Studies On Nutritional, Physiological And Ecological Characteristics Of Super Rice Under Different Water Managements

Super rice (Oryza sativa L.) was proposed as a new breeding objective in 1996, after breeding for dwarfs and the others, using hybrid heterosis. The researches were conducted in the experimental station of China National Rice Research Institute (30° 05' N, 119°56' E) during 2002-2004. Using the typical super rice varieties in the field and experimental tanks, a series of research were conducted to study the effects on yield, leaf area, leaf photosynthesis, stomatal conductance, specific leaf weight, non-structural carbohydrate (NSC), oxidation-reduction potential (ORP), and nitrogen accumulation, remobilization and partitioning under various water managements.Research on the relationship between the NSC of the culm and sheath in relation to the panicle characteristics of super rice showed that the higher the NSC of the culm and sheath at flowering stage and the lower at mature stage, the higher the seed setting rate was. The higher the average of every kernel NSC at flowering stage, the higher 1000-grain weight was. Research on the relationship between specific leaf weight (SLW) and photosynthetic rate of super rice at panicle initiation stage showed that there was significant difference between the SLW and photosynthetic rate under the various densities. The linear and positive relationship between the SLW and photosynthetic rate was observed from the same variety.Research on effect of shallow water depth with wetting and drying (SWD) irrigation on photosynthesis and grain yield in super rice was conducted to determine whether SWD could influence leaf photosynthesis of rice plants under field conditions. Experiments using SWD irrigation were carried out at three transplanting densities (7.5, 13.5 and 19.5 plants/m2) with or without the addition of organic manure. A significant increase in single-leaf net photosynthetic rate by SWD was observed with portable photosynthesis systems in all three independent experiments. The effect of SWD on photosynthesis was greater in zero-manure than in 15000 kg manure ha'1 treatment. The increase in photosynthetic rate by SWD was 11.2% averaged across all treatments in three experiments. The effect of SWD on stomatal conductance was smaller and less consistent than on photosynthetic rate. SWD significantly increased SLW in both varieties used. SWD with the density of 13.5 plants/m2 significantly increased the leaf area index and dry matter weight. SWD with all three densities also increased the leaf N content, with the highest of 15.1% and 22.8% in two cultivars respectively, compared with the conventional control. Grain yield was significantly increased by SWD, and a 10% average increase in grain yield by SWD was observed. SWD with 13.5 plants/m2 had the highest grain yield in both genotypes with or without 15000kg manure ha-1 treatment. The increase in grain yield was due to an increase in total biomass production rather than harvest index. These results suggest that SWD can promote rice growth and yield through mechanisms that improve single-leaf net photosynthetic rate.Research on nitrogen accumulation, remobilization and partitioning of super rice under different irrigation methods showed: The amount of N partitioned to the grain relative to total aboveground N at maturity, remobilized N and leaf N content at 20 days after flowering (DAF) of the traditional irrigation (TRI) was lower than that of the SWD. The difference in total N accumulated between TRI and SWD was apparent at flowering. During grain-filling period, the SWD accumulated significantly more N than the TRI. Grain N content is the sum of the N accumulated during the GFP and the N remobilized to the grain during panicle development. Calculated values for remobilized N together with values of N accumulated during the GFP agreed fairly well with grain N content. There were consistent differences between SWD and TRI for the amount of N remobilized from vegetative tissue to grain. There were also significant differences between SWD and TRI in their ability to accumulate N during the GFP. A comparison of the correlation...