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1.
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
2.
3.
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
4.
Rafiqa Améziane Céline Richard-Molard Eliane Deléens Jean-François Morot-Gaudry Anis M. Limami 《Planta》1997,202(3):303-312
In chicory, we examined how NO3
− supply affected NO3
− uptake, N partitioning between shoot and root and N accumulation in the tuberized root throughout the vegetative period.
Plants were grown at two NO3
− concentrations: 0.6 and 3 mM. We used 15N-labelling/chase experiments for the quantification of N fluxes between shoot and root and for determining whether N stored
in the tuberized root originates from N remobilized from the shoot or from recently absorbed NO3
−. The rate of 15NO3
− uptake was decreased by low NO3
− availability at all stages of growth. In young plants (10–55 days after sowing; DAS), in both NO3
− treatments the leaves were the strongest sink for 15N. In mature (tuberizing) plants, (55–115 DAS), the rate of 15NO3
− uptake increased as well as the amount of exogenous N allocated to the root. In N-limited plants, N allocation to the tuberized
root relied essentially on recent N absorption, while in N-replete plants, N remobilized from the shoot contributed more to
N-reserve accumulation in the root. In senescing plants (115–170 DAS) the rate of 15NO3
− uptake decreased mainly in N-replete plants whereas it remained almost unchanged in N-limited plants. In both NO3
− treatments the tuberized root was the strongest sink for recently absorbed N. Remobilization of previously absorbed N from
shoot to tuberized root increased greatly in N-limited plants, whereas it increased slightly in N-replete plants. As a consequence,
accumulation of the N-storage compounds vegetative storage protein (VSP) and arginine was delayed until later in the vegetative
period in N-limited plants. Our results show that although the dynamics of N storage was affected by NO3
− supply, the final content of total N, VSP and arginine in roots was almost the same in N-limited and N-replete plants. This
indicates that chicory is able to build up a store of available N-reserves, even when plants are grown on low N. We also suggest
that in tuberized roots there is a maximal capacity for N accumulation, which was reached earlier (soon after 100 DAS) in
N-replete plants. This hypothesis is supported by the fact that in N-replete plants despite NO3
− availability, N accumulation ceased and significant amounts of N were lost due to N efflux.
Received: 14 October 1996 / Accepted: 4 February 1997 相似文献
5.
Begoña Blasco Juan J. Rios Luis M. Cervilla Eva Sánchez-Rodríguez María M. Rubio-Wilhelmi Miguel A. Rosales Juan M. Ruiz Luis Romero 《Journal of Plant Growth Regulation》2010,29(4):477-486
Iodine is vital to human health, and iodine biofortification programs help improve human intake through plant consumption.
There is no research on whether iodine biofortification influences basic plant physiological processes. Because nitrogen (N)
uptake, utilization, and accumulation are determining factors in crop yield, the aim of this work was to establish the effect
of the application of different doses (20, 40, and 80 μM) and forms of iodine (iodate [IO3
−] vs. Iodide [I−]) on N metabolism and photorespiration. For this study we analyzed shoot biomass and the activities of nitrate reductase
(NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AAT), glutamate
dehydrogenase (GDH), glycolate oxidase (GO), glutamate:glyoxylate aminotransferase (GGAT), serine:glyoxylate aminotransferase
(SGAT), hydroxypyruvate reductase (HR) and catalase (CAT), nitrate (NO3
−), ammonium (NH4
+), organic and total N, amino acids, proteins, serine (ser), malate, and α-ketoglutaric acid in edible lettuce leaves. Application
of I− at doses of at least 40 μM reduced the foliar concentration of NO3
− with no decrease in biomass production, which may improve the nutritional quality of lettuce plants. In contrast, the application
of 80 μM of I− is phytotoxic for lettuce plants, reducing the biomass, foliar concentration of organic N and NO3
−, and NR and GDH activities. HR activity is significantly inhibited with all doses of I−; the least inhibition was at 80 μM. This may involve a decrease in the incorporation of carbonated skeletons from photorespiration
into the Calvin cycle, which may be partially associated with the biomass decrease. Finally, the application of IO3
− increases biomass production, stimulates NO3
− reduction and NH4
+ incorporation (GS/GOGAT), and optimizes the photorespiratory process. Hence, this appears to be the most appropriate form
of iodine from an agronomic standpoint. 相似文献
6.
Renata Matraszek 《Acta Physiologiae Plantarum》2008,30(3):361-370
The author studied the effect of different nickel concentrations (0, 0.4, 40 and 80 μM Ni) on the nitrate reductase (NR) activity
of New Zealand spinach (Tetragonia expansa Murr.) and lettuce (Lactuca sativa L. cv. Justyna) plants supplied with different nitrogen forms (NO3
−–N, NH4
+–N, NH4NO3). A low concentration of Ni (0.4 μM) did not cause statistically significant changes of the nitrate reductase activity in
lettuce plants supplied with nitrate nitrogen (NO3
−–N) or mixed (NH4NO3) nitrogen form, but in New Zealand spinach leaves the enzyme activity decreased and increased, respectively. The introduction
of 0.4 μM Ni in the medium containing ammonium ions as a sole source of nitrogen resulted in significantly increased NR activity
in lettuce roots, and did not cause statistically significant changes of the enzyme activity in New Zealand spinach plants.
At a high nickel level (Ni 40 or 80 μM), a significant decrease in the NR activity was observed in New Zealand spinach plants
treated with nitrate or mixed nitrogen form, but it was much more marked in leaves than in roots. An exception was lack of
significant changes of the enzyme activity in spinach leaves when plants were treated with 40 μM Ni and supplied with mixed
nitrogen form, which resulted in the stronger reduction of the enzyme activity in roots than in leaves. The statistically
significant drop in the NR activity was recorded in the aboveground parts of nickel-stressed lettuce plants supplied with
NO3
−–N or NH4NO3. At the same time, there were no statistically significant changes recorded in lettuce roots, except for the drop of the
enzyme activity in the roots of NO3
−-fed plants grown in the nutrient solution containing 80 μM Ni. An addition of high nickel doses to the nutrient solution
contained ammonium nitrogen (NH4
+–N) did not affect the NR activity in New Zealand spinach plants and caused a high increase of this enzyme in lettuce organs,
especially in roots. It should be stressed that, independently of nickel dose in New Zealand spinach plants supplied with
ammonium form, NR activity in roots was dramatically higher than that in leaves. Moreover, in New Zealand spinach plants treated
with NH4
+–N the enzyme activity in roots was even higher than in those supplied with NO3
−–N. 相似文献
7.
Summary Short-term absorption experiments were conducted with intact barley (Hordeum vulgare L.) seedlings to observe the effects of the osmotic potential (Ψπ) and salt species on nitrate uptake andin vivo nitrate reduction. The experiments consisted of growing barley seedlings for 5 days in complete nutrient solutions salinized
to (Ψπ) levels of −0.6, −1.8, −3.0, −4.2, and −5.4 bars with NaCl, CaCl2 or Na2SO4. After the absorption period, the seedlings were separated into shoots and roots, weighed, then analyzed for NO3. The nutrient solutions were sampled for NO3 analysis each day immediately before renewing the solutions. The accumulative loss of NO3 from the solutions was considered to be uptake whereas NO3 reduction was the difference between uptake and seedling content. Lowering the (Ψπ) of the nutrient solutions resulted in decreased concentrations of NO3 in the plant, little or no effect (except at the lowest (Ψπ) level) on uptake, and increased nitrate reductase activity. Increased rates of NO3 reduction were in particular associated with the Cl concentration of the nutrient solution. 相似文献
8.
M. Vuletić V. Hadži-Tašković Šukalović K. Marković J. Dragišić Maksimović 《Biologia Plantarum》2010,54(3):530-534
The activities of antioxidative enzymes and contents of proline and total phenolics were assayed in roots of two maize (Zea mays L.) genotypes grown in a medium containing nitrate (NO3
−) or both nitrogen forms, nitrate and ammonium (NH4
+/NO3
−). An increase in the activities of class III peroxidases (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), ascorbate
oxidase (AO) and proline content, and decrease in phenolic content were observed in NH4
+/NO3
− in comparison with NO3
− grown plants. When polyethylene glycol (PEG) was added to both nitrogen treatments, the content of total phenolics and proline
was increased, especially in NH4
+/NO3
− treatment. The PEG treatment decreased enzyme activities in NH4
+/NO3
− grown plants, but in NO3
− grown plants activities of POD and SOD were increased, opposite to decreased APX and AO. Isoelectric focusing demonstrated
increased activities of acidic POD isoforms in PEG treated NO3
− grown plants, and lower activities of both, acidic and basic isoforms in NH4
+/NO3
−grown plants. 相似文献
9.
Xi-Hua Cui Hosakatte Niranjana Murthy Chun-Hua Wu Kee-Yoeup Paek 《In vitro cellular & developmental biology. Plant》2010,46(5):437-444
The present study investigated the effect of nitrogen source (NH4+; NO3−) at different concentrations on the accumulation of biomass and secondary metabolites in adventitious root cultures of Hypericum perforatum L. Cultures were initiated in shake flasks by using half-strength Murashige and Skoog (MS) medium with B5 vitamins, 1.0 mg l−1 indole-3-butyric acid, 0.1 mg l−1 kinetin, 3% (w/v) sucrose, and different ratios of ammonium and nitrate (0:30, 5:25, 10:20, 15:15, 20:10, 25:5, and 30:0 mM, using NH4Cl and KNO3). The cultures were maintained in darkness. The medium supplemented with 5:25 (mM) NH4+/NO3− resulted in the optimum accumulation of biomass and total phenols and flavonoids. The antioxidant potential of a methanolic
extract, measured as the 1, 1-diphenyl-2-picrylhydrazyl and 2, 2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical
scavenging activities, of H. perforatum adventitious roots showed that antioxidant activity was high from root extracts that were grown on higher concentrations
of NO3− nitrogen (15, 20, and 25 mM). Further, assessment of hydrogen peroxide (H2O2) and malondialdehyde content of the root extracts revealed that cultures supplemented with higher levels of NO3− nitrogen (15–30 mM) were under oxidative stress, which boosted the levels of secondary metabolites in the adventitious roots.
These results suggest that optimal adventitious root biomass could be achieved with the supplementation of cultures with 5:25
ratios of MS nitrogen sources. 相似文献
10.
The accumulation of inorganic and organic osmolytes and their role in osmotic adjustment were investigated in roots and leaves
of vetiver grass (Vetiveria zizanioides) seedlings stressed with 100, 200, and 300 mM NaCl for 9 days. The results showed that, although the contents of inorganic
(K+, Na+, Ca2+, Mg2+, Cl−, NO3−, SO42− and H2PO3−)) and organic (soluble sugar, organic acids, and free amino acids) osmolytes all increased with NaCl concentration, the contribution
of inorganic ions (mainly Na+, K+, and Cl−) to osmotic adjustment was higher (71.50–80.56% of total) than that of organic solutes (19.43–28.50%). The contribution of
inorganic ions increased and that of organic solutes decreased in roots with the enhanced NaCl concentration, whereas the
case in leaves was opposite. On the other hand, the osmotic adjustment was only effective for vetiver grass seedlings under
moderate saline stress (less than 200 mM NaCl). 相似文献
11.
Michael A. Nicodemus K. Francis Salifu Douglass F. Jacobs 《Trees - Structure and Function》2008,22(5):685-695
Nitrogen (N) limits plant productivity and its uptake and assimilation may be regulated by N source, N availability, and nitrate
reductase activity (NRA). Knowledge of how these factors interact to affect N uptake and assimilation processes in woody angiosperms
is limited. We fertilized 1-year-old, half-sib black walnut (Juglans nigra L.) seedlings with ammonium (NH4
+) [as (NH4)2SO4], nitrate (NO3
−) (as NaNO3), or a mixed N source (NH4NO3) at 0, 800, or 1,600 mg N plant−1 season−1. Two months following final fertilization, growth, in vivo NRA, plant N status, and xylem exudate N composition were assessed.
Specific leaf NRA was higher in NO3
−-fed and NH4NO3-fed plants compared to observed responses in NH4
+-fed seedlings. Regardless of N source, N addition increased the proportion of amino acids (AA) in xylem exudate, inferring
greater NRA in roots, which suggests higher energy cost to plants. Root total NRA was 37% higher in NO3
−-fed than in NH4
+-fed plants. Exogenous NO3
− was assimilated in roots or stored, so no difference was observed in NO3
− levels transported in xylem. Black walnut seedling growth and physiology were generally favored by the mixed N source over
NO3
− or NH4
+ alone, suggesting NH4NO3 is required to maximize productivity in black walnut. Our findings indicate that black walnut seedling responses to N source
and level contrast markedly with results noted for woody gymnosperms or herbaceous angiosperms. 相似文献
12.
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
13.
Metabolic regulation and gene expression of root phosphoenolpyruvate carboxylase by different nitrogen sources 总被引:3,自引:1,他引:2
S. Pasqualini L. Ederli C. Piccioni P. Batini M. Bellucci S. Arcioni & M. Antonielli 《Plant, cell & environment》2001,24(4):439-447
Alfalfa (Medicago sativa L.) N-sufficient plants were fed 1·5 mM N in the form of NO3−, NH4+ or NO3− in conjunction with NH4+, or were N-deprived for 2 weeks. The specific activity of phosphoenolpyruvate carboxylase (PEPC) from the non-nodulated roots of N-sufficient plants was increased in comparison with that of N-deprived plants. The PEPC value was highest with NO3− nutrition, lowest with NH4+ and intermediate in plants that were fed mixed salts. The protein was more abundant in NO3−-fed plants than in either NH4+- or N mixed-fed plants. Nitrogen starvation decreased the level of PEPC mRNA, and nitrate was the N form that most stimulated PEPC gene expression. The malate content was significantly lower in NO3−-deprived than in NO3−-sufficient plants. Root malate accumulation was high in NO3−-fed plants, but decreased significantly in plants that were fed with NH4+. The effect of malate on the desalted enzyme was also investigated. Root PEPC was not very sensitive to malate and PEPC activity was inhibited only by very high concentrations of malate. Asparagine and glutamine enhanced PEPC activity markedly in NO3−-fed plants, but failed to affect plants that were either treated with other N types or N starved. Glutamate and citrate inhibited PEPC activity only at optimal pH. N-nutrition also influenced root nitrate and ammonium accumulation. Nitrate accumulated in the roots of NO3−- and (NO3− + NH4+)-fed plants, but was undetectable in those administered NH4+. Both the nitrate and the ammonium contents were significantly reduced in NO3−- and (NO3− + NH4+)-starved plants. Root accumulation of free amino acids was strongly influenced by the type of N administered. It was highest in NH4+-fed plants and the most abundant amides were asparagine and glutamine. It was concluded that root PEPC from alfalfa plants is N regulated and that nitrate exerts a strong influence on the PEPC enzyme by enhancing both PEPC gene expression and activity. 相似文献
14.
15.
Comparative effects of salt-stress and alkali-stress on the growth,photosynthesis, solute accumulation,and ion balance of barley plants 总被引:7,自引:0,他引:7
We compared the effects of salt-stresses (SS, 1: 1 molar ratio of NaCl to Na2SO4) and alkali-stresses (AS, 1: 1 molar ratio of NaHCO3 to Na2CO3) on the growth, photosynthesis, solute accumulation, and ion balance of barley seedlings, to elucidate the mechanism of AS
(high-pH) damage to plants and the physiological adaptive mechanism of plants to AS. The effects of SS on the water content,
root system activity, membrane permeability, and the content of photosynthetic pigments were much less than those of AS. However,
AS damaged root function, photosynthetic pigments, and the membrane system, led to the severe reductions in water content,
root system activity, content of photosynthetic pigments, and net photosynthetic rate, and a sharp increase in electrolyte
leakage rate. Moreover, with salinity higher than 60 mM, Na+ content increased slowly under SS and sharply under AS. This indicates that high-pH caused by AS might interfere with control
of Na+ uptake in roots and increase intracellular Na+ to a toxic level, which may be the main cause of some damage emerging under higher AS. Under SS, barley accumulated organic
acids, Cl−, SO4
2−, and NO3
− to balance the massive influx of cations, the contribution of inorganic ions to ion balance was greater than that of organic
acids. However, AS might inhibit absorptions of NO3
− and Cl−, enhance organic acid synthesis, and SO4
2− absorption to maintain intracellular ion balance and stable pH. 相似文献
16.
Alleviation of salinity stress in broccoli using foliar urea or methyl-jasmonate: analysis of growth,gas exchange,and isotope composition 总被引:1,自引:0,他引:1
We studied the effects of foliar application of urea or methyl-jasmonate (MeJA) on the salinity tolerance of broccoli plants
(Brassisca oleracea L. var. italica). Plant dry weight, leaf CO2 assimilation, and root respiration were reduced significantly under moderate saline stress (40 mM NaCl) but application of
either urea or MeJA maintained growth, gas exchange parameters, and leaf N–NO3
− concentrations at values similar to those of non-salinized plants. Additionally, when these two foliar treatments were applied
leaf Na+ concentration was reduced compared with control plants grown at 40 mM NaCl. However, at a higher salt concentration (120 mM
NaCl), no effect of the foliar applications was found on these parameters. Salinity also decreased leaf δ15N but increased δ13C. Our study shows the feasibility of using foliar urea or MeJA to improve tolerance under moderate saline stress. 相似文献
17.
Sylvie Ferrario-Méry Marie-Christine Thibaud Thomas Betsche Marie-Hélène Valadier Christine H. Foyer 《Planta》1997,202(4):510-521
Transformed plants of Nicotiana plumbaginifolia Viv. constitutively expressing nitrate reductase (35S-NR) or β-glucuronidase (35S-GUS) and untransformed controls were grown
for two weeks in a CO2-enriched atmosphere. Whereas CO2 enrichment (1000 μl · l−1) resulted in an increase in the carbon (C) to nitrogen (N) ratio of both the tobacco lines grown in pots with vermiculite,
the C/N ratio was only slightly modified when plants were grown in hydroponic culture in high CO2 compared to those grown in air. Constitutive nitrate reductase (NR) expression per se did not change the C/N ratio of the
shoots or roots. Biomass accumulation was similar in both types of plant when hydroponic or pot-grown material, grown in air
or high CO2, were compared. Shoot dry matter accumulation was primarily related to the presence of stored carbohydrate (starch and sucrose)
in the leaves. In the pot-grown tobacco, growth at elevated CO2 levels caused a concomitant decrease in the N content of the leaves involving losses in NO−
3 and amino acid levels. In contrast, the N content and composition were similar in all plants grown in hydroponic culture.
The 35S-NR plants grown in air had higher foliar maximum extractable NR activities and increased glutamine levels (on a chlorophyll
or protein basis) than the untransformed controls. These increases were maintained following CO2 enrichment when the plants were grown in hydroponic culture, suggesting that an increased flux through nitrogen assimilation
was possible in the 35S-NR plants. Under CO2 enrichment the NR activation state in the leaves was similar in all plants. When the 35S-NR plants were grown in pots, however,
foliar NR activity and glutamine content fell in the 35S-NR transformants to levels similar to those of the untransformed
controls. The differences in NR activity between untransformed and 35S-NR leaves were much less pronounced in the hydroponic
than in the pot-grown material but the difference in total extractable NR activity was more marked following CO2 enrichment. Foliar NR message levels were decreased by CO2 enrichment in all growth conditions but this was much more pronounced in pot-grown material than in that grown hydroponically.
Since β-glucuronidase (GUS) activity and message levels in 35S-GUS plants grown under the same conditions of CO2 enrichment (to test the effects of CO2 enrichment on the activity of the 35S promoter) were found to be constant, we conclude that NR message turnover was specifically
accelerated in the 35S-NR plants as well as in the untransformed controls as a result of CO2 enrichment. The molecular and metabolic signals involved in increased NR message and protein turnover are not known but possible
effectors include NO3
−, glutamine and asparagine. We conclude that plants grown in hydroponic culture have greater access to N than those grown
in pots. Regardless of the culture method, CO2 enrichment has a direct effect on NR mRNA stability.
Received: 17 October 1996 / Accepted: 11 February 1997 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.
Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline
conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate
the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4
of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty
loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period.
Spatial distributions of fresh weight (FW), dry weight (DW), and Na+, K+, Cl−, NO−
3, Ca2+, Mg2+, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial
distribution of Na+, Cl−, K+, NO3
−, and Ca2+ in the growing leaves were affected by salinity, while those of Mg2+, total P, and total N were not. Sodium, K+, Cl−, Ca2+, Mg2+, and total N concentrations (mmol · kg−1 FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO3
− concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation
zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na+, Cl−, Ca2+, and Mg2+ (mmol · kg−1 FW · h−1) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO3
− this was depressed. The lower supply of NO−
3 to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of
Na+ and Cl− may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca2+, Mg2+, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K+ and Ca2+ concentrations at 120 mM NaCl are probably due to the presence of high Ca2+ in the soil of this study.
Received: 13 March 1997 / Accepted: 9 June 1997 相似文献
20.
Mohd Idrees M. Naeem Tariq Aftab M. Masroor A. Khan Moinuddin 《Acta Physiologiae Plantarum》2011,33(3):987-999
A pot experiment was conducted to find out whether the foliar spray of salicylic acid (SA) could successfully ameliorate the
adverse effects of salinity stress on periwinkle. Thirty-day-old plants were supplied with Control; 0 mM NaCl + 10−5 M SA (T1); 50 mM NaCl + 0 SA (T2); 100 mM NaCl + 0 SA (T3); 150 mM NaCl + 0 SA (T4); 50 mM NaCl + 10−5 M SA (T5); 100 mM NaCl + 10−5 M SA (T6); 150 mM NaCl + 10−5 M SA (T7). The plants were sampled 90 days after sowing to assess the effect of SA on stressed and unstressed plants. Salt stress
significantly reduced the growth attributes including plant height, leaf-area index, shoot and root fresh weights, shoot and
root dry weights. Increasing NaCl concentrations led to a gradual decrease in photosynthetic parameters and activities of
nitrate reductase and carbonic anhydrase. Ascorbic acid, total alkaloids and antioxidants enzymes superoxide dismutase, catalase
and peroxidase also declined in NaCl-treated plants. The plants, undergoing NaCl stress, exhibited a significant increase
in electrolyte leakage and proline content. Foliar application of SA (10−5 M) reduced the damaging effect of salinity on plant growth and accelerated the restoration of growth processes. It not only
improved the growth parameters but also reversed the effects of salinity. Total alkaloid content was improved by SA application
both in unstressed and stressed plants. The highest level of total alkaloid content recorded in leaves of SA-treated stressed
plants was 11.1%. Foliar spray of SA overcame the adverse effect of salinity by improving the content of vincristine (14.0%)
and vinblastine (14.6%) in plants treated with 100 M NaCl. 相似文献