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1.
Summary The effects of P, N and Ca+Mg fertilization on biomass production, leaf area, root length, vesiculararbuscular mycorrhizal (VAM) colonization, and shoot and root nutrient concentrations of pretransplant rice (Oryza sativa L.) plants were investigated. Mycorrhizal plants generally had a higher biomass and P, N, K, Ca, Mn, Fe, Cu, Na, B, Zn, Al, Mg, and S shoot-tissue nutrient concentrations than non-mycorrhizal plants. Although mycorrhizal plants always had higher root-tissue nutrient concentrations than non-mycorrhizal plants, they were not significantly different, except for Mn. N fertilization stimulated colonization of the root system (colonized root length), and increased biomass production and nutrient concentrations of mycorrhizal plants. Biomass increases due to N were larger when the plants were not fertilized with additional P. P fertilization reduced the colonized root length and biomass production of mycorrhizal plants. The base treatment (Ca+Mg) did not significantly affect biomass production but increased the colonized root length. These results stress the importance of evaluating the VAM rice symbiosis under various fertilization regimes. The results of this study suggest that pretransplant mycorrhizal rice plants may have a potential for better field establishment than non-mycorrhizal plants.  相似文献   

2.
Insufficient potassium (K) nutrition produces detrimental effects on cotton (Gossypium hirsutum L.) lint yield and fiber quality. To further understand the deleterious effects caused by K deficiency, a 2‐yr (1991 and 1992) field study was conducted to determine how dry matter partitioning and nutrient concentrations of various plant tissues for the cotton genotypes, ‘DES 119’ and ‘MD 51 ne’, were altered by varying the application rate of fertilizer K and nitrogen (N). All plots received a preplant application of 112 kg N ha‐1, and half of the plots were later sidedressed with an additional 38 kg N ha‐1. Within each N treatment, half the plots received 112 kg K ha‐1, preplant incorporated, with the remaining plots not receiving any fertilizer K. Dry matter harvests were taken three times in 1991 and two times in 1992. At cutout (slowing of vegetative growth and flowering), plants that received K fertilization had a 14% more leaf area index (LAI), a 3% increase in the number of main stem nodes, and a 2% increase in plant height. However, those plants had a 12% lower specific leaf weight (SLW) than plants receiving no K fertilization. By the end of season, the of K fertilization had resulted in more stem (21%), bur (13%), seed (19%), and lint weight (20%), but harvest index was not affected. Varying the level of N fertilization did not affect any of these dry matter parameters at any harvest. In general, the larger plants produced under K fertilization had reduced concentrations of N, phosphorus (P), magnesium (Mg), and sodium (Na) in the various plant parts. While N uptake efficiency was not affected by K fertility, plants that received K fertilization had increased efficiency of fertilizer N use and of N utilization within the plant. The smaller LAI of the K deficient plants probably reduced the photosynthetic capacity per plant. A reduced assimilation capacity could explain the inefficiency of N use, lint yield reductions, and poorer fiber quality often associated with K deficiencies.  相似文献   

3.
A greenhouse experiment was carried out during the spring–summer 2009 to test the hypotheses that: (1) arbuscular‐mycorrhizal (AM) inoculation with a biofertilizer containing Glomus intraradices gives an advantage to overcome alkalinity problems, (2) mineral fertilization is more detrimental to AM development than organic fertilization on an equivalent nutrient basis. Arbuscular mycorrhizal (AM) and non‐AM of zucchini (Cucurbita pepo L.) plants were grown in sand culture with two pH levels in the nutrient solution (6.0 or 8.1) and two fertilization regimes (organic or mineral). The high‐pH nutrient solution had the same basic composition as the low‐pH solution, plus an additional 10 mM NaHCO3 and 0.5 g L–1 CaCO3. Increasing the concentration of NaHCO3 from 0 to 10 mM in the nutrient solution significantly decreased yield, plant growth, SPAD index, net assimilation of CO2 (ACO2), N, P, Ca, Mg, Fe, Mn, and Zn concentration in leaf tissue. The +AM plants under alkaline conditions had higher total, marketable yield and total biomass compared to –AM plants. The higher yield and biomass production in +AM plants seems to be related to the capacity of maintaining higher SPAD index, net ACO2, and to a better nutritional status (high P, K, Fe, Mn, and Zn and low Na accumulation) in response to bicarbonate stress with respect to –AM plants. The percentage root colonization was significantly higher in organic‐fertilized (35.7%) than in mineral‐fertilized plants (11.7%). Even though the AM root colonization was higher in organic‐fertilized plants, the highest yield and biomass production were observed in mineral‐fertilized plants due to the better nutritional status (higher N, P, Ca, and Mg), higher leaf area, SPAD index, and ACO2.  相似文献   

4.
Most studies indicating positive effects of nitrogen (N) supply on biomass water‐use efficiency (WUE) used two contrasting levels of N supply and monitored some of the relevant traits being associated with WUE. In order to investigate N effects on WUE over a wider range of N‐supply levels, oriental tobacco was cultivated in pots under six (Exp. 1) and four (Exp. 2) N levels until flowering stage. Water‐use efficiency, intrinsic water‐use efficiency (A/g), carbon isotope discrimination (CID), average daily canopy transpiration rate (EC; from 12 to 7 d before harvest), and biomass‐partitioning parameters were determined. Water‐use efficiency increased from the lowest to the highest N level and was positively correlated with biomass. Intrinsic water‐use efficiency was positively correlated with leaf N and chlorophyll concentration. Whole‐plant CID was significantly less negative under high compared to low N supply. Biomass‐partitioning parameters were only slightly affected by N supply except for leaf‐area ratio, which significantly increased with N supply. The low planting density of Exp. 2 resulted in an increase of WUE and substantially less negative whole‐plant CID compared to Exp. 1. In both experiments, EC was lower under high compared to low N supply and was negatively correlated with WUE. It is concluded that plants under high N supply realized a higher WUE via increases of A/g and a reduction of EC.  相似文献   

5.
Drought is one of the major environmental stresses altering forest productivity. However, nutrient availability can modulate drought resistance. Phoebe zhennan (gold Phoebe) is a high‐quality timber‐producing but threatened tree species in China, facing serious anthropogenic disturbances and abiotic constraints that restrict its growth and development. However, little attention has been given to designing adaptive strategies for its management by evaluating the possible role of major nutrients, particularly nitrogen (N), on its morphological and physio‐biochemical responses under water stress. To evaluate these responses, a complete randomized design was followed to investigate the effects of two irrigation levels (well‐watered and drought‐stressed conditions) and N fertilization treatments (with and without N). Drought stress significantly affected the growth of seedlings, as indicated by impaired photosynthesis, pigment degradation, disrupted N metabolism, over‐production of reactive oxygen species and enhanced lipid peroxidation. Nitrogen supplementation under drought stress had remarkable positive effects on the growth through physio‐biochemical adjustments as shown by higher level of nitrogenous compounds and up‐regulation of N‐associated metabolic enzymes activities which might be due to N‐mediated improved leaf relative water contents and photosynthetic efficiency. In addition, N application reduced oxidative stress and membrane damage, and maintained a high accumulation of osmolytes. However, in well‐watered seedlings N fertilization significantly improved root biomass and net CO2 assimilation rate suggesting high N‐use efficiency of the seedlings. These findings reveal that drought significantly affects the growth of P. zhennan, while N fertilization plays a crucial role in alleviating water stress damage by improving its drought tolerance potential at low metabolic costs. Therefore, N fertilization could be considered as an effective strategy for the conservation and management of P. zhennan in the face of future climate change.  相似文献   

6.
Plant-based diagnostic techniques such as chlorophyll meter (CM) readings and nitrogen (N) leaf concentration are used to determine the level of crop N nutrition, but research is limited on perennial crops and especially on aromatic and medicinal plants such as Greek oregano (Origanum vulgare spp. hirtum). The objectives of this study were to determine in a perennial crop species whether there is a relationship between the CM readings, N leaf concentration, and N use efficiency (NUE) and to use CM readings as a diagnostic tool for predicting dry matter yield in response to N fertilization. The CM readings varied across environments, growth stages, and fertilization treatments and were correlated with NUE. NUE was also affected by the environment, N fertilization, and interactions among these variables. This study provides new information about the effect of N application on CM readings, N leaf concentration, and NUE in a perennial crop such as oregano.  相似文献   

7.
The influence of mineral fertilization on root uptake and arbuscular mycorrhizal fungi-mediated 15N capture from labeled legume (Medicago polymorpha) residue was examined in winegrapes (Vitis vinifera) in the greenhouse, to evaluate compatibility of fertilization with incorporation of cover-crop residue in winegrape production. Plants grown in marginal vineyard soil were either fertilized with 0.25× Hoagland’s solution or not. This low fertilization rate represents the deficit management approach typical of winegrape production. Access to residue in a separate compartment was controlled to allow mycorrhizal roots (roots + hyphae), hyphae (hyphae-intact), or neither (hyphae-rotated) to proliferate in the residue by means of mesh core treatments. Leaves were weekly analyzed for 15N. On day 42, plants were analyzed for 15N and biomass; roots were examined for intraradical colonization; and soils were analyzed for 15N, inorganic N, Olsen-P, X-K, and extraradical colonization. As expected, extraradical colonization of soil outside the cores was unaffected by mesh core treatment, while that inside the cores varied significantly. 15N atom% excess was highest in leaves of roots + hyphae. In comparison, leaf 15N atom% excess in hyphae-intact was consistently intermediate between roots + hyphae and hyphae-rotated, the latter of which remained unchanged over time. Fertilization stimulated host and fungal growth, based on higher biomass and intraradical colonization of fertilized plants. Fertilization did not affect hyphal or root proliferation in residue but did lower %N derived from residue in leaves and stems by 50%. Our results suggest that even low fertilization rates decrease grapevine N uptake from legume crop residue by both extraradical hyphae and roots.  相似文献   

8.
We have previously reported that full sun‐grown Heliconia "Golden Torch”; leaves exhibited sustained decreased in PS II efficiency as compared to those grown under shade conditions. In this study, full sunlight plus low level of fertilization caused a further reduction of photosynthesis, chlorophyll content and Fv/Fm ratio while plants grown at high level of nutrient showed higher values of all these parameters. When plants grown under intermediate and deep shade, there was no significant difference in all parameters irrespective of nutrient supply. In the recovery experiments, plants without fertilizer were re‐fertilized weekly. Maximal photosynthetic rates, chlorophyll content, and Fv/Fm ratio increased gradually after re‐fertilizing the plants grown under full sunlight. However, no significant changes of these parameters were observed in plants grown under intermediate and deep shade over the same period. Total leaf nitrogen (N) was measured parallel with all the parameters. Photosynthetic rates, chlorophyll content, and Fv/Fm ratio showed a clear linear correlation with total leaf N in plants grown under full sunlight while there was no clear relationship observed in those plants grown under intermediate and deep shade. These results suggest that acclimation of Heliconia under full sunlight could be achieved by high level of nutrient fertilization.  相似文献   

9.
High soil salinity imposes osmotic stress and ion toxicity in plants, leading to substantial crop yield loss worldwide. Understanding of the quantitative and dynamic physiological responses to composite soil salt stress is limited and needs to be expanded. In this study, physiological, nutritional, and biomass yield parameters of tobacco(Nicotiana tabacum L.) grown in soil with five levels of composite soil salinity(CSS), basal CSS level(control, CK) and 3(T1), 6(T2), 9(T3), and 12(T4) times the...  相似文献   

10.
The Caatinga is a unique biome that encompasses nearly 11% of Brazil's territory and contains diverse vegetation composed of trees and bushes that have been scarcely studied from the economic perspective. In this context, Passiflora setacea may constitute a strategic alternative for agriculture because it produces fruit that has commercial potential and is tolerant to some diseases. Some species of Passiflora show more robust growth when associated with arbuscular mycorrhizal fungi (AMF) and are dependent on mycorrhization. In this study, the response of P. setacea to phosphate (P) fertilization and mycorrhization with Claroideoglomus etunicatum was evaluated. The experimental design included eight replicates of four randomized treatments: non-inoculated plants (NI), plants fertilized with phosphorus (P), mycorrhized plants (AMF), and plants that were both fertilized and mycorrhized (P+AMF). The plant height, leaf number, leaf area, fresh biomass (FB), and dry biomass (DB) of the shoots and roots, nutrient content, mycorrhizal colonization (MC), and the number of glomerospores (NG) in the rhizosphere were evaluated. The MC and the NG were reduced by phosphate fertilization. The development of the mycorrhized plants was significantly better than the NI and P treated plants for all of the variables tested. Inoculation with C. etunicatum promoted the growth of P. setacea seedlings even in the absence of phosphate fertilization, reducing production costs and strengthening the potential of P. setacea as a viable agricultural alternative for the semiarid region.  相似文献   

11.
Potassium (K) deficiency reduces photosynthesis and biomass production of crop plants and also renders them vulnerable to drought stress, whereas elevated carbon dioxide (CO2) has a positive effect on photosynthesis and yield and ameliorates the adverse effects of drought stress. This study aimed to characterize the physiological responses of wheat (Triticum aestivum L.) stressed with K deficiency under elevated CO2 and drought conditions. Increased biomass production caused by elevated CO2 as a consequence of increased photosynthesis and water use efficiency was absent in young K‐deficient wheat plants. Shoot K concentration was negatively affected by elevated CO2 particularly under K‐deficient conditions, whereas K content per plant was greatest in plants supplied with adequate K and adequate water. Specific leaf weight was increased as a consequence of carbohydrate accumulation in the source leaves of K‐deficient plants particularly under elevated CO2 and drought stress. Potassium deficiency clearly impeded the impact of elevated CO2 in both well watered as well as drought‐stressed plants. Adequate K fertilization is a prerequisite for efficient harvesting of atmospheric CO2 through increased photosynthesis, decreased transpiration, and increased biomass production under changing atmospheric CO2 and soil moisture conditions.  相似文献   

12.
Abstract

Estimating the nitrogen (N) status of plants as a function of their spectral response is a promising technique to diagnose and optimize N fertilization. An experiment was conducted in Jiquilpan (Michoacán, México) in which three N levels (0.3, 3, and 20 mM of NO3 ? in the irrigation water) were applied to strawberry (Fragaria vesca) in a randomized complete block design with three replicates. The spectral response of strawberry was measured at both the canopy and leaf level using individual wavebands as well as vegetation indices. Individual leaves were separated into three strata (young, mature, and old) and leaf dry matter, leaf area, and N content (% dry matter) were measured in each stratum. Leaf area, biomass, and N content differed significantly between strata. Leaf area, biomass, and N content in all strata were affected by N fertilization. At the canopy level, N content was highly correlated with green reflectance (R550) (r2=0.50) and red reflectance (R680) (r2=0.60) as well as the vegetation indices simple ratio (SR) (r2=0.56), normalized difference vegetation index (NDVI) (r2=0.56), and hyperspectral NDVI (HNDVI) (r2=0.56). For individual leaves, significant differences between strata were found with normalized total pigment to chlorophyll a ratio index (NPCI) and MERIS terrestrial chlorophyll index (MTCI) (p<0.001) as well as R550, photochemical reflectance index (PRI), red edge position (REP), and REP calculated using the MERIS satelite wavelengths (p<0.01). Relationships between spectral indices and N content at the leaf level were found with the youngest leaves only, with NPCI (p<0.01) and MTCI (p<0.05), whereas only R550 responded to N fertilization (p<0.05).  相似文献   

13.
The growth characteristics and nutrient uptake dynamics of Mytilaria laosensis Lec. seedlings treated weekly with conventional and exponential fertilizations were investigated at intervals of 3 weeks for 12 weeks in a greenhouse. Leaf area and pigment compositions were also examined at the final harvest. The fertility treatments (mg nitrogen seedling–1) included two conventional (50C and 100C) and four exponential (50E, 100E, 200E and 400E) fertilizations, and no fertilization (0) as control. The biomass and nutrient contents of M. laosensis seedlings increased exponentially with time. Steady-state nutrition of nitrogen (N) and phosphorus (P) were achieved under exponential fertilization treatment of 50?mg?N?seedling?1 (50E) and conventional fertilization treatment of 100?mg?N?seedling–1 (100C), resulting from simultaneous increase of their biomass and nutrient contents. The nutrient uptake efficiency continuously increased over time in conventionally fertilized seedlings, but it increased initially and declined or remained stable from 11 weeks after transplanting in the exponentially fertilized seedlings. At the end of the experiment, the conventionally fertilized seedlings performed remarkably better than all exponentially fertilized seedlings except for seedlings in the exponential treatment of 200?mg?N?seedling–1 (200E) in height, root collar diameter and biomass. The optimum N and P uptake occurred in 200E seedlings because their N and P contents were 71%/60% and 14%/9% higher than both conventionally fertilized seedlings (50C/100C) without significant differences in growth performance between them. The leaf areas and chlorophyll contents of seedlings increased significantly with the increase of fertilizer levels and nearly peaked at the range from 100 to 200?mg?N?seedling–1, whereas the delivery schedule (conventional and exponential) had little effect on leaf areas and chlorophyll contents of seedlings at the same nutrient level (50 or 100?mg?N?seedling–1). These findings will provide evidence to make guidelines on fertilization for nursery production of M. laosensis, and help understand the nutrient demands for this species and further benefit the development of its plantations.  相似文献   

14.
In two experiments, ‘Charm’ and ‘Delano’ chrysanthemum [Dendranthema x grandiflorum (Ramat.) Kitamura] were grown in a peat‐based root medium using standard greenhouse cultural practices. Fertilization treatments included (1) alternate liquid fertilization (ALF): water‐soluble formulation of 15N‐4.3P‐24.9K (15–10–30) at 536 mgL‐1 N alternated with tap water irrigation; (2) Constant Liquid Fertilization (CLF): 15N‐4.3P‐24.9K(15–10–30)at268 mgL‐1 Napplied at each irrigation; (3) slow release resin‐coated fertilizer (SRR): slow release formulation of 12N‐4.3P‐14.1K(12–10–17); and (4) slow release tablets (SRT): slow release formulation of 14N‐1.7P‐4.9K (14–4–6). Irrigation volume and timing of application were arbitrary for all plants in the first experiment, but they were determined gravimetrically for each treatment in the second experiment. Irrigation volumes exceeded container capacity by 20 to 30% (leaching fractions of 0.2 to 0.3). Leachate had lower electrical conductivity and higher pH with the slow release products than with liquid fertilizer. All treatments except SRT produced plants which met commercial crop standards and had adequate nutrient levels in shoot tissue. However, root dry mass was higher with slow release fertilizer than with liquid fertilizer. Rootrshoot ratios were ranked SRT>SRR>ALF=CLF. Root data suggest that an advantage of SR fertilization over LF fertilization is that greater root mass will develop. Estimations of nitrogen (N) recovery in Experiment 2 suggest that chrysanthemums grown with SRR resulted in most efficient uptake of fertilizer with 64 to 68% of applied N recovered in plant tissue (compared to 41 to 46% from LF treatments) and 18 to 21 % recovered in container leachate (compared to 32 to 41% from LF treatments).  相似文献   

15.
The result of intensive agriculture in cities is the decline in crop yields and depletion of the resource base. The aims of this study were to assess effects of nitrogen (N) or phosphorus (P) fertilization on bioavailable aluminum (Al) and their contribution on Al and nutrient uptake in Hibiscus sabdariffa. A pot experiment was led to supply a tropical soil with N and P fertilizers. P amendment decreased Al in soil solution, not N amendment. Fertilizers had effects on Al and nutrient uptake in roots and leaves of Hibiscus sabdariffa. The results also showed that the uptake of Al and nutrients depends on Al in soil solution or N supply or P supply. Only P uptake in roots and leaves was explained by combined effects of a nutrient supply × exchangeable Al. Furthermore, P supply does not limit the translocation of Al in shoots of plants in acid soils.  相似文献   

16.
Soil or foliar application of nitrogen (N) can increase plant growth and salinity tolerance in cotton, but a combination of both methods is seldom studied under salinity stress. A pot experiment was conducted to study the effects of soil application (S), foliar application (F), and a combination of both (S+F) with labeled nitrogen (15N) on cotton growth, N uptake and translocation under salinity stress (ECe = 12.5 dS m?1). Plant biomass, leaf area, leaf chlorophyll (Chl) content, leaf net photosynthetic (Pn) rate, levels of 15N and [Na+] and K+/ Na+ ratio in plant tissues were determined at 3, 7, 14 and 28 days after N application (DAN). Results showed that soil or foliar nitrogen fertilization improved plant biomass, leaf area per plant and leaf photosynthesis, and a combination of soil- plus foliar-applied N was superior to either S or F alone under salinity stress. Although foliar application favored a rapid accumulation of leaf N and soil application a rapid accumulation of root N, S+F enhanced N accumulation in both leaf and root under salinity stress. The combined N application also maintained significantly greater [K+] and K+/Na+ than either soil or foliar application alone. Therefore, the improved plant growth and salinity tolerance under S+F relative to soil or foliar N application alone was attributed to the increased total uptake of N, balanced N concentrations in different tissues through enhanced uptake and accumulation in both leaves and roots, and higher ratio of K+/Na+.  相似文献   

17.
烤烟基肥施用时间与氮肥利用的相关性研究   总被引：1，自引：0，他引：1  
烤烟是一种氮素敏感型的品质作物, 对氮素的需求非常严格。氮肥的合理施用不仅有利于提高烤烟对氮素养分的吸收利用, 也有利于提高烤烟烟叶品质。本研究采用大田试验的方法, 在湖北省烤烟主产区研究了基肥在3个不同施用时间(烤烟烟苗移栽前0 d、15 d和30 d)对烤烟氮肥利用参数的影响及其相关性。结果表明, 烤烟地上部烟叶和茎秆中干物质累积量和氮素含量均随着基肥施用时间的提前而表现出增加趋势。与移栽当天(0 d)施用基肥相比, 提前15 d、30 d施用基肥, 烤烟烟叶中干物质累积量和氮素含量分别平均增加16.4%、22.6%和1.5%、8.7%; 茎秆中则分别平均增加2.5%、12.7%和13.4%、33.9%。提前施用基肥有提高烤烟氮肥表观利用率的趋势, 但是各处理间差异不显著(P>0.05), 而在烤烟烟苗移栽前15 d、30 d施用基肥显著降低烤烟地上部氮肥农学利用率(35.2%、37.4%)和生理利用率(35.4%、41.6%)(P<0.05)。另外, 基肥施用时间与氮肥农学利用率、生理利用率和偏生产力均表现出显著或者极显著负相关关系, 而氮肥农学利用率与生理利用率和氮肥偏生产力以及氮肥生理利用率与偏生产力之间均表现出显著或极显著正相关关系。因此, 在烤烟烟苗移栽时适当提前基肥的施用时间(15~30 d)有利于提高烤烟对氮素的吸收利用, 促进烟叶中干物质的累积。  相似文献   

18.
Single‐pinched poinsettia (Euphorbia pulcherrima ’V‐14 Glory') in 15‐cm pots received constant fertigation with 50, 100, 200, and 300 mg.L‐1 nitrogen (N) from a 20N‐4.4 phosphorus (P)‐16.6 potassium (K) fertilizer with a leaching fraction (LF) of 0, 0.2, or 0.4. Plants received 25 irrigations during the 13‐week study. The shoot fresh and dry masses with 50, 100, and 300 mg.L‐1 N at the 0.4 LF were 30% larger than at the 0 LF. The 300 mg.L‐1 N fertigated plants had approximately 15% more leaf area and almost 122% more bract area than the 50 mg.L‐1 N fertigated plants. The leaf N concentration of plants fertigated with 100, 200, and 300 mg.L‐1 N was near or in the normal range of 4 to 6%, but was below the critical level of 3.5% with 50 mg.L‐1 N fertigation. In contrast, the leaf P concentration approached or exceeded the toxic level of 0.9% with 100 to 300 mg.L‐1 N. The N fertigation of 100 to 200 mg.L‐1 is adequate for producing a quality poinsettia crop. Quality poinsettias can be grown at a 0 LF if quality irrigation water is available. With 11 mg.L‐1 P via fertigation, the leaf P concentration was in the acceptable range. The P concentration in the 20N‐4.4P‐16.6K complete fertilizer was excessive for poinsettia and would contribute to unnecessary P leaching.  相似文献   

19.
Nitrogen (N) addition enhances primary productivity of terrestrial ecosystems. However, the effects of N fertilization and/or deposition on net ecosystem CO2 exchange (NEE) are not fully understood. The effects of N on NEE were investigated in two experimental cheatgrass ecosystems in Ecologically Controlled Enclosed Lysimeter Laboratories (EcoCELLs), Reno, Nevada. In this experiment, no N fertilization was added to the two EcoCELLs in the first year and two different N fertilization regimes were applied in the second year. N fertilizer was applied once to one EcoCELL (pulse fertilization, PF), and the same total amount of N in biweekly increments to the other EcoCell (gradual fertilization, GF). NEE, photosynthetically active radiation (PAR) and canopy green leaf area index (LAI) were continuously measured in the two EcoCELLs during the pretreatment and N-fertilized years. Plant N content and biomass were measured at the end of the growing season in each year. Radiation-use efficiency (RUECO2) was calculated as the ratio of gross ecosystem photosynthesis (GEP) to the intercepted photosynthetically active radiation (IPAR). The responses of NEE to IPAR were used to estimate the maximum ecosystem photosynthetic capacity (Fmax). N fertilization stimulated canopy LAI, plant N content, Fmax, RUECO2, NEE and biomass in both methods of N supply applications. PF led to higher LAI, Fmax and NEE than GF, but both had a similar RUECO2 during the early growing season. GF maintained higher LAI, Fmax, RUECO2 and NEE than PF during the late growing season. At the ecosystem level, N fertilization stimulated daily NEE directly by increasing canopy LAI, plant N content, shoot/root ratio and the maximum ecosystem photosynthetic capacity, and increased the seasonally accumulated NEE indirectly by extending the growing season. PF differed significantly from GF in its effects on NEE and RUECO2, possibly due to differential rates and timing of N availability. Our study suggested that these changes in the canopy RUECO2 and growing season under N fertilization or N deposition regimes should be considered in modeling studies of ecosystem C sequestration.  相似文献   

20.
ABSTRACT

The use of organic or reduced form of nitrogen (N) can have various beneficial effects in terms of plant nutrient uptake, metabolism, and environmental issues. In this study, the influence of soil application of reduced N-forms (ammonium, glycine, and glutamine) compared to nitrate and a no fertilizer treatment was evaluated on growth characteristics of sweet basil (Occimum basilicum L.) under a moderate lime soil conditions. The basil growth traits including root and shoot biomass were increased under application of reduced N-forms mainly glycine and glutamine compared to no fertilizer treatment. Application of reduced forms of nitrogen (ammonium, glycine, and glutamine) increased the leaf concentrations of potassium (K), magnesium (Mg), calcium (Ca), iron (Fe) and zinc (Zn), whereas the leaf N concentration was increased by ammonium and nitrate fertilization compared to unfertilized control plants. The results indicate that soil application of reduced N-forms particularly glycine and glutamine is superior to nitrate application.  相似文献   

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