Uptake and metabolism of isouron in rice (Oryza sativa L.) seedlings

Summary Isouron, a pre-emergence herbicide, inhibited the growth of rice seedlings in a nutrient solution; the critical concentration was about 0.10 mg l^-1. Isotope studies showed that isouron, added to the nutrient solution, was observed by the rice roots and translocated rapidly to the shoot. In rice seedlings, isouron was converted to six known metabolites, 3-(5-(1-dimethyl-2-hydroxy-ethy)-3-isoxazolyl]urea, 3-(5-tert-butyl-3-isoxazolyl)-1-methylurea, 3-(5-tert-butyl-3-isoxazolyl)ure, 3-amino-5-tert-butylisoxazole, 3-[5-(1,1-dimethyl-2-hydroxyethyl)-3-isoxazolyl]-1-dimethylurea, and 3-[5-(1,1-dimethyl-2-hydroxyethyl)-3-isoxazolyl]-1-methylurea, and two unknown metabolites.     

Heat shocks increase the chilling tolerance of rice (Oryza sativa) seedling radicles

The growth of rice (Oryza sativa L., cv. M202) seedling radicles, initially 10 +/- 1 mm long, was linear for the 96 h it took them to grow to 150 mm at 25 degrees C. Exposure to 5 degrees C for 24 h reduced the rate of growth by about 50%, and longer exposures caused a progressive reduction in growth. Initial radicle length significantly affected chilling sensitivity: with 2 days at 5 degrees C inhibiting growth at 25 degrees C by 23% for 1-mm radicles, 63% for 10-mm radicles, and 87% for 40-mm radicles. Heat shocks of 35 degrees C for 4 min, 40 degrees C for 3 min, 45 degrees C for 2 min, or 50 degrees C for 1 min, prior to chilling, reduced the 75% inhibition of radicle growth caused by 2 days at 5 degrees C to 34%, 25%, 14%, and 13%, respectively. The length of exposure that conferred chilling tolerance increased from less than 2 min for 50 degrees C to over 8 min for 35 degrees C. This increase in effective treatment duration was accompanied by a reduction in the maximum induced chilling tolerance. Practical application of heat-shock treatments to increase the chilling tolerance of rice seedlings may sacrifice a small reduction in maximum chilling tolerance at the lower inductive temperatures for a larger margin of safety in their application.     

Morphological and molecular evaluation of Turkish rice (Oryza sativa L.) landraces

Genetic Resources and Crop Evolution - This study was carried out to evaluate Turkish rice landraces, in 2016 and 2017. Twenty-nine morphological traits were used for morphological evolution and 10...     

水稻产量形成的生理生态研究进展

水稻产量形态规律是水稻育种和栽培的基础理论，已成为作物学研究的热点课题。从产量构成、光合生产和源库结构方面简介了水稻产量形成规律的生理生态研究进展，分析了3个方面的研究特点和构成产量形成过程的网络关系。同时水稻产量形成是一个动态过程，水稻产量性状的最终表现决定于其生长发育过程中众多基因的表达、调控和相互作用，提出应用现代发育遗传学与分子生态学的理论和方法，深入研究水稻产量的形成规律。     

Crop growth and nitrogen transformations in wheat (Triticum aestivum L.) planted after wetland rice (Oryza sativa L.)

Summary A field study was undertaken to examine the effects of various management strategies on wheat (Triticum aestivum L.) performance and N cycling in an intensively cropped soil. Microplots receiving 100 kg N ha^–1 as¹⁵NH₄ ^{+ 15}NO₃ ^– at sowing, tillering or stem elongation were compared with unfertilized microplots. Stubble from the previous rice crop was either incorporated, burnt without tillage, burnt then tilled or retained on the surface of untilled soil. Wheat grain yield ranged from 1.5 to 5.1 t ha^– and was closely related to N uptake. Plant accumulation of soil N averaged 36 kg N ha^–1 (LSD 5% = 10) on stubble-incorporation plots and 54 kg N ha^–1 on stubble-retention plots. Fertilizer N accumulation averaged 18 kg N ha^–1 (LSD 51% = 6) on stubble-incorporation plots and 50 kg N ha^–1 on stubble-retention plots. Tillage had little effect on burnt plots. Delaying N application from sowing until stem elongation increased average fertilizer N uptake from 26 to 39 kg N ha^–1 (LSD 5% = 6), but reduced soil N uptake from 50 to 37 kg N ha^– (LSD 5% = 10).Immobilization and leaching did not vary greatly between treatments and approximately one-third of the fertilizer was immobilized. Less than 1% of the fertilizer was found below a depth of 300 mm. Incorporating 9 t ha^–1 of rice stubble 13 days before wheat sowing reduced net apparent mineralization of native soil N from 37 to 3 kg ha^–1 between tillering and maturity. It also increased apparent denitrification of fertilizer N from an average 34 to 53 kg N ha^–1 (LSD 5% = 6). N loss occurred over several months, suggesting that denitrification was maintained by continued release of metabolizable carbohydrate from the decaying rice stubble. The results demonstrate that no-till systems increase crop yield and use of both fertilizer and soil N in intensive rice-based rotations.     

Asymmetric warming effects on N dynamics and productivity in rice (Oryza sativa L.)

Climate warming exhibits strong diurnal variations, with higher warming rates being observed at nighttime, which significantly affects rice (Oryza sativa L.) growth and grain yield. The objective of this study was to determine the effects of asymmetric warming (all-day warming, AW; daytime warming from 07:00 to 19:00, DW; nighttime warming from 19:00 to 07:00, NW, and a control, CK) on rice nitrogen (N) dynamics and productivity. Two rice bucket warming experiments were performed in Nanjing in Jiangsu Province, China, using the free air temperature increase (FATI) technique. The daily mean temperatures in the rice canopy in the AW, DW and NW plots were 2.0, 1.1 and 1.3ºC higher than those in the rice canopy in the CK plots, respectively. The results indicated that the total N accumulation of rice was 8.27–40.53% higher in the warming treatment than in the control during the jointing, anthesis and maturity stages. However, there was no significant difference detected among the three warming treatments. The warming treatment substantially decreased N translocation efficiency, leading to the retention of more N in the plant stems during grain filling. The warming treatment also decreased the N harvest index, N utilization efficiency based on grain yield and N utilization efficiencies based on biomass in both growing seasons. The warming treatment significantly increased the aboveground biomass (9.26–16.18%) in the jointing stage but decreased it (2.75–9.63%) in the maturity stage. Although DW increased the carbon (C) gain by photosynthesis and NW increased the C loss by night respiration, the daytime higher-temperature treatment affected rice photosynthesis and reduced its photosynthetic rate and product. This effect may be one of the primary reasons for the insignificant difference in the aboveground biomass between the DW and NW treatments. In the AW, DW and NW plots, the grain yield was reduced by an average of 10.07, 5.05 and 7.89%, respectively, across both years. The effective panicles and grains per spike tended to decrease in the warmed plots, whereas irregular changes in the 1000-grain weight were observed. Our results suggest that under the anticipated climate warming, rice productivity would further decline in the Yangtze River Basin.     

Selection of efficient vesicular-arbuscular mycorrhizal fungi for wetland rice (Oryza sativa L.)

Summary We tested the response of the wetland rice cultivar Prakash to inoculation with ten vescular-arbucular mycorrhizal (VAM) fungi (three selected from the first screening and seven isolated from local paddy fields) in a pot experiment under flooded conditions in order to select the most efficient mycorrhizal fungi to inoculate the rice nursery. A sandy clay loam soil was used as the substrate, fertilized with the recommended N and K levels (100 kg N ha^–1 as ammonium sulphate and 50 kg K ha^–1 as muriate of potash) and half the recommended level of P (25 kg ha^–1 as super phosphate). The inoculation was made into dry nursery beds and the beds were flooded when the seedlings were about 25 cm high, in 15 days. Twenty-eight-day old seedlings were transferred to pots filled with well puddled soil flooded with 5 cm of standing water. Based on the increase in grain yield and total biomass, Glomus intraradices and Acaulospora sp. were considered efficient and suitable for inoculation into rice nurseries.     

Establishment of Azorhizobium caulinodans in the rhizosphere of wetland rice (Oryza sativa L.)

 Azorhizobium caulinodans strongly colonized the rhizosphere of rice plants after incorporation of Sesbania rostrata in a field trial throughout the growing season and during the fallow period until 19 weeks after incorporation of S. rostrata. A. caulinodans became well established in the rhizosphere (7.17 log cfu g^–1 dry rice root) and colonized subsequent S. rostrata test plants. Three traditional and three improved high-yielding rice varieties were inoculated with A. caulinodans under gnotobiotic conditions. In none of the combinations did acetylene reduction activity significantly increase. Ethylene production on colonized rice roots only started after the growth medium had been supplemented with an extra C source (0.1 to 0.25% Na-lactate). This indicates that the bacterial nitrogenase activity is limited by energy supply. Four possible inoculant-carriers (peat, coir dust, bagasse, rice straw) were compared for long-term survival of the bacterial strain. Independent of the storage temperature (26  °C or 4  °C), the survival of A. caulinodans in peat and coir dust was very high during a 12-month period (>8 log cfu g^–1 dry carrier), whereas the bagasse and rice straw carriers showed a serious decline from 3 months onwards. Received: 6 April 1999     

水稻雄蕊导管发育研究

本文以水稻粤泰保持系为材料，采用ATPase定位方法研究了单核至三核花粉期雄蕊导管的发育。单核边位花粉期，分化的导管胞质变浓厚、细胞核染色质浓缩、核转变为新月形并出现凋亡小体；此外，导管内物质也可以大分子形式直接撤离。单核边位晚期，雄蕊导管发育成熟。在二核和三核花粉期，导管内重新出现具有ATPase活性的物质，同样的现象也存在于农垦58s可育花药成熟导管中。以上结果暗示水稻雄蕊导管分化存在程序性死亡及非程序性死亡多种途径，水稻成熟导管内具有ATPase活性物质可能是一种普遍现象。     

Fate of Azolla spp. and urea nitrogen applied to wetland rice (Oryza sativa L.)

Summary Using ¹⁵N, the fate of N applied to wetland rice either as Azolla or urea was studied in a field at the International Rice Research Institute (IRRI). In bigger plots nearby, yield response and N uptake were also determined with unlabelled N sources. Azolla microphylla was labelled by repeated application of labelled ammonium sulfate. Labelled and unlabelled N were used alternately in applications of Azolla or urea 0 and 42 days after transplanting, in order to determine the effect of the time of application on the availability of Azolla N. The quantities of Azolla N incorporated were 23% more than those of urea N (30 kg N ha^–1) in the isotope plots or 7% less in the yield response plots. Grain yield and total N uptake by the rice plants in the yield-response plots were higher in the urea-treated plots than in the Azolla-treated plots, but the physiological effect of Azolla N (grain yield response/increase in N uptake) was higher than that of rea. The labelled N balance was studied after the first and second crops of rice. Losses of labelled N after the first crop were higher from urea (30%–32%) than from Azolla (0%–11 %). Losses in N applied as a side dressing 42 days after transplanting were less than those of N applied basally. No further losses of ¹⁵N occurred after the first crop. The recovery of Azolla ¹⁵N in the first crop of rice was 39% from the basal application and 63% from the side dressing. The recovery of urea ¹⁵N was 27% from the basal application and 48% from the side dressing. Recoveries of residual N from both Azolla and urea during the second rice crop were similar. Laboratory incubation of the Azolla used and the changes in labelled exchangeable N in the soil showed that at least 65% of Azolla N (4.7% N content) was mineralized within 10 days.     

锌铬复合污染对水稻根系抗氧化酶活性的影响

为了研究水稻在金属复合污染条件下的适应过程,该文就成都平原两种常见的重金属污染元素(锌、铬)对土壤复合处理后,进行水稻盆栽试验.结果表明,锌铬复合污染条件下,在水稻不同生育期,水稻根系3种抗氧化酶(SOD,POD和CAT)活性随锌、铬浓度的增加而表现出不同的变化趋势.在水稻分蘖期,随铬浓度的增加,水稻根系SOD活性和POD活性呈先降后升的变化趋势;随锌浓度的增加,水稻根系SOD活性和POD活性呈升高的趋势;而水稻根系CAT活性则随锌、铬浓度的增加呈一定的降低趋势.在水稻孕穗期,随锌、铬浓度的增加,水稻根系SOD活性呈先降后升的变化趋势,POD活性及CAT活性则呈降低的趋势.在水稻灌浆结实期,水稻根系SOD、POD及CAT活性均呈一定的降低趋势.水稻籽粒产量随锌、铬浓度的增加呈降低的趋势.锌、铬浓度对水稻籽粒产量产生了复合效应,并与水稻籽粒产量有极显著的线性回归关系.这表明水稻通过调节自身的生理代谢能提高对锌铬复合污染的生态适应性,这能为培育适合重金属污染地区生长的水稻品种提供理论基础.     

Increased zinc supply does not inhibit cadmium accumulation by rice (Oryza sativa L.)

Rice (Oryza sativa L.) grown on cadmium (Cd)-contaminated soils has caused health problems in Asian subsistence rice farmers. For other crops, normal co-contaminant zinc (Zn) inhibits the increased uptake of Cd. We used a multi-chelator-buffered nutrient solution to characterize the interaction of Zn and Cd in uptake-translocation of Cd in “Lemont” rice. The activity of free Zn²⁺ varied from 10^?7.6 to 10^?5.2 M, while free Cd²⁺ held constant at 10^?10.7 M. Zinc activity 10^?5.6 M and higher was phytotoxic to rice, resulting in severe chlorosis, reduced growth, and increased Cd transport to shoots. In contrast to previous studies with wheat, lettuce, and spinach, free Zn²⁺ maintained at adequate to sub-phytotoxic levels (10^?7.6 to 10^?6.1) did not inhibit Cd uptake by rice. The inability of Zn to inhibit Cd uptake by rice is a key factor in Cd risk from zinc-lead mine waste contaminated soil compared with other crops.     

UV-B辐射增强对水稻多胺含量及其相关酶活性的影响

试验研究表明,处理前期(7～14d)UV-B辐射增强使“汕优63”水稻精氨酸脱羧酶(ADC)、鸟氨酸脱羧酶(ODC)和S-腺苷蛋氨酸脱羧酶(SAMDC)活性分别增加165.74％、104.60％和89.60％,“南川”(NC)运3种酶活性分别增加59.91％、41.30％和23.68％,新品系“IR_(65600-85)”在UV-B辐射胁迫下多胺脱羧酶活性表现与前2品种略不同,即ADC和ODC活性分别提高115.93％、14.45％,而SAMDC活性下降33.01％。处理后期(21～28d)随UV-B辐射累积量的增加,这3种酶活性均有所下降,其中ODC和SAMDC活性降幅大于ADC,其中“汕优63”ADC、和ODC活性分别比对照增加89.72％、3.71％,“南川”则分别增加73.95％、27.38％,“IR_(65600-85)”ADC活性增加94.41％,ODC、活性却下降13.57％。处理后期(21～28d)3类水稻“汕优63”、“南川”和“IR_(65600-85)”SAMDC分别下降40.06％、19.20％和38.21％。多胺氧化酶(PAO)活性变化趋势则相反,即处理前期(7～14d)呈不同程度下降趋势,处理后期(21～28d)则呈极显著上升趋势,其结果引起多胺(PA)含量特别是腐胺(Put)含量明显上升。水稻对UV-B辐射增强的反应具有基因型差异。     

Alkylperoxyl radical scavenging activity of red leaf lettuce (Lactuca sativa L.) phenolics

Although lettuce may provide relatively low levels of antioxidative phytochemicals which may contribute to human health, lettuce leaf extracts in fact contained compounds with high specific peroxyl radical scavenging activities. After determining the extraction conditions that minimized phenolic oxidation and produced the highest oxygen radical absorbance capacity (ORAC) values, the phenolic compounds from red leaf lettuce were separated by reverse-phase high-performance liquid chromatography (HPLC). The primary phenolic compounds in the leaf tissue extracts were mono- and dicaffeoyltartaric acid (CTA and DCTA), mono- and dicaffeoylquinic acid (CQA and DCQA), quercetin 3-malonylglucoside (QMG), quercetin 3-glucoside (QG), cyanidin 3-malonylglucoside (CMG), and an unknown phenolic ester (UPE). Significant levels of DCQA were only found after wounding. Using the new fluorescein-based ORAC assay procedures, fractions from the HPLC analyses were assayed for peroxyl radical absorbance capacity. Using absorbance to estimate concentration, the decreasing order of contribution to the total ORAC value of an extract from wounded tissue was QMG > DCQA > CMG > DCTA > UPE > QG > CTA. The decreasing order of the specific peroxyl radical scavenging activities was CMG > QG > DCTA > DCQA > QMG > UPE > CQA > CTA. Since the concentrations of plant flavonoid and phenolic acid esters are sensitive to environmental factors, this information may be used to develop pre- and postharvest conditions which increase the dietary benefits of leaf lettuce.     

不同类型水稻籽粒灌浆的生理生化特性研究

以3个较大穗型的不同类型水稻品种(组合)“IR_(65600-85)”、“培矮64S/E32”、“Ⅱ优86”为材料,试验研究水稻籽粒灌浆特性及其有关生理生化活性变化结果表明,3个水稻的强势粒起始生长势均高于弱势粒,从而更早进入灌浆盛期;ADPG焦磷酸化酶活性强势粒高峰值均出现在花后6d,弱势粒峰值出现在花后12d;淀粉合成酶活性强势粒在花后0～18d高于弱势粒,尔后弱势粒高于强势拉,但“IR_(65600-85)”弱势粒后期活性仅弱高于强势粒,造成3个水稻的弱势粒灌浆不如强势粒,尤其是“IR_(65600-85)”弱势粒生理生化活性更低,其籽粒充实最差,结实率也最低。     

Influence of vesicular-arbuscular mycorrhizal fungi (Glomus etunicatum L.) on mobilization of zinc in wetland rice (Oryza sativa L.)

In a greenhouse trial, rice (Oryza sativa L.) cultivar Pusa Basmati-1 was grown in a Zn-deficient Typic Ustochrept soil from IARI farm, New Delhi, India. The experimental design included two rates of inoculation with vesicular-arbuscular mycorrhizal fungi (VAMF), Glomus etunicatum (nil and inoculated) and different combinations of organic (farmyard manure, FYM) and inorganic (NPK, ZnSO₄) fertilizers. The results revealed that a high intensity of root colonization in rice inoculated with G. etunicatum could be achieved by raising seedlings in P- and Zn-deficient soil in the nursery under aerobic conditions. Moreover, the VAMF that infected rice seedlings in the nursery also survived when the same seedlings were transplanted into pots under waterlogged conditions. The application of ZnSO₄ significantly increased the inflow of Zn to rice roots at the panicle-initiation stage (40 days after transplanting) relative to NPK. The former treatment also increased root length, root weight, root volume and total uptake of Zn and thereby increased the grain and dry matter yields. Alternatively, these variables were substantially enhanced by inoculating rice with the VAMF, G. etunicatum. The VAMF-colonized rice plants were more active in acquiring Zn from either added or native sources than non-colonized plants, and consequently the available-Zn content in soil was lower after the harvest of rice.     

Cytosolic glutamine synthetase is present in the phloem sap of rice (Oryza sativa L.)

The presence of glutamine synthetase (GS) in the rice sieve tube was examined. Proteins in the rice phloem sap from leaf sheaths were separated by sodium dodecylsulfate–polyacrylamide gel electrophoresis, transferred to polyvinylidine difluoride membranes and immunoblotted with anti-GS1 antibody. A cross-reacting band, thought to be GS1, was detected in the phloem sap. Moreover, the phloem sap contained a significant amount of GS transferase activity. Previous studies have shown that the concentrations of substrates and cofactors in the rice phloem sap are sufficient for cytosolic GS reaction. These data suggest that physiologically active GS1 is present in rice phloem sap, which might convert glutamate to glutamine in vivo .