced during development.The ontogeny of these 'recalcitrant' seeds is compared withthat of 'orthodox' seeded species and the implication of sigmoid-shapedcurves for the relationship between seed moisture content andgermination are considered.Copyright 1993, 1999 Academic Press Aesculus hippocastanum L., horse chestnut, seed development, water status, germination, desiccation intolerance, desiccation rate     

Changes in Endogenous Growth Kegulators in Loblolly Pine Seeds During the Process of Stratification and Germination

The seeds of loblolly pine (Pirns taeda L.) were cold-stratified for 0, 14, 28, 42, and 56 days. Endogenous growth regulators were extracted from these seeds, and also from the germinating and the 28-day warm stratified seeds. Partially purified extracts were separated on chromatographic paper. The chromatograms were cut into 10 equal segments, and these were tested for biological activity using three different btoassays. The results indicated that the unstratified seeds and those stratified up to a period of 28 days contained very little or no growth promoter (GA-like substances), and a relatively high concentration of an inhibitor (presumably abscisic acid), Following 42-day stratification, the promoter concentration gradually increased while the inhibitor level fell almost to zero. A high level of promoter but no inhibitor was detected in germinating seeds. No auxin-like activity was noted in the unstratified seeds. This activity slowly increased up to a period of 28 days and remained at this level for the subsequent stratification periods. However, the activity greatly increased in the germinating seeds. Very little changes in the levels of growth regulators were noted in warm-stratified seeds as compared to the unstrati-fied controls.     

黄瓜种子萌发过程中Ca~(2 )分布的变化

采用细胞化学方法 ,研究了黄瓜种子中贮藏Ca2 的分布特点及其在萌发过程中的变化动态。干种子的子叶细胞中贮藏有大量的蛋白体、油脂体 ,Ca2 沉淀颗粒大量分布于胞质、胞间隙以及细胞质膜上。大多数蛋白体中有 1至数个圆球形或椭圆体形含Ca2 的球状晶体。相比之下 ,胚芽和胚根细胞中Ca2 较少。种子萌发早期 ,子叶中的贮藏钙及晶体溶解释放出的Ca2 部分转运到生长发育中的胚芽和胚根中。随着萌发的继续 ,胚根和胚芽细胞中的Ca2 不会持续增多 ,反而下降     

Sterol Changes during Germination of Nicotiana tabacum Seeds

The identity, composition, and concentration of the total, free, esterified, and glycosidic sterol fractions were determined during germination of tobacco seeds. The total, free, and esterified sterols increased, with stigmasterol and campesterol accounting for most of the increase. Steryl glycosides decreased during germination, and stigmasteryl and sitosteryl glycosides showed the largest decrease. During germination, sitosterol was the major sterol in all fractions but stigmasterol and campesterol showed the greatest changes. The fatty acid composition of the steryl esters and acylated steryl glycosides most closely resembled the di- and triglycerides.     

预浸和发芽过程中番茄种子细胞核的倍性变化

用细胞流检仪（ｆｌｏｗｃｙｔｏｍｅｔｅｒ）检测番茄种子细胞核倍性水平时发现：当年成熟的番茄种子胚细胞核ＤＮＡ绝大多数为２Ｃ水平,胚乳细胞核则为３Ｃ水平,说明成熟番茄种子细胞一般休止停留在Ｇ１期。同时我们也发现极少量的胚和胚乳细胞核分别为４Ｃ和６Ｃ水平,说明这些细胞已经进行了ＤＮＡ内复制。供试番茄种子浸种后１２ｈ左右完成吸水过程,２ｄ后胚根可突破种皮发芽。随着种子吸水过程的完成,胚根尖部分细胞开始进入ＤＮＡ复制期（Ｓ期）,而且此类细胞的数量增加迅速,一直到种子发芽。番茄胚根尖细胞进入４Ｃ的数量的多少与种子萌发时期有明显相关,４Ｃ／２Ｃ比率越大说明越接近发芽。渗控处理可以增加番茄种子胚根细胞４Ｃ／２Ｃ比率,因而明显提高种子的发芽速率。结果还表明;渗控处理的番茄种子再度干燥后４Ｃ／２Ｃ比率不变,这说明干燥可以固定细胞周期。     

Metabolism of C-Maltose in Avena fatua Seeds During Germination

Non-dormant and dormant seeds of Avena fatua metabolize ¹⁴C-maltose in different ways: in non-dormant seeds, ¹⁴C-maltose administered to the endosperm is readily converted to sucrose in the scutellum and translocated to the embryo; in dormant seeds, little sucrose is synthesized from ¹⁴C-maltose, and maltose and glucose tend to accumulate in the endosperm. It is suggested that biosynthesis of sucrose is essential for effective transport of the endosperm reserve to the embryonic axis in germinating seeds.     

Metabolic control principles and 31P NMR

31P NMR is a unique research tool for studying metabolism during exercise. This communication gives the underlying theory and experimental data for obtaining the transfer characteristic relating work and NMR-determined metabolic paramenters, particularly the ratio of free inorganic phosphate to phosphocreatine (Pi/PCr). Furthermore, illustrations of the types of transfer characteristics observed in different individuals and different training regimens can be obtained, including both hyperbolic (Michaelis-Menten) and sigmoid transfer characteristics. With a hyperbolic transfer characteristic, oxygen delivery appears to be adequate to support the exercise regimen over the range studied (up to 50% of Vmax), whereas with a sigmoid transfer characteristic, there appears an imprint of limited oxygen delivery on the kinetics from rest up to 50% of Vmax. These two types of transfer functions are appropriate to explain the transition to anaerobic metabolism (anaerobic threshold), with a hyperbolic transfer characteristic representing a graded transition; and a sigmoid transfer characteristic representing an abrupt transition. A sigmoid transfer characteristic may involve greater lactate accumulation at submaximal exercise levels, and in both types of transfer characteristic sufficient aerobic lactate is formed to meet the metabolic demand for pyruvate. The results suggest an important role for 31 P NMR in studies of energy-related metabolites as a means of determining exercise performance in terms of regulation of tissue oxidative metabolism and oxygen delivery to tissue.     

A Role for Trigonelline During Imbibition and Germination of Coffee Seeds

Abstract: Trigonelline was investigated as an NAD reserve during germination of coffee ( Coffea arabica L.) seeds. Seeds were germinated on filter paper moistened with water or in agar and the endogenous content of trigonelline, nicotinic acid and NAD investigated in the endosperm, embryo and germination medium. Seeds were also fed with [ carboxyl -¹⁴C]trigonelline and the distribution of the radioactivity in these compounds was investigated. In addition, trigonelline demethylase was detected in coffee for the first time, showing a K_m of 1.13 mM. The activity increased with germination. These data clearly show that in seeds there is a significant conversion of trigonelline to NAD, although a concomitant biosynthesis of the alkaloid is also observed. It is concluded that trigonelline is indeed a reserve molecule for NAD biosynthesis but this function may be limited to the very early stages of germination or restricted to specific tissues, such as the embryo.