施氮量和花后土壤含水量对强筋小麦籽粒淀粉合成及品质的影响

以强筋小麦品种'济麦20'为材料,在防雨池栽培条件下研究了施氮量和花后土壤含水量对强筋小麦籽粒淀粉合成及其品质的影响,以明确强筋小麦获得高产优质的花后适宜土壤含水量及施氮量.结果表明:在同一施氮量下,适宜的花后土壤含水量(60%～70%)籽粒游离态淀粉合成酶(SSS)和束缚态淀粉合成酶(GBSS)活性在籽粒发育过程中一直最高,有利于直链淀粉、支链淀粉的积累和支链淀粉/直链淀粉比的提高,提高峰值粘度、低谷粘度、最终粘度和衰减值;花后土壤含水量过高(80%～90%)或过低(40%～50%)均导致籽粒SSS和GBSS活性降低,从而使直链淀粉、支链淀粉的积累量降低,减小支链淀粉/直链淀粉比,使峰值粘度、低谷粘度、最终粘度降低.(2)在同一土壤含水量下,增施氮肥不利于灌浆前期SSS和GBSS活性和直链淀粉、支链淀粉积累量的提高,并且随着土壤含水量增加增施氮肥该趋势加重;适量增施氮肥能提高支链淀粉/直链淀粉比和峰值粘度、低谷粘度、最终粘度,过多或过少施氮则降低支/直比和峰值粘度、低谷粘度、最终粘度.研究认为,在本试验条件下,适量增施氮肥(纯氮225 kg/hm2)或适宜的花后土壤含水量(60%～70%)可促进强筋小麦籽粒淀粉的合成,有效改善其淀粉品质.     

Limitations to the Accumulation of Starch in the Developing Wheat Grain

The postulate that photosynthetic capacity limits the rate ofaccumulation of starch and dry matter in the developing wheatgrain has been tested by defoliating plants growing in the field,and by culturing detached ears on solutions of sucrose. In mostcases complete defoliation did not reduce the amounts of starchor dry matter produced 4 to 10 days later, or affect the amountsof sucrose in the grain. Increasing the potential supply ofsucrose above normal levels by culturing did not lead to increasesin either the deposition of starch or the quantity of sucrosein the grain. Removing leaves caused small depressions in thegain in fresh weight of the grain, and where defoliation didreduce the accumulation of starch there was no comparable effecton the amount of sucrose in the grain. Accordingly, it is concludedthat the postulate stated above is invalid. The case in support of the concept that it is the mechanismregulating the passage of sucrose into the grain which imposesa limitation on the accumulation of starch is presented.     

Effect of Seawater on Photosynthesis and Dry Matter Accumulation in Developing Rice Grains

To understand the physiology of rice under seawater salinity, potted rice plants were irrigated with different concentrations of Japan seawater (electrical conductivity 0.9, 5.7, 11.5, or 21.5 mS cm^-1) from 10 d after transplanting (DAT) to 35 DAT, and from 75 to 100 DAT. Seawater salinity decreased the net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, transpiration rate, leaf water and osmotic potentials, and relative water content, and increased leaf temperature. The contents of chlorophylls, carotenoids, and total sugars significantly decreased in the leaves but content of non-reducing sugars decreased only slightly. With increasing salinity the Na⁺ concentration increased, while Ca²⁺, Mn²⁺, and K⁺ concentrations decreased. Salinity decreased the contents of sugars and proteins, dry mass, and rate of dry mater accumulation in developing grains.     

土壤干旱对冬小麦旗叶乙烯释放、多胺积累和细胞质膜的影响

土壤水分亏缺时,小麦旗叶的乙烯释放量增加,三种多胺（精胺、亚精胺、腐胺）的含量在小麦灌浆初期显著增加,而在小麦灌浆末期除腐胺外均降低。外施５００ｍｇ／Ｌ的亚精胺溶液能减弱小麦叶片的膜脂质过氧化程度。土壤水分亏缺时膜透性增大,膜脂过氧化物丙二醇含量升高,导致不饱和脂肪酸指数下降,亚麻酸含量下降。严重土壤水分胁迫下,过氧化物酶的活性升高。这些结果表明土壤干旱损害小麦旗叶质膜,促其衰老。研究表明,随着受旱程度的提高,小麦旗叶遭受的损伤逐渐加重,植株对土壤干旱的适应性亦逐渐降低。     

Effect of Light on Cell Division in Developing Callus Cultures

Explants removed from the Jerusalem artichoke tuber and exposedto white light in the presence of 2, 4-D, when cultured in liquidmedia, exhibit much smaller dividing populations than similartissue not exposed to light. White light, which is effectiveonly in the presence of 2, 4-D and during the period beforethe onset of DNA replication, is required only in small amountsto promote a maximum effect, although inhibition of cell divisionwas never complete Light does not interfere with the timingof the cell cycle but exerts an influence on the size of thedividing population. The results presented are consistent witha hypothesis which postulates that a substance or substancesessential for cell division is reduced in amount by exposureto light. The extent of the first synchronous division is probablytherefore determined by the supply of this substance.     

Adenylate and Nicotinamide Nucleotides in Developing Wheat Grains

Contents of ATP and ADP per grain increased during grain developmentup to 21–35 d after anthesis (DAA). A sharp increase inAMP level was observed at 42 DAA. Of the four nicotinamide nucleotides,NAD was most abundant. Energy charge values were more than 0.7during active grain filling stages and less than 0.6 when rateof starch deposition was low. Triticum aestivum L. (Wheat), adenylates, nicotinamide nucleotides, energy charge, grain, starch     

Photosynthesis in the Pericarp of Developing Wheat Grains

Oxygen exchange in grains of wheat was measured in both lightand dark over the period of grain development. Between 10 dand 30 d after anthesis, the rate of photosynthesis exceededthe rate of respiration. Peak photosynthetic activity was observedat 20 d after anthesis, coinciding with maximum chlorophyllcontent in the pericarp green layer. Removal of the pericarptransparent layer increased rates of oxygen exchange in boththe light and the dark. Attempts to inhibit photosynthesis withDCMU were only successful with the pericarp transparent layerremoved. Key words: Wheat, pericarp, photosynthesis     

花后土壤水分状况对小麦籽粒淀粉和蛋白质积累关键调控酶活性的影响

在温室盆栽条件下,以2个不同蛋白质含量的冬小麦(Triticum aestivum L．)品种皖麦38和扬麦9为材料,研究了花后第4天开始的土壤干旱(SRWC=45％～50％)和渍水对籽粒蛋白质和淀粉积累关键调控酶活性的影响。小麦叶片和籽粒的测定结果均表明,小麦源库器官中籽粒蛋白质和淀粉积累的关键调控酶活性变化趋势在2个品种间基本一致。与对照(SRWC=75％～80％)相比,干旱和渍水均明显降低了花后旗叶中蔗糖含量和磷酸蔗糖合成酶(SPS)活性,而氨基酸含量和谷氨酰胺合成酶(GS)活性略有下降。干旱和渍水均降低了籽粒库蔗糖合成酶(SS)和结合态淀粉合成酶(GBSS)活性,可溶性淀粉合成酶(SSS)活性降低尤甚。其中干旱处理下SS的下降比渍水更为明显。与对照相比,渍水明显降低了籽粒谷丙转氨酶(GPT)和GS活性,而干旱的影响较小。相关性分析结果表明籽粒淀粉产量和含量与SPS,SSS和GBSS活性的关系比与SS活性的关系更为密切,籽粒蛋白质产量和含量与叶中GS和籽粒中GPT活性的关系比与籽粒中GS关系活性更为密切。这些结果表明小麦源库器官中调控籽粒蛋白质和淀粉积累的关键酶活性变化是花后不同水分状况影响籽粒淀粉和蛋白质特性的重要因素。     

谷氨酰胺供应水平对离体培养小麦穗籽粒淀粉和蛋白质及其组分含量的影响

选用籽粒蛋白质含量不同的小麦(Triticum aestivum)品种,运用离体穗培养技术,研究了谷氨酰胺供应水平对小麦穗籽粒重、淀粉和蛋白质及其组分积累的影响.实验结果表明,随着培养基中谷氨酰胺供应水平的提高,粒重、籽粒淀粉和蛋白质积累量均呈单峰曲线,在6 g·L-1谷氨酰胺水平时达到最大值;籽粒氨基酸和蛋白质含量随谷氨酰胺浓度的提高呈上升趋势,而淀粉含量呈下降趋势.籽粒清蛋白和球蛋白含量的变化与总蛋白质含量变化趋势一致,而醇溶蛋白和麦谷蛋白含量在2～6 g·L-1谷氨酰胺浓度范围内呈上升趋势,此后则无明显变化.     

谷氨酰胺供应水平对离体培养小麦穗籽粒淀粉和蛋白质及其组分含量的影响

选用籽粒蛋白质含量不同的小麦(Triticam aestivum)品种, 运用离体穗培养技术, 研究了谷氨酰胺供应水平对小麦穗籽粒重、淀粉和蛋白质及其组分积累的影响。实验结果表明, 随着培养基中谷氨酰胺供应水平的提高, 粒重、籽粒淀粉和蛋白质积累量均呈单峰曲线, 在6 g.L-1谷氨酰胺水平时达到最大值; 籽粒氨基酸和蛋白质含量随谷氨酰胺浓度的提高呈上升趋势, 而淀粉含量呈下降趋势。籽粒清蛋白和球蛋白含量的变化与总蛋白质含量变化趋势一致, 而醇溶蛋白和麦谷蛋白含量在2~6 g.L-1谷氨酰胺浓度范围内呈上升趋势, 此后则无明显变化。     

Accumulation and Conversion of Sugars by Developing Wheat Grains: V. THE ENDOSPERM APOPLAST AND APOPLASTIC TRANSPORT

The volume and composition of the endosperm apoplast of thedeveloping wheat grain, comprising endosperm cavity and intercellularfree-space, was examined in relation to kernel growth rate andsize. Samples of the cavity sap were collected by centrifugationof kernels during the linear phase of grain growth. The cavitysap contained 10–50 mM sucrose, a small amount of hexosesbut a high concentration of oligosaccharides (up to 9 timesthat of sucrose). In comparing cvs Yandilla King and Cleveland,high growth rate was associated with high cavity sap sucroseconcentration but with low K⁺ concentration. K⁺ concentrationin the endosperm cells (124 mM) was about 5 times higher thanin the cavity sap (10–40 mM). Cavity sap pH was 6.3–6.6.The uptake of sucrose by endosperm cells was partly inhibitedby PCMBS, an inhibitor of membrane-bound carriers. Several necessaryconditions for proton cotransport during sucrose uptake by endospermcells were met. The volume of the intercellular free-space, estimated by membranepermeating (¹⁴C-mannitol, ¹⁴C-sucrose) or non-permeating (³H-PEG900)markers averaged 2.2 µl or 5–7% of the water ingrains of cvs Yandilla King, Cleveland and SUN 9E. The cavityvolume was highly variable but tended to be larger in largergrains. Pulse labelling of ¹⁴CO₂ to flag leaves showed that ¹⁴C-sucrosewas the principal ¹⁴C-assimilate in the cavity sap and was convertedto insoluble compounds in the endosperm while the cavity sapoligosaccharides acquired negligible label in 6 h. Key words: Wheat, Endosperm apoplast, Sugars     

Asparagine Enhances Starch Accumulation in Developing and Germinating Lupin Seeds

Regulation of starch accumulation in yellow (Lupinus luteus L.), white (L. albus L.), and Andean lupin (L. mutabilis Sweet) developing and germinating seeds was investigated. Research was conducted on cotyledons isolated from developing seeds as well as on organs of germinating seeds, that is, isolated embryo axes, excised cotyledons, and seedling axes and cotyledons. All organs were cultured in vitro for 96 h in different carbon (60 mM sucrose) and nitrogen (35 mM asparagine or 35 mM nitrate) conditions. Ultrastructure observation showed one common pattern of changes in the number and size of starch granules caused by sucrose, asparagine, and nitrate in both developing and germinating seeds. Sucrose increased the number and size of starch granules. Asparagine additionally increased starch accumulation (irrespective of sucrose nutrition) but nitrate had no effect on starch accumulation. Asparagine treatment resulted in a significant decrease in soluble sugar level in all organs of germinating lupin seeds of the three species investigated. The above-mentioned changes were most clearly visible in white lupin organs. In white lupin, starch granules were visible even in cells of sucrose-starved isolated embryo axes where advanced autophagy occurs. The importance of asparagine-increased starch content in the creation of a strong source–sink gradient in developing and germinating lupin seeds is discussed.     

淀粉含量不同的玉米自交系籽粒淀粉积累及其关键酶活性

以2个高淀粉和2个低淀粉玉米自交系为材料,分析了玉米籽粒淀粉的动态积累规律,同时对高低淀粉玉米籽粒灌浆过程中淀粉生物合成关键酶活性的动态变化及其与淀粉积累动态的相关性进行讨论分析。研究结果表明:灌浆过程中4个自交系淀粉含量变化趋势均呈sigmoid型曲线。灌浆过程中ADPG-PPase(腺苷二磷酸葡萄糖焦磷酸化酶)、SSS(可溶性淀粉合成酶)、GBSS(颗粒结合淀粉合成酶)活性均呈单峰曲线变化,峰值都出现在20～30DAP(授粉后天数)。2个高淀粉自交系的Q酶(淀粉分支酶)活性也呈单峰曲线变化,峰值也出现在20DAP,而2个低淀粉自交系的Q酶活性则呈双峰曲线变化,2个峰值分别出现在15～20DAP和30～35DAP。4个自交系籽粒淀粉的积累速率与各自交系ADPG-PPase、SSS和GBSS的活性变化呈极显著正相关。各自交系关键酶活性之间,ADPG-PPase、SSS和GBSS三者间活性变化呈极显著正相关,这3种酶活性变化与Q酶活性变化也呈不同程度的正相关。     

Accumulation and Conversion of Sugars by Developing Wheat Grains : VII. Effect of Changes in Sieve Tube and Endosperm Cavity Sap Concentrations on the Grain Filling Rate

The extent to which wheat grain growth is dependent on transport pool solute concentration was investigated by the use of illumination and partial grain removal to vary solute concentrations in the sieve tube and endosperm cavity saps of the wheat ear (Triticum aestivum L.). Short-term grain growth rates were estimated indirectly from the product of phloem area, sieve tube sap concentration, and ³²P translocation velocity. On a per grain basis, calculated rates of mass transport through the peduncle were fairly constant over a substantial range in other transport parameters (i.e. velocity, concentration, phloem area, and grain number). The rates were about 40% higher than expected; this probably reflects some unavoidable bias on faster-moving tracer in the velocity estimates. Sieve tube sap concentration increased in all experiments (by 20 to 64%), with a concomitant decline in velocity (to as low as 8% of the initial value). Endosperm cavity sucrose concentration also increased in all experiments, but cavity sap osmolality and total amino acid concentration remained nearly constant. No evidence was found for an increase in the rate of mass transport per grain through the peduncle in response to the treatments. This apparent unresponsiveness of grain growth rate to increased cavity sap sucrose concentration conflicts with earlier in vitro endosperm studies showing that sucrose uptake increased with increasing external sucrose concentration up to 150 to 200 millimolar.     

休闲期深翻覆盖对旱地小麦土壤水分及籽粒蛋白质积累的影响

采用大田试验研究旱地小麦休闲期不同时间深翻不同材料覆盖对土壤水分、籽粒蛋白质形成的影响及其生理机制。结果表明:前茬小麦收获后45 d深翻覆盖较15 d可提高播前120～300 cm土壤蓄水量,而降低开花期0～300 cm(除80 cm土层外)土壤蓄水量;显著提高籽粒蛋白质及其组分含量、蛋白质产量、谷/醇比,提高旗叶GS活性及花后10～15 d、25 d旗叶GOGAT活性,均以渗水地膜覆盖效果较好。结果还表明,播前80～200 cm、开花期260～280 cm土壤蓄水量与旗叶GS、旗叶GOGAT活性显著相关,且与旗叶GS活性关系更密切。籽粒蛋白质组分含量、谷/醇比、蛋白质产量与旗叶GS、旗叶GOGAT活性显著相关,且与旗叶GS活性相关性较密切,尤其是谷/醇比。播前和开花期120～300 cm土壤蓄水量与籽粒蛋白质及其组分含量显著相关,播前60～220 cm、开花期240～300 cm土壤蓄水量与谷/醇比显著相关。总之,休闲期等雨后深翻覆盖有利于蓄积休闲期降雨,有利于提高播前深层土壤水分,最终提高籽粒蛋白质品质及质量,且采用渗水地膜覆盖效果最好。     

Rates of Cell Division in Developing Barley Endosperms

Counts of nuclei in enzyme digested endosperms of barley cultivarBomi show that the final number of cells, 170000, is reachedbetween 18 and 21d after anthesis. Based on the number of cellprofiles in transverse mid-grain sections, starchy endospermcells divide up to day 14. Thereafter, cell proliferation isrestricted to the aleurone layer. Hordeum vulgare, starchy endosperm, aleurone, mitotic activity, light microscopy     

干旱与氧化胁迫对小麦根氧化还原状态和叶片ABA积累的影响

通过分析一氧化氮(nitric oxide,NO)、活性氧(reactive oxygen species,ROS)和干旱胁迫对小麦根氧化还原状态和叶片脱落酸(abscisic acid,ABA)积累的影响,探讨了干旱胁迫下NO和H2O2调节ABA合成的可能机制。结果表明:干旱胁迫处理初期小麦根还原型谷胱甘肽含量降低、抗氧化酶活性发生振荡变化,细胞氧化还原状态向氧化型转变。NO和H2O2能模拟干旱胁迫的作用使细胞状态向氧化型转变,还可以使小麦叶片ABA积累量上升。干旱胁迫下NO和H2O2对ABA合成的调节作用可能是通过调节细胞氧化还原状态进行。     

Effect of Water Stress on Cell Division and Cdc2-Like Cell Cycle Kinase Activity in Wheat Leaves

In wheat (Triticum aestivum) seedlings subjected to a mild water stress (water potential of −0.3 MPa), the leaf-elongation rate was reduced by one-half and the mitotic activity of mesophyll cells was reduced to 42% of well-watered controls within 1 d. There was also a reduction in the length of the zone of mesophyll cell division to within 4 mm from the base compared with 8 mm in control leaves. However, the period of division continued longer in the stressed than in the control leaves, and the final cell number in the stressed leaves reached 85% of controls. Cyclin-dependent protein kinase enzymes that are required in vivo for DNA replication and mitosis were recovered from the meristematic zone of leaves by affinity for p13^suc1. Water stress caused a reduction in H1 histone kinase activity to one-half of the control level, although amounts of the enzyme were unaffected. Reduced activity was correlated with an increased proportion of the 34-kD Cdc2-like kinase (an enzyme sharing with the Cdc2 protein of other eukaryotes the same size, antigenic sites, affinity for p13^suc1, and H1 histone kinase catalytic activity) deactivated by tyrosine phosphorylation. Deactivation to 50% occurred within 3 h of stress imposition in cells at the base of the meristematic zone and was therefore too fast to be explained by a reduction in the rate at which cells reached mitosis because of slowing of growth; rather, stress must have acted more immediately on the enzyme. The operation of controls slowing the exit from the G1 and G2 phases is discussed. We suggest that a water-stress signal acts on Cdc2 kinase by increasing phosphorylation of tyrosine, causing a shift to the inhibited form and slowing cell production.     

Adenosine Diphosphate-Glucose Pyrophosphorylase Control of Starch Accumulation in Rust-infected Wheat Leaves

The variation in starch content in healthy and Puccinia striiformsi-infected wheat leaves was measured from 5 to 15 days after inoculation. The starch content of diseased leaves relative to healthy leaves decreased from 5 to 9 days, increased from 9 to 12 days to twice that of healthy leaves, and decreased from 12 to 15 days after inoculation. Electron micrographs of plant tissues indicated that the starch accumulated in the chloroplasts of host cells adjacent to fungal hyphae. Variations in sugar phosphates, ATP, and inorganic phosphate were measured during the infection process. ADP-glucose pyrophosphorylase was extracted and partially purified from healthy and diseased leaves. When proportionate concentrations of sugar phosphates and inorganic phosphate found in healthy and diseased leaves during the infection process were placed in the assay mixture, ADP-glucose pyrophosphorylase activity was similar to the pattern of starch accumulation and was almost the inverse of the variation observed in inorganic phosphate in diseased leaves during the infection process. A mechanism to explain the accumulation of starch is presented and discussed. This mechanism is based on the regulation of ADP-glucose pyrophosphorylase by changes in effector molecule concentrations during the infection process. Reasons for these changes are presented.