不同耐密性玉米品种光合特性对弱光响应的差异

以郑单958、东单90为试材,研究不同耐密性玉米品种光合特性对弱光胁迫响应的差异。结果表明,正常光照条件下郑单958光合性能优于东单90。郑单958在弱光胁迫后与其正常光照(对照)相比表观量子效率(AQY)增大,光合速率(Pn)、最大净光合速率(P max)、光补偿点(LCP)、光饱和点(LSP)均降低,表现出对弱光的光能利用效率明显高于对照,对强光利用效率较低。东单90在弱光胁迫后与其正常光照(对照)相比AQY降低,P max、LCP、LSP均升高,表现为对强光利用效率高,对弱光利用效率与对照基本相同。叶绿素荧光参数表明,郑单958弱光胁迫后PSⅡ光化学反应中心活性降低、高光强下光能利用效率降低主要是由于叶片光合活性下降;东单90弱光胁迫后对高光强的光利用效率升高的原因是叶片经弱光胁迫后减少了光合过程中的热耗散。     

A canopy photosynthesis model to predict the dry matter production of cocksfoot pastures under varying temperature, nitrogen and water regimes

Daily net canopy photosynthesis (P_n) of cocksfoot (Dactylis glomerata L.) was predicted for combinations of temperature, herbage nitrogen (N) concentration and water status from the integration of models of leaf photosynthesis of the light‐saturated photosynthetic rate (P_max), photosynthetic efficiency (α) and the degree of curvature (θ) of leaf light‐response curves. The effect on P_n, maximum P_n (P_{n max}) and the optimum leaf area index (LAI at P_{n max}) was examined when any one of these factors was limiting. The ranges that gave the optimum values of P_n (P_{n max} = 30·8–33·5 g CO₂m^?2 d^?1) for temperature (19–22°C) and N concentration (40–50 g N kg^?1 DM) were smaller than those for net leaf photosynthesis. Also, P_n fell to 0 at a lower level of water stress (pre‐dawn leaf water potential, ψ_lp = ?12·5 bar) than for P_max. The canopy photosynthesis model was then used to compare predicted and measured dry matter (DM) production for cocksfoot pastures grown under a diverse range of environmental conditions with field data from New Zealand and Argentina. To predict DM production leaf area index and leaf canopy angle were included from field measurements. The model explained about 0·85 of the variation in cocksfoot DM production for the range of 6·5–134 kg DM ha^?1 d^?1. The canopy model overestimated the DM production by 0·10 which indicates that a further P_max function for leaves of different ages and a partitioning sub‐model may be needed to improve predictions of DM production.     

Growth, gas exchange, water relations, and ion composition of Phaseolus species grown under saline conditions

We examined the effects of salinity on four wild (Phaseolus angustissimus, Phaseolus filiformis, P. microcarpus, and P. vulgaris) and two cultivated (P. acutifolius and P. vulgaris L.) Phaseolus species. Relative growth rate (RGR, g g⁻¹ per day), unit leaf rate (ULR, g m⁻² per day), leaf area ratio (LAR, m² g⁻¹), specific leaf area (SLA, m² g⁻¹), leaf weight ratio (LWR, g leaf g⁻¹), and rate of ion uptake were calculated for the period between 10 and 20 days after planting. Salinity significantly reduced RGR, ULR, LAR, and SLA whereas LWR showed no definite trend. In all species, except in P. filiformis, ULR, but not LAR, was significantly correlated with RGR, indicating that ULR was an important factor underlying the salinity-induced differences in RGR among species. In P. filiformis, high salinity reduced SLA, and consequently LAR. The significant correlation of SLA and LAR with RGR suggested that growth components affecting leaf area expansion were the primary factors explaining the inhibition of growth in this species. Increasing salinity progressively decreased leaf water vapor conductance. The rate of CO₂ assimilation decreased gradually with salinity, showing significant reductions only at the highest salt level (80 mM NaCl). Approximately two-thirds of the reduction in CO₂ assimilation rate at high salinity was attributable to reduced stomatal conductance. In P. filiformis, however, neither stomatal conductance nor CO₂ assimilation were affected by salt stress. Leaf water and osmotic potentials declined significantly as stress intensified. However, osmotic adjustment permitted the maintenance of positive turgor throughout the growth period. Salinity had a significant effect on tissue concentrations of Na⁺, K⁺, Ca²⁺, and Cl⁻ and on the uptake rate of Na⁺, K⁺, Ca²⁺, and Cl⁻. Thus, in addition to the toxic effects of high concentrations of Na⁺ and Cl⁻ in plant tissue, saline-induced changes in mineral nutrient uptake likely contributed to the reduction of plant growth. It appears that salt tolerance in P. filiformis is associated with Na⁺ exclusion and organ Na⁺ compartmentation in roots and stems as well as sustained K⁺ concentration in leaves and better stomatal control through osmotic adjustment. All other Phaseolus species are Na⁺ excluders, and maintained turgor-driven extension growth by accumulating Cl⁻ (osmotic adjustment), but subsequent weight gain reductions suggest that this led to ion toxicity.     

Change in Hydraulic Resistance and Shoot Morphology of Napiergrass (Pennisetum purpureum Schumach.) under Shaded Condition

Abstract

Acclimation to light condition is associated with change in water transport system in napiergrass. In this study, the effects of shading on shoot hydraulic resistance and morphology of napiergrass (Pennisetum purpureum Schumach.) were investigated. In the plants under shading (to 30% of full sunlight) for 30 days (S plants), total hydraulic resistance of a shoot (Rshoot) increased from that of full sunlight (control). In the plants grown under shade condition for 24 d followed by full sunlight conditions for 6 d (SF), the Rshoot value was intermediate between that of control and S plants. A similar response to shading was found in total hydraulic resistance of a stem (R_stem), which accounted for more than 60% of Rshoot, but the total hydraulic resistance of the leaves was not significantly affected by shading. Leaf length, leaf area and stem length were larger, but the stem cross-sectional area (SA) was smaller in S and SF plants than in the control plants. SF plants showed similar leaf length, leaf area and stem length to those in S plants, but the SA in SF plants was slightly larger. Normalization of R_stem by SA and stem length decreased the difference among the treatments, indicating the increase of Rshoot and R_stem under shading resulted from the decrease of SA and the increase of stem length.     

低温冷凉地区超高产春玉米群体生长分析研究

以“三合模式”为基础,从产量构成、光合性能、源库3方面对东北雨养玉米产区产量水平高于1.5×104kg/hm2的不同密度玉米群体进行研究。结果表明:在东北雨养地区玉米要获得高于1.5×104kg/hm2的产量,须选择耐密性品种,密度介于80000～87000株/hm2,叶片光能持续期长,吐丝后光合势大于2.87×106m2/(d·hm2),叶面积比率与叶面积维持在合理水平,生育期平均净同化率大于5.21g/(m2·d),营养生长时期相对生长率迅速,吐丝到灌浆期相对生长率稳定,吐丝后干物质积累量高于16192.48kg/hm2,转化率大于83.6%,经济系数维持在0.5左右。     

Correlation of Leaf Nitrogen,Chlorophyll and Rubisco Contents with Photosynthesis in a Supernodulating Soybean Genotype Sakukei 4

Abstract

Soybean requires more nitrogen (N) than gramineous crops because it accumulates a large amount of N in seeds, and its photosynthetic rate per leaf N is low. The supernodulating genotype Sakukei 4 has a superior symbiotic N₂ fixation capability, and thereby is potentially high-yielding. In our previous study, Sakukei 4 was characterized by having a superior ability to maintain high leaf N content and high photosynthetic rate. The objectives of this study were to know photosynthetic characteristics of Sakukei 4 in detail, especially, the responses to CO₂ concentration and light intensity, and to elucidate how the photosynthetic characteristics of Sakukei 4 are associated with the amounts of photosynthesis-related N compounds (chlorophyll and Rubisco). The three genotypes (Sakukei 4 - supernodulating cultivar derived from Enrei, Enrei - normally nodulating cultivar, En1282-non-nodulating line derived from Enrei) were grown at various N levels in this study. The CO₂ exchange rate (CER) in Sakukei 4 was higher than, or equal to that in Enrei at wide ranges of CO₂ concentrations (150-700 μmol mol-¹) and light intensities (200-1,500 μmol m-² s-¹ PPFD). Sakukei 4 had higher leaf N (N_l), chlorophyll (Chl_L) and Rubisco (Rub_L) contents per leaf area, but lower chlorophyll and Rubisco contents per leaf N content (Chl_L/N_l, Rub_L/N_l) than Enrei. The specific leaf weight (SLW) and leaf area trended to be lower in Sakukei 4 than in Enrei. These results indicate that the superior photosynthetic rate in Sakukei 4 is attributed to higher total N, chlorophyll and Rubisco contents per leaf area, but not to high rate of allocation of total N to these N compounds.     

京单38不同播期子粒灌浆特性研究

以郑单958为对照,设置春播（5月14日）和夏播（6月13日）两个播期处理,研究玉米品种京单38在不同生态条件下的子粒灌浆特性。结果表明,京单38的百粒干物重高于对照品种郑单958,春、夏播条件下增幅分别为14.74%和20.26%,春播百粒干物重较夏播高1.87%。京单38的子粒灌浆速率高于郑单958,春、夏播最大灌浆速率分别较对照高42.27%和49.50%,夏播最大灌浆速率较春播高9.42%。相关和通径分析表明,最大灌浆速率与粒重呈极显著正相关,与郑单958相比,京单38子粒灌浆速率高且灌浆速度快,春、夏播条件下均可获得较高的粒重。     

Effect of nitrogen supply on leaf growth,leaf nitrogen economy and photosynthetic capacity in potato

Literature reports show little effect of nitrogen supply on radiation use efficiency in potato and in other dicotyledonous C₃ species. This paper tests the hypothesis that potato reduces leaf size rather than leaf nitrogen concentration and photosynthetic capacity when nitrogen is in short supply. Four pot experiments with different rates of nitrogen supply were conducted in glasshouses. For two leaf numbers measurements were made of leaf area, P_max (rate of photosynthesis for saturating irradiance), specific leaf weight, and concentrations of total nitrogen and nitrate, all as a function of leaf age.Area per leaf was sensitive to nitrogen supply (about a factor 3 between extreme N treatments). P_max declined with leaf age. There were no systematic effects of nitrogen supply on P_max and on its change with leaf age, except that in some cases P_max of leaves of high N treatments was lower than P_max of low N treatments during part of the life span (leaf age of ca. 20–50 days). The dominant effect of nitrogen supply was on leaf size and not on P_max or leaf N content. P_max versus areal organic nitrogen concentration (g N m⁻² leaf area) showed considerable scatter and, for a given nitrogen concentration, a slightly lower P_max for high N treatments than for low N treatments. Comparison with other species showed a comparatively low value of P_max in potato.     

京科968的灌浆特征与产量性能分析

以京科968为材料, 采用春播、夏播2种播期, 设置45 000、60 000、75 000株/hm²共3种密度处理, 对其灌浆特征与产量性能进行分析。结果表明, 粒重与灌浆速率最大时的生长量(W_max)、最大灌浆速率(G_max)、活跃灌浆天数(P)呈极显著正相关, 与达到最大灌浆速率的天数(T_max)、灌浆起始势(R₀)呈显著或极显著负相关。平均叶面积指数、穗数、产量与密度呈正相关;平均净同化率、穗粒数、千粒重与密度呈负相关;平均叶面积指数与穗数与产量都呈极显著正相关。     

Display practices and changes in riboflavin content of non-fermenting palm juice

Changes in riboflavin content of industrially bottled palm juice stored at different light intensities similar to display patterns practised by traders was studied. The loss of riboflavin in the first 24 hours was significantly higher than in the second 24 hours in both transparent (P<0.001) and green bottles (P<0.02) exposed to bright sunlight. Riboflavin loss from samples stored in transparent bottles occurred at a faster rate (24–71% of initial) than from samples in green bottles (0–29%) over a 36-hour period. Further loss of riboflavin did not occur over the next 36 hours due to cool weather conditions. In contrast, only 6% of initial riboflavin was lost after 72 hours of continuous exposure to fluorescent light: this increased by 53% by the ninth week. The data showed that riboflavin loss from bottled palm juice varied with the container, the environmental conditions and period of storage. It is recommended that palm juice should be displayed in dark bottles and protected from bright light.     

六倍体小黑麦重要性状的改良潜力探究

小黑麦是近代创建的禾本科新作物,具有生物量大、抗逆性好等特点,适宜农牧结合区种植。为明确小黑麦重要性状的改良潜力并为粮饲兼用型小黑麦杂交育种提供依据,以我国的冬性小黑麦兰小黑和CIMMYT的春性小黑麦CM-12、CM-13及其构建的三个杂交F₁、F₂群体为材料,对苗相、株高、单株穗数、穗长、小穗数、叶片特性、茎秆特性等重要农艺性状进行田间考察,分析各性状的配合力,并计算3个F₂群体各个性状的遗传变异系数、遗传力等参数,以探索各重要性状的改良潜力。结果表明,冬性与春性小黑麦的杂交群体比春性与春性杂交群体具有较高的变异系数和遗传力;小黑麦的穗颈长、旗叶宽、旗叶长等性状遗传力较高,变异系数较大,利用分离群体对这些性状进行遗传选择的潜力较大,具有可行性。     

小麦品种东农冬麦2号根中TaEXPA7部分同源基因的克隆及表达特性分析

膨胀素(expansin)是植物生长发育过程中诱导细胞壁松弛和伸展的蛋白,包括EXPA、EXPB、EXLA、EXLB四个基因家族,对植物根系的形成及快速发育具有重要作用。本试验以寒地冬小麦品种东农冬麦2号两叶一心期的根为材料,克隆了TaEXPA7基因的3个CDS全长,其氨基酸序列同源性较高,仅信号肽处有两个氨基酸不同,其核酸序列长度均为777bp,编码258个氨基酸,分别命名为TaEXPA7-A、TaEXPA7-B、TaEXPA7-D,且分别定位于2AL、2BL、2DL染色体。蛋白均含有DPBB-1和Pollen-allerg-1两个保守结构域,分子量为27 670.74Da,等电点为8.09,均为疏水性蛋白;与节节麦、二穗短柄草的相似性分别为99%和92%。采用两叶一心期的根进行qRT-PCR分析发现,TaEXPA7-A/B/D三个基因在根尖中的表达量均较高,伸长区和成熟区次之;对冬小麦根进行低温、干旱和激素处理后,这三个基因均下调表达,并且TaEXPA7-B基因的相对表达量较高,TaEXPA7-D的相对表达量较低。由此可见,多倍体小麦不同染色体上的基因在应对不同环境胁迫时,表达以及应答模式存在差异,并且在不同的环境胁迫下,发挥主导作用的染色体也存在差异;此外,该基因在根中的表达可能与低温、干旱以及外源激素的胁迫有一定的关系,可能是促进根系生长的重要基因。     

不同氮效率小麦品种苗期根系氮代谢及其吸收能力差异分析

为了解不同氮效率小麦品种根系氮代谢特征及其吸收能力的差异,明确小麦氮高效利用的生理机制,在水培条件下,研究了氮高效小麦品种漯麦18和氮低效小麦品种西农509的根系氮代谢特征和对NO-3、NH+4吸收的动力学特征。结果表明,漯麦18的根系GS活性、硝酸还原酶活性、游离氨基酸含量、可溶性蛋白质含量均高于西农509;而西农509的根系硝态氮和铵态氮含量高于漯麦18;漯麦18根系对NO-3、NH+4吸收的最大吸收速率(Vmax)显著高于西农509;漯麦18根系对NO-3、NH+4的亲和力(以Km的倒数衡量)低于西农509。结果说明,氮高效型小麦品种根系对NO-3、NH+4的吸收能力和同化能力均显著高于氮低效型小麦品种;小麦根系对NO-3、NH+4的吸收和同化是相互促进的关系。     

Effect of fertilization treatments on yield parameters and mucilage and fat contents in roots of moghat (Glossostemon bruguiri Desf.)

Moghat plants,Glossostemon bruguieri, Desf., received three levels of both N and K fertilizers, either alone or in combination, with a basic dose of P for all the treatments. The results with one and two year old plants revealed the importance of potassium for higher yield of roots, reflected in greater length and diameter. The lower level K₁ was enough to attain that goal and the N₁K₁ treatment was the best in this regard. On the other hand, N fertilization rather favoured the vegetative growth and seed yield. Both N and K fertilization decreased the mucilage content of the roots, but increased their fat content. The root yield after two years increased by 72% compared with one year old plants. That increment was rather dependent on the root diameter than its elongation. The mucilage content was doubled, while the fat content decreased.     

Some characteristics of reduced leaf photosynthesis at midday in maize growing in the field

Maize was grown in the high-radiation arid summer environment of Davis, California, and its leaf photosynthetic rate was measured over diurnal courses on cloudless days with the leaf held perpendicular to the sunlight. On days of high atmospheric vapor pressure deficit (VPD), leaf photosynthesis reached a maximum in the late morning and then decreased gradually as the day progressed, though the soil was well irrigated. When CO₂ concentration in the measurement chamber was raised to about 1000 μmol mol⁻¹, photosynthesis was enhanced, but more in the afternoon than in the morning. As a result, rates measured at high CO₂ in the morning and afternoon were essentially the same. There was also no difference in the curves of photosynthetic rate (A) versus intercellular CO₂ concentration (C_i) for the morning and afternoon. Hence, photosynthetic capacity was similar for the two periods and there was no evidence of photoinhibition by the high photosynthetic photon flux density at noon. Further, C_i and photosynthetic rates A measured over a range of photon flux density were lower in the afternoon than in the morning. These results indicate that A at noon and early afternoon was more limited than in the morning by epidermal conductance (mostly stomatal). On a day of low VPD, however, midday depression in A and epidermal conductance were not evident for the well-irrigated plants. Without irrigation and with leaves at a lower midday water potential, midday reduction in conductance and A was much more marked, beginning late in the morning. Epidermal conductance of maize grown in the field in Davis is are not sensitive to VPD. Therefore, the midday reduction in conductance and A was more likely the result of low leaf water potential caused by high transpiration rates.     

Effects of Organic Farming Practices on Photosynthesis,Transpiration and Water Relations,and Their Contributions to Fruit Yield and the Incidence of Leaf-Scorch in Pear Trees

Summary

This study involved a comparison of two pear (Pyrus communis L. cv. Nijuseki) orchards in the South Nagano area that were managed according to either chemical farming (CF) or organic farming (OF) practices. Leaf-scorch was not observed in the pear orchard under OF but was severe under CF. Fruit yield was 62% higher for the pear orchard farmed organically. Photosynthetic capacity (P _C) was 33% higher under OF. Leaf symplastic water fraction (z _sym) and osmotic concentration (C _FT) were higher for pear trees under OF than for those under CF. Both stomatal (a) and cuticular (b) transpiration were faster for excised pear leaves under CF and, as a consequence, the leaf water retention ability (WRA) of leaves under CF was lower than for those under OF. Results suggest that the higher yield of pear trees with organic farming management, compared with chemical farming, is attributed to high P _C and that the absence of leaf-scorch is attributed to a high water retention ability that is associated with a high symplastic cell water fraction and high tissue osmotic concentration.     

新疆杂草黑麦的光合特性分析及综合评价

为探究新疆杂草黑麦光合特性,筛选出高光效优异种质资源,对15个新疆杂草黑麦居群在开花期进行了光合参数的测定及分析。结果表明,新疆杂草黑麦居群间光合性状存在显著差异。通过主成分分析将5个光合性状简化为2个综合指标,分别反映光合能力和水分利用,可反映全部信息的88.67%。通过聚类分析将15个居群分为3大类,其中第Ⅲ大类的居群材料89R6、89R30、89R33、89R59、89R66的净光合速率、蒸腾速率、气孔导度和水分利用率均较高,其产量相关性状也表现较好,可作为麦类作物高光效种质加以利用。     

A molecular dynamics simulation on the self-assembly of ABC triblock copolymers. 2. Effects of block sequence

The effect of block sequence on the self-assembly of ABC-type triblock copolymers in the ordered state is investigated using an isothermal-isobaric molecular dynamics simulation. The block sequence has an important effect on the morphology of ABC triblock copolymers. Different morphologies are observed depending on the block sequence as well as the block composition. The triblock copolymers with the volume fraction of 1:1:1 (f _A=f _B=f _C=0.33) show the three phase and four layered lamellar structures irrespective of the block sequence. The A₃₂B₁₆C₃₂ triblock copolymer withf _B=0.2 shows a morphology in which cylinders of midblock B are formed at the interface between A and C lamellae, whereas the morphology of triblock copolymer B₁₆C₃₂A₃₂ and C₃₂A₃₂B₁₆ show a cylindrical core-shell structure and a lamellar type morphology, respectively. The A₂₀B₄₀C₂₀ triblock copolymer with the block B as a major component shows a tricontinuous structure, whereas both B₄₀C₂₀A₂₀ and C₂₀A₂₀B₄₀ triblock copolymers exhibit the lamellar structures. When the block B has larger volume fraction withf _B=0.75, the matrix is composed of block B, and other two blocks A and C form spherical domains.     

Soybean inoculation: Dose, N fertilizer supplementation and rhizobia persistence in soil

The effect of rate of application of Sinorhizobium (Ensifer) fredii SMH12 or Bradyrhizobium japonicum USDA110 inoculants on grain yields of soybean [Glycine max (L.) Merrill] cv. Osumi was studied in a field experiment laid out in Southern Spain. All inoculant doses tested (10⁴, 10⁵, 10⁶ and 10⁷ rhizobia/seed) produced higher seed yields than those obtained in un-inoculated plots. Increments in nodule dry weight, seed yield and seed N content were observed when the number of rhizobia applied to seed increased from 10⁴ up to 10⁷. The addition of N fertilizer to inoculated soybean plants (50 kg N/ha applied at R1 or R4 stage) did not increase seed yields in comparison with treatments that were only inoculated. Survival of strains SMH12 and USDA110 was monitorized for three years in two different soils of Southern Spain after soybean inoculation. Rhizobia survival was varied dependent on the soil and the rhizobia strain used.     

转精氨酸酶基因ZmARG玉米后代株系的遗传稳定性分析和功能验证

以T4、T5代转ZmARG基因玉米株系AKF65和受体自交系KF513为试材,对目标基因的整合表达、酶活性及产量相关农艺性状进行检测。结果表明,PCR、Southern和RT-PCR检测证明,ZmARG基因以单拷贝的形式插入基因组,在转录水平上能够稳定表达,且两个世代中稳定遗传。转基因株系灌浆期叶片中的精氨酸酶活力显著高于对照,萌发种子和苗期根中极显著高于对照,种子萌发时酶活力最高。转基因株系百粒重、穗重和小区产量显著高于对照,穗长极显著高于对照,其他各产量相关农艺性状差异不显著。