Factors of affecting the spring back of compressedPaulownia wood

In order to increase its hardness and gravity as well as dimension stability, the technology of hot-compressing onPaulownia wood was studied. The main factors of affecting the spring back of the compressedPaulownia samples were discussed. It was discovered that every factor in the experiment had obvious effects on wood hardness and dimension stability of compressed wood. When the MC (Moisture Content) of experimental specimens was 13.89%, it was useful to spray water on the surface of samples before hot pressing. The best result was the recovery of compression set could decrease from 90.69% of untreated wood to 45.51% of soaking specimens into PF (Phenol Formaldehyde) water solution. The hot pressing time was 8 min at 190°C. Responsible editor: Zhu Hong     

IAA与亚种间杂交稻籽粒发育的关系及烯效唑的调节

 以汕优413及其父本品种中413为材料,研究了内外源IAA在籽粒发育过程中的作用及植物生长延缓剂S-07对其强、弱势粒灌浆过程的影响。在灌浆前期,强势粒抑制弱势粒的发育,外源IAA可代替强势粒的这种抑制作用;灌浆过程中强、弱势粒内源IAA的变化动态存在差异,其中强势粒的内源IAA在开花后急剧上升,8 d左右达最高峰;而弱势粒的IAA水平开花后则有一段约12 d的“滞缓期”,在开花后20 d左右才有一高峰出现。强弱势粒对3H-IAA的合成和吸收能力差异可能是导致其内源IAA水平不平衡的原因之一。孕穗末期喷施S-07可部分抑制强势粒的发育而相对促进弱势粒的发育,提高弱势粒千粒重;孕穗末期喷施S-07溶液可降低强势粒但提高弱势粒灌浆前期的内源IAA水平。     

近地层臭氧浓度升高对常规稻颖花形成的影响：FACE研究

FACE(free air gas concentration enrichment)研究使用标准的作物管理技术,在完全开放的大田条件下运行,代表了目前人类对未来大气环境的最好模拟。利用独特的大型稻田FACE平台,以典型的常规水稻品种武粳15(粳稻)和扬稻6号(籼稻)为供试材料,研究近地层臭氧(O3)浓度升高(比大气背景臭氧浓度平均增高26%)对常规水稻颖花形成的影响。结果表明:(1)高浓度O3对供试品种全穗以及一、二次枝梗颖化分化数均无显著影响;(2)高浓度O3使供试品种全穗和二次枝梗颖花退化数和退化率均显著增加,颖花退化增多是由于现存一次枝梗上二次枝梗大量退化而引起的二次颖花退化所造成;(3)颖花退化数在颖花分化数中所占比例很低,故高浓度O3对两供试品种全穗和一、二次枝梗颖花现存数以及稻穗构成均无显著影响。结合前报可知,选用常规水稻品种以及增施保花肥可能是未来近地层高浓度O3环境下稻作生产重要的适应措施。     

Physiological mechanism underlying spikelet degeneration in rice

The phenomenon of degenerated spikelets is very common in cereals, and considered as a serious physiological defect and a main constraint to grain production. Understanding the physiological mechanism in which spikelet degeneration occurs would have great significance in enhancing yield potential in grain crops. Taking rice as an example, the paper reviewed the physiological mechanism underlying spikelet degeneration, with focus on the roles of phytohormones in regulating the process. There are several hypotheses for the spikelet degeneration, such as resource limitation, self-organization, and primigenic dominance. However, convincing evidences are not enough to support the assumptions. Phytohormones including auxins, cytokinins, gibberellins, abscisic acid, and ethylene are involved in regulating spikelet degeneration in cereals. The new phytohormones of brassinosteroids and polyamines have been observed to suppress spikelet degeneration in rice. The interactions among or between plant hormones may play a more important role in regulating spikelet degeneration. However, the information on such interactions is very limited. Some agronomic practices, especially proper water and nitrogen management, could reduce spikelet degeneration but the mechanism underlying remains unclear. Further research is needed to understand the cross-talk among/between phytohormones on spikelet degeneration, to reveal the physiological and molecular mechanism in which phytohormones and their interactions regulate the degeneration of spikelets, to exploit approaches to decrease spikelet degeneration and to elucidate their mechanism.     

Breeding efforts to mitigate damage by heat stress to spikelet sterility and grain quality

Global warming is predicted to aggravate the risk of unstable crop production. It is of great concern that damage to rice spikelet sterility and grain quality will increase, resulting in yield and economic losses. To secure the global food supply and farmers’ income, the development of rice cultivars with heat resilience is a pressing concern. Regarding spikelet sterility, rice cultivars with heat tolerance at different growth stages have been identified in recent years. The early-morning flowering (EMF) trait is effective in heat escape because it shifts the time of day of flowering to earlier in the morning when it is cooler. Although varietal differences are very small, there are some genetic resources for EMF in wild rice accessions. Regarding heat-induced grain chalkiness, heat-tolerant japonica cultivars for mitigating white-back type of chalky grains (WBCG) were found. Quantitative trait loci for heat tolerance at flowering, EMF, and for WBCG in grain quality have been mapped on the rice chromosomes. Further genetic efforts have been successfully connected to the development of near-isogenic lines for each trait with tagged molecular markers. These breeding materials are quite unique and useful in facilitating marker-assisted breeding toward the development of heat-resilient rice in terms of spikelet sterility and grain quality.     

源库调节对常规粳稻花后营养器官碳水化合物及氮磷钾转运的影响

 【目的】阐明抽穗期源库关系对常规粳稻花后营养器官干物质、非结构性碳水化合物（NSC）和氮、磷、钾矿质元素等转运的影响,明确促进水稻植株养分高效再利用的粒叶比。【方法】以淮稻5号和宁粳3号两个常规粳稻品种为材料进行大田试验,分别于抽穗期选择茎生绿叶6片且开花进程一致的单茎,采用剪叶疏花的方法调节源库关系,将处理后当天每穗颖花数与单茎叶面积的比值定义为粒叶比,测定抽穗至成熟期叶片、茎鞘中干物质、NSC及氮、磷、钾的含量,计算相关物质的转运率,并分析其与粒叶比的关系。【结果】与对照（L₀S₀）相比,剪叶处理（L_1/2S₀）通过提高粒叶比,显著降低了结实率和千粒重,其中淮稻5号分别降低了8.6%-10.5％和19.0%-8.0%,宁粳3号分别降低了9.7%-20.4%和5.7%-12.6%;而疏花处理通过降低粒叶比,显著提高了结实率和千粒重,其中淮稻5号平均提高了3.4%-6.7%和1.2%-18.7%,宁粳3号平均提高了2.0%-4.3%和6.9%-17.3%,同一品种不同疏花处理之间的结实率和千粒重无显著的差异,但年份之间的表现并不一致,2014年水稻季的气候条件更有利于籽粒灌浆充实,其结实率和千粒重及提高幅度普遍高于2013年。剪叶处理显著提高了常规粳稻抽穗至成熟期叶片和茎鞘中干物质、NSC及氮、磷、钾等矿质元素的转运率,两品种间差异较小,不同年份间未表现出实质性的差异;而疏花处理则显著降低了抽穗至成熟期叶片和茎鞘中干物质、NSC及氮、磷、钾等的转运率,且疏花越多降低幅度越大,不同品种和不同年份间未表现出实质性的差异,但叶片和茎鞘干物质、NSC转运对疏花的响应存在根本性区别,随着疏花增多,叶片中干物质和NSC转运率下降,而茎鞘中干物质和NSC转运在表观上出现滞留不外运的现象。进一步分析叶片和茎鞘中干物质、NSC及氮、磷、钾的转运率（y）与抽穗期粒叶比（x）的关系,发现上述指标间均存在y=（a+bx）/x曲线相关关系,在粒叶比较小时,叶片和茎鞘中各种物质的转运率均随粒叶比增大而急剧提高,当粒叶比增大至一定程度后,各种物质的转运率均趋近于潜在最大值,不再随粒叶比的增大而显著提高,不同物质潜在最大转运率虽然不同,但都在粒叶比1.5左右接近这一极限值,且淮稻5号和宁粳3号两个品种之间也未出现明显分异。【结论】相对较高的粒叶比有利于促进常规粳稻花后营养器官干物质和非结构性碳水化合物及氮、磷、钾等的转运,粒叶比与常规粳稻花后营养器官干物质、非结构性碳水化合物、氮、磷、钾等的转运率存在着密切的曲线相关关系,并在粒叶比1.5左右达到近似最大转运率,抽穗期粒叶比1.5左右可作为常规粳稻氮、磷、钾矿质养分高效再利用的品种选育与栽培调控指标。     

扦插基质与激素处理对油茶扦插生根的影响研究

以广东省野生油茶母树嫩枝或1 a插穗为试验材料,探讨不同基质、激素溶液和浸穗时间对油茶扦插育苗效果的影响.研究结果表明:以100％细沙为扦插基质时,生根率、侧根数和侧根长,分别为66.84％、2.88条和2.78 cm,显著大于其它处理(P＜0.05);3种激素(IAA、NAA、ABT6)处理中,采用ABT6溶液处理的生根率和侧根长最大,侧根数较多,均显著大于CK (P ＜0.05);浸穗处理中,25 mg/L ABT6溶液浸泡2h处理的生根率最高,为84.37％,侧根数和侧根长也较多,分别为3.49条和2.31 cm.因此进行油茶秋季扦插繁殖时,插穗宜采用25 mg/L ABT6溶液浸泡2h后,扦插于100％细沙基质上.     

Mapping and candidate gene analysis for a new top spikelet abortion mutant in rice

Grain numbers is one of the determinations for rice yield and directly associated with spikelet numbers per panicle and its normal development. Lots of genes responsible for spikelet numbers and spikelet early development have been identified, but the molecular information about the spikelet development at later development is still limited. Here, we isolated a rice spikelet abnormal development mutant, which shows degenerated spikelet at the top panicle and named aborted top spikelet mutant 1(Ats1). The spikelets derived from the middle and bottom branches per panicle of Ats1 show normal development with those of wild type. However, a large number of branches and spikelets with arrested development were often observed only on apex panicle. The abnormality did not appear until the stage In8 when rachises elongate rapidly and reproductive organs get mature, based on observations through SEM analysis. The aborted spikelet could develop the complete floral organs with a pair of rudimentary glume, a pair of empty glume, two lodicule, six stamens and one carpel. But all these floral organs did not develop maturity. Genetic analysis on two F₂ populations indicated that the Ats1 was controlled by a single dominant gene. By using bulked segregant analysis of F₂ population developed from Ats1 crossing with Songjing6, ATS1 was mapped on chromosome 8 between RM3819 and RM5556. Then, the fine mapping was performed with 1078 F₂ population developed from Ats1 and IR36. The ATS1 locus was finely mapped in an 85.7 kb region between RM22448 and STS8‐2 with 8 genes according to the rice annotation project database. Sequence analysis of the candidate genes within the delimited region of the Ats1 and Akihikari showed two‐nucleotide changes, including single‐nucleotide substitutions corresponding to an amino acid substitution from asparagine to lysine acid in exons 3 and a 1‐bp deletion resulting in a premature stop codon in exon 22 at the candidate gene, LOC_Os08g06480. A cleaved amplified polymorphic sequence (CAPS) marker, CAPS‐ats1, was developed from the 1‐bp deletion site. The complete cosegregation of the CAPS genotypes with the matching phenotypes were observed in the F₂ populations. This suggested that Os08g06480 is most likely the ATS1 gene. These results will provide more information for better understanding of the molecular mechanism governing top spikelet abortion within a short developmental period.     

早籼稻品种遗传改良进程中群体质量的演变特征

以1934～2006年育成,在我国南方广泛种植的16个代表性早籼稻品种为材料,参照生产实践及品种演变阶段,按育成时间将供试品种划分为高秆品种、矮秆品种、矮抗品种、优超品种4种类型,采用常规栽培方法研究其群体质量的演变特征。结果表明,早籼稻品种改良进程中,花后群体光合生产能力增强,干物质积累增加,齐穗期总颖花量增加,高效叶面积率与颖花根流量略有下降,有效叶面积率与成穗率变化不大,单茎茎鞘重呈先下降后略有上升的趋势。早籼稻群体进一步改良的有效途径是增强根系活力,促进根系水分与矿物质的吸收及根系物质向籽粒的转运;提高高效叶面积率,增加花后光合产物积累和总颖花量,进而提高粒叶比,达到源库协调。     

水稻不同粒位籽粒淀粉与蛋白质累积动态差异

 以中熟籼稻（扬稻6号）和中熟粳稻（扬粳9538）为材料,研究了穗上不同粒位籽粒灌浆过程中粒重、淀粉、可溶性糖和粗蛋白质含量等动态变化,以期通过分析灌浆物质累积动态差异探讨不同粒位间籽粒品质差异形成的生理原因。穗上不同粒位籽粒灌浆物质累积动态存在显著差异,同一穗上早开花籽粒起步灌浆早,初期灌浆速率快;灌浆前、中期籽粒中淀粉和直链淀粉累积速率、累积量与籽粒开花顺序较为一致,即早开花籽粒大于迟开花籽粒,而不同粒位籽粒间的可溶性糖含量变化则与之相反。灌浆在粒位间的差异扬粳9538大于扬稻6号。成熟期籽粒直链淀粉含量则与开花顺序无必然联系。粗蛋白质含量随灌浆进程呈倒“S”型趋势,即灌浆前期下降较快,至最低点后略有回升,前期下降速率迟开花籽粒大于早开花籽粒,但蛋白质含量在整个灌浆阶段则以迟开花籽粒大于早开花籽粒,二次枝梗大于一次枝梗籽粒,穗下部籽粒高于其他部位籽粒。灌浆前、中期同枝梗上较早开花籽粒含水量下降幅度大于迟开花的籽粒,一次枝梗上第1粒尤为明显。以上结果说明,可溶性碳水化合物的供给可能不是弱势粒发育不良的限制因子,弱势粒灌浆充实不良可能与其较低的生理活性有关。