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1.
Poornananda Madhava Naik Shirugumbi Hanamanthagouda Manohar Hosakatte Niranjana Murthy 《Acta Physiologiae Plantarum》2011,33(4):1553-1557
The present work deals with optimization of adventitious shoot culture of Bacopa monnieri for the production of biomass and bacoside A and has investigated the effects of macro elements (NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4) and nitrogen source [NH4
+/NO3
−] of Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium (MS) on accumulation of biomass and bacoside A content. Optimum number of adventitious shoots (99.33 shoots explant−1), fresh weight (1.841 g) and dry weight (0.150 g) were obtained in the medium with 2.0× strength of NH4NO3. The highest production of bacoside A content was also recorded in the medium of 2.0× NH4NO3, which produced 17.935 mg g−1 DW. The number of adventitious shoot biomass and bacoside A content were optimum when the NO3
− concentration was higher than that of NH4
+. Maximum number of shoots (70.00 shoots explant−1), biomass (fresh weight 1.137 g and dry weight 0.080 g) and also bacoside A content (27.106 mg g−1 DW) were obtained at NH4
+/NO3
− ratio of 14.38/37.60 mM. Overall, MS medium supplemented with 2.0× NH4NO3 is recommended for most efficient bacoside A production. 相似文献
2.
Praveen Nagella Hosakatte Niranjana Murthy 《Plant Cell, Tissue and Organ Culture》2011,104(1):119-124
Withania somnifera is an important medicinal plant that contains withanolides and withaferins, both bioactive compounds. We have tested the
effects of macroelements and nitrogen source in W. somnifera cell suspension cultures with the aim of optimizing the production of biomass and withanolide A. The effects of the macroelements
NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4 at concentrations of 0.0, 0.5, 1.0, 1.5 and 2.0× strength and of the nitrogen source [NH4
+/NO3
− (mM/mM) ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20,
and 14.38/37.60 (mM)] in Murashige and Skoog medium were tested for biomass and withanolide A production. The highest accumulation
of biomass [147.81 g l−1 fresh weight (FW) and 14.02 g l−1 (dry weight (DW)] was recorded in the medium containing a 0.5× concentration of NH4NO3, and the highest production of withanolide A content was recorded in the medium with 2.0× KNO3 (4.36 mg g−1 DW). The NH4
+/NO3
− ratio also influenced cell growth and withanolide A production, with both parameters being larger when the NO3
− concentration was higher than that of NH4
+. Maximum biomass growth (110.45 g l−1 FW and 9.29 g l−1 DW) was achieved at an NH4
+/NO3
− ratio of 7.19/18.80, while withanolide A production was greatest (3.96 mg g−1 DW) when the NH4
+/NO3
− ratio was 14.38/37.60 mM. 相似文献
3.
4.
Root segments from seedlings of Panax ginseng produced adventitious roots directly when cultured on 1/2 MS solid medium lacking NH4NO3 and containing 3.0 mg l−1 IBA. Using this adventitious root formation, we developed rapid and efficient transgenic root formation directly from adventitious
root segments in P. ginseng. Root segments were co-cultivated with Agrobacterium tumefaciens (GV3101) caring β-glucuronidase (GUS) gene. Putative transgenic adventitious roots were formed directly from root segments on medium with 400 mg l−1 cefotaxime and 50 mg l−1 kanamycin. Kanamycin resistant adventitious roots were selected and proliferated as individual lines by subculturing on medium
with 300 mg l−1 cefotaxime and 50 mg l−1 kanamycin at two weeks subculture interval. Frequency of transient and stable expression of GUS gene was enhanced by acetosyringon (50 mg l−1) treatment. Integration of transgene into the plants was confirmed by the X-gluc reaction, PCR and Southern analysis. Production
of transgenic plants was achieved via somatic embryogenesis from the embryogenic callus derived from independent lines of
adventitious roots. The protocol for rapid induction of transgenic adventitious roots directly from adventitious roots can
be applied for a new Agrobacterium tumefaciens-mediated genetic transformation protocol in P. ginseng. 相似文献
5.
Animal waste causes environmental problems like eutrophication of ground and surface water or the pollution of the atmosphere
because of its high NH4
+ content. The aim of our study was to fix the nitrogen of swine waste as biomass. Therefore, an isolated alga, Chlorella sp., and bacteria naturally living in liquid manure were grown in batch cultures (containing diluted swine waste supplied
with a nutrient solution) and continuous cultures (undiluted liquid manure) to achieve reduction of NH4
+ and total organic carbon (TOC) contents. For continuous cultivation, a photobioreactor of our own design was used. The batch
cultivation of Chlorella sp. and bacteria in swine waste resulted in good growth of both groups of organisms and in a reduction of 25% NH4
+ and 80% TOC. In the continuous cultivation a steady state was not achieved owing to a change in the composition of the bacterial
population. NH4
+ was totally removed, but NO2
− (up to 100 mM) was transiently released. NO3
− was not detected. These effects might be explained by the presence of heterotrophic nitrifiers, which are able to oxidize
NH4
+ to NO2
− and to reduce NO2
− to gaseous compounds.
Received: 21 January 1999 / Received revision: 9 March 1999 / Accepted: 14 March 1999 相似文献
6.
Qing Liu Huajun Yin Jinsong Chen Chunzhang Zhao Xinying Cheng Yunyan Wei Bo Lin 《Ecological Research》2011,26(3):637-648
The impacts of global climatic change on belowground ecological processes of terrestrial ecosystems are still not clear. We
therefore conducted an experiment in the subalpine coniferous forest ecosystem of the eastern edges of the Tibetan Plateau
to study roots of Picea asperata seedlings and rhizosphere soil responses to soil warming and nitrogen availability from April 2007 to December 2008. The
seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0 or 25 g m−2year−1 N). We used a free air temperature increase from an overhead infrared heater to raise both air and soil temperature by 2.1
and 2.6°C, respectively. The results showed that warming alone significantly increased total biomass, coarse root biomass
and fine root biomass of P. asperata seedlings. Both total biomass and fine root biomass were increased, but coarse root biomass was significantly decreased by
nitrogen fertilization and warming combined with nitrogen fertilization. Warming induced a prominent increase in soil organic
carbon (SOC) and NO3
−-N of rhizosphere soil, while nitrogen fertilization significantly decreased SOC and NH4
+-N of rhizosphere soil. The warming, fertilization and warming × N fertilization interaction decreased soil microbial C significantly,
but substantially increased soil microbial N. These results suggest that nitrogen deposition combined with warmer temperatures
under future climatic change possibly will have no effect on fine root production of P. asperata seedlings, but could enhance the nitrification process of their rhizosphere soils in subalpine coniferous forests. 相似文献
7.
Gyöngyi Kenesi Hesham M. Shafik Attila W. Kovács Sándor Herodek Mátyás Présing 《Hydrobiologia》2009,623(1):191-202
The aim of this research was to test whether NH4
+ and NO3
− affect the growth, P demand, cell composition and N2 fixation of Cylindrospermopsis raciborskii under P limitation. Experiments were carried out in P-limited (200 μg l−1 PO4-P) chemostat cultures of C. raciborskii using an inflowing medium containing either 4,000 μg l−1 NH4-N, 4,000 μg l−1 NO3-N or no combined N. The results showed the cellular N:P and C:P ratios of C. raciborskii decreased towards the Redfield ratio with increasing dilution rate (D) due to the alleviation of P limitation. The cellular C:N and carotenoids:chlorophyll-a ratios also decreased with D, predominantly as a result of an increase in the chlorophyll-a and N content. The NH4
+ and NO3
− supply reduced the P maintenance cell quota of C. raciborskii. Consequently, the biomass yield of the N2-grown culture was significantly lower. The maximum specific growth rate of N2-grown culture was also the lowest observed. It is suggested that these differences in growth parameters were caused by the
P and energy requirement for heterocyte formation, nitrogenase synthesis and N2 fixation. N2 fixation was partially inhibited by NO3
− and completely inhibited by NH4
+. It was probably repressed through the high N content of cells at high dissolved N concentrations. These results indicate
that C. raciborskii is able to grow faster and maintain a higher biomass under P limitation where a sufficient supply of NH4
+ or NO3
− is maintained. Information gained about the species-specific nutrient and pigment stoichiometry of C. raciborskii could help to access the degree of nutrient limitation in water bodies.
Handling editor: Luigi Naselli-Flores 相似文献
8.
Xi-Hua Cui Hosakatte Niranjana Murthy Chun-Hua Wu Kee-Yoeup Paek 《Plant Cell, Tissue and Organ Culture》2010,103(1):7-14
In this study, we investigated the influence of initial sucrose concentration on the accumulation of biomass, phenols, flavonoids,
chlorogenic acid, and hypericin in adventitious root cultures of Hypericum perforatum L. Cultures were initiated in shake flasks by using half-strength Murashige and Skoog (MS) medium, 1.0 mg l−1 indolebutyric acid (IBA), 0.1 m g l−1 kinetin, and different concentrations 0, 1, 3, 5, 7, or 9% in w/v) of sucrose and were maintained in darkness. The medium
supplemented with 3% (w/v) sucrose resulted in the optimum biomass accumulation, but higher sucrose concentrations (5, 7,
and 9%) inhibited biomass accumulation due to the relatively higher osmotic pressure. However, the amount of total phenols,
flavonoids, chlorogenic acid, and total hypericin was increased with the roots grown in the medium supplemented with 5, 7,
and 9% (w/v) sucrose. The antioxidant potential of methanolic extract [1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic
acid; ABTS) radical scavenging activities] of H. perforatum adventitious roots was also assessed and correlated with the metabolite accumulation. Cultures maintained with higher initial
sucrose concentration (5, 7, and 9% w/v) showed increased accumulation of phenols, flavonoids, chlorogenic acid, and total
hypericin, and this might be due to the osmotic stress at elevated sucrose concentrations. To verify the effect of osmotic
stress on lipid peroxidation, the levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), and proline were determined in the adventitious roots and the results revealed a marked increase
in the concentrations of these compounds. These results suggest that optimal adventitious root biomass could be achieved in
the MS medium with 3% (w/v) sucrose and increased sucrose concentration resulted in osmotic stress and, in turn, induces the
accumulation of secondary metabolites. 相似文献
9.
Marcel Tutor Ale Jørn Dalgaard Mikkelsen Anne S. Meyer 《Journal of applied phycology》2011,23(3):345-351
Controlled cultivation of marine macroalgal biomass such as Ulva species, notably Ulva lactuca, is currently studied for production of biofuels or functional food ingredients. In a eutrophic environment, this macrophyte
is exposed to varying types of nutrient supply, including different and fluctuating levels of nitrogen sources. Our understanding
of the influences of this varying condition on the uptake and growth responses of U. lactuca is limited. In this present work, we examined the growth response of U. lactuca exposed to different sources of nitrogen (NH4+; NO3−; and the combination NH4NO3) by using photo-scanning technology for monitoring the growth kinetics of U. lactuca. The images revealed differential increases of the surface area of U. lactuca disks with time in response to different N-nutrient enrichments. The results showed a favorable growth response to ammonium
as the nitrogen source. The NH4Cl and NaNO3 rich media (50 μM of N) accelerated U. lactuca growth to a maximum specific growth rate of 16.4 ± 0.18% day−1 and 9.4 ± 0.72% day−1, respectively. The highest biomass production rate obtained was 22.5 ± 0.24 mg DW m−2·day−1. The presence of ammonium apparently discriminated the nitrate uptake by U. lactuca when exposed to NH4NO3. Apart from showing the significant differential growth response of U. lactuca to different nitrogen sources, the work exhibits the applicability of a photo-scanning approach for acquiring precise quantitative
growth data for U. lactuca as exemplified by assessment of the growth response to two different N-sources. 相似文献
10.
This study examined whether ‘Risnod2’ and ‘Risnod27’ non-nodulating mutants of pea (Pisum sativum L.) provided with increasing concentrations of nitrate could achieve a growth and nitrogen accumulation comparable to their
parental N2-fixing cv. Finale. In the cv. Finale, nodule number, nodule dry mass accumulation, total C2H2-reducing activity of nodulated roots (TAR) and estimated N2 fixation were considerably inhibited at 5.0 and 10.0 mM root medium NO3
− concentrations. In contrast a 0.63 mM level stimulated both the nodule dry mass and TAR. The cv. Finale N2-fixing plants grown on 0 to 2.5 mM NO3
− levels had higher shoot N concentrations than the Nod− mutants, but within the 5.0 to 10.0 mM levels the Nod− mutants approached or even overtopped the N concentration of the cv. Finale plants. Compared with a high positive correlation
found in the Nod− mutants, shoot N concentration in the cv. Finale was negatively correlated with the root medium NO3
− concentration. The pattern of nitrogen content in shoot dry mass was very similar to that seen in the shoot dry mass accumulation.
The Nod− mutants grown on the 5.0 and/or 10.0 mM NO3
− level had plant dry mass, shoot nitrogen concentration, shoot nitrogen content, and root/shoot dry mass ratio comparable
with those of the nodulating cv. Finale grown on the same nitrate levels. 相似文献
11.
Song Quan Wu Mei Lan Lian Ri Gao So Young Park Xuan Chun Piao 《In vitro cellular & developmental biology. Plant》2011,47(6):719-724
Astragalus membranaceus is one of the most widely used traditional medicinal herbs in China, but the time required to generate a useful product in
the field production is long. The growth of adventitious root cultures was compared between cultures grown in solid, liquid,
or a 5-L balloon-type bubble bioreactor. The maximum growth ratio (final dry weight/initial dry weight) was determined for
adventitious roots grown in the bioreactor. Studies carried out to optimize biomass production of adventitious roots compared
adventitious root growth from various inoculum root lengths, inoculum densities, and aeration volume in the bioreactors. The
maximum growth ratio occurred in treatments with a 1.5-cm inoculum root length, with 30 g (fresh weight) of inoculum per bioreactor
or with an aeration volume of 0.1 vvm (air volume/culture medium volume per min). The polysaccharide, saponin, and flavonoid
content of roots from bioreactor-grown cultures were compared to roots from field-grown plants grown for 1 and 3 yr. Total
polysaccharide content of adventitious roots in the bioreactor (30.0 mg g−1 dry weight (DW)) was higher than the roots of 1-yr-old (13.8 mg g−1 DW) and 3-yr-old (21.1 mg g−1 DW) plants in the field. Total saponin (3.4 mg g−1 DW) and flavonoid (6.4 mg g−1 DW) contents were nearly identical to 3-yr-old roots and higher than that of 1-yr-old roots under field cultivation. 相似文献
12.
Carbon-14 pulse labeling technique was used to study the effect of rooting medium salinity and form and availability of N
on growth and rhizodeposition of wheat (Triticum aestivum L.). Thirty days old plants grown in continuously aerated Arnon and Hoagland nutrient solution were subjected to 14C pulse labeling for 24 h and transferred to aqueous rooting medium containing 0, 150, and 300 mM NaCl in all combinations
with different forms (calcium nitrate, ammonium sulphate, and ammonium nitrate) and amounts (0.5, 1.0, 1.5, and 2.0 times
the standard N concentration (150 ppm) of Arnon and Hoagland plant growth medium). Plant samples immediately after pulse labeling,
following 7 days of growth under different rooting medium conditions, and the freeze-dried rooting medium were analyzed for
total C and 14C. Length and fresh/dry weight of root and shoot portions and calculated values of unaccounted 14C were determined. Presence of NaCl in the rooting medium led to a decrease in root and shoot portions. However, NO3
−-fed plants showed better growth than NH4
+-fed plants at all the three salinity levels. Salinity in rooting medium led to higher rhizodeposition and lower loss of 14C. Relatively higher proportion of 14C was released as rhizodeposits and retained in root/shoot portions of plants fed with NH4
+ or NH4
++NO3
−, than those with NO3
−, while less was respired. The specific activity of the rhizodeposits (kBq 14C g−1 C) was also higher under saline conditions. The rhizodeposits in NH4
+-fed plants were more highly labeled as compared to NO3
−-plants. 相似文献
13.
Rozita Omar M. A. Abdullah M. A. Hasan M. Marziah M. K. Siti Mazlina 《Biotechnology and Bioprocess Engineering》2005,10(3):192-197
The effects of macronutrients (NO3
−, NH4
+ and PO4
3−) on cell growth and triterpenoids production inCentella asiatica cell suspension cultures were analyzed using the Box-Behnken response surface model experimental design. In screening and
optimization experiments, PO4
3− as a single factor significantly influenced cell growth where increasing the phosphate level from 0.1 to 2.4 or 2.6 mM, elevated
cell growth from 3.9 to 14–16 g/L. The optimum values predicted from the response surface model are 5.05 mM NH4
+, 15.0 mM NO3
− and 2.6 mM PO4
3−, yielding 16.0 g/L cell dry weight with 99% fitness to the experimental data. While the NH4
+-NO3
− interaction influenced cell growth positively in the optimization experiment, NH4
+ and NO3
− as single factors; and interactions of NO3
−-PO4
3−, NH4
+-PO4
3− and NH4
+-NO3
− were all negative in the screening experiment. Cell growth and the final pH level were positively affected by PO4
3−, but negatively affected by NH4
+ and NH4
+-PO4
3− interactions. The different effects of factors and their interactions on cell growth and final pH are influenced by a broad
or narrow range of macronutrient concentrations. The productions of triterpenoids however were lower than 4 mg/g cell dry
weight. 相似文献
14.
Effect of activated charcoal and 6-benzyladenine on in vitro nitrogen uptake by Lagerstroemia indica 总被引:1,自引:0,他引:1
A sterile hydroponic culture system suitable for studying nitrogen (N) uptake ofLagerstroemia indica L.in vitro was developed. Four different treatments were assayed: with and without activated charcoal (AC and NAC, respectively), with
and without 50 μM of 6-benzyladenine (+BA and −BA, respectively). Medium pH, electrical conductivity (EC), NO3
− and NH4
+ concentrations were measured weekly. At the end of the culture, propagules were sampled and SPAD indices, and shoot and root
fresh weights were determined. Explants grown in media with activated charcoal were able to take up both NO3
− and NH4
+, although NH4
+ uptake was lower. Subsequently the pH of the media was maintained between 5.5–6.0. In treatments with no addition of activated
charcoal, NH4
+ uptake was preferential and the pH dropped to 3.1. Explants in these conditions were unable to raise the pH by taking up
NO3
−, especially when root morphogenesis was inhibited by addition of BA. Supply of this PGR produced root growth inhibition,
which was almost complete in the treatment without activated charcoal. This component significantly reduced the inhibitory
effect of 50 μM BA on root growth.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
As part of the Kushiro Wetland Restoration Project, we evaluated the effect of the tree-cutting (February 2003) on soil water
chemistry for 3 years in an alder (Alnus japonica) shrubland on the peat soil in the Kushiro Wetland, the largest wetland in Japan. The alder stand was divided into two types;
low stature and high stature stands, mean heights being 1.5 and 2.6 m, respectively. The treatment plot with tree cutting
and the reference plot measuring 25 m × 25 m each were established in both stands, and a soil incubation experiment was also
conducted by trenching the root zone of wetland vegetation in the treatment plots in both stands in the summer of 2004. The
tree cutting did not substantially increase the concentrations of ammonium ion (NH4
+) and nitrate ion (NO3
−) in the soil water, although a gradual and slight increase of NO3
− concentration was found after the tree-cutting only in the high stature stand (<10 μmol/l). This increase in the NO3
− concentration in the high stature stand was probably due to the rhizosphere oxidation of wetland herbaceous vegetation, and
was accompanied by the increase of Ca2+ concentration. The soil incubation experiment showed no significant change of the nitrogen concentration, suggesting that
inorganic nitrogen was immobilized and NO3
− was denitrified intensively in this wetland peat soil. The results of this study suggested that this wetland ecosystem had
a high potential to stabilize the soil water chemistry. 相似文献
16.
M. Eeva P. Vuorela P. Tammela M. Nyman S. Ojala K. Fagerstedt H. Haario H. Vuorela 《Biologia Plantarum》2007,51(1):27-33
A mathematical computer-aided model CELLOP was constructed in which the desirability functions in a three-dimensional experimental
design can be used to find the optimal growing conditions for plant cells. CELLOP is intended for the optimisation of 3 to
6 physical, chemical, or biological variables in the cultivation conditions of plant cell cultures. The model was used to
optimise the culturing conditions (calcium, inorganic nitrogen, and sucrose concentrations) for coumarin-producing, spontaneously
embryogenic cell lines of angelica Angelica archangelica L. subsp. archangelica and hogs fennel Peucedanum palustre (L.) Moench. For A. archangelica the overall optimum concentrations were 0.47 mM Ca2+, 5.06 mM NO3
−, 0.40 mM NH4
+, and 96.25 mM sucrose. The dry mass was 24.7 % higher and the coumarin content 40.5 % higher than those achieved in the standard
75 % Gamborg B5 medium. For A. archangelica the highest embryogenic activity was reached in the media containing 1.25 mM Ca2+. In the case of P. palustre the overall optimum concentrations were 1.60 mM Ca2+, 2.84 mM NO3
−, 0.23 mM NH4
+, and 85.10 mM sucrose. For P. palustre the dry mass production increased by 61.8 % and the coumarin content by 58.1 % compared to the values achieved in the Gamborg
B5 medium. For P. palustre the highest embryogenic activity was reached in the presence of 50.0 mM NO3
− and 4.01 mM NH4
+. 相似文献
17.
R. Thomas James Wayne S. Gardner Mark J. McCarthy Stephen A. Carini 《Hydrobiologia》2011,669(1):199-212
Total nitrogen (TN) in Lake Okeechobee, a large, shallow, turbid lake in south Florida, has averaged between 90 and 150 μM
on an annual basis since 1983. No TN trends are evident, despite major storm events, droughts, and nutrient management changes
in the watershed. To understand the relative stability of TN, this study evaluates nitrogen (N) dynamics at three temporal/spatial
levels: (1) annual whole lake N budgets, (2) monthly in-lake water quality measurements in offshore and nearshore areas, and
(3) isotope addition experiments lasting 3 days and using 15N-ammonium (15NH4
+) and 15N-nitrate (15NO3
−) at two offshore locations. Budgets indicate that the lake is a net sink for N. TN concentrations were less variable than
net N loads, suggesting that in-lake processes moderate these net loads. Monthly NO3
− concentrations were higher in the offshore area and higher in winter for both offshore and nearshore areas. Negative relationships
between the percentage of samples classified as algal blooms (defined as chlorophyll a > 40 μg l−1) and inorganic N concentrations suggest N-limitation. Continuous-flow experiments over intact sediment cores measured net
fluxes (μmol N m−2 h−1) between 0 and 25 released from sediments for NH4
+, 0–60 removed by sediments for NO3
−, and 63–68 transformed by denitrification. Uptake rates in the water column (μmol N m−2 h−1) determined by isotope dilution experiments and normalized for water depth were 1,090–1,970 for NH4
+ and 59–119 for NO3
−. These fluxes are similar to previously reported results. Our work suggests that external N inputs are balanced in Lake Okeechobee
by denitrification. 相似文献
18.
Supplying both N forms (NH4
++NO3
−) to the maize (Zea mays L.) plant can optimize productivity by enhancing reproductive development. However, the physiological factors responsible
for this enhancement have not been elucidated, and may include the supply of cytokinin, a growth-regulating substance. Therefore,
field and gravel hydroponic studies were conducted to examine the effect of N form (NH4
++NO3
− versus predominantly NO3
−) and exogenous cytokinin treatment (six foliar applications of 22 μM 6-benzylaminopurine (BAP) during vegetative growth versus untreated) on productivity and yield of maize. For untreated plants,
NH4
++NO3
− nutrition increased grain yield by 11% and whole shoot N content by 6% compared with predominantly NO3
−. Cytokinin application to NO3
−-grown field plants increased grain yield to that of NH4
++NO3
−-grown plants, which was the result of enhanced dry matter partitioning to the grain and decreased kernel abortion. Likewise,
hydroponically grown maize supplied with NH4
++NO3
− doubled anthesis earshoot weight, and enhanced the partitioning of dry matter to the shoot. NH4
++NO3
− nutrition also increased earshoot N content by 200%, and whole shoot N accumulation by 25%. During vegetative growth, NH4
++NO3
− plants had higher concentrations of endogenous cytokinins zeatin and zeatin riboside in root tips than NO3
−-grown plants. Based on these data, we suggest that the enhanced earshoot and grain production of plants supplied with NH4
++NO3
− may be partly associated with an increased endogenous cytokinin supply. 相似文献
19.
Patricia Torres-Cañabate Eric A. Davidson Ekaterina Bulygina Roberto García-Ruiz Jose A. Carreira 《Biogeochemistry》2008,91(1):1-11
Evidence for abiotic immobilization of nitrogen (N) in soil is accumulating, but remains controversial. Identifying the fate
of N from atmospheric deposition is important for understanding the N cycle of forest ecosystems. We studied soils of two
Abies pinsapo fir forests under Mediterranean climate seasonality in southern Spain—one with low N availability and the other with symptoms
of N saturation. We hypothesized that biotic and abiotic immobilization of nitrate (NO3
−) would be lower in soils under these forests compared to more mesic temperate forests, and that the N saturated stand would
have the lowest rates of NO3
− immobilization. Live and autoclaved soils were incubated with added 15NO3
− (10 μg N g−1 dry soil; 99% enriched) for 24 h, and the label was recovered as total dissolved-N, NO3
−, ammonium (NH4
+), or dissolved organic-N (DON). To evaluate concerns about possible iron interference in analysis of NO3
− concentrations, both flow injection analysis (FIA) and ion chromatography (IC) were applied to water extracts, soluble iron
was measured in both water and salt extracts, and standard additions of NO3
− to salt extracts were analyzed. Good agreement between FIA and IC analysis, low concentrations of soluble Fe, and 100% (±3%)
recovery of NO3
− standard additions all pointed to absence of an interference problem for NO3
− quantification. On average, 85% of the added 15NO3
− label was recovered as 15NO3
−, which supports our hypothesis that rates of immobilization were generally low in these soils. A small amount (mean = 0.06 μg N g−1 dry soil) was recovered as 15NH4
+ in live soils and none in sterilized soils. Mean recovery as DO15N ranged from 0.6 to 1.5 μg N g−1 dry soil, with no statistically significant effect of sterilization or soil type, indicating that this was an abiotic process
that occurred at similar rates in both soils. These results demonstrate a detectable, but modest rate of abiotic immobilization
of NO3
− to DON, supporting our first hypothesis. These mineral soils may not have adequate carbon availability to support the regeneration
of reducing microsites needed for high rates of NO3
− reduction. Our second hypothesis regarding lower expected abiotic immobilization in soils from the N-saturated site was not
supported. The rates of N deposition in this region may not be high enough to have swamped the capacity for soil NO3
− immobilization, even in the stand showing some symptoms of N saturation. A growing body of evidence suggests that soil abiotic
NO3
− immobilization is common, but that rates are influenced by a combination of factors, including the presence of plentiful
available carbon, reduced minerals in anaerobic microsites and adequate NO3
− supply. 相似文献
20.
Michel Edmond Ghanem Cristina Mart��nez-And��jar Alfonso Albacete Hana Posp��?ilov�� Ian C. Dodd Francisco P��rez-Alfocea Stanley Lutts 《Journal of Plant Growth Regulation》2011,30(2):144-157
Mixed nitrate/ammonium fertilization can partially alleviate the negative effects of salinity on growth of some plant species
compared to all-nitrate or all-ammonium fertilization. To gain insights about the mechanisms involved, tomato (Solanum lycopersicum L. cv Moneymaker) plants were grown hydroponically for 3 weeks with two NO3
−/NH4
+ fertilization regimes (6/0.5 and 5/1.5; Ntotal = 6.5 mM) in the absence (control) or presence of salt stress (100 mM NaCl). Ammonium enrichment had no effect on growth
and other parameters under control conditions. Under salinity, however, ammonium enrichment improved shoot and root biomass
by 20% and maintained leaf PSII efficiency close to control levels. These changes were related to higher leaf K+, NO3
−, and NH4
+ concentrations and activities of the N-assimilatory enzymes glutamate synthase (GOGAT) and glutamine synthase (GS) in the
leaves. Ammonium enrichment also attenuated the salt-induced increase in leaf abscisic acid (ABA) concentration and decrease
in leaf concentrations of indole 3-acetic acid (IAA) and the cytokinins trans-zeatin (tZ) and trans-zeatin riboside (tZR). Enhanced cytokinin status was probably due to maintenance of root-to-shoot cytokinin transport and decreased leaf induction
of the cytokinin-degrading enzyme cytokinin oxidase/dehydrogenase (CKX) under ammonium-enriched conditions. It is concluded
that nitrogen form modifies salinity-induced physiological responses and that these modifications are associated with changes
in plant hormone status. 相似文献