Seasonal relationships between leaf nitrogen content (photosynthetic capacity) and leaf canopy light exposure in peach (Prunus persica)

Abstract Field gas exchange measurements on intact peach (Prunus persica (L.) Batsch) leaves indicate that leaf nitrogen content (N_L) and leaf weight per unit leaf area (W_a) are highly correlated with CO₂ assimilation rate (A) and mesophyll conductance (g_m). Therefore, N_L and W_a were used to study seasonal relationships between leaf carboxylation capacity and natural light exposure in tree canopies. From mid-season onwards, N_L and W_a were linearly correlated with light exposure expressed as the amount of time during a clear day that a leaf was exposed to a photosynthetic photon flux density (Q) of ≥ 100 μmol m^?2 s^?1. The data support the hypothesis that whole-tree photosynthesis is optimized by partitioning of photosynthetic capacity among leaves in deciduous tree canopies with respect to natural light exposure.     

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。     

两个品种转基因抗虫棉光合生理的CO2响应

栽培环境条件的改变会对转基因作物产生深远影响。以2种不同转基因棉花及其亲本对照为材料,研究了盆栽种植条件下不同棉花品种在蕾期和吐絮期光合生理特性CO2响应特征。结果表明,与各自的常规棉对照比较,两种转基因抗虫棉单叶净光合速率CO2响应的特征参数表观初始羧化效率(CE)、表观暗呼吸速率(Rd)和最大净光合速率(Pmax,c)虽有一定程度的变化,但其差异均未达到显著水平。在高CO2浓度范围内(700μmol.mol-1),转基因抗虫棉单叶净光合速率和水分利用率(WUE)的CO2响应曲线特征发生变化,且与品种及生育时期有关。两种转基因抗虫棉在不同生育时期的气孔导度(Gs)对CO2浓度的响应特征与其常规棉对照相似,短期CO2浓度增高对转基因抗虫棉的气孔导度没有显著性影响。     

氮肥运筹对小麦产量、氮素利用效率和光能利用率的影响

连续2年在西南冬麦区的重庆、仁寿、广汉、西昌4个地点,开展3种施氮水平(每公顷纯氮0、120、180 kg,简写为N₀、N₁₂₀、N₁₈₀)和3种氮肥分配模式(N_A:底肥100%;N_B:底肥70%+苗肥30%;N_C:底肥60%+拔节肥40%)的田间试验,监测小麦花后冠层叶片SPAD值、群体光合速率(CAP)、光能利用等生理参数和籽粒产量,计算氮素利用效率、光能利用率等.结果表明: 随施氮水平增加,小麦上三叶SPAD值、CAP、光合有效辐射(PAR)截获率和产量均呈增加趋势,而氮肥农学利用效率、生产效率、吸收效率和利用效率呈降低趋势.氮肥后移的增效作用因施氮水平而异,SPAD于N₁₈₀增效明显,而CAP于N₁₂₀增效明显,不同氮肥管理模式的光能利用率因地点而异.氮肥后移能明显提高小麦氮肥农学效率、生产效率、吸收效率和氮素表观回收率,但氮肥利用效率则略有减少.氮肥后移效果N_C总体优于N_B处理.不同地点比较,广汉的SPAD值、CAP、PAR截获率、氮肥利用参数较高,其产量也相应最高;西昌的产量、SPAD值及氮素利用效率较高,但其光能利用率和CAP较低;重庆和仁寿的SPAD值、光能利用率及氮素利用效率均较低,其产量也最低.小麦生物产量与各地点的籽粒产量、CAP、SPAD值和PAR累积截获量均呈显著或极显著的正相关关系.表明不同生态区域增施氮肥都能促进小麦增产,氮肥后移可进一步优化产量结构、改善氮肥和光能利用效率,但存在年份和地点差异,各地需要制定有针对性的氮肥管理模式.     

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.     

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.     

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).     

Estimating photosynthetic radiation use efficiency using incident light and photosynthesis of individual leaves

It has been theorized that photosynthetic radiation use efficiency (PhRUE) over the course of a day is constant for leaves throughout a canopy if leaf nitrogen content and photosynthetic properties are adapted to local light so that canopy photosynthesis over a day is optimized. To test this hypothesis, 'daily' photosynthesis of individual leaves of Solanum melongena plants was calculated from instantaneous rates of photosynthesis integrated over the daylight hours. Instantaneous photosynthesis was estimated from the photosynthetic responses to photosynthetically active radiation (PAR) and from the incident PAR measured on individual leaves during clear and overcast days. Plants were grown with either abundant or scarce N fertilization. Both net and gross daily photosynthesis of leaves were linearly related to daily incident PAR exposure of individual leaves, which implies constant PhRUE over a day throughout the canopy. The slope of these relationships (i.e. PhRUE) increased with N fertilization. When the relationship was calculated for hourly instead of daily periods, the regressions were curvilinear, implying that PhRUE changed with time of the day and incident radiation. Thus, linearity (i.e. constant PhRUE) was achieved only when data were integrated over the entire day. Using average PAR in place of instantaneous incident PAR increased the slope of the relationship between daily photosynthesis and incident PAR of individual leaves, and the regression became curvilinear. The slope of the relationship between daily gross photosynthesis and incident PAR of individual leaves increased for an overcast compared with a clear day, but the slope remained constant for net photosynthesis. This suggests that net PhRUE of all leaves (and thus of the whole canopy) may be constant when integrated over a day, not only when the incident PAR changes with depth in the canopy, but also when it varies on the same leaf owing to changes in daily incident PAR above the canopy. The slope of the relationship between daily net photosynthesis and incident PAR was also estimated from the photosynthetic light response curve of a leaf at the top of the canopy and from the incident PAR above the canopy, in place of that measured on individual leaves. The slope (i.e. net PhRUE) calculated in this simple way did not differ statistically from that calculated using data from individual leaves.     

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.     

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.     

Genetic analysis of some seed quality characters in upland cotton (Gossypium hirsutum L.)

Summary A set of diallel crosses involving ten parents was evaluated over two locations to determine the genetic control of protein per cent, oil per cent, seed index, percentage of mature seeds and number of seeds per boll. The analysis of pooled data showed that percentage of mature seeds was controlled by additive (D) and non-additive (H₁ and H₂) genetic effects. Overdominance was noticed. For seed index the D component measuring additive, and the H₂ component measuring dominance, variation were significant. Protein content and oil content were primarily under the control of non-additive (H₁ and H₂) genetic effects, while for number of seeds per boll the variability was accounted for by dominance (H₁) effects only. The development of pure lines through appropriate methods is suggested.Part of the thesis of the senior author, submitted in partial fulfilment for the Ph.D. degree     

玉米叶片水分利用效率的保守性

水分利用效率是植物个体或生态系统水分利用过程的重要特征参数,可表征不同时空尺度的植物碳-水耦合关系,对植物适应气候变化研究具有重要意义。以玉米为例,利用中国气象局固城农业气象野外科学试验基地2013—2014年玉米不同灌溉方案模拟试验资料,对不同叶位叶片的水分利用效率特征及其影响因素进行分析。结果表明:植株顶部第1片叶片水分利用效率在拔节期和乳熟期呈现明显的峰值,反映出明显的周期变化规律及其与叶片生理生态特征的紧密相关。在相同环境条件下,不同叶位叶片的水分利用效率不存在显著性差异,即玉米叶片水分利用效率具有空间稳定性与叶龄保守性。同时,研究指出叶片光合速率和蒸腾速率在叶位之间的协调变化是导致空间稳定性和叶龄保守性的主要原因。研究结果可为植物水分关系研究提供参考,也可为水分利用效率的尺度化研究提供依据。     

不同光环境下亚热带常绿阔叶树种和落叶阔叶树种幼苗的叶形态和光合生理特征

由于地球环境的演变,亚热带常绿阔叶林中常有落叶阔叶成分的存在,但从生态角度,其存在的机理尚不清楚.通过比较研究常绿阔叶优势树种大头茶与落叶阔叶树种枫香幼苗的叶形态和光合生理特征对不同光环境(旷地、林窗、林下)的响应,尝试解释落叶成分遗留的基础.结果表明:①枫香具有较小的比叶重(LMA)和较高的光合氮利用效率(PNUE),在高光环境中,并未受到光抑制,具有较高的光合可塑性,尤其在林窗,表现出较大头茶高3倍的光合能力(Pnmax),保证了其在较短的生长季节积累更多的光合产物,增强与常绿树种的竞争力;②常绿阔叶树种大头茶具有较大的LMA,在旷地受到严重的光抑制,将更多的氮用于化学防御中.在林窗和林下具有相对高的Pnmax,生长幅度较广,但在林下将更多的氮投入到比生长更为重要的生存消耗中.而枫香在林下响应表现为Rubisco活性降低,光合受阻;③两树种在林窗均表现出较高的光合适应性,具有最大的光合能力(Pnmax)及合理的氮在光合机构中的分配系数,说明林窗是它们更新的最佳环境.但枫香的光合作用更依赖于光照,而大头茶则更依赖于CO2浓度;④总之,落叶阔叶树种以其较高的形态可塑性和对高光的光合生理可塑性能够在常绿阔叶林种生存、生长,并成为常绿阔叶林中固有成分的主要原因之一.     

棉花叶片氮含量的空间分布与光合特性

在棉花生长旺季,将冠层按高度分多层测定了田间叶片含氮量和叶片净光合速率对光合有效辐射通量密度的响应(光响应曲线,Pn-PPFD response curve)及相应的生物指标.结果表明,各层叶片氮含量与光合作用关系密切,各层平均值大小依次为上层＞中层＞下层,对应层叶片的最大净光合速率Pmax、表观暗呼吸速率Rd、光补偿点LCP及光饱和点LSP均从上到下依次递减,与氮含量分布一致,而表观光合量子效率AQY则略有不同;氮含量的指数衰减系数 kn =0.762(R2=0.593),根据观测结果,棉田叶片氮含量(N)空间分布可以用相对累积叶面积指数(Lc/Lt)为自变量的指数方程来模拟,从而为建立光合作用机理模型与进行生产力奠定基础.     

The consequences of delayed greening during leaf development for light absorption and light use efficiency

Many species of rainforest plants have an unusual form of leaf development such that leaves delay greening until after full leaf expansion. Chlorophyll accumulation was measured during leaf development in five woody rainforest species, three with white young leaves, and two with ‘normal’ greening. In the three species with white leaves, the chlorophyll content of the expanding leaves was about 0.4mg dm^?2, whereas in the two species with green young leaves, chlorophyll content was about 2.1 mg dm^?2. Chlorophyll accumulation in greenhouse and field experiments was independent of light level. During leaf expansion, species with delayed chloroplast development only absorb 18–25% of the maximum possible light, compared with 80% for species with normal greening. Furthermore, species with delayed greening have low chlorophyll contents and reduced absorption for at least 30 d after full expansion. At a PPFD typical of the forest under story, the photosynthetic light use efficiency based upon incident radiation was 0.030–0.036 for species with delayed chloroplast development and 0.068–0.085 for the two species with normal greening. The lower light use efficiency of white species was primarily due to decreased light absorption. However, they also had a slightly lower light use efficiency based upon absorbed radiation, suggesting that development of other components of the photo-synthetic apparatus also may be delayed. Despite the fact that delayed greening decreases light absorption and light use efficiency during leaf development, it is extremely common in shade-tolerant species. We suggest that an advantage of delayed greening is that resources are not invested in the leaf until it is fully expanded and better defended from herbivores.     

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.     

In vitro induction of multiple shoots and plant regeneration in cotton (Gossypium hirsutum L.)

Induction of multiple shoots in cotton (Gossypium hirsutum L. cv. Anjali-LRK 516) has been achieved with cotyledonary nodes devoid of cotyledons and apical meristems. Explants from 35-day-old seedlings yielded the maximum number of shoots (4.7 shoots/explant) using Murashige and Skoog (MS) basal medium supplemented with 6-benzylaminopurine and kinetin (2.5 mg/1 each). Explants from 35-day-old seedlings raised in glass bottles produced a higher number of multiple shoots (8.3 shoots/explant) than those grown in glass tubes and cultured on the same shoot induction medium. Elongation of multiple shoots was obtained on liquid or agar MS basal medium without phytohormones. In vitro shoots were rooted on half-strength agar-solidified MS basal medium or with 0.05 or 0.1 mg/1 naphthaleneacetic acid. Hardening and survival of tissue culture plantlets was 95% under greenhouse conditions.Abbreviations BAP 6-Benzylaminopurine - GA₃ Gibberellic acid - MS Murashige and Skoog medium - NAA -Napthaleneacetic acid     

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...