Yield and growth characteristics of erect panicle type rice (Oryza sativa L.) cultivar,Shennong265 under various crop management practices in Western Japan

Erect panicle rice cultivars utilize solar energy effectively and have improved ecological growing conditions. Among such cultivars, Shennong265 has been grown successfully throughout Northern China. Nevertheless, no studies have yet examined the relationships between crop dry matter productivity, weather conditions, and nitrogen uptake of the erect panicle type rice cultivar in Japan. The objective of our study was to evaluate the productivity of erect panicle rice Shennong265 in Western Japan under varied conditions. Three rice cultivars, Shennong265, Nipponbare, and Takanari were grown in the field under different fertilizer and plant density conditions in Western Japan; using this information, we compared yield and growth characteristics of Shennong265 with those of Nipponbare and Takanari. Although Shennong265 had radiation use efficiency similar to that of the high yielding cultivar (Takanari) and much higher leaf nitrogen content than Takanari and Nipponbare, the average grain yield of Shennong265 grown under normal fertilizer and plant density conditions was approximately 6.9 t ha^?1 as against 6.2 t ha^?1 for Nipponbare and 9.6 t ha^?1 for Takanari. These results suggest that, while Shennong265 has a high yield potential, the environmental conditions including climate, fertilizer, and planting period provided in this study were not suitable for achieving its maximum yield. The reduced performance of Shennong265 may be caused by insufficient fertilizer after heading and by shorter growth periods, as well as by the climate of Western Japan. Additional fertilizer application during the heading stage and earlier transplanting may be needed to obtain higher Shennong265 yields in Western Japan.     

盐粳228群体特征及对氮的响应

2010年对盐粳228进行氮肥试验,研究该品种高产群体特征及对氮的响应。结果表明:该品种抽穗后干物质积累占籽粒产量的71%~81%,茎叶的表观转运率少,容易获得高产。该品种抽穗期适宜的叶面积指数(LAI)为7.0~7.5,叶色呈"三黑三黄"节奏变化,后期生长速率(CGR)高,收获指数(HI)介于0.8~1.1之间。氮肥的适量施用(330kgN.hm-2)不仅可以保证叶色"三黑三黄"节奏变化,建立抽穗期适宜LAI的群体,还可以保持高产株型特征,提高抽穗后期的LAI、叶面积维持期、CGR和HI,最终实现高产。     

超高产水稻的干物质生产特性研究

 以我国近年育成的超高产水稻品种为材料, 在福建龙海和云南涛源研究分析了超高产水稻品种的高产生理特性。结果表明超高产水稻品种积累了高额的生物量。 稻谷产量随干物质积累总量的增加而提高，产量主要取决于生物产量的高低，而收获指数对稻谷产量的贡献较小。超高产水稻干物质生产优势在中期和后期，产量随中期和后期干物质净积累量的增加而提高。中期和后期的群体生长率(CGR)与产量呈高度正相关，而前期CGR与产量的关系不密切。茎叶干物质输出量构成籽粒产量平均为24％（福建龙海）和33％（云南涛源），茎叶干物质输出量和抽穗后干物质积累量均与稻谷产量呈极显著正相关。在同一地点，对干物质积累的作用，CGR显著大于生长日数。     

N applications that increase plant N during panicle development are highly effective in increasing spikelet number in rice

Efficient use of nitrogen fertilizer is critical in improving yield stability in rice. The objective of this study was to determine the effect of nitrogen (N) top-dressing on the number of total spikelet (fertile plus sterile) production and evaluate the effect among rice cultivars. We analyzed 136 sets of experimental data on growth and spikelet production for three lowland cultivars, grown under various regimes of N over 10 seasons at Kyoto, Ibaraki and Kanagawa, Japan. In each season, one to three of the lowland cultivars, Nipponbare (japonica), Koshihikari (japonica) and Takanari (indica), were studied. In 1986, 1995 and 1999-2001, the N regimes included basal application only, light basal and heavy top-dressing from the panicle initiation stage onward, heavy basal and heavy top-dressing from the spikelet formation stage onward, and no applications. In 2002 and 2005-2008, we set up experimental plots with varied time of N top-dressing, with or without N basal application. Takanari had the largest spikelet number averaged over all plots and was considered better efficient in spikelet production per applied N than the other cultivars. Although the trend is not clear, the effect of time of top-dressing on spikelet number was generally the greatest when N was top-dressed from 35 to 30 days before heading. The variation of observed spikelet number was analyzed with a linear regression of plant N 14 days before heading and by a model that estimates spikelet production accounting for plant N 14 days before heading and crop growth rate (CGR) during the 14-day period preceding heading. For the variation of spikelet number within each cultivar, the linear function model expressed the observed spikelet number than the two function model with R² 0.43** versus 0.13*-0.28** for the former and later models, respectively. When the results of all cultivars were combined, the two function model was much better for estimation of spikelet number than the linear function model (R² = 0.36** vs. 0.20*). This indicates that yearly and varietal variation of spikelet number was caused mainly by plant N status at the late spikelet differentiation stage. The varietal variation in spikelet production efficiency is explained by CGR during this 14-day period. We concluded that N applications that increase plant N 14 days before heading is highly effective in maximizing spikelet production among cultivars.     

Effects of Dry Matter Production,Translocation of Nonstructural Carbohydrates and Nitrogen Application on Grain Filling in Rice Cultivar Takanari,a Cultivar Bearing a Large Number of Spikelets

Abstract

The effects of dry matter production and the remobilization of nonstructural carbohydrates (NSC) on grain filling were investigated using the Indica-based Japonica crossed rice cultivar Takanari, which can bear a large sink. For three years,beginning in 1994, shade treatments were conducted with different nitrogen applications to develop large variations in plant growth. The percentage of ripened spikelets showed the greatest correlation with the total amount of carbohydrate supply per spikelet during 10 to 20 days after heading, calculated by adding the amount of dry matter increase to the amount ofNSC decrease in leaf sheaths and culms during the period. Between the two components, the dry matter increase was more important. The NSC reserve played a role in compensating for the shortage of carbohydrate supply from assimilates after heading and showed a tendency to increase the percentage of ripened spikelets when dry matter production after heading was limited. However, the maximum ratio of compensatory translocation from the NSC reserve was estimated to be only 48%, becauseofsmaller reservoir size compared with the demand. The NSC reserve at heading was not significantly increased by increasing the dry matter production before heading. It was concluded that to increase grain filling ability it is more effective to increase the dry matter production after heading than that before heading. Nitrogen application showed negative effectson the translocation of reserve NSC. It is important to optimize the nitrogen content to maximize the total source of carbohydrate supply.     

Effects of Soil Moisture Depletion for One Month before Flowering on Dry Matter Production and Ecophysiological Characteristics of Wheat Plants in Wet Soil during Grain Filling

Abstract

The period from mid-March to April in the wheat-growing season in Japan corresponds to a wet period known as “Natanezuyu”. After this wet period, the weather remains rather dry until June. Fluctuations in soil moisture conditions during the growing season might be expected to affect the growth of wheat. Therefore, we compared the grain yield, dry matter production and ecophysiological characteristics of wheat grown with adequate moisture during the ripening stage after it had been grown under adequate (W-plot) or deficient (D-plot) soil moisture conditions for about one month before heading. The grain yield in the D-plot was higher by about 15 to 40% than that in the W-plot, with greater dry matter production. The larger dry weight in the D-plot resulted from a higher rate of crop growth before and after heading, which was due to a larger leaf area and higher net assimilation rate. During the ripening stage, leaf senescence of plants was delayed and the rate of photosynthesis fell more slowly in the D-plot than in the W-plot. Root systems developed better, resistance to water transport from root to leaves was lower, the exudation rate of roots was higher, and the cytokinin activity in xylem exudates from roots was higher in the D-plot. These characteristics of roots might have caused the significant difference in the growth and physiology of the aboveground parts of the plants. Our results indicate that encouragement of the development of the root systems, for example, by drainage during the wet period might be important for improving the grain yield of wheat in Japan.     

种植方式对水稻和陆稻氮素吸收利用的影响

 以武香粳99-8（水稻）和中旱3号（陆稻）为材料，研究了种植方式对水稻和陆稻生育后期N素吸收利用的影响。与水种稻（对照）相比，中旱3号覆膜旱种时产量显著低于对照，武香粳99-8覆膜旱种时和对照没有显著差异，裸地旱种产量均为最低。覆膜旱种和裸地旱种抽穗期植株的含N率较低，抽穗至成熟期植株含N率下降速率为水种＞裸地旱种＞覆膜旱种。抽穗和成熟期植株吸N量大小为水种＞覆膜旱种＞裸地旱种。旱种稻成熟期茎鞘中的N素分配显著高于对照，籽粒显著低于对照，品种间叶片有所不同。抽穗期旱种稻的N素物质生产效率显著高于对照。成熟期覆膜旱种N素物质生产效率最低。旱种稻N素籽粒生产效率（中旱3号覆膜旱种除外）和N素收获指数较对照增加，大小为裸地旱种＞覆膜旱种＞水种。与武香粳99-8相比，中旱3号抽穗后植株含N率下降快，植株N素积累量较小，叶片和籽粒中N素分配比例高，茎鞘低；N素物质生产效率（成熟期）、N素籽粒生产效率和N素收获指数高，产量低。     

Differences in lamina joint anatomy cause cultivar differences in leaf inclination angle of rice

ABSTRACT

Leaf erectness is an important agronomic trait for improving canopy photosynthesis in rice. It is well known that leaf inclination angle (LIA) decreases after expansion during ripening. However, the high-yielding indica cultivar ‘Takanari’ retains a greater LIA during ripening than the high-quality japonica cultivar ‘Koshihikari’. To clarify the cause of the cultivar difference in LIA, we investigated anatomical characteristics of the lamina joint of a flag leaf. We found a close linear correlation between LIA at the centre and at the base of the leaf blade in both cultivars during ripening. The length of the lamina joint increased significantly more on the adaxial side of a leaf (the margin of the collar) than on the abaxial side (the abaxial side of the central part of the collar) in ‘Koshihikari’ after leaf expansion, but there was no clear difference in ‘Takanari’. We found a close linear correlation between the ratio of lamina joint length on the adaxial to abaxial sides and LIA in ‘Koshihikari’ and ‘Takanari’ during ripening. In ‘Koshihikari’, the average length of cells on the adaxial side increased significantly after leaf expansion, with no significant increase in that on the abaxial side and no significant change in cell number on either side. In ‘Takanari’, cell length and cell number showed no significant changes on either side of the lamina joint. We conclude that the cultivar difference in LIA during ripening is caused mainly by cell elongation on the adaxial side of the lamina joint.

List of Abbreviations: k: light extinction coefficient; LIA: leaf inclination angle; QTL: quantitative trait locus     

Effects of Flag Leaves and Panicles on Light Interception and Canopy Photosynthesis in High-Yielding Rice Cultivars

Abstract

The effects of flag leaves and panicles on canopy photosynthesis in a leading cultivar (Nipponbare) and two high-yielding rice cultivars (Takanari and Ghugoku 117) bred in Japan were compared. The total dry matter production was in the order of Takanari > Ghugoku 117 > Nipponbare. Canopy photosynthesis was highest in Takanari throughout the growth season, and was higher in Chugoku 117 than in Nipponbare during the ripening period. The photosynthetic rate in the flag leaf was in the order of Nipponbare > Takanari > Chugoku 117. The light extinction coefficient of canopy was higher in Takanari than in the others. At the middle ripening stage, canopy photosynthesis increased 35 and 17% in Nipponbare and Takanari, respectively, by the removal of panicles and decreased 37 and 48%, respectively, by the removal of flag leaves. In Chugoku 117, canopy photosynthesis was hardly influenced by these treatments. Clearly, the panicles intercept more radiation at the upper layer of the canopy in Nipponbare than in Takanari and flag leaves contribute more to canopy photosynthesis in Takanari than in Nipponbare. However, these effects were small in Chugoku 117. In conclusion, Takanari produces more dry matter than the others due to larger, wider, longer and more erect 1st (flag) and 2nd leaves above the panicles, which intercept more radiation. Chugoku 117 had erect panicles which allowed more radiation to penetrate into the deeper layer of the canopy, resulting in a high dry matter production. The lower panicle height relative to leaf layer and erect panicles are important characteristics for higher yield in rice.     

播后镇压和冬前灌溉对冬小麦干物质转移和氮素利用效率的影响

为明确播后镇压和冬前灌溉对高产冬小麦干物质和氮素转移及氮素利用效率的影响,以冬小麦品种石新828和石麦12为材料,采用裂区田间试验,于开花期和成熟期,测定不同器官的干物质和氮积累量和转移量、籽粒产量、蛋白质产量、氮吸收效率和氮肥生产效率。结果表明,冬灌和镇压处理下,2个品种开花期和成熟期的干物质积累量下降,开花前各营养器官干物质的转移量、转移率及对籽粒的贡献率均降低,但开花后籽粒中的干物质积累量增加。冬灌处理小麦成熟期的总干物质积累量和产量下降。冬灌处理下,石新828开花后籽粒中的氮积累量增加,开花后氮素对籽粒的贡献率提高,但各器官的氮转移量显著降低,籽粒氮积累总量显著减少,氮吸收效率下降;冬灌对石麦12成熟期籽粒氮素积累量影响不显著。与不镇压相比,镇压处理下,2个品种开花期的氮积累总量和不同器官中的氮积累量均降低,而成熟期各器官氮积累量及分配比例的差异均不显著。镇压处理与不镇压处理相比,2个品种开花前营养器官中的氮转移量、转移率和贡献率均降低,但是开花后的氮积累量及其对籽粒氮的贡献率提高,其中,镇压的石麦12开花前氮转移量、贡献率和开花后氮积累量、贡献率与不镇压的差异达显著水平;成熟期籽粒氮素积累量的差异不显著。建议在足墒播种条件下不必进行冬灌,应根据播种前后土壤和水分条件确定是否需要镇压。     

Effects of Soil Moisture Conditions before Heading on Growth of Wheat Plants under Drought Conditions in the Ripening Stage: Insufficient Soil Moisture Conditions before Heading Render Wheat Plants More Resistant to Drought during Ripening

Abstract

Plants growing on soil with insufficient moisture need deep and dense roots to avoid water stress. In crop plants, the production of dry matter during ripening of grains is critically important for grain yield. We postulated that shoot growth would be suppressed but root growth would continue under an insufficient soil moisture condition before heading, while shoot growth would be more vigorous than root growth under a sufficient soil moisture condition. We anticipated that the plants growing under an insufficient soil moisture condition before heading would produce more dry matter and grain under an insufficient soil moisture condition during ripening. In order to examine our hypotheses and to determine the fundamental conditions for improving grain yield and efficient use of irrigated water under limited irrigation, we grew wheat plants (Triticum aestivum L., cv. Ayahikari) in pots (30 cm in diameter, 150 cm in height) with insufficient soil moisture (PD-D pots) or sufficient soil moisture (PW-D pots) for six weeks before heading followed by full irrigation, and then insufficient soil moisture condition during ripening. The growth of shoots was suppressed significantly but that of roots was not before heading in PD-D plants, with a higher resultant ratio of root to shoot than in PW-D plants. The former retained a high leaf water potential and, therefore, were able to produce more dry matter and grain during soil moisture depletion during ripening as compared with the latter plants. We also obtained similar results with field-grown plants.     

氮高效玉米杂交种的筛选及氮效率相关特性分析

选用生产中常用的8个玉米杂交种作为材料,在高氮和低氮条件下进行氮高效杂交种的筛选和氮高效指标研究。主成分分析结果表明,郑单958、金山27、郑单17为氮高效品种。通径分析表明,吸收效率对氮效率的贡献均大于利用效率,不论是否施氮,植株氮积累均以花前为主,但花后差异显著,花前氮积累对氮效率的贡献较大。不论施氮与否,完熟期全株干重、吐丝期穗三叶含氮量、花前氮积累量、穗位叶光合速率均是重要的筛选指标,不施氮肥时子粒含氮量也是重要的筛选指标。     

不同氮利用率粳稻品种的碳氮积累与转运特征及其生理机制

【目的】探明不同氮利用率水稻品种的氮素积累与转运特征及其机制。【方法】2个氮高效品种(武运粳30号和连粳7号)和2个氮低效品种(扬粳4038和宁粳1号)种植于大田,设置2个施氮量：全生育期不施氮(0 N)和全生育期施氮180 kg/hm² (180N),比较分析了不同氮利用率粳稻品种干物质生产、氮素积累与转运差异及其机制。【结果】与氮低效品种相比,氮高效品种具有较高的产量、氮肥利用率、总颖花量和结实率,较高的花前干物质转运量和花后干物质积累量,分蘖至穗分化始期和抽穗至成熟期较高的净同化率和作物生长率,抽穗期较高的糖花比,灌浆期较高的籽粒库活性、籽粒中脱落酸与1-氨基环丙烷-1-羧酸含量的比值和茎鞘中较高的非结构性碳水化合物的转运和蔗糖合成相关酶活性以及蔗糖转运蛋白基因的表达量,抽穗后较高的氮转运、氮素吸收量,灌浆期较高的比叶氮含量、叶片中细胞分裂素含量、氮代谢酶活性以及氮素转运相关基因的表达量。【结论】氮高效品种穗分化前和抽穗后较高的物质生产效率以及灌浆期较高的碳氮转运与积累是产量和氮肥利用率协同提高的重要机制。     

Contribution of Nitrogen Absorbed during Ripening Period to Grain Filling in a High-Yielding Rice Variety,Takanari

Absract

High-yielding rice varieties require a large accumulation of N in panicles. The objectives of this study were to clarify the change in N allocation during the ripening period (Exp. 1) and to quantify the contribution of N absorbed during the ripening period to panicle N at maturity (Exp. 2) in the high-yielding variety Takanari in comparison with that in Nipponbare as a control. In Exp. 1, ¹⁵N-labeled N (¹⁵N) was applied at heading to investigate the distribution of newly absorbed N as well as the allocation of plant N. In Exp. 2, split ¹⁵N application was performed during the filling period to estimate the above contribution. In Exp. 1, the allocation of plant N and absorbed ¹⁵N to the panicles was larger and that to the leaves was smaller in Takanari than in Nipponbare during the ripening period, although Takanari accumulated more N at maturity. The difference in N allocation suggested that the difference in N demand in panicles would be larger than that in N uptake. In Exp. 2, the varietal difference in the grain filling duration was observed: Nipponbare accumulated little N in the panicles after 28 d after heading (DAH), while Takanari accumulated about a quarter of its panicle N during that time. An estimate showed that in Takanari, 13.5% of the panicle N was derived from N absorbed after 28 DAH. These results suggest that the utilization of newly absorbed N until a later period after heading is important for the achievement of high yields.     

Comparison of dry matter production and associated characteristics between direct-sown and transplanted rice plants in a submerged paddy field and relationships to planting patterns

In a previous study, we demonstrated that rice plants, broadcast in a submerged paddy field, had a high grain yield that was due to the production of a greater weight of dry matter, as compared with conventionally transplanted plants, when lodging did not occur. In the present study, we examined possible causes of the greater production of dry matter by plants broadcast in a submerged paddy field by comparing the characteristics of plants subjected to different methods of cultivation [the direct-sown plants (DSP) and transplanted plants (TP)] and with different planting patterns (51.3 hills m⁻² and one plant per hill, namely, planting pattern I; and 17.5 hills m⁻² and three plants per hill, namely, planting pattern III). The dry weight of aboveground parts at harvest and the grain yield were larger for DSP than for TP when we compared plants with the same planting pattern, and they were larger for plants in planting pattern I than for those in pattern III when we compared plants with the same cultivation method. Differences in grain yield reflected differences in dry matter production. The factors responsible for the differences in dry matter production among plants depended on the growth stage. At the tillering stage, the number of tillers and, therefore, the leaf area index (LAI) increased rapidly and the interception of solar radiation by the canopy was larger in the DSP than in the TP, irrespective of the planting pattern. These factors were related to the higher crop growth rate (CGR) in the DSP than the TP. After the panicle formation stage, when the canopy closed completely and the interception of solar radiation exceeded 90%, the canopy consisted of more erect leaves and the extinction coefficient of the canopy was smaller for plants in planting pattern I than for those in pattern III, irrespective of the cultivation method. These features were responsible for the larger CGR of plants in planting pattern I than in pattern III. The plants in planting pattern I produced a larger number of crown roots than those in pattern III. During the ripening stage, the decrease in exudation rate was smaller, the amount of nitrogen accumulated was larger, and levels of chlorophyll and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) remained higher in the former plants than in the latter, irrespective of the cultivation method. These characteristics might also contribute to the elevated production of dry matter by the plants in planting pattern I.     

水稻品种的耐低磷性及其农艺生理性状

【目的】 本研究旨在探明水稻耐低磷性的评价指标和耐低磷品种的农艺生理特征。【方法】以11个江苏省近70年来的代表性粳稻品种作为材料,进行水培种植,设置低磷(标准营养液中磷浓度的1/20)处理,以正常磷浓度(国际水稻研究所标准营养液配方)为对照。【结果】 耐低磷指数(低磷产量×耐低磷系数/所有供试品种低磷处理的平均产量)、干物质指数(低磷干物质量/对照干物质量)与耐低磷系数(低磷产量/对照产量)及低磷处理下的产量呈显著或极显著正相关。将耐低磷指数和干物质指数作为评价水稻品种耐低磷性的指标。根据两指标值的大小将供试品种分成3类：强耐低磷品种,耐低磷指数和干物质指数均≥1;中耐低磷品种,耐低磷指数和干物质指数均>0.6, 耐低磷指数或干物质指数<1;弱耐低磷品种或低磷敏感型品种,耐低磷指数或干物质指数≤0.6。与弱耐低磷品种相比,强耐低磷品种在低磷处理下具有根量大、根系活力强,分蘖早期分蘖数多,总叶面积指数(LAI)和高效LAI大、有效LAI比例高,库容量大,抽穗期茎鞘中糖积累量多,抽穗至成熟期物质生产能力强等特征。与对照相比,低磷处理增加了磷素产谷利用率(稻谷产量/磷吸收量)和磷收获指数(籽粒中磷/成熟期植株中总吸收的磷)。在低磷下的磷素产谷利用率,强耐低磷品种高于弱耐低磷品种。【结论】 耐低磷指数和干物质指数可以作为耐低磷品种的筛选指标;在低磷处理下,根量大、分蘖早期分蘖数多、库容量大、抽穗至成熟期物质生产能力强是耐低磷性强和磷利用效率高水稻品种的重要农艺生理特征。     

The effect of planting pattern on the rate of photosynthesis and related processes during ripening in rice plants

Rice plants (Oryza sativa L.) planted in such a manner that each hill contains one plant (pattern I) produce more dry matter than plants planted such that each hill contains three plants (pattern III), particularly during the ripening stage. As one of the causal factors of the difference in dry matter production, the rate of photosynthesis and related physiological processes were investigated in direct-sown rice plants cultivated in a submerged paddy field after heading. The rate of photosynthesis was similar at full heading for plants from patterns I and III. When the rate of photosynthesis decreased during the period of ripening, plants from pattern I maintained higher rates of leaf photosynthesis than plants from pattern III. This was primarily related to the maintenance of higher leaf photosynthetic activity in pattern I plants. Plants from pattern I maintained higher leaf levels of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and nitrogen during the ripening stage than plants from pattern III. Close liner relationships were observed between the levels of Rubisco and the rate of photosynthesis as well as between the levels of nitrogen and Rubisco.Nitrogen accumulation in aboveground parts and partitioning of nitrogen to leaves maintained significantly higher levels during the ripening stage in plants from pattern I than plants from pattern III. This resulted in the higher leaf levels of nitrogen in pattern I plants during the ripening stage. Plants from pattern I had a significantly greater number of crown roots and root length densities, and maintained relatively higher cytokinin fluxes from roots to shoot during the ripening stage than plants from pattern III. The free cytokinin, trans-zeatin was responsible for the larger total flux for the cytokinins in pattern I plants. These root characteristics may also contribute to the maintenance of the higher levels of Rubisco and nitrogen in leaves in plants from pattern I.     

氮肥后移对玉米冠层内物质分配及氮素利用的影响

研究不同施氮量、不同施肥时期对玉米产量与氮素利用的影响,对玉米干物质生产、氮素积累与分配进行分析。结果表明,施氮量为180 kg/hm2时,产量表现为基施处理最高,较拔节期、大喇叭口期施肥处理分别提高1.17%、7.69%;施氮量为75 kg/hm2时,拔节期施肥处理产量最高,较基施、大喇叭口期施肥处理分别提高10.31%、4.61%。大喇叭口期施肥处理的干物质积累与氮素积累量少,氮肥利用效率低,说明氮肥后移需考虑植株前期对氮素的需要。拔节期施肥处理产量与基施处理产量和氮素积累量相当或提高,植株干物质积累增加,冠层内茎叶干物质比例协调,生育后期穗下层茎叶干物重下降缓慢,氮素利用效率高。施氮量为75 kg/hm2,氮肥适当后移可提高氮肥利用率。     

培肥方式对陇中旱农区玉米光合特性和产量的影响

依托2012年设在陇中旱农区的田间定位试验,设置单施化肥(CF)、有机肥+化肥(SC)、单施有机肥(SM)、单施玉米秸秆(MS)和不施肥对照(NA)5个处理,研究培肥方式对全膜双垄沟播玉米叶绿素含量(SPAD)、光合特性、叶面积指数、干物质积累和产量的影响。结果表明,单施化肥和有机肥化肥配施显著增强了玉米光合作用,4种培肥方式均增加了玉米叶片叶绿素含量和叶面积指数,CF、SC、SM和MS处理较NA分别增加了74.6%和80.0%、64.5%和74.0%、18.9%和28.9%、12.9%和25.8%。在各生育时期,CF和SC处理干物质积累量显著高于NA处理。CF和SC处理显著提高了玉米产量,子粒产量较NA分别增加了148.7%和119.1%,生物产量较NA分别增加了118.4%和105.0%。在陇中旱农区应用全膜双垄沟播技术种植玉米,化肥单施和有机肥配施化肥均可通过增加叶片叶绿素含量和叶面积指数改善光合作用,从而提高玉米产量。要维持玉米产量的可持续提高,有机肥化肥配施更加适宜。     

Varietal Differences in Photosynthetic Rates in Rice Plants,with Special Reference to the Nitrogen Content of Leaves

Abstract

The photosynthetic rate in the fl ag leaf of rice at the full heading stage was examined in three japonica varieties, Koshihikari, Aikoku and Asanohikari, and the indica high-yielding variety Takanari at the same level of leaf nitrogen. At an ambient CO₂ concentration of 350 µL L-₁, Takanari had a higher photosynthetic rate and stomatal conductance than the japonica varieties when plants were compared at a leaf nitrogen content of approximately 1.5 g m-₂. Stomatal conductance increased considerably with increases in leaf nitrogen content in the japonica varieties. As a result, at a leaf nitrogen content of approximately 2.0 g m-₂, differences in terms of the photosynthetic rate among varieties were small. By contrast, there were no clear varietal differences in Rubisco content at any identical nitrogen content of leaves. We conclude that stomatal conductance is responsible for the varietal differences in photosynthetic rate examined at the same leaf nitrogen content.