Genotypic Variation of Stomatal Conductance in Relation to Stomatal Density and Length in Rice (Oryza sativa L.)

Abstract

Stomatal conductance (g_s) is an important trait responsible for the genotypic difference in gas diffusion for photosynthesis and transpiration in rice (Oryza sativa L.). We measured g_s, stomatal density and stomatal length (guard-cell length) at two weeks before heading for 64 accessions from a rice diversity research set of germplasm (RDRS) and for three high-yielding cultivars (HYC) under field conditions. Considerable variations in g_s, and stomatal length were observed among varieties in RDRS, and it was considered that RDRS covers the species diversity of the stomatal characteristics in rice. When it was compared among the varieties with similar plant earliness, g_s was higher in HYC than in most varieties of RDRS. Stomatal density did not correlate with g_s, and there was a negative correlation between stomatal density and stomatal length. However, noticeable variance existed in the latter relation, where HYC exhibited a higher stomatal density and slightly shorter stomatal length than RDRS. High g_s in HYC is attributable to their high stomatal density and moderate specific stomatal conductance (g_s / stomatal density) while the high-g_s varieties in RDRS tended to have a lower stomatal density and higher specific stomatal conductance. Stomatal length is related to specific stomatal conductance, but there are remarkable differences between these traits. Specific stomatal conductance in HYC has not reached the upper limit for their stomatal size, which raises a possibility of further improvement of HYC in g_s.     

Effects of Silicon on Transpiration and Leaf Conductance in Rice Plants (Oryza sativa L.)

Summary

To characterize the protection effect of silicon against excessive transpiration in rice plants (Oryza sativa L.), we investigated the factors responsible for transpiration, such as cuticular conductance (gc), leaf surface wax content (WC), and stomatal movement in response to environmental stimuli, using leaves of plants grown in nutrient solution with silicon (+Si) and without silicon (–Si). The rate of transpiration of whole plants (E) under field conditions was clearly reduced by application of silica. The gc of –Si leaves under precisely regulated conditions was 33% higher than that of +Si leaves, reflecting higher adaxial gc. Silicon has little effect on WC, a factor responsible for regulation of cuticular resistance to water flux in rice leaves. These results suggest that silicon is one of the main factors responsible for regulation of gc, but that its effect was not due to an increase in the WG. Leaf conductance (gl) of –Si leaves tended to decrease more slowly than that of +Si leaves over time after changes from high to low light intensity. Moreover, it was always higher over the entire duration of the experiment, irrespective of irradiation intensity. The gl of –Si leaves was higher at lower relative humidity (RH) and the initial response to a subsequent increase in RH was slower than that of +Si leaves. A comparison of gl and gc between +Si and –Si leaves showed that the higher gl of –Si leaves was due to higher stomatal conductance. These results indicated that the reduction in E by application of silica was mainly attributable to reduction in the rate of transpiration through stomatal pores.     

Salinity-Induced Ultrastructural Alterations in Leaf Cells of Rice (Oryza sativa L.)

Summary

High concentrations of NaCl significantly reduced the fresh and dry weights and lengths of roots and shoots. NaCl exhibited a more rapid effect in water culture than in soil culture. In both water and solid cultures, root growth was suppressed more severely than shoot growth. Electron microscopic studies revealed that NaCl caused swelling of thylakoids, accumulation of starch grains and lipid droplets, distortion of grana stacking, increase in the size and number of plastoglobuli and vesiculation of cellular membrane. Mitochondria became deficient in cristae, swelled and the matrix appeared pale in salt-treated plants as compared with control plants. Disappearance of nucleolus and nuclear chromatin and destruction of vascular tissues were occasionally observed in salt-treated plants.     

Gene Expression of Enzymes for Starch and Sucrose Metabolism and Transport in Leaf Sheaths of Rice (Oryza sativa L.) during the Heading Period in Relation to the Sink to Source Transition

Abstract

Leaf sheaths of rice plants are known to temporarily accumulate starch prior to heading, which is subsequently remobilized and transported into the panicle after heading. We investigated the time course for both carbohydrate content and steady state mRNA levels of enzymes related to starch and sucrose metabolism in the rice leaf sheath (Oryza sativa L. cv. Nipponbare). Leaf sheaths from the second leaf below the flag leaf accumulated high levels of starch before heading but they rapidly decreased after heading. In contrast, the flag leaf sheath did not accumulate as much starch. In the second leaf sheath, the mRNA levels of enzymes involved in starch synthesis, ADP glucose pyrophosphorylase (EC 2. 7. 7. 27), soluble starch synthase (EC 2. 4. 1.21) and branching enzyme (EC 2. 4. 1. 18) were high before heading, which coincided with rapid accumulation of starch. The mRNA levels of sucrose synthesis enzymes, cytosolic FBPase (EC 3. 1. 3. 11) and sucrose phosphate synthase (EC 2. 4. 1. 14), and the sucrose transporter (OsSUTI) increased at the time of heading, which was largely coincident with a decrease in the mRNA levels of starch synthesis enzymes. In the flag leaf sheaths, changes in mRNA levels of starch synthesis enzymes were not pronounced, however mRNA levels of sucrose synthesis enzymes and the sucrose transporter showed a clear increase throughout the heading period. The different characteristics observed between the two leaf sheaths will be discussed in relation to the sink to source transition.     

Spatial and Temporal Variation in Photon Flux Density on Rice (Oryza sativa L.) Leaf Surface

Abstract

Spatial and temporal variations of photosynthetic photon flux density (PFD) measured using small photodiodes (Hamamatsu, model G1118) attached on the leaf surface of rice (Oryza sativa L.) differed with the orientation and inclination even at the same height of the canopy. Under sunny conditions, the fluctuation pattern of PFD was mainly determined by the orientation and inclination of the leaf surface, and not by the daily change of PFD in the open, e. g., high peaks of PFD were observed in the morning on east-oriented leaves, but only low peaks on north-oriented leaves. Under overcast conditions, however, the PFD on the leaf surface depended highly on the PFD in the open irrespective of the leaf orientation and inclination. The present study suggests that the orientation and inclination should be considered as the major factors influencing the PFD regime (spatial variation and daily total PFD) within the rice canopy. To determine the effects of spatial and temporal variations of PFD on crop productivity, the daily net assimilation of each leaf was estimated from the obtained data and the light-photosynthesis curve.     

利用同工酶标记水稻亲本遗传差异及其在杂交水稻育种中的利用

利用淀粉凝胶和聚丙烯酰胺凝胶电泳显示的同工酶差异，分析17个杂交水稻亲本、3个新株型株系和22个光壳稻、爪哇稻品种的遗传差异，研究光壳稻和爪哇稻及其与温带粳稻之间的关系，探索同工酶标记水稻亲本遗传差异在杂交稻育种中利用的可能性。在本研究中，8个同工酶18个多态性位点至少在2个基因型间存在差异。每个具有多态性的酶谱带分别以1和0记录存在与否，由同工酶数据计算的Nei’s遗传距离创建聚类树状图。聚类分析结果表明，籼稻和粳稻容易被分开，普通粳稻与光壳稻、爪哇稻混合聚在一起；光壳稻与爪哇稻之间的遗传距离要比它们与普通粳稻之间的遗传距离小。利用光壳稻、爪哇稻选育不同生态群方向的恢复系和不育系，已配组育成了强优势的杂交稻组合。     

Characteristics of Gas Exchange and Chlorophyll Fluorescence during Senescence of Flag Leaf in Different Rice (Oryza sativa L.) Cultivars Grown under Nitrogen-Deficient Condition

Abstract

Effects of nitrogen (N) deficiency on photosynthetic gas exchange and photosystem II (PSII) photochemistry of flag leaves during grain-filling stage were investigated in six rice cultivars, Kasalath (a conventional indica), IR36 (an improved indica), Shirobeniya (a conventional japonica), Nipponbare (an improved japonica), Akenohoshi (an improved japonica-indica intermediate type) and BSI429 (an improved tropical japonica, a new plant type line) grown hydroponically in N-sufficient (NS) and N-deficient (ND) solution. From 3 to 24 days after heading (DAH), net photosynthetic rate (P_n), maximum quantum yield of photosystem II (PSII) (F_v/F_m), quantum yield of PSII electron transport ( Φ_psii), and contents of chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the flag leaves decreased, particularly under the ND condition in all six cultivars. A substantial difference was observed among the ND plants for the sustainability index (SI, the ratio of the value at 24 DAH to that at 3 DAH) of P_n, F_v/F_m, Φ_psii, Chl content and Rubisco content; SIs of those parameters of Akenohoshi, BSI429, Nipponbare and Shirobeniya were higher than those of IR36 and Kasalath. The SI of P_n showed significant positive correlations with those of F_v/F_m, Φ_psii, and the contents of Chl and Rubisco under the ND condition. It was concluded that the sustainability of photosynthesis in the flag leaves was mainly due to those of PSII photochemistry and electron transport, which was associated with the maintenance of Chl and Rubisco under the ND condition.     

Rapid Swelling of Pollen Grains in Response to Floret Opening Unfolds Anther Locules in Rice (Oryza sativa L.)

Abstract

The changes in pollen grain diameter were examined in relation to the floret opening and anther dehiscence in rice (Oryza sativa L.). In the first experiment, the florets were artificially opened by excising the top of the glumes at various times before the expected natural flowering time. Pollen diameter increased rapidly in the artificially opened florets, but slowly in the controls in which the glumes were left intact. The time of anther dehiscence coincided well with the time when pollen grains reached their maximum diameter. In addition, the pollen grain diameter was significantly correlated with the percentage of dehisced anthers in the florets artificially opened at various times. These results indicate that floret opening induces the swelling of pollen grains and that the swelling is an important event for anther dehiscence. In the second experiment, anther segments with pollen left remaining intact and those with pollen removed were immersed in water. The septa in the anther segments without pollen failed to rupture in water, whereas 70% of the septa in the anther segments with pollen left remaining ruptured, indicating that the septa can be ruptured by the swelling pressure of pollen grains resulting in unfolding of anther locules. From these findings, we infer that the rapid swelling of pollen grains in response to floret opening is a driving force to rupture the septum and unfold the locules.     

Ammonia Emission from Leaves of Different Rice (Oryza sativa L.) Cultivars

Abstract

NH₃ emission from leaves of three rice (Oryza sativa L.) cultivars, Akenohoshi, Shirobeniya and Kasalath, was examined using a simple open chamber system.　In the three cultivars, NH₃ emission rate (AER) and NH₄⁺ content of leaves decreased with decreasing NH₄⁺ concentration in the root medium, but these values differed significantly with the cultivar. In the daytime, AER, NH₄⁺ content and glutamine synthetase (GS) activity in leaves changed similarly with maximum values around midday. Akenohoshi showed significantly lower AER and NH₄⁺ content but higher GS activity than Kasalath. The difference in AER among the rice cultivars may be related to the activity of GS involved in photorespiratory NH₃ recycling. Akenohoshi can be a breeding material useful for improving N recycling.     

Correlation between Chloroplast Ultrastructure and Chlorophyll Fluorescence Characteristics in the Leaves of Rice (Oryza sativa L.) Grown under Salinity

Abstract

The seedlings of Oryza sativa L. cv. Nipponbare grown by hydroponic culture for 3 wks were treated with 75, 100, 150 and 200 mM NaCl for 14, 14, 6 and 3 days, respectively, and examined for chloroplast ultrastructure in the region where chlorophyll fluorescence had been recorded. NaCl treatment decreased the ratio of variable to maximum chlorophyll fluorescence yield (F_v/F_m) and caused swelling of thylakoids. The swelling of thylakoids was quantified by the percentage of the length of swollen thylakoids to the total length of thylakoids. This value was increased with increasing NaCl concentration. Although F_v/F_m decreased at all concentrations of NaCl, the minimal fluorescence yield F₀ was not increased by the treatment with 75 or 100 mM NaCl. The percentage of the length of swelling was low at 75 and 100 mM NaCl. On the other hand, F₀ increased and the swelling of thylakoids was prominent with 150 and 200 mM NaCl treatment. These results suggest that the decrease in F_v/F_m due to the increase in F₀ under salt stress correlates with the ultrastructural damage. The decrease in F_v/F_m due to the increase in F₀ is expected to be useful as an indicator to evaluate the damage in chloroplasts, especially in thylakoid membranes, under salinity.     

Analysis of QTLs for Flag Leaf Shape and Its Response to Elevated CO2 in Rice （Oryza sativa）

To understand the responses of flag leaf shape in rice to elevated CO2 environment and their genetic characteristics,quantitative trait loci(QTLs)for flag leaf shape in rice were mapped onto the molecular marker linkage map of chromosome segment substitution lines(CSSLs)derived from a cross between a japonica variety Asominori and an indica variety IR24 under free air carbon dioxide enrichment(FACE,200μmol/mol above current levels)and current CO2 concentration(Ambient,about 370μmol/mol).Three flag-leaf traits,flag-leaf length(LL),width(LW)and the ratio of LL to LW (RLW),were estimated for each CSSL and their parental varieties.The differences in LL,LW and RLW between parents and in LL and LW within IR24 between FACE and Ambient were significant at 1%level.The continuous distributions and transgressive segregations of LL,LW and RLW were also observed in CSSL population,showing that the three traits were quantitatively inherited under both FACE and Ambient.A total of 16 QTLs for the three traits were detected on chromosomes 1,2,3,4,6,8 and 11 with LOD(Log10-likelihood ratio)scores ranging from 3.0 to 6.7.Among them,four QTLs (qLL-6*,qLL-8*,qLW-4*,and qRLW-6*)were commonly detected under both FACE and Ambient.Therefore,based on the different responses to elevated CO2 in comparison with current CO2 level,it can be suggested that the expressions of several QTLs associated with flag-leaf shape in rice could be induced by the high CO2 level.     

Identification of QTLs for Improvement of Plant Type in Rice (Oryza sativa L.) Using Koshihikari / Kasalath Chromosome Segment Substitution Lines and Backcross Progeny F2 Population

Abstract

Thirty-nine chromosome segment substitution lines (CSSLs) population derived from a Koshihikari / Kasalath cross was used for quantitative trait locus (QTL) analysis of plant type in rice (Oryza sativa L.). Putative rough QTLs (26.2～60.3cM of Kasalath chromosomal segments) for culm length, plant height, panicle number, chlorophyll content of flag leaf blade at heading and specific leaf weight, were mapped on the several chromosomal segments based on the comparison of CSSLs with Koshihikari in the field experiment for 3 years. In order to verify and narrow QTLs detected in CSSLs, we conducted QTL analyses using F₂ populations derived from a cross between Koshihikari and target CSSL holding a putative rough QTL. The qPN-2, QTL for panicle number was mapped on chromosome 2. In traits of flag leaf, the qCHL-4-1 and qCHL-4-2 for chlorophyll content was mapped on chromosome 4, and the qSLW-7 for specific leaf weight on chromosome 7. All QTLs were detected in narrow marker intervals, compared with rough QTLs in CSSLs. The qPN-2, qCHL-4-1 and qCHL-4-2 had only additive effect. On the other hand, the qSLW-7 showed over-dominance. It could be emphasized that QTL analysis in the present study with the combination of CSSLs and backcross progeny F₂ population can not only verify the rough QTLs detected in CSSLs but also estimate allelic effects on the QTL.     

不同生态环境下水稻穗部性状QTL鉴定

【目的】发掘与产量相关的穗粒性状QTL对进一步克隆和利用高产基因具有重要意义。【方法】以超级粳稻龙稻5号和典型高产籼稻中优早8号杂交衍生的重组自交系群体为试材,在4种环境下对穗部性状进行比较和QTL分析。【结果】共检测到63个穗部性状QTL,分布于除第9染色体外的11条染色体上。在4个环境下分别检测到27、27、18和35个QTL。其中,16个QTL能在2个环境下被检测到,12个在3个以上环境下稳定表达,分别占QTL总数的25.40%和19.05%;第1、3、4和5染色体的多效QTL簇能在不同环境下稳定表达,对穗部性状具有明显的调控作用。【结论】第3染色体STS3.3-STS3.6区间的qSNP3、第4染色体RM5688-RM1359区间的qSNP4.1是2个新的稳定表达的多效性QTL簇。此外,上位性效应是调控穗部性状的重要组分。     

根表铁胶膜对镉污染土壤水稻吸镉量的影响(英文)

通过采用镉污染的土壤—河砂—营养液联合培养的方法,研究了在水稻分蘖期施铁对水稻根表铁胶膜中铁及铁胶膜吸附镉的影响。设四个亚铁(Fe~(2+))处理水平分别为:0、30、50、70mg/L,研究施铁浓度与水稻根表铁氧化物胶膜的数量和吸附镉量之间的关系。结果表明,施铁处理的铁胶膜中铁的含量比不施铁(0处理)的高,但在其他三种处理 (30、 50、70mg/L)中,随施铁浓度的升高而降低。另外,施铁浓度与铁胶膜的数量呈正相关,所以,铁胶膜吸附镉与施铁浓度呈正相关。在水稻的另外三个时期:拔节、孕穗、灌浆期,对该问题将作进一步研究。     

Molecular Cloning and Characterization of Citrate Synthase Gene in Rice （ Oryza sativa）

The full-length OsCS encoding citrate synthase was isolated from rice （Oryza sativa L. subsp, japonica）, OsCS is 1477-bp long and encodes a 474 amino acid polypeptide, Its putative protein sequence is highly identical to Daucus carota, Nicotiana tabacum Beta vulgaris subsp., Arabidopsis thaliana, and Citrus junos （〉70%）. The deduced amino-terminal sequence of OsCS showes characteristics of mitochondrial targeting signal. Southern blot analysis using ORF of the OsCS as the probe indicated that this gene exists in multiple copies in rice genome. The band with predicated size of 82 kD was detected by Western blot after being induced by 0,4 mmol/L IPTG.     

稻(Dryza sativa)胚的结构及各构件的合理名称

本文根据扫描电镜观察,时稻胚发生过程及胚表面构件的形态作了描述,并对文献中存在的稻胚结构构件名称的混乱情况进行了查核。从而发现历来稻胚形态描述上与事实不符之处,如广为流传的 Juliano 论文中的图将胚芽鞘和侧鳞误以为外胚叶;容启东、星川清亲等将侧鳞误为腹鳞;《水稻的生长发育》和《稻的生长》等的中译本,则将侧鳞误为胚芽鞘等等。本文还提出了胚的结构及各构件的合理命名。     

“三系”不育系微效恢复基因表现型研究

对胞质雄性不育系的3个育性指标:套袋自交结实率、黑染花粉率、嵌合颖花率,在4个不同育性水平的不育系的多个转育世代中的表现进行了比较。结果表明,3个指标均是微效恢复基因的遗传表现型,但嵌合颖花率因为易于考查、数据绝对值大、表现稳定性好而最适合作为微效恢复基因遗传分析的量化指标。该结论的重要意义在于量化的表现型是微效恢复基因遗传规律及进一步分子研究的基础。     

一个水稻苗期温敏感白色条斑叶突变体的遗传分析及基因定位

通过对粳稻品种嘉花1号60Coγ射线诱变,从M2中筛选出一株低温敏感型白色条斑叶突变体(tws)。它在低温(20℃,24℃)条件下培养时,苗期第3和第4叶表现出白色条斑,而第5叶开始转为正常。低温条件下该突变体白斑叶片叶绿素含量明显下降。该突变体白色条斑叶性状具有温敏感性,且与叶龄相关。遗传分析表明,该突变性状受1对隐性核基因控制,定名为tws(thermo-sensitive white stripe-leaf)基因。以tws突变体与籼稻9311杂交的F2分离群体作为定位群体,利用SSR标记将该基因定位在第4染色体MM3907和MM3928之间,其物理距离约为86kb。     

一份水稻OsWOX3B基因敲除突变体的鉴定

[目的]水稻OsWOX3B基因调控叶片形态和表皮毛发育,根据表型被命名为LSY1、DEP、NUDA和GLR1等.深入了解OsWOX3B基因对水稻发育调控的功能具有重要意义.[方法]利用CRISPR/Cas9基因编辑技术对籼稻品种R401的OsWOX3B进行基因敲除.对所获材料进行突变位点分析和表型分析,同时进行相关基因...