Haemoglobin determination and its value as an early indication of peanut rhizobium efficiency

Summary A modified procedure based on the cyanmethaemoglobin method for haemoglobin (Hb) determination in peanut nodules is described. It gave reliable results when tested on peanuts at all stages of vegetative growth, including when the green pigment was present in the nodules. It was shown that early (32–34 days after planting) determination of Hb in nodules of peanuts grown in a greenhouse under bacteriologically controlled conditions can be taken as a measure of the nitrogen-fixing ability of peanut Rhizobia and thus much of the time and greenhouse facilities usually required for strain screening may be conserved. Early determination of nitrogen concentration in leaflets of peanuts proved to be also a useful measure of Rhizobium efficiency, but less sensitive than the early determination of nodule haemoglobin. Contribution from The Volcani Institute of Agricultural Research (N.U.I.A.), Bet Dagan, Israel. 1969 Series, No.1461-E.     

Re-evaluation of the role of ureides in the xylem transport of nitrogen in Arachis species

There are conflicting reports in the literature of the possible role of the ureides, allantoin and allantoic acid, in the nitrogen economy of Arachis species. Therefore, xylem sap composition in food peanut ( Arachis hypogaea L.), and two forage peanuts ( A. pintoi L. and A. glabrata Benth.) has been studied in detail. Xylem saps were collected from peanuts grown under different nutritional regimes and environmental conditions in the glasshouse and field in Australia, Malaysia and Indonesia, and the N-containing solutes analysed. The relative amounts and concentrations of ureides in these peanut exudates were compared with those of soybean ( Glycine max [L.] Merr.) – a species known to export ureides in its xylem stream as the major product of N₂ fixation.
Xylem concentrations of ureides in soybean were high in N₂-fixing plants (2.9 to 3.7 μmol ml⁻¹), representing 60 to 88% of xylem solute nitrogen, but it contributed only 9% (0.7 μmol ml⁻¹) if plants were unnodulated and supplied nitrate. In all species of peanut, concentrations of ureides measured in xylem sap were generally much smaller (0.02 to 0.37 μmol ml⁻¹; 1–7% of xylem nitrogen) and were unaffected by peanut species or cultivar, rhizobial strain, plant size, growth rate, or stage of development, and were not related to N₂ fixation (less than 0.1% of currently fixed nitrogen exported as ureides) or the assimilation of nitrate. Apparently high levels of ureides in sap from some field-grown plants were shown to be due to interference with the ureide colorimetric assay by some contaminating compound rather than represent increased ureides per se.     

不同种植方式对花生田间小气候效应和产量的影响

在大田高产条件下,研究了同一密度下不同种植方式对花生田间小气候效应及产量的影响.结果表明:增大行距和采用大小行种植方式有利于增加田间透光率,提高冠层空气温度与地表温度,降低田间相对湿度,提高田间CO2浓度,提高群体光合速率,进而增加荚果产量.但是行距过大,导致各种环境资源的浪费.采用大行距55cm小行距35cm的大小行种植方式是比较合理的种植方式.     

Leaf gas exchange,source–sink relationship,and growth response of cotton to the interactive effects of nitrogen rate and planting density

Nitrogen (N) rate and plant density (PD) are important factors for sustainable cotton production. The objective of this study is to examine the effects of nitrogen rate and plant density on plant growth, source–sink relationship, and cotton yield. A split-plot arrangement was used in the field experiment with the main plots assigned to N rate (120 and 180 kg/ha), and the sub-plots assigned to plant density (8, 10, and 12 plants/m²). Results showed significant N and PD interaction on plant growth, leaf gas exchange, and yield. Higher plant growth and cotton yield were noted under low nitrogen rate and high planting density than other treatment combinations. Leaf photosynthesis, stomatal conductance, intercellular CO₂, transpiration rate, and water use efficiency were considerably influenced by planting density and nitrogen rate. Maximum values of these traits were obtained under low nitrogen rate with high planting density or high nitrogen rate with medium planting density, while the least values were under low nitrogen rate with low planting density. Correlation analysis revealed highly significant and positive relation between leaf gas exchange and cotton yield.     

Time course of N2 fixation in common bean (Phaseolus vulgaris L.)

Field and greenhouse experiments were conducted to assess the nitrogen fixation rates of four cultivars of common bean (Phaseolus vulgaris L.) at different growth stages. The ¹⁵N isotope dilution technique was used to quantify biological nitrogen fixation. In the greenhouse, cultivars M4403 and Kallmet accumulated 301 and 189 mg N plant^–1, respectively, up to 63 days after planting (DAP) of which 57 and 43% was derived from atmosphere. Under field conditions, cultivars Bayocel and Flor de Mayo RMC accumulated in 77 DAP, 147 and 135 kg N ha^–1, respectively, of which approximately one-half was derived from the atmosphere. The rates of N₂ fixation determined at different growth stages increased as the plants developed, and reached a maximum during the reproductive stage both under field and greenhouse conditions. Differences in translocation of N were observed between the cultivars tested, particularly under field conditions. Thus, the fixed N harvest index was 93 and 60 for cultivars Flor de Mayo and Bayocel, respectively. In early stages of growth, the total content of ureides in the plants correlated with the N fixation rates. The findings reported in the present paper can be used to build a strategy for enhancing biological N₂ fixation in common bean.     

Symbiotic nitrogen fixation and nitrate reduction in two peanut cultivars with different growth habit and branching pattern structures

We have investigated the response of two peanut cultivars (TEGUA and UTRE) with different growth habits and branching pattern structures to different nitrogen (N) sources, namely, N-fertilizer or N₂ made available by symbiotic fixation, and analysed the pattern of nitrate reductase (NR) activity in these cultivars. Nitrate and amino acid contents were also examined under these growth conditions. In terms of nitrogen source, cv. TEGUA showed a better response to inoculation with Bradyrhizobium sp. SEMIA 6144 at 40 days after planting, while cv. UTRE responded better to N-fertilizer (5 mM KNO₃). Both cultivars showed different patterns of NR activity in the analyzed plant organs (leaves, roots, and nodules), which were dependent on the N source. When nitrogen became available to the plant through symbiotic N₂ fixation, the patterns of NR activity distribution were different in the two cultivars, with cv. TEGUA showing a higher NR activity in the nodules than in the leaves and roots, and cv. UTRE showing no difference in terms of NR activity among organs. The nitrate and amino acid contents showed a similar trend between the two cultivars, with the highest nitrate content in the leaves of fertilized plants and the highest amino acid content in the nodules. The high nitrate content of the leaves of cv. UTRE indicated the better response of this cultivar to N-fertilizer.     

Exogenous polyamines alleviating salt stress on peanuts (Arachis hypogaea) grown in pots

Aims Soil salinity is a major limiting factor for plant establishment, development and productivity. In recent years, the contradiction between oil crops and food crops for land is increasingly prominent. In order not to take up the land for food, peanut planting on saline-alkali land could be a promising option. However, peanuts have been rarely grown in saline-alkali land, which may be due to the reduction of peanut yield caused by salt stress. Therefore, research of peanut salt resistance has important practical significance.Methods In order to investigate the effects of exogenous polyamines on peanut (Arachis hypogaea) grown in pots under salt stress, ‘Huayu 22’, one of the peanut cultivars, was used as materials by being foliar-sprayed with 1 mmol·L^-1 putrescine (Put), 1 mmol·L^-1 spermidine (Spd) and 1 mmol·L^-1 spermine (Spm) to elucidate the role of exogenous polyamines on peanuts under 150 mmol·L^-1NaCl. Important findingsResults showed that growth, yield, chlorophyll contents and antioxidant enzyme activities of peanut seedling decreased, however, malondialdehyde (MDA) content and relative electrolytic leakage increased under salt stress. Meanwhile, exogenous polyamines significantly improved the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and reduced the relative electrolytic leakage and MDA content in peanut leaves under salt stress and thus alleviating the oxidative damage of salt stress on plasma membrane. It is obvious that exogenous polyamines could improve chlorophyll contents, plant height, number of branch and the amount of dry matter accumulation, even pod yield under salt stress. Among these three polyamines, the effects of exogenous Spm on alleviating salt stress were most effective These results showed that exogenous polyamines, especially Spm, were favorable for the seedlings to increase reactive oxygen metabolism and photosynthesis, which improved peanut growth and reduced the inhibitory effects of salt stress on peanuts.     

外源多胺对盆栽花生盐胁迫的缓解作用

为探讨外源多胺对花生(Arachis hypogaea)抗盐性的影响, 以盆栽花生‘花育22’为试验材料, 通过叶面喷施1 mmol·L^-1腐胺(Put)、1 mmol·L^-1亚精胺(Spd)、1 mmol·L^-1精胺(Spm)的方法, 研究多胺对150 mmol·L^-1 NaCl胁迫下盆栽花生的缓解作用。结果表明, 与对照(CK)相比, 盐胁迫显著抑制了花生植株的生长与荚果产量, 降低了叶绿素含量和抗氧化酶活性, 丙二醛(MDA)含量、叶片相对电导率增加; 在盐胁迫下, 叶面喷施Put、Spd、Spm处理均可有效促进花生植株的生长, 提高了超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)的活性, 增强植株抗氧化能力, 显著降低了花生叶片相对电导率和MDA的积累量, 从而缓解盐胁迫对质膜的过氧化伤害; 提高了叶绿素含量, 促进了植株高度的生长与分支数增多, 增加了干物质积累量, 从而提高了花生荚果产量; 其中, Spm处理引起的变化幅度大于Spd和Put处理。研究结果说明, 多胺有利于花生幼苗在盐胁迫下活性氧代谢和光合色素含量的提高, 促进花生植株的生长, 降低盐胁迫对花生植株的抑制作用, 且Spm处理的效果最好。     

Bicarbonate concentration as affected by soil water content controls iron nutrition of peanut plants in a calcareous soil.

Strategy I peanut plants are frequently subjected to iron deficiency when growing in calcareous soils, which contain high concentrations of bicarbonate. In calcareous soils under field conditions, it has been noted that chlorosis increases in severity after excessive rainfall or irrigation, but the chlorosis symptoms of peanuts are alleviated after waterlogged soils dry. A pot experiment was conducted simulating the chlorosis symptom observed in the field when peanut plants are exposed to fluctuating soil water content induced from rainfall or irrigation. We investigated the bicarbonate fluctuations resulting from adjustable soil water content (SWC) that could lead to bicarbonate-induced iron chlorosis of peanuts growing in calcareous soil. The experiments included three treatments of SWC (50% of water holding capacity (WHC), 80% of WHC, and 100% of WHC) under two levels of CaCO(3) concentrations (at 8.67% and 18.67%.) The results showed that the iron nutrition of peanuts could be regulated by different SWC at both CaCO(3) levels. Our observations indicate that iron deficiency chlorosis symptoms in peanuts grown in high soil water content were more severe, compared to those of peanuts in lower soil water content. A shift from high soil water content to lower soil water content could improve or eliminate the iron deficiency chlorosis symptom of peanuts. The HCO(3)(-) concentration in the peanut rhizosphere increased with increasing SWC and CaCO(3) content and it correlated with the level of soil water content. We suggest that variations in the soil water content could induce HCO(3)(-) concentration variation in the rhizosphere of peanuts. Consequently, the high HCO(3)(-) concentration, which is induced by a high water content in calcareous soil and a high CaCO(3) level, could inhibit the physiological response to iron deficiency of peanuts, resulting in iron deficiency chlorosis. The study indicates that a reasonable agricultural practice of irrigation and drainage should be considered to improve and prevent iron deficiency chlorosis of strategy I plants in calcareous soil.     

Effect of shade on the carbon and nitrogen allocation in a perennial tropical grass, Dichanthium aristatum

Changes in sward growth above ground by shade is a controversialsubject for field experimentation because the differential allocationof carbon (C) to shoots and roots is difficult to measure. Inthis experiment the effect of three levels of irradiance (100%,56% and 33% of full sunlight) on C and nitrogen (N) allocationin Dichanthium aristatum were studied under well-watered andwell-fertilized conditions. Dry matter accumulation, weightratio per organ and N allocation indices were studied duringtwo cycles of growth, after planting and after cutting. Shadehad no effect on the C and N influxes into the whole plant,showing that the N absorption is regulated by the C assimilation.However, C, and principally N, were preferentially allocatedto the laminae under reduced irradiance. Under 100% and 56%of full sunlight, more N was allocated to the stubble component.This situation was reversed in the lowest radiation level, indicatingthat N reserves, and not exclusively C reserves, may limit theregrowth of this perennial grass when growing under high levelsof shade. The higher shoot:root ratio under shade shows thedisadvantage in the use of radiation use efficiency calculatedfrom aerial biomass data when comparing differents levels ofshade. Key words: Growth, shading, reserves, C₄ species     

赤红壤植蔗坡地坡面径流及溶解态氮磷流失特征

为探究南方高强度、高频次降雨下赤红壤区坡耕地土壤侵蚀及氮磷养分流失的特征,基于野外径流小区原位观测试验,通过测定自然降雨下赤红壤植蔗坡地坡面径流和溶解态氮磷流失量,探讨自然降雨下甘蔗种植对赤红壤坡面径流及溶解态氮磷流失的影响。结果表明：(1)2019年和2020年,径流量分别为1111.3 m~3/hm~2和3269.4 m~3/hm~2,硝态氮(NO~-₃-N)流失量分别为1.39 kg/hm~2和15.60 kg/hm~2,铵态氮(NH~+₄-N)流失量分别为0.37 kg/hm~2和1.02 kg/hm~2,可溶性磷流失量分别为0.20 kg/hm~2和0.27 kg/hm~2。2019年和2020年植蔗坡地径流及溶解态氮磷流失量均集中在6月份,占流失总量的45%以上,硝态氮(NO~-₃-N)是径流氮素流失的主要形式,占79%以上。此外,2019年和2020年5月至8月,侵蚀性降雨场次分别为18次和23次,侵蚀性降雨量分别为407.8 mm和668.0 mm。(2)不同侵蚀性降雨条件下,植蔗坡地溶解态氮磷流失量及其...     

Effects of colored polyethylene film mulch on pest populations,plant growth and yield of peanut in Northern China

Polyethylene film mulching is commonly used in peanut (Arachis hypogaea L.) production, an important oil crop. Clear polyethylene film (CLEF) has previously been the only choice for all growing conditions. However, colored polyethylene film has been applied to the cultivation of crops in recent years, so testing the effects of colored film mulches on peanuts is necessary. In this study, we observed the effects of eight colored polyethylene films on devastating pest abundance, plant growth and yield, and soil conditions in peanut fields. The results showed that light-silver-gray film (LSGF), silver-black on both sides film (SGBF), and black film (BLAF) mulches were more effective in reducing the pest population (aphids, thrips, and mites) compared to plants mulched with other films. In addition, SGBF and LSGF mulching accelerated seeding emergence and benefited peanut growth, and the yield increased by about 20% compared to peanuts mulched with CLEF. The soil temperature and humidity under the LSGF and SGBF treatment were more suitable for peanut growth compared to the other film treatments. In conclusion, LSGF and SGBF mulches were appropriate choices for managing pests, maintaining optimum soil conditions, and increasing yield in peanut production.     

Soybean Mutants Lacking Constitutive Nitrate Reductase Activity : II. Nitrogen Assimilation, Chlorate Resistance, and Inheritance

Nitrogen assimilation in three nitrate reductase (NR) mutants of soybean (Glycine max L. Merr. cv Williams) was studied in the growth chamber and in the field. These mutants, LNR-2, LNR-3, and LNR-4, lack the non-NO₃⁻-inducible or constitutive fraction of leaf NR activity found in wild-type plants, but this had no effect on the concentration of nitrogen accumulated when grown on NO₃⁻ in the growth chamber. Dry weight accumulation of two of the mutants (LNR-3 and LNR-4) was decreased relative to LNR-2 and wild type. In the field, LNR-2 had dry weights and nitrogen concentrations similar to the wild type at 34 and 61 days after planting, and at maturity. Acetylene reduction activities were also similar at 61 days.     

Expression of the Arabidopsis vacuolar H+-pyrophosphatase gene AVP1 in peanut to improve drought and salt tolerance

The Arabidopsis gene AVP1 encodes an H⁺-pyrophosphatase that functions as a proton pump at the vacuolar membranes, generating a proton gradient across vacuolar membranes, which serves as the driving force for many secondary transporters on vacuolar membranes such as Na⁺/H⁺-antiporters. Overexpression of AVP1 could improve drought tolerance and salt tolerance in transgenic plants, suggesting a possible way in improving drought and salt tolerance in crops. The AVP1 was therefore introduced into peanut by Agrobacterium-mediated transformation. Analysis of AVP1-expressing peanut indicated that AVP1-overexpression in peanut could improve both drought and salt tolerance in greenhouse and growth chamber conditions, as AVP1-overexpressing peanuts produced more biomass and maintained higher photosynthetic rates under both drought and salt conditions. In the field, AVP1-overexpressing peanuts also outperformed wild-type plants by having higher photosynthetic rates and producing higher yields under low irrigation conditions.     

Elevated CO<Subscript>2</Subscript> Concentration and Drought Stress Exert Opposite Effects on Plant Biomass,Nitrogen, and Phosphorus Allocation in <Emphasis Type="Italic">Bothriochloa ischaemum</Emphasis>

Increased concentrations of atmospheric carbon dioxide (CO₂) and drought stress have greatly influenced plant growth, the status of nitrogen (N) and phosphorus (P), and N:P ratios. We identified the plant biomass, N and P distributional patterns, and N:P stoichiometry of a grass species on the Loess Plateau in China under elevated CO₂ concentration and drought stress conditions. Bothriochloa ischaemum, a C4 perennial herbaceous grass, was grown in pots at CO₂ concentrations of 400 (ambient) and 800 (elevated) μmol mol^?1 and at 60 ± 5 and 40 ± 5 % of field capacity. The elevated CO₂ concentration significantly increased plant total biomass, N concentration, N and P content, allocation of biomass to roots, and allocation of N to shoots, and increased the N:P ratios of whole plants and the shoots, especially under well-watered conditions. Drought stress significantly decreased plant biomass and plant N and P content, especially under elevated CO₂. Drought stress decreased the N:P ratios, but was only significant in the roots under ambient CO₂. Drought stress may attenuate the stimulation of plant growth and N and P acquisition by CO₂ enrichment, and projected elevated CO₂ concentrations may partially offset the negative effects of increased drought by increasing the assimilation of N and P.     

The effects of nitrate: ammonium ratios and dicyandiamide on the nitrogen response of Zea mays L. in a high rainfall area on an acid soil

Hydroponic studies under controlled environmental conditions indicated that maize plants respond better to combinations of nitrate and ammonium nutrition than to either form supplied separately but that this response depended upon the total N concentration. An attempt was made to maintain different nitrate: ammonium ratios and concentrations in the soil by the addition of a nitrification inhibitor. Five nitrate: ammonium ratios at three N application rates were tested with and without dicyandiamide (H₂NC(NH)NHCN) on a low-pH, sandy soil for two years. Treatments were applied to field-grown maize in two applications, one at planting and the other at 21 to 30 days after planting. Under favourable climatic conditions for crop growth the optimum nitrate: ammonium ratio for grain yield was between 3:1 and 1:1 over all N rates. Under unfavourable climatic conditions, ratios of 3:1 and 1:1 showed in contrast to all other ratios no grain yield depressions at high N rates. Dicyandiamide did not interact with N rates or ratios, but did increase grain yield over all N treatments under favourable conditions. N ratio interactions with N rates and dicyandiamide were also shown for N concentrations of the leaves at anthesis, for the grain at harvest and for mineral N in different soil layers at anthesis. These results imply that nitrate: ammonium ratios between 3:1 and 1:1 should be recommended at the optimum N rate on a low-pH sandy soil in a high rainfall area for maize production.     

南方红壤旱坡地花生植株对施用氮肥的响应

选用多年夏花生-冬蔬菜种植制度下的典型红壤旱坡地,通过田间试验,研究了5种氮肥水平下花生根系的形态特征、固氮能力、植株生物量以及荚果产量。结果表明:不同氮肥施用量对花生植株生物量及荚果产量影响均不显著(P=0.091);而不同处理的土壤固氮酶活性与氮肥施用量间呈极显著的负相关(R2=0.88,P=0.005);单株花生根系总长度、总表面积、总分叉数及根尖条数均随氮肥施用量的增加而减小,且与单株花生根瘤生物量呈极显著(P<0.001)正相关。     

黄土高原南部春玉米地膜栽培的水肥效应与氮肥去向

在黄土高原南部采用田间小区和微区试验,研究了春玉米地膜栽培下氮肥-水分-产量关系与氮肥去向。结果表明,相同施肥条件下地膜栽培(N120C)比平作栽培(N120UC)增产显著(46．7％),施用氮肥显著地发挥了地膜的增产潜力,处理N120(尿素氮120kg·hm^-2)、N180(尿素氮180kg·hm^-2)和N120M(尿素氮120kg·hm^-2+有机肥氮60kg·hm^-2),籽粒产量比对照CK(不施氮)分别增产41．8％、43．9％和34．7％,地膜栽培或施用氮肥都极大地改善了玉米水分生产效率(WUE)和降水利用率(RUE),试验中N120C比N120UC水分生产效率提高57．9％。降水利用效率提高54．5％;处理N120、N180和N120M比CK处理WUE分别提高38．4％、47．4％和32．4％,RUE分别提高42．3％、43．9％和34．7％,由于供试有机肥是半腐解的牛粪,比尿素氮素供给迟缓,所以对玉米产量和WUE提高幅度小,试验水分测定反映出,玉米利用的水分73．0％～83．7％来自降雨,表明决定春玉米产量的关键水分是生育期降水,玉米地膜栽培对氮肥去向有微弱影响,相对于平作玉米,氮肥总的回收率差异不大,但氮肥利用率下降7．3个百分点,土壤残留率上升6．4个百分点,土壤当季残留氮主要集中在0～20cm,不会发生向深层大量的淋溶和累积。     

温度增高、CO2浓度升高、施氮对蒙古栎幼苗非结构碳水化合物积累及其分配的综合影响

蒙古栎(Quercus mongolica)是中国东北地区天然次生林重要组成树种, 研究该树种幼苗有机碳积累及碳库容对未来气候变化的响应, 可为预测未来气候变暖情景下蒙古栎林的天然更新及幼苗的培育提供科学参考。该文旨在探讨CO₂浓度和温度升高综合作用对蒙古栎幼苗非结构性碳水化合物(NSC)积累及其分配的影响。实验环境条件用人工气候箱控制, 控制条件如下: 1) CO₂浓度倍增(700 μmol·mol^-1), 温度升高4 ℃处理(HCHT); 2) CO₂浓度正常(400 μmol·mol^-1), 温度升高4 ℃处理(HT); 3) CO₂浓度和温度均正常, 即对照组(CK); 每个气候箱幼苗分别在3种氮素水平下生长: N2 (15 mmol·L^-1, 高氮), N1 (7.5 mmol·L^-1, 正常供氮)和N0 (不施氮), 一共为9个处理。研究结果表明, 1) HCHT共同作用对NSC积累无促进作用, 但改变了植物各器官中NSC的分配比例, 叶片中可溶性糖和淀粉的积累明显增加, HCHT下N2水平有利于NSC的积累。2) HT明显影响了蒙古栎一年生幼苗NCS的积累和分配。在N2水平下, HT明显促进NSC的积累, 并增加了在主根中的分配比例。3)植株各器官可溶性糖含量的动态变化因处理不同而异。主根淀粉含量随时间逐渐增加, 而细根淀粉含量随时间逐渐减少。在未来气候变暖的情况下, 土壤中大量的氮供给, 可能将促进蒙古栎幼苗的生长、增加其碳库容和抵御不良环境的能力, 进而提高其天然更新潜力。     

Relationship between net photosynthesis and nitrogen in Scots pine: Seasonal variation in seedlings and shoots

The relationship between light saturated net photosynthesis (A_max) and nitrogen concentration (N) was studied in needles of both Scots pine seedlings, grown at three relative growth rates (2,6 and 8%) controlled by nutrient addition rate, and Scots pine shoots collected from four sites with different fertility. In the seedlings, A_max was measured on 14 different dates starting at the beginning of the second growing season and ending when growth of the new shoot and the secondary needles had finished. In shoots from the natural stands A_max of the previous-year shoots was measured on 6 dates throughout the growing season.Both in seedlings and shoots, the correlation between A_max and N was poor, when data from all sampling dates were taken together. However, A_max was correlated with N in most instances when the age of the needles was considered and the data were examined either at weekly intervals (seedlings) or separately for each sampling date (shoots). The slope of the A_max vs N relationship varied greatly between sampling dates. In the seedlings the correlation between A_max and N was strongest by the time when the new needles were developing. In the shoots the correlation was significant from mid June until mid August, while no correlation was found in the beginning and at the end of the growing season.Our data indicate that in pine needles the photosynthesis-nitrogen relationship is more complex than in broadleaved species. Contrary to the broadleaved species, where the correlation is independent of sampling time, in this conifer the time of the year affects the correlation and there are phases during the growing season when the correlation is poor or nonexistent.Abbreviations A_max light saturated net photosynthesis - kPa kilopascal - N nitrogen concentration in the needles - PFD photon flux density (400–700 nm) - RGR relative growth rate