Effect of lanthanide chloride on photosynthesis and dry matter accumulation in tobacco seedlings

To investigate the physiological effects of rare earth ions, we have studied the effect of LaCl₃ on the photosynthetic light reactions in tobacco (Nicotiana tobacum). When treated with 5–20 mg/L LaCl₃ in Hoagland solution by water culture, the dry matter accumulation of different parts in tobacco, the content of chlorophyll increased gradually, but decreased when the concentration of LaCl₃ was ≥ 50 mg/L. The optimum concentration for growth appeared to be about 20 mg/L of LaCl₃ in nutrient solution. La³⁺ promoted the activities of the Hill reaction, Mg²⁺-ATPase, and stimulated the rate of photophosphorylation in chloroplast at low concentrations, but inhibited them at high concentrations. It is concluded that La³⁺ stimulated the growth of tobacco seedlings and accelerated the photosynthetic light reactions at suitable concentration in vivo.     

亚高温下不同空气湿度对番茄光合作用和物质积累的影响

为了研究亚高温下不同空气湿度对番茄植株光合作用及物质积累的影响,本试验利用人工气候室,在11:00—15:00平均温度为33℃的亚高温条件下,设置3个空气相对湿度处理,分别为70%～80%(高湿)、50%～60%(中湿)和不加湿的30%～40%(低湿)。结果表明:在处理25d时,高湿处理番茄叶片叶绿素含量、净光合速率显著高于低湿处理,而低湿处理果实空洞率比高湿处理高18.4%(P<0.05);在33℃亚高温条件下,70%～80%的相对湿度有利于光合作用的增强和果实品质的提高。     

遮阴对夏玉米干物质积累及养分吸收的影响

以振杰2号(ZJ2)、登海605(DH605)和郑单958(ZD958)为试验材料,在大田条件下设置花粒期遮阴(S₁)、穗期遮阴(S₂)、全生育期遮阴(S₃)3个遮阴处理,以自然光照条件为对照(CK),研究了遮阴对夏玉米干物质积累和氮、磷、钾吸收的影响.结果表明: 遮阴后夏玉米籽粒产量和单株干物质积累量显著降低,降低程度与遮阴时期有关,表现为S₃>S₁>S₂,其中S₁、S₂和S₃籽粒产量平均降低61.6%、25.3%和92.8%,说明花粒期遮阴较花前遮阴对夏玉米干物质积累和籽粒产量影响更大,不同品种的变化趋势相同.夏玉米植株花前养分吸收量表现为钾>氮>磷,植株吸收总量表现为氮>钾>磷.遮阴后植株氮和磷积累量显著减少,由于遮阴后干物质较对照降低程度大于对氮、磷吸收的降低程度,各处理氮、磷相对含量有所升高;遮阴后各处理植株钾吸收量较对照显著降低,但S₂处理的钾吸收降低程度大于干物质积累降低程度,钾相对含量降低,即花前遮阴对玉米钾吸收的影响大于氮和磷.     

玉米-大豆带状套作下玉米株型对大豆干物质积累和产量形成的影响

通过田间试验, 以大豆单作为对照,设置登海605/贡选1号(RI₁)、川单418/贡选1号(RI₂)、雅玉13/贡选1号(RI₃)3种玉米 大豆带状套作种植模式,研究了玉米株型对大豆干物质积累和产量的影响.结果表明： RI₂和RI₃处理大豆的积累速率低于RI₁处理,且RI₁处理大豆叶片、茎秆和荚果的干物质积累量分别比RI₂和RI₃处理高17.6%、16.5%、13.7%和34.6%、33.1%、28.4%.带状套作大豆叶片、茎秆的分配比例均以RI₁处理最高、RI₂处理其次、RI₃处理最低,而荚果分配比例的变化趋势与其相反.与RI₂和RI₃处理相比,RI_1处理显著提高了大豆营养器官(叶+茎)干物质向荚果的转运量、转移率及其对荚果的贡献率,RI₁处理大豆的单株荚数、单株粒数、每荚粒数、单株粒质量和产量分别比RI₂和RI₃处理提高了6.8%、11.5%、4.4%、15.9%、15.6%和14.3%、22.2%、6.7%、33.4%、36.8%.带状套作大豆营养器官干物质的积累速率、转运量、转移率和贡献率与产量及产量的构成呈显著正相关,且均以RI_1处理最高,实现了紧凑型玉米对带状套作大豆干物质积累、转运和分配的有效调控,促进了产量的提高.     

Relationships between dynamics of nitrogen uptake and dry matter accumulation in maize crops. Determination of critical N concentration

The concept of critical nitrogen concentration(%N _c) has been proposed as the minimum%N in shoots required to produce the maximum aerial biomassat a given time. Several authors have shown that%N _c declines as a function of aerial biomassaccumulation (W) and the %N _c –W relationship has been proposed as a diagnostic tool of N statusin different crops, excluding maize. From data obtained in five nitrogenfertilisation experiments in irrigated maize crops, 26 critical data-pointswere selected with a precise statistical procedure. An allometric relationwas fitted and a critical %N−W relationshipmodel is proposed in maize as: If W < 1 t ha^-1%N _c = 3.40 If 1 t ha^-1≤ W ≤ 22 t ha^-1%N _c = 3.40(W)^−0.37 The model is applicable to maize crop development between emergenceand silking + 25 days. The model was tested and validated with dataobtained in a network of 17 N fertilisation experiments conducted inFrance under contrasting pedoclimatic conditions. In only nineout of 280 data-points (3.2%), the plant N status was mispredictedwhen ±5% error around %N _c wasallowed. A critical N uptake model (Nu_c, kg Nha^-1) is proposed as Nu_c = 34 (W)^0.63 A comparison between Nu_c and N uptake observedin N treatments giving the maximal grain yields has shown that maizecrops assimilate at least 30 kg N ha^-1 in a storage N poolat the silking stage. The significance of the critical%N−W and Nu−W relationships is discussed in relation to theoretical models proposed inwhole plant ecophysiology. Different relationships calculated betweenleaf area index and aerial biomass accumulation, and between N uptakeand leaf area were consistent with previous results for other crops.This strengthens the interest of the critical%N−W relationship for use as diagnostictool of nitrogen status in maize crops. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of the opaque and floury mutations on the accumulation of dry matter and protein fractions in maize endosperm.

Grains of nine opaque (o) and floury (fl) mutants of maize (Oh43o1, Oh43o2, B79o5, B37o7, W22o10, W22o11, W22o13, Oh43fl1 and Oh43fl2) were examined for the weight proportions of their component tissues and the content of eight nitrogen fractions in their endosperms. A linear regression was found connecting the amounts (mg per endosperm) of zeins and true proteins (crude proteins minus non-protein nitrogen) for the non-opaque2 mutants. The data points connecting zeins to true proteins present in the mature endosperms of six wild-type (+) inbred lines and their o2 versions were located outside (+) or within (o2) the 95% confidence range of the regression line. The data obtained from the developing and mature endosperms of the W22o7 inbred line (Di Fonzo et al., Plant Sci. Lett., 1979, 77) and the floury portion of mature endosperms of three other wild-type inbred lines fell practically on the regression line. The effects of genotype and environmental factors upon the relative accumulation rate of zeins were assessed from the present results and the data taken from the literature concerning the quantitative interdependence between zeins and true proteins in immature and mature endosperms.     

Silicon nutrition mitigates salinity stress in maize by modulating ion accumulation,photosynthesis, and antioxidants

Silicon is known to improve resistance against salinity stress in maize crop. This study was conducted to evaluate the influence of silicon application on growth and salt resistance in maize. Seeds of two maize genotypes (salt-sensitive ‘EV 1089’ and salt-tolerant ‘Syngenta 8441’) were grown in pots containing 0 and 2 mM Si with and without 50 mM NaCl. After detailed investigation of ion concentrations in different maize organs, both genotypes were further selected in hydroponic experiment on basis of their contrasting response to salinity stress. In the second experiment, pre-germinated seedlings were transplanted into nutrient solution with 0 and 60 mM NaCl with and without 2 mM Si. Both genotypes differed significantly in their response to salinity. Silicon addition alleviated both osmotic and oxidative stress in maize crop by improving the performance of defensive machinery under salinity stress. Silicon application also improved the water-use efficiency in both tested genotypes under both normal and salinity stress conditions. In conclusion, this study implies that the silicon-treated maize plants had better chance to survive under salinity conditions and their photosynthetic and biochemical apparatus was working far better than that of silicon-non-treated plants.     

Early phosphorus nutrition,mycorrhizae development,dry matter partitioning and yield of maize

We conducted a field experiment to test the hypothesis that improved phosphorus nutrition occurs in maize plants with rapid arbuscular (AM) mycorrhizae development at early developmental stages and that this also is reflected in dry matter allocation and final yield. A split-split plot design was used with previous crop (Zea mays L.-maize and Brassica napus L.-canola), tillage practices (no-tillage or conventional tillage) and P fertilization (5 levels) as factors chosen to modify mycorrhizae development at early developmental stages of maize. Previous cropping with canola resulted in decreased shoot-P concentration and shoot growth of maize at early stages. No-tillage resulted in higher shoot-P concentration but lower shoot weight than conventional tillage. Greater shoot-P uptake was related to a rapid intraradical development of mycorrhizae (previous crop of maize) or rapid connection to a mycorrhizal mycelium network (no-tillage treatments). Maize yield and harvest index were lower after cropping with canola. The yield for conventional tillage was higher than that for no-tillage but the harvest index was lower. The hypothesis was supported at early stages of maize growth by the effect of previous crop but not by results of tillage, because an unknown factor reduced growth in the no-tillage system. The hypothesis was supported at maturity by increased biomass allocation to grain relative to total shoot weight in treatments with greater shoot-P concentration at early stages.     

Response of cowpea genotypes to zinc in relation to photosynthesis,nodulation and dry matter distribution

Summary Photosynthesis, nodulation and dry matter distribution in four cowpea genotypes were examined at three levels of zinc in soil. Genotypic differences were observed in the extent of depression in yield under zinc deficiency and in the level of zinc requirement. The seed yield response to zinc was reflected mainly on the number of pods, because of better realisation of flowers into pods. These results have been discussed in relation to nodulation, dry matter distribution and zinc uptake in these genotypes.     

Temperature drop, dry matter accumulation and cold resistance of young cucumber plants

The study aimed to provide information on the involvement of plant cold resistance in a whole cucumber (Cucumis sativus L.) plant response to temperature drop treatments. The main objective was to explain the effects of a temperature drop on dry matter production and plant morphogenesis. The experimental design included temperature drops to 12°C for 0, 1, 2, 4 and 6 hours at the beginning, in the middle and at the end of the night. The overall average temperature for all treatments was 20°C. A 2-hour temperature drop resulted in the most significant reduction in plant dry weight and leaf petiole length, but the highest degree of cold resistance. With the extension of a temperature drop duration to 4--6 hours, dry matter production was similar to that in the control plants, leaf petiole length increased, but not up to the control level and cold resistance was reduced, but was still higher compared to that of the control plants. Changes in dry matter production, leaf petiole length and cold resistance, depending on the duration of the temperature drop, were interrelated and their patterns varied little with the timing (position effect) of the temperature drop. It is concluded that plant cold resistance mechanisms play an important role in a whole plant response to temperature drop treatments. Thus, plant response to temperature drop treatments can be considered as a response to stress.     

花粒期光照对夏玉米干物质积累和养分吸收的影响

选用登海605(DH605)为试验材料,在大田条件下通过花粒期遮阴(S)和增光(L)研究不同光照对花后夏玉米产量、干物质积累和氮、磷、钾养分吸收与运转特性的影响.结果表明: 遮阴后夏玉米产量、干物质积累量及氮、磷、钾养分吸收量均显著降低;而增光有利于夏玉米干物质积累量及氮、磷、钾养分吸收量和产量的提高.2011-2013年,遮阴处理的产量较对照(自然光下)分别降低了59.4%、79.0%、60.6%;增光后产量分别增加16.3%、12.9%、6.8%.遮阴对干物质积累的影响大于其对植株氮、磷吸收量的影响,植株体内氮、磷等养分含量有所上升,而钾吸收量的下降幅度大于干物质积累,钾素相对含量降低,氮、磷、钾向籽粒的分配比例降低.增光后干物质积累和氮、磷吸收量显著上升,但对氮、磷吸收的影响更大;增光条件下,氮、磷、钾等养分向籽粒的分配比例增加.
     

Acclimation of photosynthesis in canopies: models and limitations

Within a time-scale of several days photosynthesis can acclimate to light by variation in the capacity for photosynthesis with depth in a canopy or by variation in the stoichiometry of photosynthetic components at each position within the canopy. The changes in leaf photosynthetic capacity are usually related to and expressed as changes in leaf nitrogen content. However, photosynthetic capacity and leaf nitrogen never match exactly the photon flux density (PFD) gradient within a canopy. As a result, photosynthetic light use efficiency, i.e. photosynthetic performance per incident PFD, increases considerably from the top of the canopy to the lower shaded part. Many of existing optimisation models fail to express the actual pattern of nitrogen or photosynthetic capacity distribution within a canopy. This failure occurs because these optimisation models do not consider that the quantitative aspect of photosynthesis acclimation is a whole plant phenomenon. Although turnover models, which describe the distribution of the photosynthetic apparatus within a canopy as a dynamic equilibrium between breakdown and regeneration of apparatus with respect to nitrogen availability, photosynthetic rate and export of carbohydrates, produce realistic results, these models require confirmation. The mechanism responsible for changes in the relative share of light-harvesting apparatus as acclimation to irradiance remains unknown. Ability of the photosynthetic apparatus to balance properly the light harvesting capacity with electron transport and biochemical capacities is limited. As a result of this fundamental limitation, photosynthetic light use efficiency always increases with increasing thickness of the photosynthetic apparatus.     

不同颜色地膜与种植密度对春玉米干物质积累和产量的影响

为了探讨东北雨养区不同颜色地膜覆盖与种植密度对春玉米干物质积累和产量的影响机制,以良玉99为试验材料,设置3种覆盖处理(裸地、无色透明地膜和黑色地膜覆盖)和5个种植密度(60000、67500、75000、82500和90000株·hm^-2)完全组合的田间小区试验,对春玉米水热效应、干物质积累和产量性状等进行分析.结果表明: 黑膜覆盖明显提高拔节后玉米干物质积累量和生物量,其生物量较其他处理增加3.2%～8.2%;成熟期生物量随着种植密度的增加先增大后减小,以82500株·hm²最大,较其他密度处理增加5.2%～28.3%.无色透明地膜覆盖处理的前期平均土壤温度较其他处理分别提高0.4～2.7 ℃,加快了生育进程,提高了玉米茎叶干物质转运量(T)、转运率(TE)和对籽粒产量贡献率(TC);叶和茎+叶干物质的T、TE和TC均以60000株·hm^-2密度处理最大,而茎干物质转运效果以75000株·hm^-2最优.在抽穗期,黑膜处理的耗水量和日耗水强度最大,分别较其他处理增加10.6%～14.9%和10.6%～24.5%;耗水量和日耗水强度均以90000株·hm^-2密度处理最大,较其他处理分别高6.8%～15.7%和7.0%～20.0%.黑膜和82500株·hm^-2密度处理组合明显提高了玉米的水分利用效率,较其他处理增加了4.6%～40.9%,其产量较其他处理增加3.0%～39.7%.在抽穗期,玉米茎叶干物质量与玉米产量和产量构成要素的相关性最大;茎叶干物质量每减少1 kg·hm^-2,群体产量下降约0.79 kg·hm^-2;茎叶干物质量每降低10%,产量下降10%左右.在增加种植密度的基础上,采用黑色地膜覆盖可以增加春玉米干物质积累量、提高春玉米产量和水分利用效率.     

短期干旱对水稻叶水势、光合作用及干物质分配的影响

采用盆栽水分试验,研究了不同生育期短期干旱处理对水稻叶水势、光合作用和干物质分配的影响．结果表明,干旱胁迫后,水稻叶水势低于对照,午后叶水势回升缓慢。凌晨叶水势随土壤含水量的降低而降低,表现为阈值反应。叶片净光合速率与凌晨叶水势密切相关,低于凌晨叶水势临界值,水稻叶片净光合速率急剧下降在水稻抽穗期和灌浆期叶片净光合速率显著下降的凌晨叶水势临界值为-1.04和-1．13MPa,对应的土壤含水量阈值分别为饱和含水量的61.0％和50．9％,土壤水势分别为-0．133和-0．240MPa干旱胁迫下单叶净光合速率的日变化规律表现为：胁迫较轻时,单叶净光合速率在正午附近出现低谷;胁迫严重时,净光合速率全天低于对照,且不及对照的一半。短期干旱后,水稻叶、根、穗的分配指数均降低,茎鞘的分配指数升高。本研究可为水稻节水灌溉管理和水分限制下水稻的生长模拟提供生理基础和理论依据。     

Relationship between plant type and canopy apparent photosynthesis in maize (Zea mays L.)

Experiments were conducted to study the effect of plant type on canopy photosynthesis under field conditions. A chamber made of aluminium frame covered with clear plastic material was used to estimate canopy CO₂-exchange rates over a land area of 1.33 m². The plant type of maize “Shendan 7” [planophile type, original-type (OT)] was changed to erectophile type [altered-type (AT)] at silking stage. The rates of canopy apparent photosynthesis (CAP) were measured in both types of maize grown at five plant densities during the reproductive phase. It was shown that AT canopies had greater rates (about 17.2%) of CAP than did OT canopies and the yield increased by about 5.9–8.6% in AT canopies. The vertical distribution of photosynthetic photon flux density and CO₂ concentration in AT canopies were more uniform than those in OT ones. It was suggested that the compact architecture of maize canopy was excellent for photosynthesis and yield formation.     

The influence of environmental factors on apparent photosynthesis and respiration of the submersed macrophyte Elodea canadensis

Abstract Oxygen effects on apparent photosynthetic and dark respiratory O₂ exchange rates of detached leaves of Elodea canadensis Michx. (Hydrocharitaceae) were determined over a range of conditions which the submersed plant is likely to experience in shallow water. Apparent photosynthesis is inhibited by O₂ under all the experimental regimes of light, temperature, CO₂ concentration and pH. This inhibition is not caused solely by an accelerated rate of dark respiration, and the observed variations in O₂ inhibition are comparable to O₂ effects on photosynthesis and photorespiration of terrestrial C₃ plants. Percentage inhibition of apparent photosynthesis is enhanced by high O₂ and also by low CO₂. These results indicate that high O₂, high pH and low CO₂ conditions could cause major losses in photosynthetic activity under field conditions. This may account for some of the losses in biomass that are observed under still water conditions.     

水氮组合对冬小麦干物质及氮素积累和产量的影响

于2015—2017年小麦生长季在山东省泰安市农业科学研究院肥城试验基地进行田间试验,供试材料为‘泰山28',在150(A₁)、300(A₂)、450(A₃)、600 m³·hm^-2(A₄)4个灌水量和90(B₁)、135(B₂)、180(B₃)、225 kg·hm^-2(B₄)4个施氮水平下,研究水氮组合对小麦生长发育过程中干物质积累、氮素积累、水分消耗利用、光合特性、籽粒产量等的影响。结果表明: A₃B₃条件下各生育阶段的干物质积累量和氮素积累量,成熟期籽粒干物质和氮素积累量均为最大,花前花后营养器官生产储藏干物质及氮素向籽粒的运输量最高,且与其他水氮组合处理差异显著。各氮素处理下,60~200 cm土层土壤耗水量均为A₃>A₄>A₂>A₁;A₃B₃处理下的水分利用效率和氮素利用效率高于A₃B₄、A₄B₃和A₄B₄。A₃B₃处理显著提高了开花后7~28 d的旗叶净光合速率、气孔导度和蒸腾速率,有利于小麦进行光合作用合成碳水化合物。水氮组合效应显著影响籽粒产量和产量构成,且A₃B₃处理下小麦产量最高,达到9400 kg·hm^-2。综上,450 m³·hm^-2和180 kg·hm^-2的水氮组合处理可以显著提高小麦干物质和氮素积累量,并促进干物质和氮素向籽粒运输,与高水肥处理相比,可以有效提高水分利用效率和氮素利用效率,有利于增强小麦旗叶的光合能力,产生更多的碳水化合物,增加籽粒产量。