Pre-maturity α-amylase and incipient sprouting in UK winter wheat,with special reference to the variety Rialto

In 1998 and 1999 the UK winter wheat variety Rialto produced unexpected low Hagberg falling numbers that could not be directly linked to sprouting. It was proposed that these reductions in quality could be due to pre-maturity α-amylase activity (PMAA). The problem was not identified during the selection and commercial development stages. Our study tested the hypothesis that the variety Rialto is PMAA-susceptible. Analysis was done on 13 year-location combinations of field grown Rialto. Together, visual and chemical assessments of sprouting and iso-electric focusing of α-amylase isozymes identified several samples with significant α-amylase activity in the apparent absence of sprouting. In addition, tests with α-amylase sensitive Phadebas gel revealed distinctive PMAA discoloration patterns in 10–44% of the grain from the 13 samples, leading to the conclusion that Rialto is PMAA-susceptible. Diurnal temperature range accumulated for an 11 day period during a warm spell in early simulated grain development displayed a significant but negative correlation with the number of grains showing clear PMAA discoloration patterns on Phadebas gel. The number of clear PMAA grains correlated positively with rainfall accumulated over 11 days. These results suggest that PMAA can increase under conditions similar to those conducive to pre-harvest sprouting. It is however also possible that in some instances both PMAA and incipient sprouting could have produced similar patterns of α-amylase activity. In addition to tests with Rialto, Phadebas gel tests were therefore also done with the known high Hagberg varieties Option and Malacca, sprouted in a controlled environment. Results from the additional gel tests suggest that visual and chemical assessments of sprouting in the grain combined with Phadebas gel analysis could identify PMAA more reliably in grain sub-samples than Phadebas gel analysis alone.     

Abscisic acid, gibberellin and cell viability in cereal aleurone

The aleurone layer of cereals is a secretory tissue whose activity is regulated by abscisic acid (ABA) and gibberellins (GAs). Whereas GA triggers enzyme synthesis and secretion and initiates a program that culminates in cell death, ABA prevents enzyme production and cell death. Reactive oxygen species (ROS) are key players in regulating cell viability and GA sensitizes the aleurone cell to ROS. Sensitivity of GA-treated cells results in part from a reduction in steady-state amounts of mRNAs encoding enzymes that scavenge ROS. mRNAs encoding catalase, superoxide dismutase and ascorbate peroxidase are almost undetectable in aleurone layers 24 h after incubation in GA. For layers incubated in ABA, however, the amounts of these mRNAs increase. Western blotting and enzyme activity assays confirm that GA but not ABA reduced the amount and activity of ROS scavenging enzymes (Fath et al., 2001b). Substantial amounts of ROS are produced by enzymes engaged in lipid metabolism, and by the electron transport chain in the mitochondria. Aleurone layers contain abundant stores of triglycerides and ROS are produced as these lipids are rapidly converted to sugars. We hypothesize that the ROS produced in GA-treated aleurone cells bring about cell death by disrupting the plasma membrane. Aleurone cells incubated in ABA, on the other hand, are better able to maintain redox balance. ABA does not initiate rapid triglyceride metabolism, and the activities of ROS-scavenging enzymes remain high in ABA-treated cells. We conclude that GA initiates a metabolic cascade in aleurone cells that results in death from ROS. ABA maintains viability by keeping ROS under control. This revised version was published online in August 2006 with corrections to the Cover Date.     

四个不同粒重水稻品种颖果发育的比较

 以粒重差异较大的4个水稻品种为供试材料,采用树脂切片、酶解胚乳细胞和显微观察等方法,比较研究了品种间在颖果生长、胚乳细胞增殖、果皮和胚乳结构等方面的差异,探讨了影响颖果生长的因素。 大粒品种颖果发育时间较小粒品种长,其胚乳细胞数、胚乳干质量及单个胚乳细胞平均干质量均高于小粒品种。在粒重相近的情况下,籼稻颖果发育和淀粉积累快于粳稻。与小粒品种相比,大粒品种子房壁细胞中淀粉粒多,子房壁细胞生长的持续时间长,果皮及背部维管束衰亡迟。 小粒品种胚乳外层细胞在花后7 d已转化成糊粉层细胞,大粒品种胚乳外层细胞要在花后10 d才转化成糊粉层细胞。 大粒品种的库容大和生理活性期长是其颖果能显著增大的生理原因。     

麦麸结构层粉体的电特性研究

为了确定麦麸结构层粉体静电场分离的可行性,该文以高纯度麦麸糊粉层和外果皮粉体为原料,研究其介电性、导电性和电晕带电特性的差异。结果表明,麦麸粉体的介电常数随频率的增加而降低,最终趋于一致;当频率较低时,外果皮的相对介电常数明显低于糊粉层;当频率为300 MHz时,两者的介电常数之比最大达5.3;麦麸粉体的导电性差,糊粉层粉体的电阻率为2300MΩ/cm,为外果皮电阻率的5倍;经正电晕带电后,糊粉层粉体所获电荷量约为外果皮的1.7倍,具有明显差异;单位质量麦麸粉体所获电荷量随电晕电压的增加而增加,而随麦麸粉体的含水率和粒径的增大而减小。总之,麦麸结构层粉体的介电性、导电性和电晕带电性均存在明显差异,可以利用介电泳和电晕带电后的静电场分离技术对麦麸结构层进行分离纯化。     

小麦糊粉层发育研究

小麦的表层胚乳会形成糊粉层,在颖果发育过程中,糊粉层将灌浆物质转运到胚和胚乳细胞内部。选用发育不同阶段的小麦颖果,树脂包埋后结合半薄切片技术和超薄切片技术观察其糊粉层显微结构和超微结构,采用扫描电子显微镜和能谱分析技术研究糊粉层细胞的表观形态及相关元素定性半定量分析,在胚乳细胞转化为糊粉层细胞的成因、发育过程和功能等诸多方面进行深入研究。结果表明:小麦糊粉层发育过程可划分为5个阶段,成熟后的糊粉层细胞富含大量的蛋白、脂类和P、K、Ca、Mg等矿质元素,这些发育和结果上的特点为糊粉层是灌浆废物在表层胚乳积累形成提供了有力证据。     

Blue aleurone trait diagnoses developmental origin of three pistils in a floret in common wheat

The common ‘three‐pistil’ (TP) wheat mutation line expresses TPs in a floret normally containing TPs forming three grains set close back‐to‐back. The developmental origin of the TP trait in common wheat had been diagnosed non‐destructively using the blue aleurone trait. The aleurone colour of F₂ seeds grown in F₁ plants of cross TP/UC66049 was evaluated. Due to xenia, the hue of blue grain colour depended on dose of the Ba1 gene for blue aleurone in the triploid endosperm. The TP trait produced four types of segregation in three‐seed clusters: (i) white grain only, (ii) two white grains and one blue, (iii) one white grain and two blue, and (iv) three blue grains only. The observed frequency of blue–white seed within clusters followed the binominal distribution ₃C_r (0.75)^r·(0.25)^3–r, where r is the number of colour variants in three‐seed clusters (r = 0–3). Intrafloret segregation of seed colour and F₂ segregation derived from aleurone colour of F₃ seeds indicated an independent origin of the TP trait.     

Energy-dispersive x-ray analysis of phytin globoids in aleurone particles of developing rice grains

Abstract

In this study energy-dispersive X-ray analysis was used to discover changes in the composition of phytin globoids in aleurone particles of developing rice grains.

At early milky stage (the 7th to 10th day after flowering) many aleurone particles were observed as electron lucent vacuole-like particles in aleurone cells, some of which contained a small electron-dense inclusion (phytin globoid). The major mineral elements present in phytin globoids were phosphorus (P) and magnesium (Mg). Potassium (K) was also detectable but its concentration was extremely low relative to these two. Calcium (Ca) and zinc (Zn) were found as minor components. At early dough stage (the 17th to 19th day after ftowering) P, Mg and K were observed as the major mineral elements. The composition of mineral elements in phytin globoids tend to be constant in the late staae of ripening. On the other hand, minor elements, i.e. Ca and Zn, were only detectable in the early stage of ripening, suuesting that these elements accumulated in the aleurone particles only during the early stage, and in later stage their accumulation was either complete or at very low levels compared with those of K and Mg. The relative amount of Mg existing in phytin globoid remained roughly constant throughout the ripening periods, while that of K varied.

Energy-dispersive X-ray analysis of phytin globoids in developing rice aleurone particles confirmed that the accumulation of P, Mg and K in rice grains was closely related to the formation of phytin globoids. This analysis suggested further that the mechanism of accumulation of P into aleurone particles was very similar to that of Mg, while that of K differed from both. The results obtained suggested that Ca and Zn might be required in the formation of phytin globoid at the early ripening stage. EDX analysis of a protein body in the starchy endosperm revealed that there was no significant element detectable in an EDX spectrum other than sulfur. This suggests that lamellar concentric structures in protein bodies are not due to phytin.     

小麦糊粉分离与糊粉配置营养米技术研究

小麦糊粉是小麦皮层中接触胚乳的内果皮部分,含有丰富的矿物质、微量元素和膳食纤维等营养物质,由于其灰分偏高,色泽发黄,在制粉过程中将其作为副产物进入麸皮中,使主产品营养含量下降,为使该部分营养物质充分利用到主食品中,增加主食品的天然营养含量,作者利用分层脱皮碾磨的特殊提取工艺将其分离,制作糊粉营养米,添加到普通大米中,补足大米的营养。此研究采用正交实验方法设计实验,通过实验得出糊粉营养米的最佳营养配方和工艺影响参数。该研究结论为糊粉营养米的开发提供了基础,为人们膳食结构的调整指了一条新路。     

水稻胚乳组织的结构观察

【目的】阐明水稻糊粉层细胞、亚糊粉层细胞与中心胚乳贮藏细胞的结构特性。【方法】采用光镜、透射电镜与扫描电镜对水稻胚乳组织进行观察研究。【结果】糊粉层细胞分化过程中,大液泡变成小体积蛋白贮存液泡,蛋白贮存液泡又转变成糊粉粒。颖果背部比腹部有更多层糊粉层,但背部糊粉层细胞内糊粉粒的形成与积累速度却较慢。亚糊粉层细胞起初含有一些脂质体,后来脂质体消失,而其内部淀粉体与蛋白体逐渐增多。中心胚乳贮藏细胞含有淀粉体与蛋白体,蛋白体以液泡型蛋白体为主,它们可以相互融合而变大。中心胚乳贮藏细胞内的淀粉积累速度明显快于亚糊粉层细胞内的。成熟颖果的中心胚乳贮藏细胞内淀粉体最为密集,背部和侧部的亚糊粉层细胞内淀粉体排列较疏松,腹部的亚糊粉层细胞内淀粉体最为稀疏。【结论】水稻颖果背部与腹部的糊粉层细胞和亚糊粉层细胞的结构差异可能与养分吸收与转运有关;中心胚乳贮藏细胞内淀粉体发育速度快于亚糊粉层细胞。     

Chalcone synthase expression and pigments deposition in wheat with purple and blue colored caryopsis

Red and white caryopses are typical in common wheat. Genotypes with purple and blue caryopses are also described. This coloring is caused by anthocyanins which deposit in the pericarp (purple) or aleurone layer (blue). The anthocyanins biosynthetic pathway is well described. The key enzyme is chalcone synthase (CHS). It catalyzes the first step. We observed the deposition of anthocyanins in the pericarp and aleurone layer, the expression of a chalcone synthase gene and the amount of two anthocyanins - cyanidin-3-glycoside (pericarp of purple caryopses), and delphinidin-3-glycoside (aleurone layer of blue caryopses) during caryopsis development. Purple pigment deposition was not homogeneous and/or uniform. At first, small isolated spots of purple color were formed and thereafter they expanded. In blue caryopses, however, the coloring process was more homogeneous. The expression of chalcone synthase mRNA occurred five days before pigment deposition and finished earlier than expected. Amounts of cyanidin-3-glycoside and delphinidin-3-glycoside increased in a similar manner. Amounts of these fell at the end of caryopses development probably due to formation of more complex substances.