Effects of Elevated Atmospheric Carbon Dioxide Concentration on Silica Deposition in Rice (Oryza sativa L.) Panicle

Abstract

The effects of elevated carbon dioxide concentration ([CO₂]) on silica deposition on husk epidermis of rice (Oryza sativa L. cv. Akitakomachi) during the flowering stage were investigated in this study. The study was motivated by the concept that the rice yield maybe affected by global warming as a result of elevated [CO₂] environment since sterility of rice is related to the panicle silica content that influences transpiration, and elevated [CO₂] could affect plant transpiration. Silica deposition analysis was focused on the flowering stage of the rice crop grown hydroponically under two [CO₂] conditions: 350 μmol mol-¹ (ambient) and 700 μmol mol-¹ (elevated). Silica deposition on the husk epidermis from three parts of the panicle at four flowering stages were examined using a scanning electron microscope (SEM) combined with an energy dispersive X-ray microanalyzer (EDX). The results demonstrated that elevated [CO₂] significantly suppressed silica deposition on the husk epidermis at the lower part of the panicle, and at the early flowering stage when 1/3 of the panicle emerged from the leaf sheath. In the transverse section analysis of the husk, silica deposition on the husk epidermis under elevated [CO₂] was less than that under ambient [CO₂] at the late flowering stage. The less silica deposition observed on the husks at the late flowering stage under elevated [CO₂] might be related to the suppressed transpiration from the panicle by elevated [CO₂] found in a previous study.     

Factors Causing the Variation in the Temperature Coefficient of Dark Respiration in Rice (Oryza sativa L.)

Abstract

The temperature coefficient (Q₁₀) of dark respiration in rice gradually decreased in continuous darkness, fluctuating as the circadian rhythmic variation in dark respiration. The solar radiation (MJ m^-2) on the day of measurement and the nitrogen concentration in the culture solution hardly affected the Q₁₀ value. However, the plants exposed to high-intensity light (260W m^-2) for two weeks showed a higher Q₁₀ of dark respiration than those exposed to low-intensity light (70W m^-2). The seasonal variation in Q₁₀ value was not observed. The average Q₁₀ value during the growth stage measured at 15 to 25°C, 20 to 30°C, and 25 to 35°C was 2.14, 1.76, and 1.56, respectively. High crop yield in the regions where the day/night temperature difference is large may be partly explained by the high Q₁₀ at low night temperature. Thus, the Q₁₀ may be an important physiological factor determining high crop yield.     

播量及移栽基本苗对水稻新品种盐粳218产量的影响

采用小区对比试验方法,研究了播量、移栽基本苗对水稻新品种盐粳218生育及产量的影响。结果表明,降低播量可使盐粳218秧苗的干物重、充实度、带蘖率增加。处理A1B4的单产为604.4 kg/667 m2,比A3B6、A1B2、A2B3、A3B4、A1B3、A2B5、A2B4、A3B5处理分别增产了7.8%、7.0%、4.7%、3.2%、2.6%、2.2%、1.3%、1.3%,其单位面积有效穗数及颖花数、生物产量及齐穗后干物质积累量占籽粒产量百分比均较高。在播量100、200、300 g/m2前提下,对应移栽基本苗4.5万～5.5万/667 m2、5.5万～6.5万/667 m2、6.0万～7.0万/667 m2均可使盐粳218获得较高的产量与效益。     

Effect of Soil Compaction on Dry Matter Production and Water Use of Rice (Oryza sativa L.) under Water Deficit Stress during the Reproductive Stage

Abstract

The effect of a long term of soil compaction on dry matter production (DMP) and water use in rice cultivated under limited water supply during the reproductive stage is unknown. Our objectives were to determine which of the transpiration (Tr) or water use efficiency (WUE) is dominant in determining DMP under compacted and desiccated soil conditions. When irrigation in the period around the reproductive stage was terminated in artificially compacted and non-compacted fields, the rate of suppression of DMP by soil compaction was similar in the three rice cultivars, but DMP was higher in drought resistant cultivars having deep root density at the heading stage. Six cultivars were grown in pots of 1.0 m in depth containing the soils of three levels of soil bulk density (SBD). Water supply was restricted by keeping the water table in the pot deep without irrigation during the reproductive stage. DMP and Tr in all cultivars decreased with increasing SBD, and a close relationship was seen between DMP and Tr. WUE was thus a fairly stable factor for all cultivars examined. Tr was positively correlated with root length density and was relatively maintained at a high SBD in drought-resistant cultivars having a higher root length density. We concluded that water shortage under compacted soil conditions during reproductive stage suppressed the DMP, and DMP suppression accompanied a reduction of Tr due to poor root development rather than the reduction of WUE. In the drought-resistant cultivars reduction of DMP was relatively small due to their highly developed root systems that allowed high water absorption from the deep layers in the compacted soil.     

不同穴距对水稻生育及产量影响

以超级稻盐丰47为材料,采用小区对比试验方法探讨了不同穴距对水稻生长发育及产量形成的影响。结果表明,随着穴距的加大,提高了植株分蘖发生率和成穗率能力,增强了植株抗病性。行穴距为33 cm×15 cm的X2处理,其单位面积收获穗数、成熟期干物质产量以及齐穗至成熟期干物质积累量占其籽粒产量的百分比均居首位,该处理产量为697.8kg/667 m2,比X3、X1、分别增产了2.3%和5.5%。X1、X2、X3处理的单株成穗数分别为3.9、4.5、4.8株。     

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.     

Studies on Agronomic Traits of African Rice (Oryza glaberrima Steud.): IV. Changes in growth,dry matter productivity and yielding ability related to domestication from wild to cultivated form

Abstract

The changes in growth, dry matter productivity and yielding ability in the course of domestication from O. breviligulata to African rice (O. glaberrima) were examined. Between the two rice species, differences were hardly detected in plant height, culm length and final leaf number, although O. breviligulata had a wider variation of these characteristics as compared with African rice. The shorter strains tended to produce more tillers at the maximum tiller number stage, and the high tillering capacity was correlated with a low percentage of productive tillers, although the strains having a small number of grains per head showed a high percentage of productive tillers, in both species. No significant difference was detected between the two species in straw weight at maturity, and the differences in straw weight among strains were attributed to the differences in days required from transplanting to heading and to plant height. No significant difference between the two species was observed in top and total weights. The grain number per head was conversely related with panicle number in both species. Although the percentage of ripened grain tended to be slightly lower in O. breviligulata than in African rice, this may be attributed partly to the difference in grain number per hill. Single grain weight in O. breviligulata was nearly equal to that in African rice. These results suggest that agronomic traits such as growth, dry matter productivity and yielding ability have been changed only slightly in the course of domestication from O. breviligulata to African rice.     

N素基蘖与穗肥不同比例对水稻群体指标的影响

通过东风、西安两地大区试验,探讨了N素基蘖与穗肥不同比例对水稻群体各指标的影响。结果表明,N素基蘖与穗肥比为25∶3∶的GN处理,在N-n叶龄期够苗后,高峰苗得到较好控制,获得高成穗率;抽穗到成熟期干物质积累量最高,分别为708.9、743.4 kg/667 m2,两处理的产量也最高,分别为759.7、805.9 kg/667 m2;基蘖肥所占比例的增加有利于提高分蘖率,对叶龄影响不大,但过重施用基蘖肥,无效分蘖多,高效叶面积率和有效叶面积率降低,而适量增加穗肥,有利于提高高效叶面积率和有效叶面积率。     

Effect of salinity on yield and 2-acetyl-1-pyrroline content in the grains of three fragrant rice cultivars (Oryza sativa L.) in Camargue (France)

Aromatic quality of rice grains is known to vary greatly with environmental factors and cultivation methods. Among the environmental factors, soil salinity is thought to have a positive impact on the content of 2-acetyl-1-pyrroline (2AP) in grains, the key volatile compound of rice aroma. This study compared 2AP content in grains of three improved fragrant rice (Oryza sativa L.) varieties grown in two fields, differing mainly in their soil salinity level. The impact of salinity on yield and main yield components was also investigated to understand the relationship between aromatic quality and yield build-up. Soil salinity was monitored by measuring the electrical conductivity (EC) of soil solution samples extracted every week. 2AP content in grains was determined by a newly developed stable isotope dilution method involving solid-phase microextraction (SPME) and GC MS/MS analysis. The results showed an increase of 2AP content in grains with salinity for the three varieties. The relationship between 2AP and mean EC of the crop fitted a single model for the three varieties (R² = 0.728). In contrast, the impact of salinity on yield and yield components differed greatly between the three varieties. One variety appeared to be very sensitive to salt stress, with significant yield loss up to 40%, while the two other varieties proved to be resistant to the salinity levels experienced by the plants, with no significant yield loss or even higher yields in saline conditions. Nevertheless, the three varieties presented a significant negative correlation between 1000 grain weight (TGW) and the mean EC of the crop, and between TGW and 2AP content. It was concluded that the increase of 2AP content with salinity resulted partially from a 2AP concentration mechanism in smaller size grains. The direct effect of salinity on 2AP synthesis through stimulation of the proline metabolism is further discussed.     

Mechanism of High Photosynthetic Capacity in BC2F4 LinesDerived from a Cross between Oryza sativa and Wild Relatives O. rufipogon

Abstract

We found that several BC₂F₄ lines had high leaf photosynthetic rates under light-saturated and ambient CO₂ conditions. These lines are progenies of BC₂F₁ plants with high photosynthetic capacities which were generated by backcrossing between Oryza rufipogon (W630) and O. sativa cv. Nipponbare, as a recurrent parent. Some photosynthetic characteristics of the BC₂F₄ lines were investigated to identify the factors increasing photosynthetic rates. Photosynthetic rates of these lines under light-saturated conditions at 50 to 700 ppm CO₂ concentrations were higher than those in Nipponbare. The estimated-maximum photosynthetic rates under light-saturated and CO₂-saturated conditions in BC₂F₄ lines were also higher than that in Nipponbare. The photosynthetic rate under light-saturated and ambient CO₂ conditions was positively correlated with the carboxylation efficiency as an indicator of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity in vivo rather than stomatal conductance. Initial and total Rubisco activities in vitro tended to be higher in the BC₂F₄ lines than in Nipponbare. The content of active Rubisco calculated from the activation state of Rubisco was also higher in the BC₂F₄ lines than in Nipponbare. These results suggest that high photosynthetic capacities of BC₂F₁ plants can be maintained high in their progenies and high photosynthetic rates under light-saturated and ambient CO₂ conditions in the BC₂F₄ lines are achieved mainly by the high activity of Rubisco due to the high active Rubisco content.     

Potato and Human Exploration of Space: Some Observations from NASA-Sponsored Controlled Environment Studies

Future space exploration by humans will require reliable supplies of food, oxygen and clean water to sustain the expeditions. Potato is one of several crops being studied for such a “life support” role. Tests sponsored by the US National Aeronautics and Space Administration (NASA) confirmed the well-known short day tendencies for tuberisation, but also revealed that some cvs. (e.g., Norland, Denali and Russet Burbank) could tuberise well under continuous high light. Horticultural tests showed that plants grew well and tuberised readily using a nutrient film technique (NFT). CO₂ enrichment studies with potato showed typical C₃ responses in photosynthesis and yield, with maximum rates occurring near 1000 μmol mol⁻¹. The highest tuber yields from these controlled environment studies reached 19.7 kg FM m⁻² or equivalent to nearly 200 t ha⁻¹. This equated to a productivity of 38 g m⁻² DM m⁻² day⁻¹. Stand evapotranspiration (ET) rates ranged from 3.4 to 5.2 l m⁻² day⁻¹ throughout growth, while maximum ET rates for canopies could approach 10 l m⁻² day⁻¹. Harvest indices (tuber DM/total DM) typically ranged from 0.7 to 0.8, indicating that waste (inedible) biomass from potato would be less than that from many other crops. An experiment was conducted in 1995 on NASA’s Space Shuttle using excised potato leaves to study tuber formation at axillary buds during spaceflight. The results showed that tubers formed equally well in space as in the ground controls, indicating that reduced gravity should not be an impediment to tuberisation.     

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 free air carbon dioxide enrichment and nitrogen supply on growth and yield of winter barley cultivated in a crop rotation

The increase in atmospheric CO₂ concentration [CO₂] has been demonstrated to stimulate growth of C₃ crops. Although barley is one of the important cereals of the world, little information exists about the effect of elevated [CO₂] on grain yield of this crop, and realistic data from field experiments are lacking. Therefore, winter barley was grown within a crop rotation over two rotation cycles (2000 and 2003) at present and elevated [CO₂](375 ppm and 550 ppm) and at two levels of nitrogen supply (adequate (N2): 262 kg ha⁻¹ in 1st year and 179 kg ha⁻¹ in 2nd year) and 50% of adequate (N1)). The experiments were carried out in a free air CO₂ enrichment (FACE) system in Braunschweig, Germany. The reduction in nitrogen supply decreased seasonal radiation absorption of the green canopy under ambient [CO₂] by 23%, while CO₂ enrichment had a positive effect under low nitrogen (+8%). Radiation use efficiency was increased by CO₂ elevation under both N levels (+12%). The CO₂ effect on final above ground biomass was similar for both nitrogen treatments (N1: +16%; N2: +13%). CO₂ enrichment did not affect leaf biomass, but increased ear and stem biomass. In addition, final stem dry weight was higher under low (+27%) than under high nitrogen (+13%). Similar findings were obtained for the amount of stem reserves available during grain filling. Relative CO₂ response of grain yield was independent of nitrogen supply (N1: +13%; N2: +12%). The positive CO₂ effect on grain yield was primarily due to a higher grain number, while changes of individual grain weight were small. This corresponds to the findings that under low nitrogen grain growth was unaffected by CO₂ and that under adequate nitrogen the positive effect on grain filling rate was counterbalanced by shortening of grain filling duration.     

Fatty acid composition and oxidation stability of hemp (Cannabis sativa L.) seed oil extracted by supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO₂) was employed to extract oil from hemp (Cannabis sativa L.) seeds. For ground seeds, the supercritical extraction was carried out at temperatures of 40, 60 and 80 °C and pressures of 300 and 400 bar. Different solvent-ratios were applied. Supercritical CO₂ extractions were compared with a conventional technique, n-hexane in Soxhlet. The extraction yields, fatty acid composition of the oil and oxidation stability were determined. The seed samples used in this work contained 81% PUFAs, of which 59.6% was linoleic acid (ω-6), 3.4% γ-linolenic (ω-3), and 18% α-linolenic (ω-6). The highest oil yield from seeds was 22%, corresponding to 72% recovery, at 300 bar and 40 °C and at 400 bar and 80 °C. The highest oxidation stability corresponding to 2.16 mM Eq Vit E was obtained at 300 bar and 80 °C.     

Screening,Inheritance and Linkage Marker Analyses of Salt Tolerance in Mutated Scented Japonica Rice (Oryza sativa L.)

Abstract

We grew 1005 mutated scented japonica rice lines to the seventh steady genetic generation, and treated the seedlings with six true leaves with 300 mM NaCl for three days. Only the salt-tolerant line, SM61, survived. We obtained F₁, F₂ and F₃ populations from the cross between SM61 and a salt-susceptible indica variety, TCS17. After culture with 200 mM NaCl for five days, SM61 and F₁ (SM61×TCS17; TCS17×SM61) plants survived (R) while TCS17 plants did not (S). The R to S ratio in 513 F₂ plants showed a good fit to the Mendelian 3 : 1 segregation ratio by a Chi-square test indicating that the salt-tolerance of SM61 was governed by a single dominant gene. The mutated salt-tolerance gene explained close to 100% of the total phenotypic variation, and was tightly linked to RM223 (marker) located on chromosome 8, which was different from the results of previous studies investigating the relationship of QTLs with salt tolerance. This is the first report of mapping tightly linked markers of a single dominant mutated salt-tolerance gene.     

栽培稻中间型品种和籼粳交DH株系的亲和性鉴定

以籼、粳标准测验种为母本，对栽培稻一些中间型材料、籼粳交DH株系及籼粳对照品种在内的共95份材料进行杂交亲和性鉴定，结果显示：全部材料的亲和性分化呈连续分布，可分为亲籼(ICV)、亲粳(JCV)、广亲和(WCV)及非亲和(NCV)4种类型；共鉴定到55份广亲和性材料，主要为中间型(18份)和籼粳交DH株系(34份)；亲本具有广亲和性的籼粳交DH株系几乎全部具有广亲和性(占96．2％)，且广亲和性强于对照品种零轮，而亲本不具有广亲和性的籼粳交DH中也能产生广亲和株系(占25．0％～57．1％)，但广亲和性略差。认为水稻广亲和性的产生可能是由籼粳分化决定的，选育中间型广亲和系是广亲和品种选育的主要方向。     

Near-isogenic lines of IR64 (Oryza sativa subsp. indica cv.) introgressed with DEEPER ROOTING 1 and STELE TRANSVERSAL AREA 1 improve rice yield formation over the background parent across three water management regimes

Three near-isogenic lines (NILs) of Oryza sativa subsp. indica cv. IR64 (Dro1-NIL, Sta1-NIL, Dro1+Sta1-NIL) with DEEPER ROOTING 1 (DRO1), a novel gene for steeper root growth angle, and/or with Stele Transversal Area 1 (Sta1), a QTL for wider stele area, were tested under flooded lowland (FL), alternate wetting and drying lowland (AWD), and rainfed upland (UP) conditions in 2013 and 2014 to compare the effects of DRO1 and Sta1 on yield across different water management regimes. Genotypic variation and water management effects were significant for grain yield, aboveground biomass, and harvest index, as well as their interactions with year, but no significant genotype × water interaction was detected. Dro1-NIL had 14% higher yield than that of IR64 across the three water conditions due to higher harvest index, aboveground biomass, leaf area index, and number of grains. Sta1 tended to reduce the carbon isotope composition (δ¹³C), leading to a higher harvest index of Sta1-NIL than that of IR64, but grain yield was not increased. Dro1+Sta1-NIL had the highest fraction of intercepted radiation, cumulative radiation interception, and panicle number, with a small but insignificant yield improvement over IR64, but the combination of DRO1 and Sta1 did not surpass the increment from the effects of DRO1 alone. AWD in the more rainy year 2014 attained both higher water productivity and higher biomass, with significant water by year interaction for water productivity. Genotypic variation in water productivity was related with higher leaf area index and fraction interception, with Dro1-NIL larger than in IR64 and Sta1-NIL.     

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.