Starch Accumulation and Enzyme Activities Associated with Starch Synthesis in Maize Kernels

The filling rate and the starch accumulation in developing maize kernel were analyzed. The changes of enzyme activities associated with sucrose metabolism and starch biosynthesis were investigated. The purpose is to discuss the enzymatic mechanisms responsible for starch synthesis. Two types of maize cultivars （Zea mays）, high starch maize （Feiyu 3） and normal maize （Yuyu 22）, were grown in a corn field. The factors involved in starch synthesis were performed during the growth period. The kernel filling rate, the sucrose content, the starch accumulating rates and the activities of SS （sucrose synthase）, GBSS （granule-bound starch synthase）, SBE （starch branching enzyme） of Feiyu 3, which has high starch content, were significantly higher than those of Yuyu 22, which has low starch content, after 10 DAP （days after pollination）. Correlation analysis indicated that ADPGPPase （ADP-glucose pyrophosphorylase） and DBE （starch debranching enzyme） were not correlated with the starch accumulating rates and the kernel filling rate, but the SS activity at the middle and late period were highly significantly correlated with the starch accumulating rates and the kernel filling rate. The GBSS activity was highly significantly correlated with the amylose accumulating rate, but not correlated with the kernel filling rate. The SBE activity was highly significantly correlated with the amylopectin accumulating rate and the kernel filling rate. It was not ADPGPPase and DBE, but SS was the rate-limiting factor of starch biosynthesis in developing maize kernels. GBSS had an important effect on amylose accumulation, and SBE had a significant effect on amylopectin accumulation.     

Determination of Protein and Starch Content in Whole Maize Kernel by Near Infrared Reflectance Spectroscopy

Using 128 bulk-kernel samples of inbred lines and hybrids, a study was conducted to investigate the feasibility and method of measuring protein and starch contents in intact seeds of maize by near infrared reflectance spectroscopy (NIRS). The chemometric algorithms of partial least square (PLS) regression was used. The results indicated that the calibration models developed by the spectral data pretreatment of first derivative multivariate scattering correction within the spectral region of 10000 -4000 cm^-1, and first derivative straight line subtraction in 9000 - 4000 cm^-1 were the best for protein and starch, respectively. All these models yielded coefficients of determination of calibration (R^2cal) above 0.97, while R^2cv and R^2va1 of cross and external validation ranged from 0.92 to 0.95, respectively; however, the root of mean square errors of calibration, cross and external validation (RMSEE, RMSECV and RMSEP) were below l(ranged 0.3- 0.7),respectively. This study demonstrated that it is feasible to use NIRS as a rapid, accurate, and none-destructive technique to predict protein and starch contents of whole kernel in the maize quality improvement program.     

Effect of Soil Texture on Starch Accumulation and Activities of Key Enzymes of Starch Synthesis in the Kernel of ZM 9023

Three kinds of soil texture （clay-loam, mid-loam, and sand-loam soil） were used to study the effects of soil texture on starch accumulating rate and the changes in activities of the key enzymes of starch synthesis in the kernel during grain filling in high gluten content wheat ZM 9023, under conditions of pond culture. The content of starch and its components were measured according to the method of double-wave length described by Bao （1996）. ADP-glucose pyrophosphorylase （AGPP） activity was tested according to the method described by Doehlert et al. （1988）. Soluble starch synthase （SSS） and starch branching enzyme （SBE） activities were tested according to the method described by Nakamura et al. （1989）. The amylose, amylopectin, and total starch accumulating rate in the kernel of ZM 9023 were found to be a single-peak curve in three different soil textures during grain filling, and peaked 20, 15, and 15 d after anthesis, respectively. The activities of the enzymes, AGPP, SSS, and SBE, in the kernel of ZM 9023 had a single-peaked curve, which peaked 20, 15, and 15 d after anthesis, respectively. The activities of the above three enzymes of ZM 9023 were higher in the sand-loam soil. The accumulating peak of amylose formed later compared to that of amylopectin. The sand-loam soil could help high gluten content cultivars to synthesize starch.     

Study on Accumulation Rule of Carbohydrates in Soybean （Glycine max（L.） Merrill）

Three soybean cultivars, Hefeng25 （HF25）, Suinongl4 （SN14） and Longxuanl （LX1） were used as materials and the accumulation features of carbohydrates were studied in leaves and stems. The results showed that the soluble sugar content in leaves and stems appeared the same trend of higher-lower-higher in three varieties. The changes of sucrose content in leaves appeared the same rule with that of soluble sugar, that is higher-lower-higher, while presented a rising trend in stems. The content of starch in leaves varied as a change of double apexes. The content of starch in stems appeared a change of single apex. In the same stage, there were some differences among carbohydrates. The content of soluble sugar and sucrose in SN14 was higher, and the starch content was lower.     

Effects of Selenium on Maize Ovary Development at Pollination Stage Under Water Deficits

Maize ovary development is linked to kernel formation. Soil water deficit results in ovary abortion because of low water potential （ψw） resulting in inhibition of photosynthesis from anthesis to silking stage. Thus, drought is a key factor causing yield losses in maize, especially near the time of pollination. Earlier studies have indicated that selenium （Se） maintains antioxidative defence systems and enhances sugar and starch accumulation. The effects of Se on maize ovary development were studied in drought stress conditions. Maize ovary development was studied through observations on starch, membrane integrity, fresh weight and dry weight in drought-treated or unstressed glasshouse-grown plants, and crop yield, yield structure, leaf, stem and ear biomass accumulation were also analyzed. Results indicated that Se increased the stress tolerance of the crop, even though ovary abortion was not eliminated by Se treatments under low ψw. Under well-watered control conditions, Se had also negative effects. When the first ear was not succesfully pollinated or the ovaries aborted, the plants developed more ears. Even though these later formed ears did not produce kernels, they significantly increased the dry weight of the plants under water deficit. It could be concluded that The optimal concentration for maize of Se applied through roots is about 0.01 mg kg^-1 （supplied as Na2SeO4） soil or less.     

Molecular Characteristics of New Wheat Starch and Its Digestion Behaviours

In order to understand the effect of starch molecular characteristics on the gel structure, which subsequently influence the gel digestion behaviours, three wheat starches, control （conventional wheat starch）, two new wheat cultivars with different genetic backgrounds （by knocking out SBE IIb and SBE IIa, respectively） were used in this study. In comparison with control, slight differences in the morphology of the starch granules of new wheat 1 were observed, whereas the starch granules of new wheat 2 had irregular shapes both for A-type granules and B-type granules. Starch molecular weight size was determined by SE-HPLC, and the results indicate that there was a subtle increase in the amylose content in the starch of new wheat 1 compared to that of control. The starch of new wheat 2 had the highest amylose content, and the molecular weight （MW） of its amylopectin was the lowest among the three starches. Fourier transform infrared spectroscopy （FTIR） was employed to investigate starch gel structure and the results suggest that the molecules of starch gel from new wheat 2 are more likely to re-associate to form an organized conformation. The digestion behaviours of the three starch gels were measured using a mixture of pancreatin a-amylase and amyloglucosidase. The results indicated that the starch gels of control and new wheat 1 had very high digestibility of 91.7 and 91.9%, respectively, whereas the digestibility of wheat 2 starch gel was only 36.2%. In comparison with the digestion curve pattems of control and new wheat 1 starch gels, the new wheat 2 exhibited a much lower initial velocity. These results indicated that the molecules in the starch of new wheat 2 are more readily to re-associate to form an organized structure during gel formation because of its unique molecular characteristics.     

Coronatine Induces an Accumulation of Anthocyanin and Starch in Purple-fleshed Sweetpotato （ Ipomoea batatas Lam.）

[Objective] The objective of this research was to examine the effects of COR on anthocyanin and starch content in storage roots of two PFS genotypes, and to explore the relationships between anthocyanin synthesis and starch accumula- tion. [Method] A field experiment was carried out to determine the changes in yielc components, yield, contents of anthocyanin and starch, activities of phenylalanine ammonia-lyase （PAL） and adenosine 5-diphosphate glucose pyrophosphorylase （AG- Pase） in two genotypes of PFS （Ipomoea batatas L., var. ＇Ayamurasaki＇ and ＇Jishu18＇）. [Result] The application of COR significantly increased starch and antho- cyanin content in storage roots of Jishu18 across developmental stages by inducing the activities of PAL and AGPase, and finally enhanced yield by promoting fresh weight of storage roots. Ayamurasaki was insensitive to treatment with COR al- though its PAL activity temporally increased. The starch and anthocyanin content of Aya, and the anthocyanin content of Jishu18 increased progressively across devel- opmental stages with or without COR application, but the starch content of Jishu18 increased initially, then decreased before increasing again without application of COR. Treatment with COR reduced downward trend of starch accumulation in Jishu18. Thus, the effect of COR on accumulation of anthocyanin and starch in storage roots of PFS differs according to genotypes. [Conclusion] The application of 0.05 μmol/L COR may increase starch and anthocyanin content in PFS genotypes with lower starch and anthocyanin content in storage roots.     

Effect of Drought Stress During Flowering Stage on Starch Accumulation and Starch Synthesis Enzymes in Sorghum Grains

Starch content is a key factor affecting sorghum grain quality. The research of sorghum grain starch accumulation and the related synthesis enzyme activities has great signiifcance for understanding the mechanisms of starch metabolisms. The differences between a high and a low starch content sorghum hybrids （Tieza 17 and Liaoza 11, respectively） in grain starch accumulation and the related synthesis enzyme activities were assessed following imposition of water stress during lfowering stage. The total starch, amylase and amylopectin accumulation all decreased at the mid-late stage of grain iflling under drought stress during lfowering stage. The maximum and mean accumulation rates also decreased. During grain iflling, soluble starch synthase （SSS）, granule-bound starch synthase （GBSS）, starch branching enzyme （SBE）, and starch debranching enzymes （DBE） activities were all affected, though differently. Drought stress reduced starch accumulation in a larger extent for Tieza 17 than Liaoza 11. Drought stress during lfowing stage reduced starch synthesis enzyme activities, thus reducing starch accumulation in grains, and the differences between starch components were also demonstrated under drought stress.     

Variation of carbon partitioning in newly expanded maize leaves and plant adaptive growth under extended darkness

Plants must maintain a balance between their carbon(C) supply and utilization during the day–night cycle for continuous growth since C starvation often causes irreversible damage to crop production. It is not well known how C fixation and allocation in the leaves of crops such as maize adapt to sudden environmental changes. Here, to quantify primary C fixation and partitioning in photosynthetic maize leaves under extended darkness and to relate these factors to plant growth, maize seedlings were subjected to extended darkness(ED) for three successive days at the 6 th leaf fully expanded stage(V6). ED reduced plant growth and leaf chlorophyll levels but not the rate of net CO_2 exchange. As a result of the reduction in photoassimilates, the accumulation of starch and total soluble carbohydrates(TSC) in mature leaves also decreased under ED. However, the percentage of the daily C fixation reserved in mature leaves increased. These transient C pools were largely composed of TSC and were mainly used for consumption by increased nocturnal respiration rather than for transport. As the days went on, both the amount of C accumulated and the percentage of the daily fixed C that was reserved in leaves decreased, which could be largely accounted for by the attenuated starch synthesis in all treatments. The activities of ADPglucose pyrophosphorylase and soluble starch synthase decreased significantly over time. Therefore, this study concluded that both starch and TSC are involved in the coordination of the C supply and plant growth under a sudden C shortage but that they may be involved in different ways. While the ratio of reserved C to daily fixed C increased to maintain blade function under acute C starvation, both the amount and the proportion of C reserved in mature leaves decreased as plant growth continued in order to meet the growth demands of the plant.     

微胚乳玉米籽粒中淀粉积累规律的研究

[目的]研究微胚乳玉米籽粒中淀粉积累规律。[方法]以高油115玉米作为对照,对微胚乳玉米胚和非胚部位中淀粉的积累规律进行研究。[结果]微胚乳玉米胚部位的淀粉积累速度稍低于高油115,非胚部位的淀粉积累速度则远低于高油115,收获时高油115的淀粉百分含量达微胚乳玉米的3．4—4．5倍。高油115收获时的胚淀粉重比只有3％-4％,而微胚乳玉米中胚淀粉重比可达16％-22％。此外,不同微胚乳玉米材料淀粉积累速度不尽一致,收获时不同微胚乳玉米材料的淀粉含量也具有较大差异。[结论]微胚乳玉米籽粒中淀粉积累缓慢。     

微胚乳玉米籽粒中淀粉积累规律的研究

1材料与方法1．1材料微胚乳玉米ME558和ME5912为笔者所在的课题组组配的F1组合。高油115（Gaoyoul15）购于中国农大种子公司。1．2田间种植、取样和测定方法田间试验采用完全随机设计,2006年3-7月在广西大学农学院试验农场种植,姊妹交人工授粉。授粉后第7-42天取样,每隔7d采样1次。将授粉21d后的玉米籽粒的胚与非胚部位剥离,之后分别测定淀粉含量、水分含量。水分含量用烘干法测定。     

微胚乳玉米子粒中蛋白质积累规律的分析

以高油115玉米作为对照,对微胚乳玉米胚和非胚部位中蛋白质的积累规律进行了分析。结果表明,这两类玉米胚部位中的单粒蛋白质重均呈直线增长趋势;在非胚部位,高油115玉米非胚单粒蛋白质重没有消减现象,微胚乳玉米非胚单粒蛋白质重在授粉后28 d达到峰值,之后下降,但其非胚蛋白质质量分数则有明显增长。收获时微胚乳玉米整粒子粒的蛋白质质量分数可达20%,为高油115的2倍左右。     

微胚乳玉米非胚部位在籽粒发育过程中淀粉磷酸化酶活变化规律的研究

[目的]研究微胚乳玉米非胚部位在籽粒发育过程中淀粉磷酸化酶活的变化规律。[方法]以高油115玉米作为对照,对微胚乳玉米非胚部位中淀粉磷酸化酶活性的变化规律进行测定。[结果]微胚乳玉米非胚部位的淀粉磷酸化酶活性在授粉后21—28d达到峰值,其峰值极显著高于对照玉米高油115。不同微胚乳玉米材料间非胚部位的淀粉磷酸化酶活性峰值存在极显著差异。简单相关分析表明,在玉米籽粒发育期间,玉米非胚部位的淀粉磷酸化酶活性平均值或最大值均与单粒淀粉重呈极显著负相关关系。[结论]在微胚乳玉米非胚部位,较高的淀粉磷酸化酶活性水平使其淀粉降解迅速,最终导致其收获时积累的淀粉含量极显著低于高油115。     

微胚乳玉米籽粒发育过程中淀粉酶活性变化规律的研究

以高油115玉米作为对照，对微胚乳玉米籽粒中淀粉酶活性的变化规律进行了研究。结果表明，在玉米籽粒发育期间，微胚乳玉米和高油115胚部位单粒淀粉酶活性基本上随籽粒发育而呈增长趋势；不同微胚乳玉米材料非胚部位单粒淀粉酶活性的变化趋势未见有一致规律，高油115非胚部位淀粉酶活性主要呈现下降趋势；微胚乳玉米胚与非胚部位均未见其淀粉酶活性明显高于高油115。     

微胚乳超高油玉米籽粒胚乳消减及油分积累的规律

[目的]研究微胚乳超高油玉米籽粒胚乳消减和油分积累规律。[方法]以高油玉米115为对照,研究2种微胚乳超高油玉米籽粒的胚、胚乳、种皮及相应油分的积累规律。[结果]微胚乳超高油玉米在籽粒发育过程中胚乳干重在发育的第27 d达最大,第37 d消减基本结束;胚的重量一直增加,种子成熟时和胚乳的重量相当;整粒干重第32 d达最大。3个玉米品种授粉后的种皮干重一直增加,第32 d基本稳定,整粒油分37 d前一直增加,之后趋于稳定。微胚乳超高油玉米胚乳的油分在17~27 d增加较慢,27~37 d增加迅速,37 d到成熟期下降,比高油115的高很多;胚的油分在17~27 d增加,27 d到成熟期略下降。高油玉米115胚和胚乳的重量一直增加,胚乳的油分一直很低,胚的油分在17~27 d增加。[结论]该研究为微胚乳超高油玉米的籽粒胚乳消减机理研究提供了参考。     

微胚乳超高油玉米的研究进展

对微胚乳超高油玉米含油率与其农艺性状的相关性、显微结构、遗传育种模型和种质创新、生理生化与油分积累的变化规律、种子萌芽和N、K施用量的影响等方面进行了综述,并对微胚乳超高油玉米的研究前景进行了分析和展望。     

微胚乳玉米抗旱性研究

以普通玉米正大619和Y1为对照种,研究微胚乳玉米组合MEM1、MEM2、MEM3、MEM4叶片丙二醛含量、相对电导率、ASI和抗旱指数,对微胚乳玉米进行抗旱性鉴定。结果表明：在较肥土壤和瘠薄土壤里,由干旱胁迫引起的微胚乳玉米叶片丙二醛含量、ASI、相对电导率的变化规律与普通玉米一致。MEM1和MEM3在较肥土壤和瘠薄土壤里都表现出较好的抗旱性,综合抗旱性仅次于正大619。     

微胚乳超高油玉米籽粒可溶性总糖含量的动态研究

[目的]为微胚乳超高油玉米的改良及种质资源研究提供参考。[方法]以高油玉米115为对照,研究互为正反交的2种微胚乳超高油玉米籽粒的胚、非胚部位及整粒可溶性总糖含量的动态变化。[结果]微胚乳超高油玉米Ⅰ和对照的胚可溶性总糖单粒含量在授粉后49 d达到峰值,微胚乳超高油玉米Ⅱ则在授粉后42 d达到峰值。2种微胚乳超高油玉米非胚部位及整粒的可溶性总糖含量均在授粉后28 d达最高值。微胚乳超高油玉米Ⅰ非胚部位及整粒的可溶性总糖鲜重百分含量均在授粉后21 d出现较小峰值,49 d达到最大峰值。授粉后21～42 d,2种微胚乳超高油玉米的胚、非胚部位及整粒的可溶性总糖鲜重百分含量都高于对照,且微胚乳超高油玉米Ⅰ高于微胚乳超高油玉米Ⅱ。3种玉米籽粒生长发育的大部分时期非胚部位的可溶性总糖单粒含量高于胚。[结论]非胚部位可溶性总糖的动态变化在玉米籽粒发育过程中起决定性的作用。     

不同基因型玉米气孔数量及形态差异研究

[目的]研究不同基因型玉米的气孔数量及形态差异。[方法]以超甜玉米(华威6号)、爆裂玉米(特爆2号)、糯玉米(西星黄糯6号)、高油玉米(高油115)和普通玉米(郑单958)为材料,研究不同品种玉米穗位叶解剖结构的差异。[结果]不同基因型玉米上表皮及下表皮气孔的形态及数量均存在差异,不同基因型玉米的上表皮气孔数均小于下表皮气孔数。[结论]研究结果可为挖掘不同基因型玉米的产量潜力提供理论依据。