小麦花后弱光引起籽粒淀粉的粒度分布及组分含量的变化

在籽粒灌浆阶段(花后1～30 d)对小麦进行光强为自然光照45%的弱光处理,研究了小麦籽粒淀粉粒度分布和组分含量的变化.结果表明,小麦籽粒淀粉粒体积分布呈双峰曲线,峰值分别在5.1～6.1 μm和20.7～24.9 μm,两峰值间的低谷出现在9.9 μm左右.表面积分布和数目分布分别表现为双峰和单峰曲线.小麦花后弱光显著降低2.8～9.9 μm淀粉粒体积百分比,增加22.8～42.8 μm淀粉粒体积百分比.同时花后弱光显著降低<0.8 μm和2.8～9.8 μm淀粉粒表面积百分比,增加0.8～2.8 μm和>9.9 μm淀粉粒表面积百分比.可见灌浆期弱光显著降低籽粒B型(＜9.9 μm)淀粉粒体积和表面积百分比,而A型(＞9.9 μm)淀粉粒比例相对增加.与A型淀粉粒相比,B型淀粉粒对弱光的反映更敏感.小麦弱光处理籽粒淀粉及其组分含量显著低于对照,但其直/支比较对照高.相关分析表明,籽粒直/支比与2.8～9.9 μm淀粉粒体积百分比呈显著负相关,而与22.8～42.8 μm淀粉粒体积百分比呈显著正相关.花后不同阶段弱光显著增加A型淀粉粒体积百分比、降低B型淀粉粒体积百分比,其中灌浆中、后期弱光影响程度较前期大.表明,弱光条件下小麦籽粒淀粉合成底物优先供应淀粉粒的生长,而非形成更多的淀粉粒.     

灌溉与旱作条件下源库关系对小麦籽粒淀粉粒度分布的调节效应

在灌溉和旱作两种栽培条件下,研究了源库关系对小麦籽粒淀粉粒度分布特征的影响.结果表明,山农8355(大穗型)各处理A型淀粉粒体积分布、表面积分布百分比成熟期较灌浆中期明显提高,灌溉栽培条件下增幅分别在17.65%～22.88%、35.8%～39.05%,旱作栽培条件下增幅分别在1.46%～2.82%、7.05%～8.12%;山农8355各处理B型淀粉粒体积分布、表面积分布百分比成熟期较灌浆中期明显降低,灌溉栽培条件下降幅分别在34.78%～40.47%、11.73%～13.77%,旱作栽培条件下降幅分别在5.08%～7.67%、2.52%～3.43%.济南17(多穗型)各处理下成熟期与灌浆中期的A、B淀粉粒体积分布、表面积分布百分比,其变化趋势与山农8355相同,其中A型淀粉粒灌溉栽培条件下增幅分别在1.56%～5.98%、2.96%～9.92%,旱作栽培条件下增幅分别在1.76%～4.52%、1.28%～8.63%;B型淀粉粒灌溉栽培条件下降幅分别在3.46%～12.27%、1 02%～4.18%,旱作栽培条件下增幅分别在5.31%～9.87%、0.58%～3.13%.在灌溉和旱作栽培条件下源库调节对两品种A、B型淀粉粒粒度分布的影响趋势表现为,减源处理A型淀粉粒较同期同品种对照处理的体积分布、表面积分布百分比显著提高,减库处理较同期同品种对照处理显著降低,B型淀粉粒粒度分布变化趋势则与之相反.     

水稻强弱势籽粒核酸和蛋白质含量的差异

水稻抽穗当天,强势粒(上部一次枝梗籽粒)子房中总RNA、mRNA含量都高于弱势粒(下部二次枝梗籽粒),蛋白质含量却低于弱势粒.抽穗后第5天,强势粒子房中总RNA含量仍然高于弱势粒,mRNA含量两者差异不大,蛋白质含量依然低于弱势粒.抽穗后0～5d,强势粒子房中总RNA、mRNA含量变化不大,蛋白质含量下降显著;弱势粒子房中总RNA含量上升显著,mRNA含量、蛋白质含量变化不大.抽穗当天和抽穗后第5天,强势粒子房中有一些小分子rRNA带出现;弱势粒则相反,小分子rRNA基本上看不见.     

施氮水平对小麦籽粒谷蛋白大聚合体粒径分布的调控效应

谷蛋白大聚合体(GMP)是决定小麦品质形成的重要因素,在小麦籽粒发育过程中,GMP以球形颗粒形式贮藏在小麦籽粒胚乳中,其含量及颗粒大小受亚基组成及环境条件的影响。本研究以不同穗型冬小麦品种为材料,通过大田试验探讨了施氮水平与小麦籽粒谷蛋白大聚合体含量及其颗粒粒径分布的关系。结果表明,在0—240kg?hm-2范围内增施氮肥能显著提高小麦籽粒中GMP的含量,施氮量继续增加则不利于小麦籽粒 GMP积累。小麦籽粒GMP颗粒粒径分布范围为0.375—256 μm;GMP颗粒的体积和表面积分布均呈双峰曲线,数目分布呈单峰曲线。在0—240kg?hm-2范围内增施氮肥能显著提高>10μmGMP颗粒数目百分比和体积百分比,表明施氮能促进大颗粒GMP的形成。不同品种对施用氮肥的反应呈现差异。大穗型品种泰山9818籽粒GMP含量及颗粒粒径分布对氮肥的反应较为敏感。     

小麦花后水分亏缺和复水对同化物转运和籽粒灌浆的影响

为了阐明水分亏缺对小麦花后同化物转运和籽粒灌浆的影响及其生理机制的相关变化,以盆栽小麦旱作品种‘长旱58’为材料,自花后9 d起,设置正常供水(WW)、中度干旱胁迫后复水(MD)和重度干旱胁迫后复水 (SD)3个水分处理,比较干旱胁迫后复水处理对小麦籽粒产量、产量构成因素及水分利用效率、强弱势粒灌浆动态、旗叶光合性能、茎鞘非结构性碳水化合物(NSC)转运、籽粒形成关键酶活性变化等的影响。结果表明：(1)与WW相比,MD处理显著增加了小麦穗粒数和千粒重,进而提高籽粒产量、水分利用效率和小麦弱势粒的最大灌浆速率和平均灌浆速率,对强势粒则无显著影响,而SD处理则显著降低了穗粒数、千粒重、强弱势粒的最大灌浆速率和平均灌浆速率,但水分利用效率显著高于WW处理。(2)MD处理植株旗叶在小麦灌浆过程中维持了与WW基本相同的净光合速率,同时在小麦花后9~20 d时MD处理下气孔导度和蒸腾速率变化不明显,而在SD处理下气孔导度和蒸腾速率则急剧下降;另外,与WW相比,在整个灌浆期MD处理下旗叶叶绿素含量变化不显著,而SD处理下叶绿素含量呈大幅下降趋势。(3)MD处理提高了小麦弱势粒蔗糖合成酶和腺苷二磷酸葡萄糖焦磷酸化酶活性;同时使灌浆中后期有较高的果聚糖水解酶(FEH)活性和较低果聚糖含量,显著增强了茎鞘同化物质转运,提高茎鞘储藏物质对粒重的贡献率。研究发现,中度水分胁迫后复水处理小麦植株具有较好的叶片性能、花后较多的茎鞘同化物向籽粒转运以及较高的弱势粒库活性,从而提高旱作小麦弱势粒灌浆速率,增加穗粒数和粒重, 进而提高籽粒产量。     

不同灌水处理对强筋小麦谷蛋白大聚合体粒度分布和品质的影响

在田间条件下,以两个优质强筋小麦品种(藁城8901和济麦20)为供试材料,研究了不同灌水处理(全生育期不灌水、拔节期灌1次水、越冬期和拔节期灌2次水、越冬期、拔节期和灌浆期灌3次水,每次灌水量675 m³·hm^-2)对强筋小麦谷蛋白大聚合体含量与粒度分布、品质和产量的影响.结果表明: 两个小麦品种的面团形成时间、面团稳定时间、面包体积、籽粒产量、谷蛋白大聚合体含量以及体积加权平均粒径、表面积加权平均粒径、粒径>100 μm的体积百分比和表面积百分比均以灌2水处理最高.相关分析显示,两个小麦品种的面团形成时间、面团稳定时间和面包体积与粒径<10 μm和10～100 μm的谷蛋白大聚合体颗粒体积百分比呈显著负相关,而与粒径>100 μm的谷蛋白大聚合体颗粒体积百分比、体积加权平均粒径和表面积加权平均粒径呈显著正相关.水分供应过多或过少均不利于籽粒产量和品质的同步改善,灌溉水平可通过改变谷蛋白大聚合体粒度分布影响小麦籽粒品质.     

糯玉米胚乳淀粉粒粒度分布形成的酶学机理

以7个糯玉米品种为材料,测定其籽粒发育过程中淀粉粒粒度分布及淀粉合成相关酶活性的变化,分析两者之间的关系。结果表明,随着籽粒发育,糯玉米淀粉粒平均粒径逐渐增大,可溶性淀粉合成酶(SSS)和淀粉分支酶(SBE)活性呈单峰曲线变化。籽粒发育前期,小淀粉粒(≤7.4μm)所占体积较大;随着籽粒发育,小淀粉粒所占体积减少,大淀粉粒(>7.4μm)所占体积增多;籽粒发育后期,大淀粉粒所占体积较大。相关分析表明, SSS和SBE活性与大淀粉粒体积增大速率和平均粒径增大速率均呈显著或极显著正相关。因此, SSS和SBE是影响糯玉米胚乳淀粉粒粒度分布形成的主要酶, SSS和SBE活性越高,淀粉粒平均粒径越大,大淀粉粒所占体积越多。     

三种粒型小麦品种胚乳细胞增殖动态研究

以三种粒型小麦品种(系)为材料,观察了不同品种和同一品种不同粒位籽粒胚乳细胞增殖动态。结果表明,用Richards方程能较好地模拟胚乳细胞增殖动态。强势粒胚乳细胞分裂起始势高,达到最高增殖速率的时间短,活跃分裂期长,可分裂出更多的胚乳细胞。弱势粒胚乳细胞增殖起始势低,细胞分裂速率变化缓慢,其最终胚乳细胞数显著低于强势拉。不同品种间胚乳细胞数有一定的差异,表现为大粒饱满品种(鄂思1号)>不饱满品系(95A-10)>小粒饱满品种(华麦8号)。胚乳细胞增殖速率变化为单峰曲线,强势粒胚乳细胞增殖速率曲线偏左,弱势粒胚乳细胞增殖速率曲线偏右。     

花后高温对不同耐热性小麦品种籽粒淀粉形成的影响

以耐热性不同的2个小麦品种济麦20和鲁麦21为材料,分别于花后5～9d（T1）和15～19d（T2）进行高温处理,研究了小麦花后不同阶段高温对籽粒淀粉积累、淀粉粒分布及相关酶活性的影响。结果表明,花后高温显著降低籽粒淀粉积累量;显著降低籽粒淀粉及支链淀粉含量,但提高直链淀粉含量、直／支链淀粉比例。处理间比较,他处理对籽粒淀粉积累的影响程度较T1处理大。品种间比较,高温对济麦20的影响程度较鲁麦21大。高温使A型淀粉粒的体积、数量和表面积比例显著增加,B型淀粉粒的体积、数量和表面积比例显著降低。T1处理后,两品种籽粒蔗糖含量、蔗糖合酶（SS）和腺苷二磷酸葡萄糖焦磷酸化酶（AGPP）、可溶性淀粉合酶（SSS）、束缚态淀粉合酶（GBSS）和淀粉分支酶（SBE）活性均略高于对照;但济麦20、鲁麦21上述指标分别于花后15、20d开始低于对照。他处理后,两品种籽粒蔗糖含量、SS、AGPP、SSS、GBSS和SBE活性显著低于对照,济麦20上述指标的降幅较鲁麦21大。与其它淀粉合成相关酶相比,高温对籽粒GBSS活性的影响程度较小。两品种处理间籽粒蔗糖含量、SS、AGPP、SSS、GBSS及SBE活性的变化趋势,与淀粉积累量的变化趋势基本一致。说明灌浆期高温使籽粒淀粉积累量降低,一方面是由于籽粒蔗糖供应较低引起糖源不足;另一方面则是由于灌浆中后期淀粉合成相关酶活性下降使淀粉合成受抑所致。     

AlA对冬小麦不同粒位籽粒灌浆影响的动态模拟及特征分析

以百农矮抗58为材料,采用大田试验的方法,研究了在始穗期喷施不同浓度(10mg/L、30 mg、50 mg/L)的5-氨基乙酰戊酸(5-Aminolevulinic acid,ALA)对冬小麦不同粒位籽粒灌浆特性的影响.应用Richards方程对10～50 mg/L ALA处理下冬小麦3个粒位(第Ⅰ、Ⅱ、Ⅲ粒位)的籽粒灌浆过程进行了模拟.建立在Richards方程基础上的籽粒生长分析显示:与对照相比,10～50 mg/L ALA处理使第Ⅰ和第Ⅲ粒位的千粒重分别增加了1.3～2.4g、3.4～4.7,较对照差异显著,第Ⅱ粒位的粒重与对照差异不显著;10～50 mg/L ALA处理使冬小麦3个粒位籽粒的平均灌浆速率和最大灌浆速率增大,灌浆活跃持续期延长,到达最大灌浆速率的时间提前.阶段灌浆特征参数的比较表明,在籽粒灌浆的渐增期,10～50 mg/L ALA处理使冬小麦3个粒位籽粒的平均灌浆速率增加,灌浆持续期缩短;在籽粒灌浆的快增期,使3个粒位籽粒的平均灌浆速率增加,灌浆持续期延长.在籽粒灌浆的缓增期,使强势粒(第Ⅰ、第Ⅱ粒位)的平均灌浆速率减小,灌浆持续期延长,但使弱势粒(第Ⅲ粒位)的平均灌浆速率增加,灌浆持续期延长.表明在灌浆的前期和中期,10～50 mg/L ALA处理可促进各粒位籽粒提早启动灌浆,并提高其灌浆速率,在灌浆后期减弱了强势粒对弱势粒籽粒灌浆充实的优势,从而有利于弱势粒的灌浆充实.从总体上讲,10～50 mg/L ALA对弱势粒(第Ⅲ粒位)粒重的影响程度大于强势粒(第Ⅰ和第Ⅱ粒位),其中30 mg/L ALA促进籽粒增重的效果最明显.     

Activities of key enzymes for starch synthesis in relation to growth of superior and inferior grains on winter wheat (Triticum aestivum L.) spike

Weight of individual grains is a major yield component in wheat. The non-uniform distribution of single grain weight on a wheat spike is assumed to be closely associated with starch synthesis in grains. The present study was undertaken to determine if the enzymes involved in starch synthesis cause the differences in single grain weight between superior and inferior grains on a wheat spike. Using two high-yield winter wheat (Triticum aestivum L.) varieties differing in grain weight and three nitrogen rates for one variety, the contents of amylose and amylopectin, and activities of enzymes involved in starch synthesis in both superior and inferior grains were investigated during the entire period of grain filling. Superior grains showed generally higher starch accumulation rates and activities of enzymes including SS (sucrose synthase), UDPGPPase (UDP-glucose pyrophosphorylase), ADPGPPase (ADP-glucose pyrophosphorylase), SSS (soluble starch synthase) and GBSS (starch granule bound starch synthase) and subsequently produced much higher single grain weight than inferior grains. Nitrogen increased enzyme activities and starch accumulation rates, and thus improved individual grain weight, especially for inferior grains. The SS, ADPGPPase and SSS were significantly correlated to amylopectin accumulation, while SS, ADPGPPase, SSS and GBSS were significantly correlated to amylose accumulation. This infers that SS, ADPGPPase and starch synthase play key roles in regulating starch accumulation and grain weight in superior and inferior grains on a wheat spike.     

Endosperm enrichment and physicochemical properties of superior and inferior grain starch in super hybrid rice

• A significant asynchronous phenomenon exists in super hybrid rice because of the differences in spike and spikelet positions, which affect the accumulation and properties of starch. However, little is known about the endosperm enrichment and physicochemical properties of starch in superior and inferior grains in super hybrid rice.
• Rice YY2640 was selected as study material to investigate the enrichment and physicochemical properties of starch in superior and inferior grains in super rice using semi‐thin sections, X‐ray diffraction and related technologies.
• Superior grain filling was a continuous process, whereas inferior grain only started 8–10 days after anthesis. The order of starch accumulation starts in the central endosperm, then in the endosperm of the proximal vascular bundle and finally in the aleurone layer. Compared with the inferior grains, the superior grains have a higher 1000‐grain weight, apparent amylose content, total starch content, average starch granule size, relative crystallinity, solubility and a resonance peak ratio at 1022/995 cm^?1, whereas the swelling power and ratio of the resonance peak at 1045/1022 cm^?1 were lower. The final degree of hydrolysis of HCl, AAG and PPA of the superior grains were significantly lower than those of the inferior grains.
• The findings indicate that the different physicochemical properties of starch were mainly related to the development order of superior and inferior grains and the spatial enrichment of starch.

     

Block-Surface Staining for Differentiation of Starch and Cell Walls in Wheat Endosperm

A staining technique for differentiating starch granules and cell walls was developed for computer-assisted studies of starch granule distribution in cells of wheat [Triticum aestivum L.] caryopses. Blocks of embedded caryopses were sectioned, exposing the endosperm tissue, and stained with iodine potassium iodide (IKI) and Calcofluor White. Excessive tissue hydration during staining was avoided by using stains prepared in 80% ethanol and using short staining times. The IKI quenched background fluorescence which facilitated the use of higher concentrations of Calcofluor White. Cell wall definition was improved with the IKI-Calcofluor staining combination compared to Calcofluor alone. The high contrast between darkly stained starch granules and fluorescent cell walls permitted computer assisted analysis of data from selected hard and soft wheat varieties. The ratio of starch granule area to cell area was similar for both wheat classes. The starch granule sizes ranged from 2.1 μm³ to 22,000 μm³ with approximately 90% of the granules measuring less than 752 μm³ (ca. 11 μm in diameter). Hard wheat samples had a greater number of small starch granules and a lower mean starch granule area compared to the soft wheat varieties tested. The starch size distribution curve was bimodal for both the hard and soft wheat varieties. Three-dimensional starch size distribution was measured for four cells near the central cheek region of a single caryopsis. The percentage of small granules was higher at the ends than at the mid-section of the cells.     

The Cytological and Histochemical Studies of Developing Soybean,Cotyledons

In the late globular proembryos, three regions could be identified, i. e. the cotyledon primordium, the epiphysis and the hypocotyl-hypophysis. In the cotyledon primordia, the mitotic frequency of the cells was comparitively high, the directions of the mitotic planes were mostly perpendicular to the long axis of the embryo, the size of the nucleolus was comparitively large, and the cytoplasm density was high. In the epiphysis region, however, the mitotic frequency of the cells was low, the size of the nucleolus was small, and as the first pair of leaf primordia appeared the mitotic frequency of the cells in that region began to increase. In the hypocotyls hypophysis region the mitotic frequency of the cells as well as the size of the nucleolus lied in between the corresponding values of those of the above two regions, the cytoplasm density was low and the size of the vacuoles was large. As the proembryo continued to develop the direction of the mitotic plane changed gradually, from mostly perpendicular to the long axis of the embryo to mainly inclined, or even parallel to that axis. As a result, the proembryo developed from a heart-shaped embryo into a torpedo-shaped embryo. After the first pair of leaf primordia appeared from the young embryo, the vacuoles in the cells of the cotyledons grew in size rapidly. About twenty to twenty five days after flowering, the starch grains, the protein bodies and the lipid granules began to accumulate in the cells of the cotyledons and gradually increased both in size as well as in quantity. About fifty days after flowering the diameter of the starch grains reached its maximum value of 6.2–7.0 μm, and decreased in value thereafter till the time of harvesting when most of the starch grains disappeared except those in the palisades. On the other hand, fifty to sixty days after flowering, the diameters of the lipid granules and of the protein bodies reached their maximum values of 5.4–7.0 μm and 6.2–7.0 μm, respectively. The observation revealed that the formation of the protein bodies was related to the vacules.     

Relationship between structural and biochemical characteristics and texture of corn grains

The texture of corn grains is a fundamental characteristic for the industry as well as for grain producers and processors. To further understand the mechanisms involved in grain hardness, contrasting corn cultivars for grain hardness and protein quality were evaluated. The cultivars were Cateto L237/67 (hard endosperm and low protein value), QPM BR 451 (semi-hard endosperm and high protein value); Bolivia-2 (floury endosperm and low protein value), and Opaque-2 (floury endosperm and high protein value). Evaluations were carried out at 10, 20, 30, 40, 50, and 60 days after pollination in developing corn grains and in the mature grain. In developing grains, evaluation consisted in the determination of the area, percentage of starch granules, distribution of starch granules, and protein bodies in the endosperm. In mature corn grains, the parameters evaluated were: density, percentage of total proteins, levels of lysine and tryptophan, and banding pattern of zeins. The results indicate that the higher physical resistance of corn grains from the cultivars analyzed is influenced by the high percentage of total proteins, high synthesis of 27-kDa zeins, presence of protein bodies, and perfect organization of starch granules in the endosperm, independent of their sizes.     

Pathways of Androgenesis and Observations on Cultured Pollen Grains in Rice (Oryza saliva Subsp. Keng)

(1) Pathways A-V, A-G, A-GV, and B existed in androgenesis of rice. Usually B pathway was predominant. Degeneration could happen on androgenic grains via each pathway during the early stage of androgenesis. (2) Statistics suggested that the multinucleate grains might be converted to multicellular grains by a later formation of cell walls and were consequently one of the sources of callus. (3) Androgenic grains was usually of medium size (35–40 μm) with dense protoplasm. In isolated pollen culture, the diameter of androgenic grains increased 2.5–5μm per day. Before the breakdown of exine, the cell walls seemed to be thickened and the grains would contract abruptly. (4) Small, slowly-moving starch granules were usually contained within multicellular grains cultured isolately. They were speculated to participate actively in the metabolism of androgenic grains.     

Production Factors Involved in the Formulation of Erynia neoaphidis as Alginate Granules

Granular formulations of the aphid-pathogenic fungus Erynia neoaphidis were produced by entrapping mycelia in alginate polysaccharide polymers. Four Swiss isolates were compared for the numbers of conidia discharged from the surface of alginate granules in standardized laboratory assays and two were considered to be suitable for further development. Conidiation was achieved from granules produced using nozzle diameters of 2.0. 1.0 and 0.5 mm from glass burettes or a novel vibrating tip apparatus. The mean diameters of dried granules varied from 0.5 to 1.8 mm. The addition of sucrose, potato starch or chitin in alginate solutions significantly improved the numbers of discharged conidia. W ith freshly produced granules, there was a 14.2- fold increase in sporulation from 6.3 to 89.7 conidia mm - 2 using 2% (w/v) sucrose. Increases of 1.6-to 2.3-fold, from 11.0 to 17.7 and 25.2 conidia mm - 2, were observed using 5% (w/v) starch or chitin respectively. The overnight drying of granules in a laminar flow hood and storage for 4 days at 4 C made differences in sporulation more obvious. There was a 15.5-fold difference in conidial numbers of 12.4 and 0.8 conidia mm - 2 from granules with and without sucrose respectively. For starch and chitin, there were 76.0-and 46.5-fold increases from 0.4 to 30.4 and 18.6 conidia mm - 2respectively. Fresh or dried alginate granules containing 2% sucrose and 5% starch gave 8.6-26.6% infection in laboratory bioassays with nymphs of pea aphid, Acyrthosiphon pisum , which were not significantly different when compared with infections of 6.7-22.9% using agar cultures or unsupplemented granules. Further studies on desiccation and storage regimes are required in order to improve the short-term shelf-life of E. neoaphidis alginate granules.     

Enzymatic Improvement of the Cooking Quality of Aged Rice: A Main Mode of Protease Action

This study aims to improve the stickiness and brightness of cooked rice from aged rice grains by removing its albumins and globulins with proteases. In newly–harvested grains, the proteins were easily removed by extraction with water which contained minerals from rice. In aged grains, however, the proteins were already denatured and extracted with difficulty. Proteases hydrolyzed even the denatured proteins to make them extractable. As a result, starch granules on the surface of grains were liberated. Some proteases also hydrolyzed a starch granule-associated protein, and consequently, made the starch highly gelatinizable by heating. The protease treatment of aged grains was effective for two main reasons: liberation of starch granules and removal of the granule-associated protein. During cooking of rice the liberated starch without the associated proteins gelatinized to give rise to stickiness. The gelatinized starch is considered to form a more isotropic film on the surface of every cooked rice grain to give brightness as well.