Relationship between Dry Weight at Heading and the Number ofSpikelets on Individual Rice Tillers

Abstract

The objectives of this study were to identify the growth parameters involved in determining the number of spikelets on an individual tiller (ST) and to elucidate how ST is determined in rice (Oryza sativa L.). We examined the correlation of ST with the dry weight (DWT), leaf area (LAT), and the amount of nitrogen (NT) at heading for individual tillers grown under different conditions that were expected to affect spikelet production. In 1999, the japonica rice cultivars “Mineasahi” (short-duration), “Hinohikari” (intermediate-duration), and “Akebono” (long-duration) were transplanted in a paddy field on two different dates (EARLY and LATE). In 2000, Hinohikari was grown under three different treatments (gibberellic acid application, nitrogen topdressing, and thinning of hills at panicle initiation) and without treatment (control). Covariance and partial correlation analyses indicated that ST was positively and essentially correlated with DWT rather than with LAT and NT. The regression of ST on DWT was stable within each cultivar regardless of the treatment, year, tiller order, and number of differentiated spikelets. The slope of the regression was the steepest in the short-duration cultivar. These results suggest that the steep slope is desirable for high-yielding cultivars with large panicles. We conclude that ST is mostly determined by dry matter production of an individual tiller regardless of the number of differentiated spikelets. We present a diagram showing the relationship between dry matter production and the number of differentiated, surviving, and degenerated spikelets on an individual tiller.     

小麦茎顶端原基发育模拟模型的研究

本文系统地模拟了小麦植株茎顶端不同类型原基的发育过程，建立了叶原基分化、小穗原基分化和小花原基分化、退化、败育、受精结实及籽粒生长的子模型。模型引入每小穗分化的最大小花原基数、退化的最大小花原基数和籽粒潜在重量3个遗传参数，分别反映了不同小麦品种小花分化、退化和籽粒生长等方面的遗传差异。利用南京地区     

利用小穗培养克服小麦与玉米杂种的幼胚败育

本研究的结果表明,小穗培养是克服小麦与玉米杂种幼胚败育的一个有效手段。让小麦与玉米的杂交穗在植株上生长14～16天时,获得杂种幼胚的频率仅为0.2％,而在授粉后2天采用小穗培养,则使获得杂种幼胚的频率提高到4.2％,获得杂种幼胚的效率提高21倍。     

不同激素培养基对小麦×玉米杂种幼胚发育的影响

本研究结果表明，采用２，４－Ｄ浸穗法结合低浓度激素培养进行小穗培养，可以明显改善小麦和玉米杂交种颖果、幼胚及胚乳的发育状况，得胚率由２．１％提高到１２．０％；同时表明低浓度激素对杂种发育有着明显的调节作用，但２，４－Ｄ和ＧＡ优于ＫＴ。     

水稻籽粒受容活性及其控制 Ⅳ.汕优63不同部位籽粒的结实能力

1988～1991年,在群体水培条件下,采用大穗型中籼杂交稻汕优63,设计不同生育期氮、磷处理21个,改变结实期灌浆物质的供应水平,研究稻穗上、中、下部一、二次枝梗籽粒的结实能力。结果表明:在灌浆物质供应水平较低时,不同部位籽粒的结实率、千粒重大小与开花早迟顺序一致,随着灌浆物质供应水平的提高,迟开颖花的结实率、千粒重可超过先开颖花,一、二次枝梗籽粒表现有类似趋势,证明迟开颖花的生理劣势可以转变;提高颖花根活量能明显提高稻穗不同部位籽粒的结实率和千粒重,挺高幅度一、二次枝梗籽粒均表现为下部>中部>上部,当颖花根活量达到一定程度时,迟开颖花的千粒重将高于先开颖花。     

Agronomic Performance of F1 Hybrids of Rice (Oryza sativa L.) in Japonica-Indica Crosses

Summary

Generally F₁ hybrids from crosses between japonica and indica rice show variable degrees of sterility. Previous studies revealed that among the indica rice, the Aus type has sexual affinity with japonica cultivars giving higher fertility in F₁ hybrids. Therefore, we made an effort to obtain higher grain yield by producing F₁ hybrids between japonica and Aus-type indica. A field experiment was conducted to investigate the heterosis in these F₁ hybrids for dry matter accumulation, spikelet fertility, yield and yield attributes, to find cross combinations with higher grain yield, and examined the relationships of grain yield with some agronomic characters. F₁ hybrids flowered earlier than their parent cultivars. Heterosis for dry matter accumulation was positive at the panicle initiation stage, at heading and at maturity. The average heterosis for number of panicles, grain and straw yield per plant, number of spikelets per panicle and 1000-grain weight was positive. A few F₁ hybrids showed positive heterosis for number of filled grains per panicle, spikelet fertility and harvest index; but the average heterosis for these traits was negative. Among the yield components, a higher number of panicles per plant and higher number of spikelet per panicle contributed to higher grain yield in F₁ hybrids. A significant and positive relationship existed between spikelet fertility and grain yield per plant. The higher grain yield was attributed to higher dry matter production rather than higher harvest index in F₁ hybrids, although low spikelet fertility limited yield potential in some F₁ hybrids.     

Proteins and Carbohydrates in Developing Rice Panicles with Different Numbers of Spikelets: —Cultivar difference and the effect of nitrogen topdressing—

Abstract

Proteins and carbohydrates in developing rice panicles were analyzed to see whether these parameters control spikelet number in rice. Two rice cultivars and 2 levels of nitrogen topdressing were used to obtain panicles with different numbers of spikelets. A japonica rice cultivar, Nipponbare, with topdressing (H) had 1.8 times more spikelets per panicle than that without topdressing (L). Moreover, the number of spikelets per panicle in an indica rice cultivar, Takanari, without topdressing was 2.7 times larger than that in Nipponbare-L. Panicles with more spikelets (LP) in Nipponbare-H and Takanari-L showed slower growth than those with few spikelets (SP) in Nippanbare-L in an early stage. LP, however, increased markedly in size thereafter, eventually exceeding SP, in length and fresh weight. Soluble protein content was higher in LP than SP in an early stage, but this difference was hardly detected in a late stage. No clear difference was observed in sugars or starch between LP and SP. Analysis of soluble and insoluble proteins by SDS-polyacrylamide gel electrophoresis showed that bands corresponding to insoluble proteins with a molecular weight about 42 kDa were present at higher intensities in LP than in SP. These results suggest that the spikelet number in rice is controlled by the soluble protein content in an early stage and insoluble proteins with a molecular weight of 42 kDa during panicle development, but not by the carbohydrates in developing panicles.     

高CO2浓度和剪叶疏花对水稻‘Y两优2号’ 产量形成的影响

利用稻田FACE(Free Air CO_2 Enrichment)平台,以创造世界高产纪录的超级稻组合‘Y两优2号’为试验材料,CO_2处理设环境CO_2浓度[(382.5±2.0)μmol·mol-1]和高CO_2浓度(增200μmol·mol-1)两个水平,齐穗期源库改变设对照、剪除剑叶(剪1叶)、剪除所有功能叶(剪3叶)以及相间剪除一次枝梗(疏花),研究开放条件下高CO_2浓度对不同源库处理水稻产量及其构成因子的影响。结果表明,对没有进行剪叶疏花处理的水稻(即对照)而言,高CO_2浓度使‘Y两优2号’籽粒产量平均增加12%,这主要与每穗颖花数和结实能力均略有增加有关。高CO_2浓度使剪1叶、剪3叶处理水稻的产量分别增加26%和57%,这主要与饱粒率和所有籽粒平均粒重均大幅增加有关。对齐穗期疏花处理水稻而言,高CO_2浓度导致的产量增幅与对照水稻接近。与对照相比,齐穗期剪1叶、剪3叶处理使水稻籽粒产量分别降低17%和52%,均达极显著水平,这主要与饱粒率和所有籽粒平均粒重均显著下降有关;尽管齐穗期疏花处理使水稻结实能力显著增加,但因每穗颖花数减半,产量大幅下降(-29%)。籽粒最终产量对高CO_2浓度的响应与饱粒率和所有籽粒平均粒重的响应呈显著正相关。以上结果表明,水稻齐穗期人为改变源库比例(特别是剪叶)可以改变籽粒结实能力和最终产量对高CO_2浓度的响应。     

水稻待测粳型亲籼系的亲籼性鉴定

[目的]选育粳型亲籼系。[方法]选用6个籼稻、6个粳稻和6个广亲和测验种,以F,代花粉育性和小穗育性为指标,测定了5个待测粳型亲籼系的亲籼性。[结果]待测粳型亲籼系G2123、G2417、G2410和G3005亲籼、不亲粳,为特异亲籼系;G2615不亲籼,也不亲粳,为不亲和系。同时探讨了粳型亲籼系亲籼性测定时的测验种、育性指标、花粉育性和小穗育性的测定方法,分析了G2417高亲籼性的原因。[结论]G2417自交结实率（小穗育性）95．1％,与6个籼稻测验种杂交的F,代平均结实率（小穗育性）94．9％,是个亲籼性极好、综合性状优良的亲籼系。     

小麦品种间不同穗粒位籽粒蛋白质及其组分积累规律的研究

利用强、中、弱三种筋型小麦品种 ,研究了不同穗位和粒位籽粒蛋白质及其组分的积累规律。结果表明 ,各部位籽粒蛋白质及其组分遵循相同的积累规律 ,体现了籽粒充实过程中氮代谢总趋势的一致性。不同粒位籽粒蛋白质积累相对含量 ,从开花后 12天开始 ,所有处理均表现为 :强势粒 >弱势粒 ;不同穗位籽粒蛋白质积累的相对含量 ,不同品种不同施肥处理表现并非完全一致。表明籽粒着生部位和发育时间的早晚及生理机制的差异影响蛋白质的积累过程及最终合成 ,且这种差异受施肥调控 ,并具有一定的基因型差异。