Rice caryopsis development I: Dynamic changes in different cell layers

Rice caryopsis as one of the most important food sources for humans has a complex structure that is composed of maternal tissues including the pericarp and testa and filial tissues including the endosperm and embryo. Although rice caryopsis studies have been conducted previously, a systematic characterization throughout the entire developmental process is still lacking. In this study, detailed morphological examinations of caryopses were made during the entire 30‐day developmental process. We observed some rapid changes in cell differentiation events and cataloged how cellular degeneration processes occurred in maternal tissues. The differentiations of tube cells and cross cells were achieved by 9 days after pollination (DAP). In the testa, the outer integument was degenerated by 3 DAP, while the outer layer of the inner integument degenerated by 7 DAP. In the nucellus, all tissues with the exception of the nucellar projection and the nucellar epidermis degenerated in the first 5 DAP. By 21 DAP, all maternal tissues, including vascular bundles, the nucellar projection and the nucellar epidermal cells were degenerated. In summary, this study provides a complete atlas of the dynamic changes in cell differentiation and degeneration for individual maternal cell layers of rice caryopsis.     

Evaluation of protocols used in 2-d electrophoresis for proteome analysis of young rice caryopsis

In order to obtain a high-resolution electrophorogram of rice young panicle proteome, we evaluated various protocols commonly used in two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE) of proteins, including gel staining protocol, pH range of immobilized pH gradient (IPG) strips and sample loading quantity. Results showed that a silver staining protocol using sensitized solution containing glacial acetic acid, sodium acetate and sodium thiosulfate (reported by Heukeshoven and Dernick in 1988) and a Coomassie Brilliant Blue staining method using solution containing G-250, ammonium sulfate and phosphoric acid (reported by Pink et al in 2010) demonstrated the superior staining effect. In addition, we also showed that higher resolution was achieved when IPG gel strip with pH range of 5-8 was used, compared to that with pH range of 4-7. Finally, the optimal loading quantity was determined as 130 μg using the 17 cm-long nonlinear IPG strip with pH 5-8 in combination with the silver nitrate staining protocol. The evaluated results would be helpful in proteome analysis of young rice caryopsis.     

Structural and histochemical studies on grain-filling in the caryopsis of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

The endosperm and embryo that constitute the filial tissues of rice caryopsis are isolated from the maternal tissues by the absence of any symplastic continuity. Nutrients are transported to the endosperm through a single ovular vascular trace present on the ventral side of the ovary. Initially solute enters through the chalaza into the nucellar projection and then into the endosperm. At later stages transport occurs through the nucellar epidermis, centripetally towards the endosperm. The cell walls of the nucellar epidermis are provided with rib-like thickenings. A comparison of grain-filling in C₃ and C₄ cereals suggests that rice has structural features allied to C₃ cereals, such as wheat, but with significant differences.     

水稻颖壳颜色的研究及进展

水稻是世界上一半以上人口的主食,对于我国乃至世界的粮食安全具有举足轻重的作用。颖壳是水稻的重要花器官结构,主要由内、外稃组成。目前最常见颖壳颜色为黄色,而黑色、金黄色、褐色等较为少见,研究表明这主要是由于类黄酮的积累不同导致的。通过分析水稻黑色颖壳性状的遗传机制,并以当前报道的两种异常颖壳(金黄壳、褐壳)突变体为对象,解析了相应颜色颖壳的呈色机理;阐述了类黄酮生物合成基因对颖壳颜色的影响,为剖析水稻颖壳的色素沉积模式提供理论参考;对有色稻壳的应用前景做了分析,为观赏稻的选育指明了方向。     

水稻红米的遗传分析与组织学研究

用来源于倍加单倍体的红米水稻（rdh）与无色米水稻做正反交,结果表明：杂种F1种子颜色由其所着生的母体植株基因型决定.当rdh作母本时,所结下的F1种子全是红色,当蜀恢527,蜀恢168,蜀恢368三个具有无色颖果皮（简称无色米）水稻作母本时,所结下的F1种子全是无色的.而且不管母本有没有颜色,所产生的F2种子都是红色,F3代产生红色种子与无色种子的单株分离,而且红色种子的单株对无色种子的单株是3：1（1%水平达极显著）,根据杂种F1、F2和F3代种子颜色和植株分离比例,rdh种子红色表现型是由单显性基因控制的,并受母性影响.组织学研究发现rdh颖果皮有3个基本的结构层：果皮、种皮和糊粉层.果皮是类黄酮色素累积的部位,红色色素就在果皮层累积.在未成熟的种子中,种皮是累积叶绿素的部位,在成熟种子中叶绿素消失.在未成熟的种子中,糊粉层白色.显微镜分析灌浆期的rdh种子不显红色,而显绿色,绿色来自于种皮,果皮无色透明.风干期的rdh种子显示：红色色素在果皮层累积,同期种皮的绿色清晰可见.rdh成熟种子红色色素急剧增加,同期绿色渐渐消失,最后肉眼观测不到.组织切片显示种子外皮中,果皮是最厚的一层,糊粉层次之,种皮最薄.果皮外层由4列较小的长方形细胞构成,里层由5～8列不规则的细胞构成.种皮由3列薄壁细胞构成.糊粉层由5～8列椭圆形细胞构成.色素累积的发育时间实验显示红色的沉积是从种子风干期开始到完全成熟期为止.在蜀恢527无色种子中,绿色色素从受精后开始积累,到风干期达到最深;然后绿色开始变浅,成熟种子中没有绿色.比较而言,rdh种子在发育早期,从灌浆到风干期呈现的颜色与蜀恢527相同,均是绿色;但从风干期开始,较多的红色色素开始累积,到种子接近成熟,红色仍在加深,这时种皮的绿色还隐约可见;直到种子完全成熟,红色达到最深,同时绿色渐渐消失.     

Genetic Analysis and Histological Study of Red Seed in Rice

Reciprocal crosses between red and achromatic rice revealed that the seed color of F₁ was determined by its female parent. According to the seed color and plant segregation ratio of F₁, F₂, and F₃ generations, the red phenotype of red double-haploid seed was determined by a dominant, monogene with maternal effect. Histological study showed that the red pigments accumulated in the pericarp layer only. The assay of developmental timing of pigment accumulation showed that the red color accumulated from desiccation stage to perfectly maturation stage of the seeds.     

Fluidized-bed steam gasification of rice hull

Steam gasification of grain by-products can be a significant biomass conversion technology because of the need to utilize agricultural waste for non-food applications including energy resources. The most obvious beneficiary will be the developing countries whose economies are often tied to agricultural produce and are lacking in conventional fuels. One agricultural by-product that shows promise is the rice hull; it is found in abundance in the rice mills of producer countries and is considered as a waste material. Although gasification of rice hull has been proposed as a potential waste disposal and energy recovery method, little has been done to fully realize this proposition. In the present work, data were obtained for steam gasification of rice hull in a bench-scale fluidized-bed gasifier, a technology which has proven to be feasible for other grain by-products. The produced gas, which is rich in hydrogen, has been found to have a heating value ranging between 12.1 and 11.1 MJ m⁻³ at the respective reactor temperatures of 700 and 800°C; energy recovery varies between 35 and 59%.     

Rice caryopsis development Ⅱ: Dynamic changes in the endosperm

The rice endosperm plays crucial roles in nourishing the embryo during embryogenesis and seed germination. Although previous studies have provided the general information about rice endosperm, a systematic investigation throughout the entire endosperm developmental process is still lacking. In this study, we examined in detail rice endosperm development on a daily basis throughout the 30‐day period of post‐fertilization development. We observed that coenocytic nuclear division occurred in the first 2 days after pollination (DAP), cellularization occurred between 3 and 5 DAP, differentiation of the aleurone and starchy endosperm occurred between 6 and 9 DAP, and accumulation of storage products occurred concurrently with the aleurone/starchy endosperm differentiation from 6 DAP onwards and was accomplished by 21 DAP. Changes in cytoplasmic membrane permeability, possibly caused by programmed cell death, were observed in the central region of the starchy endosperm at 8 DAP, and expanded to the whole starchy endosperm at 21 DAP when the aleurone is the only living component in the endosperm. Further, we observed that a distinct multi‐layered dorsal aleurone formed near the dorsal vascular bundle, while the single‐ or occasionally two‐cell layered aleurone was located in the lateral and ventral positions of endosperm. Our results provide in detail the dynamic changes in mitotic divisions, cellularization, cell differentiation, storage product accumulation, and programmed cell death that occur during rice endosperm development.     

Importance of the caryopsis in root growth and georeaction

Geocurvature of horizontally placed apical segments of maize (cv. INRA 258), the lateral curvature of half-decapitated segments in vertical position, and the curvatures of intact primary roots (horizontal or vertical) still attached to their caryopses were analysed in white light. The results may be explained in terms of the growth properties of certain endogenous regulators. The caryopsis could be the source of some precursors of growth inhibiting substances produced or released in the cap cells and also of growth activators. The relative effects of these factors – acting in the elongating zone of growing roots – clearly depend on the orientation of the caryopsis.     

施氮对水稻植株和颖果发育及稻米品质的影响

以'扬稻6号'和'粳稻941'为材料,在施氮总量相同条件下分别设置低分蘖肥高孕穗肥和高分蘖肥低孕穗肥2个施氮处理,通过盆栽试验研究施氮量和施氮时期对水稻植株生长、颖果发育和稻米品质的影响.结果表明:水稻植株鲜重、干重、分蘖数和株高随分蘖期氮肥用量增加而增加;增加孕穗期氮肥用量比例能显著提高抽穗期水稻剑叶和颖果光合速率、颖壳叶绿素含量、呼吸速率、颖果CAT及SOD活性;增加孕穗期氮肥用量还能提高水稻籽粒出糙率、精米率、整精米率,降低稻米垩白率,改善稻米的碾米品质和营养品质.因此,增加分蘖期施氮比例能促进水稻植株生长,而提高孕穗期施氮量则有利于水稻颖果发育和稻米品质改善.     

转反义Wx基因水稻颖果中与淀粉合成和积累相关酶活性的变化

将反义Wx基因转入水稻,导致Wx蛋白不同程度减少,颖果中的直链淀粉含量不同程度下降,总淀粉含量显著降低,直链淀粉与总淀粉的比值极显著降低。在水稻颖果发育过程中,ADPG-PPase、GBSS、SSS和SBE的活性在灌浆前期迅速升高,达最大值后很快下降,在灌浆中后期下降趋缓。Wx蛋白减少后的转基因水稻颖果中的GBSS活性明显下降,下降幅度与直链淀粉含量相一致,而且活性高峰期比其亲本有所提前。转基因水稻颖果中ADPG-PPase和SSS的活性在颖果发育的前中期,SBE则在中后期高于相应的亲本。     

粒重差异显著的两种水稻颖果发育比较

为了探讨控制水稻(Oryza sativa L.)颖果发育的因素,选择了颖果干重有显著差异的Ootikara(大粒,36mg/粒)和Habataki(小粒,18 mg/粒)两个水稻品种,比较颖果重量、胚乳细胞数、果皮和胚乳的结构以及某些生理活性等变化.结果指出:与Habataki相比,Ootikara子房壁细胞和颖果的持续生长期长,最终颖果的胚乳细胞数目和每个细胞的平均干重大;Ootikara颖果的脱氢酶和H2O2酶活性、穗的呼吸速率、剑叶的绿色程度和光合速率等维持高水平的时间长;Ootikara子房背部维管束失去功能的时间也较迟.结果表明,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.     

粒重差异显著的两种水稻颖果发育比较

为了探讨控制水稻(Oryza sativa L.)颖果发育的因素,选择了颖果干重有显著差异的Ootikara (大粒,36mg/粒)和Habataki (小粒,18 mg/粒)两个水稻品种,比较颖果重量、胚乳细胞数、果皮和胚乳的结构以及某些生理活性等变化。结果指出:与Habataki相比, Ootikara子房壁细胞和颖果的持续生长期长,最终颖果的胚乳细胞数目和每个细胞的平均干重大; Ootikara颖果的脱氢酶和H2O2酶活性、穗的呼吸速率、剑叶的绿色程度和光合速率等维持高水平的时间长;Ootikara子房背部维管束失去功能的时间也较迟。结果表明,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。     

Ethanol production from rice hull using Pichia stipitis and optimization of acid pretreatment and detoxification processes

The goal of this study was to produce ethanol from rice hull hydrolysates (RHHs) using Pichia stipitis strains and to optimize dilute acid hydrolysis and detoxification processes by response surface methodology (RSM). The optimized conditions were found as 127.14°C, solid:liquid ratio of 1:10.44 (w/v), acid ratio of 2.52% (w/v), and hydrolysis time of 22.01 min. At these conditions, the fermentable sugar concentration was 21.87 g/L. Additionally, the nondetoxified RHH at optimized conditions contained 865.2 mg/L phenolics, 24.06 g/L fermentable sugar, no hydroxymethylfurfural (HMF), 1.62 g/L acetate, 0.36 g/L lactate, 1.89 g/L glucose, and 13.49 g/L fructose + xylose. Furthermore, RHH was detoxified with various methods and the best procedures were found to be neutralization with CaO or charcoal treatment in terms of the reduction of inhibitory compounds as compared to nondetoxified RHH. After detoxification procedures, the content of hydrolysates consisted of 557.2 and 203.1 mg/L phenolics, 19.7 and 21.60 g/L fermentable sugar, no HMF, 0.98 and 1.39 g/L acetate, 0 and 0.04 g/L lactate, 1.13 and 1.03 g/L glucose, and 8.46 and 12.09 g/L fructose + xylose, respectively. Moreover, the base‐line mediums (control), and nondetoxified and detoxified hydrolysates were used to produce ethanol by using P. stipitis strains. The highest yields except that of base‐line mediums were achieved using neutralization (35.69 and 38.33% by P. stipitis ATCC 58784 and ATCC 58785, respectively) and charcoal (37.55% by P. stipitis ATCC 58785) detoxification methods. Results showed that the rice hull can be utilized as a good feedstock for ethanol production using P. stipitis. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:872–882, 2016     

沙埋对无芒雀麦种子萌发和幼苗生长的影响

研究了沙埋对浑善达克沙地植物群落中多年生禾草无芒雀麦种子萌发、出苗和幼苗生长的影响.结果表明:无芒雀麦种子能在深度≤12cm的沙埋中萌发,≤8cm的沙埋中出苗.在此范围内,随着沙埋深度的增加,无芒雀麦种子的萌发率和出苗率逐渐降低.沙埋深度在植株高度的33%时,无芒雀麦1周龄和2周龄幼苗均全部存活,且总生物量≥对照(未沙埋幼苗);当沙埋深度增至植株高度的66%时,1周龄和2周龄幼苗的存活率分别降至70%和25%,生长也受到抑制;而遭受全部沙埋时,1周龄和2周龄幼苗均不能存活.遭受沙埋后,无芒雀麦幼苗分配较多的生物量用于地上部分的生长,其生物量分配模式改变可能是无芒雀麦幼苗对沙埋环境的重要适应对策.     

Salinity intrusion and rice farming in the mangrove-fringed Konkoure River delta,Guinea

Field and model studies were undertaken of the hydrodynamics and salinity intrusion in the mangrove-fringed, 320km² Konkoure River delta, Guinea. The mangroves directly fringing the main channel of the Konkoure River are best flushed, while those mangroves draining smaller coastal streams are least flushed. Large seasonal and spatial variations of salinity exist in the delta. Hypersalinity and slow flushing (residence time 14–30 days) occur in the dry season in some areas of the delta. These areas appear unsuitable for rice farming and may be best managed on a sustainable basis for fishery and forestry resources.     

Effects of Rice Hull Particle Size and Content on the Mechanical Properties and Visual Appearance of Wood Plastic Composites Prepared from Poly(vinyl chloride)

This research aims to develop Wood Plastic Composites (WPCs) from rice hull and poly(vinyl chloride) (PVC). The influences of the rice hull particle size and content on the mechanical properties and the visual appearance of the WPC decking board were investigated. The experimental results revealed that the impact strength tended to decrease with increasing rice hull content. The composites with larger particle sizes exhibited higher impact strength. Under tensile and flexure load, higher rice hull content induced greater modulus and ultimate strength when the rice hull was applied at less than 60 phr. Beyond this concentration, the modulus and the strength dropped due to the formation of rice hull agglomerates. The smaller particles of the milled rice hull, the greater tendency there was for them to act as a pigment to form a darker shade close that of the rice hull on the composite decking board. The larger particle sizes were 106 μm and beyond simply embedded in the white PVC matrix.     

Possible involvement of the cytoskeleton in the regulation of barley caryopsis dormancy and germination

This study was conducted on barley cv. Ars. caryopses collected at full ripeness and divided into two batches. From one batch (dormant caryopses) polysomes were isolated from embryos immediately after harvesting and after two days of germination. From the other batch (non-dormant caryopses) the same was done after eight months storage in a dry state. A low ionic strength cytoskeleton-stabilizing buffer was used for the isolation of polysomes. Four different fractions of polysomes were examined: free polysomes (FP), membrane-bound polysomes (MBP), cytoskeleton-bound polysomes (CBP) and cytoskeleton-membrane-bound polysomes (CMBP). In germs grown from non-dormant caryopses, the first two fractions (FP + MBP) made up about 78 % of the total ribosomal material, whereas in embryos of dormant, imbibed caryopses, two last fractions (CBP + CMBP) made up about 71 %. The percentage of polysomes after 48 hours of imbibition of dormant caryopses in the FP, MBP and CBP was only about 13 % (i.e., 87 % monosomes), whereas a greater proportion (19.4 %) was found in the CMBP. The highest incorporation of ³H-uridine and ¹⁴C-amino acids (after 48 hours of germination and 0.5, 3 and 6 hrs incubation with precursors) took place in trhc CMBP both in dormant and non-dormant caryopses The major amount of the two polysome fractions associated with the cytoskeleton (CBP and CMBP) and the higher activity of CMBP in protein synthesis in embryos of dormant, imbibed triticale caryopses may indicate a significant role for polysomes associated with the cytoskeleton in the control of protein synthesis in dormant and germinating caryopses.     

浅谈农田生态与水稻病虫害之关系

湖南素以“鱼米之乡”著称。全省拥有耕地面积3.47×10~6ha,1986年水稻播种面积4.33×10~6ha,总产2.6316×10~(10)kg。水稻各个生育时期都有病虫发生。现就影响病虫种群结构的几项主要生态因素分述如下。