Nitrogen resorption and photosynthetic activity over leaf life span in an evergreen shrub, Rhododendron ferrugineum, in a subalpine environment

Here, the advantages for a shrub of having long vs short-lived leaves was investigated in Rhododendron ferrugineum by following nitrogen(15N) and carbon(14C) resorption and translocation, and photosynthetic capacity over the life span. Mean leaf life span was 19 months. Nitrogen (N) resorption in attached leaves occurred mainly in the first year (23%) and reached a maximum of 31% in the second. Although, resorption was similar in attached and fallen 1-yr-old leaves, it was on average one-third higher in fallen than in attached older leaves. Final N resorption of a leaf compartment reached 41%, half occurring from healthy leaves during the first year. Photosynthetic capacity decreased slightly during the life span. Before shoot growth, plant photosynthesis was mainly supported by 1-yr-old leaves, although the contribution of the 2-yr-old leaves was nonnegligible (15% of the capacity and higher carbon transfer toward the roots). After shoot growth, the current-year leaves made the greatest contribution. Our results suggest that short-lived leaves (half of the cohort) are mainly involved in a photosynthetic function, having a high photosynthetic capacity and drawing most of their resorbed N towards current-year leaves; and long-lived leaves are also involved in a conservative function, increasing N resorption and mean residence time (MRT).     

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.

     

Effects of intercropping on photosynthetic rate and net photosynthetic nitrogen use efficiency of maize under nitrogen addition

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。     

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。     

Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species

The effect of leaf aging on photosynthetic capacities was examined for upper canopy leaves of five tropical tree species in a seasonally dry forest in Panama. These species varied in mean leaf longevity between 174 and 315 d, and in maximum leaf life span between 304 and 679 d. The light-saturated CO2 exchange rates of leaves produced during the primary annual leaf flush measured at 7-8 mo of age were 33-65% of the rates measured at 1-2 mo of age for species with leaf life span of < 1 yr. The negative regression slopes of photosynthetic capacity against leaf age were steeper for species with shorter maximum leaf longevity. In all species, regression slopes were less steep than the slopes predicted by assuming a linear decline toward the maximum leaf age (20-80% of the predicted decline rate). Maximum oxygen evolution rates and leaf nitrogen content declined faster with age for species with shorter leaf life spans. Statistical significance of regression slopes of oxygen evolution rates against leaf age was strongest on a leaf mass basis (r = 0.49-0.87), followed by leaf nitrogen basis (r = 0.48-0.77), and weakest on a leaf area basis (r = 0.35-0.70).     

羌塘高原降水梯度带紫花针茅叶片氮回收特征及影响因素

植物回收衰老叶片的氮是植物重要的养分保持和环境适应机制,在寒旱贫瘠的生境更是如此。为了理解降水梯度上植物对高寒贫瘠环境的养分适应特征,研究了羌塘高寒草原优势物种紫花针茅叶片氮回收策略及其与环境因子的关系。结果表明,降水梯度带上紫花针茅叶片具有较高的叶氮水平和氮回收能力。生长季盛期紫花针茅绿叶平均氮含量为(23.87±3.92)g/kg,高于中国草地平均水平(20.9 g/kg)及全球平均值(20.1 g/kg);绿叶氮含量与年降水量(MAP)呈显著负相关,干旱端(西部)绿叶中氮含量明显高于湿润端(东部)。枯叶养分回收后的氮水平(NRP)很低,平均为(6.76±1.42)g/kg,叶片平均氮回收效率(NRE)为(71.25±6.46)%,明显高于中国温带草原和全球的平均水平(46.9%—58.5%)。枯叶中氮回收水平对叶片氮回收效率起决定作用,是维持高养分回收效率的物质基础。NRE与MAP、土壤全氮(TN)和土壤无机氮呈显著负相关;NRP与TN相关性不显著,但与土壤无机氮显著负相关。尽管NRE与NRP呈显著负相关,但二者与绿叶氮含量均没有显著相关性。年均气温、海拔对NRE和NRP影响均不显著。因此,紫花针茅叶片极高的NRE和低NRP反映了它对极端干旱贫瘠环境的养分保持能力,通过内部氮循环来降低养分流失。土壤氮的有效性是影响紫花针茅叶片氮回收能力的关键因子,降水通过影响土壤氮的有效性以及绿叶中氮含量间接影响紫花针茅叶片氮回收效率。     

Relationship between leaf nitrogen and photosynthetic rate for three NAD-ME and three NADP-ME C4 grasses

Theoretical considerations have suggested that there may be differences in photosynthetic nitrogen use efficiency (PNUE) among plants that use different biochemical variants of C(4) photosynthesis. To test this hypothesis we examined the leaf nitrogen content and photosynthetic rates of six grass species (three of C(4) subtype NAD-ME and three of C(4) subtype NADP-ME) grown over a wide range of nitrogen supply. While there were significant differences among the species in various traits, there were no consistent differences between the C(4) subtypes in either leaf nitrogen content at a given level of nitrogen supply or in the leaf nitrogen-photosynthesis relationship. We suggest that species-level variation in photosynthetic nitrogen use efficiency among C(4) species is large enough to mask any differences that may be due to C(4) subtype.     

中国东部南北样带森林优势植物叶片的水分利用效率和氮素利用效率

通过测定中国东部南北样带主要森林生态系统中10种优势植物(兴安落叶松、蒙古栎、水曲柳、紫椴、色木槭、红松、杉木、木荷、马尾松、锥栗)叶片的碳氮含量(Cmass、Nmass)、同位素丰度(δ13C、δ15N)以及光合响应曲线,分析了不同优势植物叶片的水分利用效率和氮素利用效率之间的差异及其相互关系.结果表明： 不同生活型植物叶片的Nmass和δ15N差异显著,表现为阔叶植物>针叶植物,落叶植物>常绿植物;最大光合速率(Pn max)表现为针叶植物>阔叶植物,落叶植物>常绿植物;植物叶片的瞬时水分利用效率(WUEi)和长期水分利用效率(WUE)均表现为阔叶植物>针叶植物,常绿植物>落叶植物;植物叶片的瞬时氮素利用效率(NUEi)和长期氮素利用效率(NUE)则表现出相反的规律,且常绿植物和落叶植物叶片的NUE差异显著;WUEi和WUE之间相关性不显著,而NUEi和NUE之间呈显著正相关.植物叶片的水分利用效率与氮素利用效率显著负相关.两种资源利用效率均受植物生活型的影响,并且存在一定的制约关系.     

增温和氮素添加降低荒漠草原多年生植物氮素回收效率

植物营养器官在枯萎过程中将部分氮素转移到储藏组织之中,是植物适应生境的重要策略。以位于内蒙古荒漠草原的增温和添加氮素的交互试验为平台,对建群种短花针茅(Stipa breviflora)以及优势种无芒隐子草(Cleistogenes songorica)、银灰旋花(Convolvulus ammannii)、冷蒿(Artemisia frigida)和木地肤(Kochia prostrata)等5种多年生植物绿叶期和枯叶期氮浓度,以及氮素回收效率进行了研究。结果表明:增温处理下,植物绿叶期和枯叶期的平均氮素浓度提高了5.5%和11.3%,氮素回收效率显著降低了7.0%。氮素添加使绿叶期植物氮浓度显著提高了5.2%,使植物氮素回收效率降低2.9%。增温和氮素添加对植物枯叶期、绿叶期氮浓度和氮素回收效率有显著的交互作用。氮浓度和氮素回收效率对增温和氮素添加的响应在5个物种间都有显著差异,即这种响应具有物种特异性。研究表明独立的增温和氮素添加以及两者的交互作用都降低该荒漠草原生态系统中植物氮素回收效率,这些结果将为气候变化条件下荒漠生态系统氮素回收效率变化趋势的预测提供数据支持和实验证据。     

Specific leaf area, leaf nitrogen content, and photosynthetic acclimation of Trifolium repens L. seedlings grown at different irradiances and nitrogen concentrations

Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO₃ ⁻, i.e. N₅ to N₂₅) and two irradiances, I (200 and 400 μmol m⁻² s⁻¹ of photon flux density, i.e. I ₂₀₀ and I ₄₀₀). Net photosynthetic rate (P _N), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (F_v/F_m), and actual photochemical efficiency of photosystem 2 (PS2) (Φ_PS2) increased from N₅ to N₁₅ and decreased with N₁₅ to N₂₅. P _N, PNUE, and Φ_PS2 were higher at I ₄₀₀ than at I ₂₀₀, but F_v/F_m and leaf Chl contents at I ₄₀₀ were lower than at I ₂₀₀. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (N_m) were similar, the SLA and N_m increased from N₅ to N₂₅ and they were higher at I ₂₀₀ than at I ₄₀₀. The nitrogen contents per unit area (N_a) increased from N₅ to N₂₀, but decreased from N₂₀ to N₂₅. The N_a was higher at I ₂₀₀ than at I ₄₀₀ when Trifolium repens grew at N₅ and N₁₀, but it was higher at I ₄₀₀ than at I ₂₀₀ at N₁₅ to N₂₅.     

亚热带幼林树木功能性状与叶片氮磷重吸收率的关系

本研究以亚热带29种3年生人工纯林为对象,研究了29个树种功能性状与氮磷重吸收效率的关系。结果表明: 29种幼林平均氮、磷重吸收效率分别为50.5%和57.3%。22种丛枝菌根树种的氮重吸收效率平均为52.7%,显著高于7种外生菌根树种(45.1%)。29个树种的细根组织密度与氮重吸收效率呈显著正相关,7种外生菌根树种细根直径与磷重吸收效率呈显著正相关,22种丛枝菌根树种的功能性状对氮重吸收效率和磷重吸收效率无显著影响。在29个树种中,菌根类型、比叶面积、细根组织密度、叶厚度及叶厚度与菌根类型的相互作用共同解释氮重吸收效率变异的27%,比根长、细根碳含量、细根碳氮比、菌根类型、叶片碳含量及叶片碳含量与菌根类型的相互作用共同解释磷重吸收效率变异的35%。因此,亚热带树种根系功能性状能较好地预测了氮、磷养分重吸收效率,综合多个功能性状可以更好地揭示不同生物因子对养分重吸收的相对重要性。     

有机肥替代部分化肥对水稻光合速率、氮素利用率和产量的影响

农业生产中合理施用有机肥对实现化肥零增长、提高土壤肥力和保证粮食稳产高产至关重要.本试验在辽宁省沈阳市稻田以'沈农9816'为供试材料,设置7种不同处理,分别为不施氮肥(CK)、低氮150 kg ? hm-2(LN)、中氮240 kg ? hm-2(MN)、高氮330 kg·hm-2(HN)、中氮有机肥替代10％(OM...     

Relationships between photosynthetic activity and silica accumulation with ages of leaf in Sasa veitchii (Poaceae, Bambusoideae)

BACKGROUND AND AIMS: Bamboos have long-lived, evergreen leaves that continue to accumulate silica throughout their life. Silica accumulation has been suggested to suppress their photosynthetic activity. However, nitrogen content per unit leaf area (N(area)), an important determinant of maximum photosynthetic capacity per unit leaf area (P(max)), decreases as leaves age and senescence. In many species, P(max) decreases in parallel with the leaf nitrogen content. It is hypothesized that if silica accumulation affects photosynthesis, then P(max) would decrease faster than N(area), leading to a decrease in photosynthetic rate per unit leaf nitrogen (photosynthetic nitrogen use efficiency, PNUE) with increasing silica content in leaves. METHODS: The hypothesis was tested in leaves of Sasa veitchii, which have a life span of 2 years and accumulate silica up to 41 % of dry mass. Seasonal changes in P(max), stomatal conductance, N(area) and silica content were measured for leaves of different ages. KEY RESULTS: Although P(max) and PNUE were negatively related with silica content across leaves of different ages, the relationship between PNUE and silica differed depending on leaf age. In second-year leaves, PNUE was almost constant although there was a large increase in silica content, suggesting that leaf nitrogen was a primary factor determining the variation in P(max) and that silica accumulation did not affect photosynthesis. PNUE was strongly and negatively correlated with silica content in third-year leaves, suggesting that silica accumulation affected photosynthesis of older leaves. CONCLUSIONS: Silica accumulation in long-lived leaves of bamboo did not affect photosynthesis when the silica concentration of a leaf was less than 25 % of dry mass. Silica may be actively transported to epidermal cells rather than chlorenchyma cells, avoiding inhibition of CO2 diffusion from the intercellular space to chloroplasts. However, in older leaves with a larger silica content, silica was also deposited in chlorenchyma cells, which may relate to the decrease in PNUE.     

Plant nitrogen concentration, use efficiency, and contents in a tallgrass prairie ecosystem under experimental warming

Plant nitrogen (N) relationship has the potential to regulate plant and ecosystem responses strongly to global warming but has not been carefully examined under warmed environments. This study was conducted to examine responses of plant N relationship (i.e. leaf N concentration, N use efficiency, and plant N content in this study) to a 4‐year experimental warming in a tallgrass prairie in the central Great Plains in USA. We measured mass‐based N and carbon (C) concentrations of stem, green, and senescent leaves, and calculated N resorption efficiency, N use efficiency, plant N content, and C : N ratios of five dominant species (two C₄ grasses, one C₃ grass, and two C₃ forbs). The results showed that warming decreased N concentration of both green and senescent leaves, and N resorption efficiency for all species. N use efficiencies and C : N ratios were accordingly higher under warming than control. Total plant N content increased under warming because of warming‐induced increases in biomass production that are larger than the warming‐induced decreases in tissue N concentration. The increases in N contents in both green and senescent plant tissues suggest that warming enhanced both plant N uptake and return through litterfall in the tallgrass ecosystem. Our results also suggest that the increased N use efficiency in C₄ grasses is a primary mechanism leading to increased biomass production under warming in the grassland ecosystem.     

江西阳际峰30种阔叶树叶片氮磷含量及再吸收效率

养分再吸收是植物养分利用的重要策略,体现了植物对养分留存、利用和适应环境的能力.为研究亚热带不同生活型(常绿与落叶)阔叶树养分含量与养分再吸收的关系,以江西阳际峰国家级自然保护区内30种阔叶树为研究对象,测定成熟和衰老叶片氮(N)和磷(P)含量,分析常绿和落叶树种叶片N和P含量及其再吸收效率差异,揭示阔叶树种叶片养分再...     

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).     

Season effects on leaf nitrogen partitioning and photosynthetic water use efficiency in mango

The key parameters of photosynthetic capacity (maximum carboxylation rate (V_cmax), electron transport capacity (J_max) and dark respiration rate (R_d)) and the slope (m) of the stomatal conductance model of Ball et al. [Progress in photosynthetic research, Martinus Nijhoff, Dordrecht, 1987] were measured for a whole growing season in fully expanded leaves of 12-year-old mango trees cv. Cogshall in La Réunion island. Leaf nitrogen partitioning into carboxylation (P_c) and bioenergetic (P_b) pools were computed according to the model of Niinemets and Tenhunen [Plant Cell Environ 1997;20: 845–66]. V_cmax, J_max, R_d, P_c and P_b remained relatively stable over the whole study period, with the exception of the period of linear fruit growth when J_max, R_d and P_b were slightly lower, and leaf non-structural carbohydrate content higher. During the pre-floral and floral periods, m decreased by more than 50%, indicating an increase in photosynthetic water use efficiency and m increased again during the period of linear fruit growth. Our results show that, in tropical orchard conditions characterized by mild seasonal climatic changes and non-limiting water supply, leaf nitrogen partitioning is rather stable. Our results also advocate for more studies on the effect of phenology on m and photosynthetic water use efficiency, which is of paramount importance for building coupled biochemical models of photosynthetic carbon assimilation.     

巴郎山糙皮桦叶片光合氮利用效率的海拔响应

为深入认识植物对环境变化的响应和适应,以分布在川西巴郎山的糙皮桦为研究对象,选择海拔2200、2500、3100和3400 m 4个分布点,测定计算了各分布点叶片光合氮利用效率(PNUE)、CO₂扩散导度(叶肉细胞导度g_m与气孔导度g_s)和氮分配比例(Rubisco氮分配比例P_R、生物力能学组分氮分配比例P_B、捕光组分氮分配比例P_L与细胞壁氮分配比例P_CW)等参数,分析了其沿海拔的变化趋势以及叶片PNUE与其他参数的相关关系.结果表明: 糙皮桦叶片PNUE、P_R和P_B在海拔2500和3100 m相对较高;叶片g_s和g_m则随海拔升高而增加,P_L随海拔升高而降低.糙皮桦叶片P_R和P_B与PNUE呈显著正相关关系,说明P_R和P_B是PNUE随海拔变异的重要内部因素.糙皮桦叶片光合系统氮分配比例P_P在海拔2500和3100 m相对较高,叶片P_CW随海拔升高而降低,叶片其他组分氮分配比例P_other随海拔升高而增加,说明随海拔的升高,糙皮桦叶片趋向将更大比例的氮分配于除光合系统和细胞壁外的其他组分中.