间作对氮调控玉米光合速率和光合氮利用效率的影响

研究间作后作物光合碳同化和光合氮利用效率(PNUE)对氮投入的响应, 对阐释间作产量优势的氮调控效应, 指导间作氮肥管理有重要意义。本研究设置玉米(Zea mays)单作、玉米间作两种种植模式的4个氮水平(N0, 0 kg·hm ^-2; N1, 125 kg·hm ^-2; N2, 250 kg·hm ^-2; N3, 375 kg·hm ^-2), 分析间作与施氮量对玉米叶片特征、光合参数、PNUE和产量的影响。结果表明: 与单作相比, 间作显著增加玉米叶片的叶干质量和比叶质量; 各施氮水平(除N3)下, 间作中靠近马铃薯(Solanum tuberosum)侧的玉米叶面积均显著高于单作玉米。单间作对比发现, 间作提高了玉米光饱和点和暗呼吸速率。单作、间作靠玉米侧(I-M)、间作靠马铃薯侧(I-P)的玉米PNUE均随施氮量增加而降低, 降幅以I-P最大; 施氮量低于250 kg·hm ^-2时, 相同施氮量下的玉米PNUE和净光合速率(P_n)均以I-P最高, I-M和单作次之。间作显著提高了玉米产量(土地当量比>1)。该研究中当施氮量≤250 kg·hm ^-2时, 间作I-P的玉米叶片P_n和PNUE显著提高可能是间作玉米产量提高的重要原因。     

Effects of nitrogen addition on photosynthetic characteristics of Leymus chinensis in the temperate grassland of Nei Mongol,China

Aims The increased atmospheric nitrogen (N) deposition due to human activity and climate change greatly causes grassland ecosystems shifting from being naturally N-limited to N-eutrophic or N-saturated, and further affecting the growth of grass species. The aims of this study are: 1) to evaluate the effects of different N addition levels on morphology and photosynthetic characteristics of Leymus chinensis; 2) to determine the critical N level to facilitate L. chinensis growth.
Methods We conducted a different N addition levels experiment in dominant species in the temperate steppe of Nei Mongol. The aboveground biomass, morphological and leaf physiological traits, pigment contents, chlorophyll a fluorescence parameters and biochemical parameters of L. chinensis were investigated.
Important findings Our results showed that aboveground biomass first increased and then decreased with the increased N, having the highest values at the 10 g N·m^-2·a^?1 treatment, but the 25 g N·m^-2·a^?1 still significantly increased the aboveground biomass relative to 0 g N·m^-2·a^?1. Leymus chinensis accommodate low N situation through allocating less N to carboxylation system and decreasing leaf mass per area (LMA) in order to get more light energy. Moderate N addition captured more light energy through increasing total chlorophyll (Chl) contents and decreasing the ratio of Chl a/b. Moderate N addition increased LMA, carboxylation efficiency, maximum carboxylation rate (V_cmax), maximum electron transport rate (J_max) and decreased J_max/V_cmax, thus allocating more N to carboxylation system to enhance carboxylation capability. Moreover, the photochemical activity of PSII was increased through higher effective quantum yield of PSII photochemistry, electron transport rate and photochemical quenching coefficient. Excessive N addition had negative effects on physiological variables of L. chinensis due to lower carboxylation capability and photochemical activity of PSII, further leading to decreased net photosynthetic rate, whereas increased non-photochemical quenching coefficient and carotenoids played the role in the dissipation of excess excitation energy. Overall, moderate N addition facilitated the photosynthetic characteristics of dominant species, but excessive N addition inhibited photosynthetic characteristics. The most appropriate N addition for the growth of L. chinensis was 5-10 g N·m^-2·a^?1 in the temperate steppe of Nei Mongol, China.     

Effects of nitrogen and silicon application on leaf nitrogen content and net photosynthetic rate of Elymus nutans in alpine meadow

AimsElymus nutans is one of the dominant plant species in alpine meadow. Purpose of this research was to study the effects of nitrogen and silicon application on leaf nitrogen content and net photosynthetic rate in this species to provide scientific basis for fertilization practice in alpine meadow.MethodFour levels nitrogen combined with four levels silicon was applied to E. nutans plants in the alpine meadow. Leaf nitrogen content and net photosynthetic rate of E. nutans were measured.Important findings The results showed that there was a significant improvement in leaf nitrogen content and net photosynthetic rate of the E. nutans with nitrogen or silicon application alone; However, there was a significant interaction between nitrogen and silicon treatments on leaf nitrogen content and net photosynthetic rate; Combining with the three different levels nitrogen, low level silicon (Si₁) application did not increase leaf nitrogen content and net photosynthetic rate, but middle level silicon (Si₂) could significantly increase the leaf nitrogen content; Combining with the low (N₁) or middle (N₂) level nitrogen, middle level silicon (Si₂) application could significantly increase the net photosynthetic rate; Compared with that control without fertilization, the middle level nitrogen combined with the same level silicon treatment had the highest average of leaf nitrogen content and net photosynthetic rate, which increased by 119.99% and 85.70%, respectively. This study indicated application of nitrogen combined with silicon application enhanced leaf nitrogen content and net photosynthetic rate of E. nutans, and 8 g·m^-2silicon application had the best result among other treatments.     

玉/豆和玉/薯模式下氮肥运筹对玉米氮素利用和土壤硝态氮残留的影响

过量施用氮肥造成的环境问题日益严重,氮肥合理使用已成为人们研究的热点.本文研究了西南玉米两种主要套作模式下氮肥运筹对玉米氮素利用和土壤硝态氮残留的影响.结果表明：连续分带轮作种植玉/豆模式后,玉米收获期植株中的氮素积累较玉/薯模式平均提高了6.1%,氮收获指数增加了5.4%,最终使氮肥利用效率提高4.3%,氮素同化量提高了15.1%,氮肥偏生产力提高了22.6%;玉米收获后硝态氮淋溶损失减少,60～120 cm土层中硝态氮残留玉/豆模式较玉/薯模式降低了10.3%,而0～60 cm土层中平均提高了12.9%,有利于培肥地力,两年产量平均较玉/薯模式高1249 kg·hm^-2,增产22%;增加施氮量提高了植株氮素积累,降低了氮肥利用率,显著提高了表层土壤中硝态氮的累积,60～100 cm土层中硝态氮的累积量在0～270 kg·hm^-2处理间差异不显著,继续增加施氮量会显著增加土壤硝态氮的淋溶;氮肥后移显著提高了土壤0～60 cm土层硝态氮的积累.两种模式下施氮量和底追比对玉米氮素吸收和硝态氮残留的影响结果不一致,玉/豆模式以施氮180～270 kg·hm^-2、按底肥∶拔节肥∶穗肥=3∶2∶5的施肥方式有利于提高玉米植株后期氮素积累、氮收获指数和氮肥利用效率,减少了氮肥损失,两年最高产量平均可达7757 kg·hm^-2;而玉/薯模式在180 kg·hm^-2、按底肥∶穗肥=5∶5的施肥方式下,氮素积累利用及产量均优于其他处理,两年平均产量为6572 kg·hm^-2,可实现两种模式下玉米高产、高效、安全的氮肥管理体系.
     

玉米花生间作和磷肥对间作花生光合特性及产量的影响

揭示玉米(Zea mays)和花生(Arachis hypogaea)间作提高花生对弱光利用能力的光合特点及磷(P)肥效应, 对阐明间作花生适应弱光的光合机理和提高间作花生的产量具有重要意义。该试验于2011-2012年在河南科技大学试验农场分析了间作花生功能叶的叶绿素含量与构成、光响应曲线和CO₂响应曲线特点和荧光参数。结果表明: 与单作花生相比, 施P与不施P条件下玉米和花生间作显著(p < 0.01)提高了花生功能叶的叶绿素b含量, 降低了叶绿素a/b, 显著提高了光系统II最大光化学效率(F_v/F_m)、实际光化学效率(Φ_PSII)、光化学猝灭系数(q_P)、表观量子效率(AQY)和弱光时的光合速率, 显著降低了气孔导度、二磷酸核酮糖羧化酶羧化速率(V_cmax)、电子传递速率(J_max)和磷酸丙糖利用速率(TPU); 与不施P相比, 施P有利于提高间作花生功能叶的叶绿素含量, 显著提高了Φ_PSII、q_P、V_cmax、J_max和TPU, 说明间作花生通过提高功能叶的叶绿素b含量, 改变叶绿素构成, 提高了光系统II的F_v/F_m、Φ_PSII和q_P, 增强了对光能的捕获和转化能力, 提高了对弱光的利用能力, 而并非提高了对CO₂的羧化固定能力; 施P有利于提高间作花生对弱光的利用能力和产量, 土地当量比提高了6.2%-9.3%。     

Diaheliotropic leaf movement enhances leaf photosynthetic capacity and photosynthetic light and nitrogen use efficiency via optimising nitrogen partitioning among photosynthetic components in cotton (Gossypium hirsutum L.)

• Phototropic leaf movement of plants is an effective mechanism for adapting to light conditions. Light is the major driver of plant photosynthesis. Leaf N is also an important limiting factor on leaf photosynthetic potential. Cotton (Gossypium hirsutum L.) exhibits diaheliotropic leaf movement. Here, we compared the long‐term photosynthetic acclimation of fixed leaves (restrained) and free leaves (allowed free movement) in cotton.
• The fixed leaves and free leaves were used for determination of PAR, leaf chlorophyll concentration, leaf N content and leaf gas exchange. The measurements were conducted under clear sky conditions at 0, 7, 15 and 30 days after treatment (DAT).
• The results showed that leaf N allocation and partitioning among different components of the photosynthetic apparatus were significantly affected by diaheliotropic leaf movement. Diaheliotropic leaf movement significantly increased light interception per unit leaf area, which in turn affected leaf mass per area (LMA), leaf N content (N_A) and leaf N allocation to photosynthesis (N_P). In addition, cotton leaves optimised leaf N allocation to the photosynthetic apparatus by adjusting leaf mass per area and N_A in response to optimal light interception.
• In the presence of diaheliotropic leaf movement, cotton leaves optimised their structural tissue and photosynthetic characteristics, such as LMA, N_A and leaf N allocation to photosynthesis, so that leaf photosynthetic capacity was maximised to improve the photosynthetic use efficiency of light and N under high light conditions.

     

玉米-大豆间作和施氮对玉米产量及农艺性状的影响

为研究玉米-大豆间作模式和施氮水平对玉米产量、主要农艺性状及生长动态的影响,进行2个种植模式(玉米单作和玉米-大豆间作)和2个施氮水平(0 kg/hm2,150 kg/hm2)的双因素随机区组试验,以期揭示施氮和间作对玉米产量的影响规律,为提高玉米-大豆间作系统产量提供一定的理论依据。研究结果表明:(1)与不施氮相比,施氮显著增加了春秋两季间作玉米产量,分别达到23.81%和40.99%。施氮处理下的间作玉米地上部生物量较不施氮提高了29.91%,单作模式下显著提高了40.34%,两者差异均达到显著水平。(2)与不施氮相比,施氮150 kg/hm2条件下春玉米单作和间作模式百粒重分别提高了18.92%和19.23%,秋玉米单作和间作模式百粒重分别提高了31.03%和32.75%,差异均达到显著水平。与不施氮相比,施氮150 kg/hm2条件下,单作和间作模式均显著提高秋玉米穗长。与不施氮相比,施氮150 kg/hm2条件下,单作秋玉米的穗粗提高了18.67%,差异显著。(3)施氮和间作均能促进玉米干物质累积、提高株高和叶绿素(SPAD值),且表现为施氮效果高于间作效果。总体来看,种植模式和施氮水平对玉米产量、主要农艺性状和生长动态均有一定影响,且施氮效果优于间作效果。由于土壤具有一定的供氮能力,而间作豆科能为玉米供给一定量的氮素,故对于春玉米而言,施氮效果仅在百粒重中表现,随着土壤原有氮素被玉米吸收利用减少后,供氮能力下降,在秋玉米中施氮效果显著提高。     

黑龙江省次生林主要组成树种光合能力与叶片含氮量研究

以黑龙江省次生林主要组成树种蒙古栎、白桦、水曲柳、山杨、胡桃楸、黄波罗为研究对象,测定自然状态下这6个树种的光合能力,并分析光合能力与叶片含氮量之间的关系.研究结果表明,树种的光合能力存在明显的季节变化,不同树种间的光合能力、光合潜力存在差异.生长季中,胡桃楸具有最高的光合能力最大值,白桦具有最高的年平均光合能力,蒙古栎具有最大的光合潜力.蒙古栎叶片含氮量与光合能力线性正相关(r=0.97),白桦、水曲柳叶片含氮量与光合能力呈二次曲线相关(r=0.61,r=0.51).     

Effects of a nitrogen fixing plant Vigna radiata on growth,leaf stomatal gas exchange and hydraulic characteristics of the intercropping Juglans regia seedlings

采用砂培方法, 在温室内将一年生核桃(Juglans regia)嫁接苗木和绿豆(Vigna radiata)进行间作, 研究绿豆对核桃苗木生长、水分平衡和光合特性的影响。该研究设有5种处理, 即: 对照(核桃单作, 正常供应氮素); 核桃单作, 不添加氮素; 核桃绿豆间作, 不添加氮素; 核桃绿豆间作, 正常供应氮素; 绿豆单作, 不添加氮素。结果显示: 种植绿豆可以增加土壤氮含量和核桃茎内氮含量, 但对核桃叶和根系中的氮含量影响不明显。种植绿豆显著增加不施氮核桃的高生长和直径生长, 但降低了正常供氮核桃的生长。无论种植绿豆与否, 不供氮处理降低了核桃的总叶面积, 提高了根冠比。核桃叶片气孔气体交换对各处理的响应和生长有相同的趋势。缺氮显著降低了核桃叶柄在中午的导水率、提高了导水损失率; 种植绿豆显著提高不供氮核桃的导水率而且明显降低了其导水损失率。然而, 种植绿豆使正常供氮的核桃降低了导水率, 加剧了导水损失率。同时, 绿豆受到间作的竞争压力, 产量和生物量有所下降。由研究结果可知, 在贫瘠的土壤上, 固氮植物绿豆改善了间作的核桃的氮营养, 有益于核桃木质部发育、水分平衡以及光合代谢。但是在氮充足的土壤中, 种植绿豆反而降低了核桃的水分供应, 影响其气体交换和生长。     

氮肥和种植密度对达乌里胡枝子的生长与生物固氮的影响

氮供给和种植密度是影响植物生长的两个重要因素。豆科植物因其生物固氮能力而在受到氮限制的生态系统中具有重要作用, 氮含量增加促进植物生长的同时也会抑制豆科植物的生物固氮能力, 种植密度会通过种内竞争影响豆科植物的生长和生物固氮能力, 然而少有研究关注氮肥添加和种植密度对豆科植物生长和生物固氮能力的影响。该研究以达乌里胡枝子(Lespedeza davurica)为研究对象, 通过温室盆栽实验, 探究氮肥和种植密度对其生长和生物固氮的影响。实验设置4个氮添加水平(0、5、10、20 g·m^-2·a^-1)和3种种植密度(1、3、6 Ind.·pot^-1, 约32、96、192 Ind.·m^-2)。结果发现: 1)施肥和密度增加均影响了达乌里胡枝子的生长。叶片碳(C)、氮(N)含量、净光合速率随施氮量增加而增加, 氮添加也促进了植物的生长, 当施氮量为10 g·m^-2·a^-1时植物产量达到最大。叶片C、N含量、净光合速率随种植密度增加而下降, 密度增加可以促进每盆的总生物量, 但对单个植株的生长有负效应。2)氮肥对根瘤形成有抑制作用, 但种植密度增加会缓解氮肥对生物固氮能力带来的“氮阻遏”。该实验条件下, 当施氮量为10 g·m^-2·a^-1, 种植密度为3 Ind.·pot^-1, 或施氮量为5 g·m^-2·a^-1, 种植密度为6 Ind.·pot^-1时, 能最大程度发挥“施氮增产”和种植密度缓解“氮阻遏”的作用。氮添加降低了达乌里胡枝子的根瘤生物量和对根瘤形成的投资(根瘤生物量占总生物量的比例), 从而抑制达乌里胡枝子的生物固氮。种植密度增加导致达乌里胡枝子因种内竞争增加而使资源获取受限, 从而增加对根瘤的投资和根瘤生物量来获得更多来自大气中的氮。3)结构方程结果显示, 氮肥和种植密度通过直接或间接作用, 解释了64%的达乌里胡枝子生物量变化和42%的根瘤生物量变化。上述结果表明合理优化豆科植物的施肥量和种植密度可能对人工草地种植以及退化草地恢复管理具有重要意义。     

Effects of drought-rewatering-drought on photosynthesis and growth of maize

Aims Our objective was to investigate the responses of maize photosynthesis and growth to repeated drought.Methods Maize seedlings were exposed to different soil water deficit for three weeks, then rewatering for one week, and again to different water deficit for three weeks, to examine the effects of repeated drought on photosynthesis and growth.Important findings After the first water deficit treatments, under severe drought, plant height, total leaf area of individual plant, shoot and root biomass declined significantly, also transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), net photosynthetic rate (P_n), maximum net photosynthetic rate (A_max), but light compensation point and dark respiration rate increased significantly. Under medium drought, plant height, leaf area, and shoot biomass decreased significantly, but root biomass did not vary, hence, the ratio of roots to shoots (R/S) increased. Moreover, plants did not show significant differences in photosynthetic parameters. After rewatering, photosynthesis and growth rate of plants previously exposed to water deficit could recover to the levels of well-watered plants, but plant height and leaf area did not recover to the levels of the control. When maize were subjected to recurrent drought, plants pre-exposed to medium drought showed no significant difference in plant height, biomass, and photosynthetic parameters, but a significant decrease in leaf area, compared to plants only exposed to second medium drought. Plants pre-exposed to severe drought had significantly higher T_r, G_s, C_i, P_n, A_max, and, apparent quantum yield but significantly lower plant height, leaf area, and biomass than plants without previous exposure. These results indicated that the first severe drought significantly reduced photosynthetic capacity and maize growth, rewatering could recover photosynthesis and growth rate to the levels of well-watered plants, but could not eliminate the adverse influence of the first drought on growth. The first medium drought could stimulate the growth of maize root system and significantly increased R/S, which can enhance maize drought resistance to subsequent repeated drought, and maintain the total biomass in the control level; the first severe drought could enhance maize drought resistance to subsequent repeated drought in the aspect of photosynthesis, but could not compensate for the adverse effect of early drought on plant growth. Hence, in practice, drought hardening should be limited in the level of medium drought, and avoiding severe drought.     

Crop nitrogen use and soil mineral nitrogen accumulation under different crop combinations and patterns of strip intercropping in northwest China

Increasing crop nitrogen use efficiency while also simultaneously decreasing nitrogen accumulation in the soil would be key steps in controlling nitrogen pollution from agricultural systems. Long-term field experiments were started in 2003 to study the effects of intercropping on crop N use and soil mineral N accumulation in wheat (Triticum aestivum L. cv 2014)/maize (Zea mays L. cv Shendan16), wheat/faba bean (Vicia faba L. cv Lincan No. 5) and maize/faba bean intercropping and monocropping systems. Monocropping was compared with two types of strip intercropping: continuous intercropping (two crops intercropped continuously on the same strips of land every year) and rotational intercropping (two crops grown adjacently and rotated to the other crop??s strip every year). Maize/faba bean intercropping had greater crop N uptake than did wheat/faba bean or wheat/maize. Wheat/maize accumulated more mineral N in the top 140 cm of the soil profile during the co-growth stage from maize emergence to maturity of wheat or faba bean. Continuously intercropped maize substantially decreased soil mineral N accumulation under wheat and faba bean rows (60?C100 cm soil depth) at maize harvest. Soil mineral N accumulation under wheat rows increased with rotational intercropping with faba bean. Rotational intercropping may potentially alleviate the adverse effects of wheat on N use by other crops and increase the nitrogen harvest index of wheat, maize and faba bean. Intercropping using species with different maturity dates may be more effective in increasing crop N use efficiency and decreasing soil mineral N accumulation.     

Variations and interrelationships of foliar hydraulic and photosynthetic traits for Larix gmelinii

Aims Variations and potential trade-offs of leaf hydraulic and photosynthetic traits are essential for assessing and predicting the effect of climate change on tree survival, growth and distribution. Our aims were to examine variations and interrelationships of leaf hydraulic and photosynthetic traits in response to changes in site conditions for Dahurian larch (Larix gmelinii)—a dominant tree species in Chinese boreal forests.Methods This study was conducted at the Maoershan Forest Ecosystem Research Station. A transect of 27 year-old Dahurian larch plantation was established that consisted of five plots extending from the valley to the ridge of a slope. The predawn leaf water potential (Ψ_pre), area- and mass-based leaf hydraulic conductance (K_area and K_mass, respectively), resistance to embolism capacity (P₅₀), leaf mass per area (LMA), net photosynthetic rate (A), and leaf nitrogen content (N) were measured in August 2016.Important findings The Ψ_pre, K_area, K_mass, P₅₀, A, LMA, and N all varied significantly among the plots (p < 0.05), indicating significant intra-specific variations in these traits in response to the changes in site conditions. The P₅₀ was significantly (p < 0.05) correlated with Ψ_pre, K_area or K_mass, suggesting that a trade-off between hydraulic efficiency and safety exist within the species to some degree. There were significant (p < 0.05) pairwise correlations between A, LMA, and N. Nevertheless, there was no significant (p < 0.05) correlation between the measured photosynthetic traits and hydraulic traits. We concluded that the intra-specific variations and multiple interrelationships of the leaf hydraulic and photosynthetic traits for the larch reflect the plasticity of its leaf traits and strategies of its survival and growth as a result of its acclimation to diverse site conditions.     

Effects of nitrogen deficiency on photosynthetic traits of maize hybrids released in different years

BACKGROUND AND AIMS: New maize (Zea mays) hybrids outperformed old ones even at reduced N rates. Understanding the mechanisms of the differences in performance between newer and older hybrids under N deficiency could provide avenues for breeding maize cultivars with large yield under N deficiency, and reduce environmental pollution caused by N fertilizers. METHODS: N deficiency effects on grain weight, plant weight, harvest index, leaf area and photosynthetic traits were studied in the field for six maize hybrids released during the past 50 years to compare their tolerance and to explore their physiological mechanisms. KEY RESULTS: N deficiency decreased grain yield and plant weight in all hybrids, especially in the older hybrids. However, there was no significant difference in harvest index, rate of light-saturated photosynthesis (Psat) 20 d before flowering, leaf area or plant weight at flowering between the N-deficient and control plants of all hybrids. Dry matter production after flowering of the N-deficient plants was significantly lower than that of the control plants in all hybrids, especially in the older hybrids, and was mostly due to differences in the rate of decrease in photosynthetic capacity during this stage. The lower Psat of the older hybrids was not due to stomatal limitation, as there was no significant difference in stomatal conductance (gs) and intercellular CO2 concentration (Ci) between the hybrids. N deficiency accelerated senescence, i.e. decreased chlorophyll and soluble protein contents, after anthesis more for the earlier released hybrids than for the later ones. N deficiency decreased phosphoenolpyruvate carboxylase (PEPCase) activity significantly more in older hybrids than newer hybrids, and affected the maximal efficiency of PSII photochemistry (Fv/Fm) only in the old hybrids and at the late stage. CONCLUSIONS: Compared with older (earlier released) hybrids, newer (later released) hybrids maintained greater plant and grain weight under N deficiency because their photosynthetic capacity decreased more slowly after anthesis, associated with smaller non-stomatal limitations due to maintenance of PEPCase activity, and chlorophyll and soluble protein content.     

氮硅添加对高寒草甸垂穗披碱草叶片全氮含量及净光合速率的影响

该文以青藏高原高寒草甸优势种垂穗披碱草(Elymus nutans)为研究对象, 探究不同水平氮肥与硅肥混合添加后对其叶片全氮含量和净光合速率的影响, 以期对高寒草甸牧场施肥提供一定的理论依据。研究发现: 氮、硅单独添加时, 均可提高垂穗披碱草叶片全氮含量以及净光合速率; 氮、硅配施处理对叶片全氮含量和净光合速率均存在显著的交互作用; 低(N₁)、中(N₂)、高(N₃) 3种不同浓度的氮肥处理下, 低硅(Si₁)添加对垂穗披碱草叶片全氮含量以及净光合速率没有显著的促进作用, 而添加中浓度硅肥(Si₂)可显著提高垂穗披碱草叶片全氮含量; 低、中浓度施氮水平下, 中浓度硅肥可显著促进垂穗披碱草光合作用; 叶片全氮含量和净光合速率最大平均值均出现在中浓度氮、硅肥配施下, 与不施肥相比分别提高了119.99%和85.70%; 就该试验而言, 施加氮肥的同时, 适当添加一些硅肥能够更好地提高垂穗披碱草叶片全氮含量和净光合速率, 且硅的添加量为8 g·m^-2时效果较好。     

绿狐尾藻光合色素组成及氮磷化学计量学特征对外源铵的响应

绿狐尾藻(Myriophyllum aquaticum)对高浓度铵(NH⁺₄)具有较高的耐受性, 是处理养殖废水的优选植物。探究外源铵对绿狐尾藻光合色素组成及氮(N)、磷(P)化学计量学特征的影响, 对提高绿狐尾藻人工湿地系统的处理效率具有重要意义。该研究设置0、0.1、1、5、15、30 mmol·L^-1 6个NH₄⁺浓度, 室内培养21天, 测定分析不同铵浓度下绿狐尾藻叶绿素含量、N含量、P含量和N:P的变化特征。结果表明, 随外源铵浓度增加, 绿狐尾藻的相对茎高和相对生物量先升高后降低, 且通过拟合曲线方程发现, 外源铵在16.22和12.58 mmol·L^-1时, 其相对茎高和相对生物量达到最大值。随外源铵浓度的增加, 绿狐尾藻叶片叶绿素含量显著降低, 而茎中叶绿素含量增加, 且叶绿素a含量变化的幅度比叶绿素b大, 但对叶绿素a/b影响不显著, 仅在5 mmol·L^-1处理时茎叶绿素a/b显著下降。随外源铵浓度增加, 与CK相比, 叶片和茎的N含量分别显著增加了85%-235%和127%-373%, 叶片P含量增幅为49%-51%。当外源铵浓度不大于15 mmol·L^-1时, 叶片和茎的N含量、N:P增加速度较快, 且相对茎高和相对生物量增长较快。相关分析表明, 叶片N、P含量和N:P与总叶绿素含量呈极显著负相关关系, 而在茎中呈显著或极显著正相关关系。综上所述, 外源铵浓度在12-16 mmol·L^-1范围内时, 绿狐尾藻生长良好, 生物量更大, N和P的吸收量更高, 从而利用其构建的人工湿地可以有效去除污染废水的N、P, 达到高效净化水体的目的。     

光合电子流对光响应的机理模型及其应用

光合电子流对光响应的机理可以揭示植物光合电子流与光强、植物捕光色素分子物理特性之间的关系。该文讨论了光合电子流对光响应的机理模型的特性以及捕光色素分子的物理性质, 并利用此模型拟合了山莴苣(Lagedium sibiricum)、一年蓬(Erigeron annuus)和紫菀(Aster tataricus)的光合电子流对光响应的曲线。由此模型不仅可以得到植物的最大光合电子流、饱和光强、初始斜率等参数, 还可以获得捕光色素分子有效光能吸收截面和处于最低激发态的捕光色素分子数对光的响应关系。结果表明: 随光强的增加, 山莴苣的捕光色素分子的有效光能吸收截面下降最快, 紫苑的下降速度最慢; 山莴苣处于最低激发态的捕光色素分子数增长速度最快, 紫苑的增长速度最小。捕光色素分子的有效光能吸收截面随光强增加而下降、处于最低激发态的捕光色素分子数随光强增加而增加的特性将减少其光能的吸收和激子的传递, 因而有利于减少强光对植物产生的光伤害。     

施氮和间作对土壤团聚体钾素分配及作物钾吸收的影响

基于2个氮水平(低氮和高氮)下连续种植6年的玉米单作、马铃薯单作及玉米马铃薯间作田间定位试验,采用湿筛法对土壤进行团聚体分级,并测定各粒级全钾、交换性钾和非交换性钾含量,研究氮水平和种植模式对土壤团聚体相关钾素分配的影响。结果表明:土壤团聚体以中团聚体(0.25~2 mm)为主,所分配钾素占土壤钾储量60.6%~65.0%。种植模式和施氮量显著影响团聚体非交换性钾含量和储量,但对全钾、交换性钾无显著影响。高氮水平下,间作比单作加权值提高大团聚体(>2 mm)全钾和非交换性钾储量57.6%和73.6%,中团聚体(0.25~2 mm)全钾和非交换性钾储量21.1%和41.5%。间作增加了玉米钾吸收,但降低了马铃薯钾吸收量。除马铃薯单作外,>0.25 mm团聚体的交换性钾、非交换性钾占比与作物钾吸收量呈显著正相关。总之,间作和施氮可提高土壤中较大粒级团聚体非交换性钾和全钾储量,对促进土壤钾素保存和持续供应有积极意义。     

Hydraulic and photosynthetic characteristics differ between co-generic tree and liana species: a case study of Millettia and Gnetum in tropical forest

木质藤本是热带森林的重要组成部分, 显著影响森林的结构和功能。已有研究发现木质藤本与乔木的水力结构存在显著差异: 木质藤本的缠绕或攀缘茎细小, 但其木质部具有粗大的长导管, 输水效率高, 抗栓塞能力低。为降低基因型差异对比较结果的影响, 该研究选取热带崖豆藤属(Millettia)和买麻藤属(Gnetum)的乔木和木质藤本, 比较同属内不同生长型植物的水力和光合性状的差异, 分析水分传导效率与抗栓塞能力之间以及水力与光合性状之间的相关关系。结果发现: (1)崖豆藤属植物水力性状的种间差异大, 与生活型和需光性有关。耐阴的木质藤本反而具有较低的水分传导效率和较高的抗栓塞能力。(2)买麻藤属植物是裸子植物较为进化的类群(具有导管和阔叶), 其乔木的水分传导效率很低, 但是其木质藤本的水分传导效率高于其他阳生性的被子植物。(3)不论乔木还是木质藤本, 水分传导的有效性与安全性在枝条和叶片水平上均没有显著的权衡关系。(4)与同属乔木相比, 木质藤本的叶片较枝条的抗栓塞能力更强, 在旱季具有更高的最大净光合速率和气孔导度, 支持了木质藤本的“旱季生长优势假说”。该研究揭示了热带木质藤本水力性状的多样性和重要性, 为阐明环境变化对这一重要植物类群的影响, 需要对它们的水力特征进行更广泛的研究。     

玉米/花生间作行比和施磷对玉米光合特性的影响

试验于2014—2015年设玉米/花生间作2∶2(R₁)、2∶4(R₂)和2∶8(R₃)三种间作模式,研究了间作行比和施磷对玉米冠层光照日变化、功能叶的SPAD值、光合-光强响应曲线和光合-CO₂响应曲线的影响,以探究间作玉米适应强光的光合机理.结果表明: 间作玉米冠层日均光照表现为R₃>R₂>R₁;大口期至灌浆期,间作玉米穗位叶的SPAD值、表观量子效率(AQY)、光补偿点(LCP)、光饱和点(LSP)、光饱和时的最大净光合速率(LSP_n)、羧化效率(CE)、最大电子传递速率(J_max)、磷酸丙糖利用率(TPU)、气孔导度(g_s)、蒸腾速率(T_r)和净光合速率(P_n)均表现为R₃>R₂>R₁,胞间CO₂浓度(C_i) 则为R₁>R₂>R₃;蜡熟期R₃间作玉米的AQY、LSP_n、g_s、CE、J_max和TPU均低于R₂间作玉米;施磷能提高AQY、LSP_n、CE、V_{c max}、J_max和TPU等光合参数.这说明间作玉米g_s、AQY、CE、V_{c max}、J_max和TPU随着光强增加逐渐提高是其增强利用强光能力的关键,但超过一定光强易早衰,施磷肥有助于增强玉米对强光的利用和延缓叶片衰老.