Observation and isolation of the amyloplasts ribosomes in cotyledon cells of lotus

Ribosome-like particles have been found in the proplastids in young cotyledon cells of lotus (%Nelumbo nucifera Gaertn% L.). Following the development of young embryo, some lamellar structures and tubular complex occurred in the plastids in young cotyledon cells, and some ribosome-like particles appeared in the loose region of these membrane system and stroma. About 15- 20 d after fertilization, with the further development of plastid, a large number of starch and DNA were synthesized in the plastids, and the plastids contained abundant and clear morphologically ribosomes, some of which presented spiral structure. About 16-18 d after fertilization, amyloplasts were isolated and purified from cotyledon of lotus, and ribosomes bands were obtained by use of sucrose density gradient centrifugation of ribosomes isolated from amyloplasts. RNA and protein contents of ribosomes have also been determined.

Caryopsis Development and Main Quality Characteristics in Different indica Rice Varieties

A comparison on the caryopsis development, rice quality characteristics and the size, shape, structure of the endosperm amyloplasts （starch granules） between two indica rice varieties was made, The main quality traits in Yangdao 6 were better than those in Xiangzaoxian 33; In the early period after fertilization the dry matter in Yangdao 6 was accumulated more slowly than that in Xiangzaoxian 33 but faster in the later period, and the starch was accumulated strongly in the later period; There were two kinds of amyloplasts： single and compound amyloplasts, being 4.4 um and 9.5 um in diameter on average with the range of 2.4-8.0 um and 5.7-19.5 um, respectively. In the case of Xiangzaoxian 33, most of the single amyloplasts were elliptic or round with loose arrangement and great difference in size, and the coefficient of variation was high. While in the Yangdao 6, most of the amyloplasts were single, well developed, polyhedral, crystalline and compactly arranged, and the coefficient of variation was low. The amyloplasts in the dorsal region of endosperm were developed better than those in the ventral and central regions. The chalkiness in the endosperm resulted from badly-developed and loose-arranged starch granules, which was closely relevant to the transport of filling materials.

Effects of Nitrogen Application Time on Caryopsis Development and Grain Quality of Rice Variety Yangdao 6

A pot experiment was conducted to study the effects of different nitrogen application time （during the tillering or the booting stages） with the same nitrogen rates on the caryopsis development and grain quality of rice variety Yangdao 6. The increased nitrogen fertilizer （urea）, especially applied during the booting stage, could evidently increase the milled rice rate, head rice rate and protein content in rice grains compared with the control （no nitrogen application）, and decrease chalky grain rate and amylose content. Moreover, the increased nitrogen fertilizer significantly affected the caryopsis development and enhanced the grain weight when nitrogen applied during the tillering and the booting stages, especially during the booting stage. During caryopsis development the increased nitrogen fertilizer applied during the tillering and booting stages could obviously decrease the total starch and amylose contents, but not obviously for the amylopectin content in rice grain. Increased topdressing of nitrogen fertilizer, especially applied during the booting stage, had significant effect on the development and structures of amyloplasts and proteinoplasts. That is, it could change the distribution, number and shape of amyloplasts and proteinoplasts in the endosperm cells especially in grain abdomen, Compared with the control the arrangements of amyloplasts and proteinoplasts were closer, with more numbers, higher density and less interspaces each ohter. Furthermore, most amyloplasts showed polyhedron under the increased nitrogen fertilizer level.

Preliminary study on a gravity－insensitive rice mutant

A gravity-insensitive mutant was isolated from rice (Oryza sativa L. cv. Zhonghua 11) transformed by Agrobacterium tumefaciens. The mutant's shoot growth (prostrate growth) was insensitive to gravity; whereas root growth displayed a normal positive gravitropism. Histological observation of root caps and leaf sheaths indicated that there was no significant difference in the number and size of amyloplasts in cells of the mutant and cells of the wild type.

Relationships of Ethylene Evolution Rate and 1-Aminocylopropane-1-Carboxylic Acid Concentration in Grains during Filling Period with Appearance Quality of Rice

To elucidate the relationship between ethylene evolution from the grains and the appearance quality of rice, ten different rice genotypes were used to determine the ethylene evolution rate, 1-aminocylopropane-1-carboxylic acid （ACC） concentration in grains during grain filling and the appearance quality of rice, and the effects of chemical regulators on concentrations of ethylene and ACC in the grains during grain filling were also investigated to verify the roles of ethylene in the rice quality formation. The ethylene evolution rates and ACC concentrations in grains during the mid and late grain filling stages were very significantly and positively correlated with chalky kernel percentage and chalkiness. The cultivars with a low ACC concentration in grains exhibited a close amyloplast arrangement and small space between starch granules, whereas those with a high ACC concentration in grains showed a loose arrangement and wide space between the granules. Application of 1 μmol/L ACC to panicles at mid and late grain filling stages significantly loosened amyloplast arrangement and increased chalky kernel percentage, chalky area and chalkiness, and the results were reversed when 1 μmol/L amino-ethoxyvinylglycine, an inhibitor of ACC synthesis enzyme, was applied to panicles. A practice of moderate dry-wet alternate irrigation reduced ethylene evolution and ACC concentration in grains and thereby reduced chalkiness. The results suggested that ethylene and ACC in grains play an important role in the endosperm structure and appearance quality of rice, and the appearance quality would be improved by reducing ethylene evolution and ACC in grains through either variety breeding and selection, or chemical regulations or cultivation techniques.

Accumulation of glycolipids in wheat grain and their role in hardness during grain development

Grain hardness is an important parameter for wheat quality. To understand the role of glycolipids in the formation of grain hardness, the glycolipid contents in wholegrain wheat flour and the starch granule surfaces of oven-dried and freeze-dried hard and soft wheat grain were analyzed. Changes in endosperm structure and amyloplast membrane integrity during grain development were also examined by electron microscopy. The monogalactosyldigylcerol(MGDG) and digalactosyldigylcerol(DGDG) contents of the starch surface were significantly higher in soft wheat than in hard wheat, regardless of the drying method or developmental stage. Throughout grain development, MGDG content was significantly higher in the starch surface of freeze-dried hard wheat than in the starch surface of oven-dried hard wheat. In contrast, the MGDG content of the starch surface was significantly higher in freeze-dried soft grain at 14 and 35 days after anthesis. No significant difference was observed in puroindoline protein(PIN) accumulation in wholegrain flour from wheat that was dried using the two methods, whereas PIN accumulation on the starch surface of freeze-dried grain was lower than that on the starch surface of oven-dried grain.The gap between the amyloplast membrane and starch granules was larger in hard wheat than in soft wheat, as shown by transmission electron microscopy. For the same wheat cultivar, this gap was larger for oven-dried than for freeze-dried grain. The content of polar lipids in the starch surface was closely related to grain hardness, and the breakdown of the amyloplast membrane may determine the location of polar lipids on the starch surface.