共查询到20条相似文献,搜索用时 62 毫秒
1.
Relationship between potassium fertilisation and nitrate assimilation in leaves and fruits of cucumber (Cucumis sativus) plants 总被引:1,自引:0,他引:1
The effect of application of different potassium rates on some parameters of nitrate metabolism and yield in cucumber plants (Cucumis sativus) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of applications of K+ at three rates in the form of K2SO4 (Kl: 0.075 mg ml?1, K2: 0.15 mg ml?1, and K3: 0.30 mg ml?1). The results showed a positive effect of higher K+ fertilisation (0.30 mg ml?1) on uptake, translocation and reduction of NO3? in leaves compared with the lowest K+ rate. In addition, the higher K+ rates strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, thereby perhaps also enhancing the maximal commercial yield. In conclusion, for improved cucumber cultivation under greenhouse conditions, 0.15 mg ml?1 of K+ gave maximal yield, while the application of 0.30 mg ml?1 increased the metabolism and efficient utilisation of NO3?. 相似文献
2.
Greenhouse-grown cut flower roses are often irrigated with moderately saline irrigation water. The salt/ballast ions are either present initially in poor quality raw water or reclaimed municipal water, or accumulated in greenhouse irrigation water that is captured and reused. Such ions can inhibit root absorption of essential nutrients. The objective of this work was to quantify the influence of NaCl concentration on the uptake of nitrate and potassium by roses and develop a predictive model of uptake inhibition based on NaCl, NO3 ?, and K+ concentration. One year-old rose plants (Rosa spp. ‘Kardinal’ on ‘Natal Briar’ rootstock) were moved into growth chambers where nitrogen and potassium depletion were monitored during 6 days. Eight different initial NaCl treatments varying from zero to 65 mol m?3 were used and within these there were two initial NO3 ? and K+ concentrations: high concentration (HC, 7.0 mol m?3 and 2.6 mol m?3 NO3 ? and K+ respectively) or low concentration (LC, 3.5 mol m?3 and 1.3 mol m?3 NO3 ? and K+ respectively). Plant NO3 ? uptake was negatively affected by NaCl concentration. NO3 ? maximum influx (Imax) declined from 5.1 µmol to 2.5 µmol per gram of plant dry weight per hour as NaCl concentration increased from zero to 65 mol m?3. A modified Michaelis–Menten (M–M) equation taking into account inhibition by NaCl provided the best fit for NO3 ? uptake in response to varying NaCl concentration. K+ uptake was unaffected by NaCl concentration. A M–M equation that did not include inhibition was suitable for describing K+ uptake at varying NaCl concentration. The resulting empirical models could assist with decision making, such as: adjustment of NO3 ? fertilization based on NaCl concentration, necessity of water desalinization, or determination of the desired leaching fraction. 相似文献
3.
This study investigated the separate and combined effects of nitrate (NO3 ?) and cytokinin additions on continuous ryegrass regrowth after defoliation and the underlying mechanisms. Our results showed that frequent defoliation reduced the biomass of newly grown leaves and roots, the root soluble carbohydrate contents, the root vitality (an indicator of root absorption capacity), and the leaf contents of NO3 ?, zeatin and zeatin riboside (Z + ZR), and isopentenyl adenine and isopentenyl adenosine (IP + IPA). NO3 ?addition to the roots or leaves increased the biomass of newly grown leaves as well as the leaf contents of NO3 ?, Z + ZR, and IP + IPA without increasing the root-to-shoot delivery of endogenous cytokinin. Interestingly, cytokinin directly added to the leaves also increased the biomass of newly grown leaves and their Z + ZR and IP + IPA contents, suggesting that nitrate-induced leaf cytokinin production mediates the growth-promoting effects of nitrate. We also found that cytokinin had a direct whereas NO3 ? had an indirect effect on the biomass of newly grown leaves. Taken together, our results indicate that leaf cytokinin production induced by NO3 ? absorbed through the roots plays a key role in continuous ryegrass regrowth after defoliation. 相似文献
4.
This study evaluated effects of foliar spraying 24‐epibrassinoide (24‐EBL) on the growth of salt‐stressed canola. Seedlings at the four‐leaf stage were treated with 150 mm NaCl and different concentrations of 24‐EBL (10?6, 10?8, 10?10, 10?12 m ) for 15 days. A concentration of 10?10 m 24‐EBL was chosen as optimal and used in a subsequent experiment on plant biomass and leaf water potential parameters. The results showed that 24‐EBL mainly promoted shoot growth of salt‐stressed plants and also ameliorated leaf water status. Foliar spraying of salt‐stressed canola with 24‐EBL increased osmotic adjustment ability in all organs, especially in younger leaves and roots. This was mainly due to an increase of free amino acid content in upper leaves, soluble sugars in middle leaves, organic acids and proline in lower leaves, all of these compounds in roots, as well as essential inorganic ions. Na+ and Cl? sharply increased in different organs under salt stress, and 24‐EBL reduced their accumulation. 24‐EBL improved the uptake of K+, Ca2+, Mg2+ and NO3? in roots, which were mainly transported to upper leaves, while NO3? was mainly transported to middle leaves. Thus, 24‐EBL improvements in ion homeostasis of K+/Na+, Ca2+/Na+, Mg2+/Na+ and NO3?/Cl?, especially in younger leaves and roots, could be explained. As most important parts, younger leaves and roots were the main organs protected by 24‐EBL via improvement in osmotic adjustment ability and ion homeostasis. Further, physiological status of growth of salt‐stressed canola was ameliorated after 24‐EBL treatment. 相似文献
5.
Xue-Yan Liu Keisuke Koba Yu Takebayashi Cong-Qiang Liu Yun-Ting Fang Muneoki Yoh 《Biogeochemistry》2013,114(1-3):399-411
Nitrate (NO3 ?) is an important form of nitrogen (N) available to plants. The measurements of NO3 ? concentration [NO3 ?] and isotopes (δ15N and δ18O) in plants provide unique insights into ecosystem NO3 ? availability and plant NO3 ? dynamics. This work investigated the variability of these parameters in individuals of a broadleaved (Aucuba japonica) plant and a coniferous (Platycladus orientalis) plant, and explored the applicability of tissue NO3 ? isotopes for deciphering plant NO3 ? utilization mechanisms. The NO3 ? in washed leaves showed concentration and isotopic ratios that were much lower than that in unwashed leaves, indicating a low contribution of atmospheric NO3 ? to NO3 ? in leaves. Current leaves showed higher [NO3 ?] and isotopic ratios than mature leaves. Moreover, higher leaf [NO3 ?] and isotopic enrichments (relative to soil NO3 ?) were found under higher soil NO3 ? availability for A. japonica. In contrast, leaves of P. orientalis showed low [NO3 ?] and negligible isotopic enrichments despite high soil NO3 ?. Higher [NO3 ?] was found in both fine and coarse roots of the P. orientalis plant, but significant isotopic enrichment was found only in coarse roots. These results reflect that the NO3 ? accumulation and isotopic effects decreased with leaf age, but increased with soil NO3 ? supply. Leaves are therefore identified as a location of NO3 ? reduction for A. japonica, while P. orientalis did not assimilate NO3 ? in leaves but in coarse roots. This work provided the first organ-specific information on NO3 ? isotopes in plant individuals, which will stimulate further studies of NO3 ? dynamics in a broader spectrum of plant ecosystems. 相似文献
6.
Luc Claessens Christina L. Tague Peter M. Groffman John M. Melack 《Biogeochemistry》2010,98(1-3):63-74
We examined the effect of concentration on nitrogen uptake patterns for a suburban stream in Maryland and addressed the question: How does NO3 ? uptake change as a function of concentration and how do uptake patterns compare with those found for NH4 +? We applied a longitudinal (stream channel corridor) approach in a forested stream section and conducted short-term nutrient addition experiments in late summer 2004. In the downstream direction, NO3 ? concentrations decreased because of residential development in headwaters and downstream dilution; NH4 + concentrations slightly increased. The uptake patterns for NO3 ? were very different from NH4 +. While NH4 + had a typical negative relationship between first-order uptake rate constant (K c ) and stream size, NO3 ? had a reverse pattern. We found differences for other metrics, including uptake velocity (V f ) and areal uptake rate (U). We attributed these differences to a stream size effect, a concentration effect and a biological uptake capacity effect. For NO3 ? these combined effects produced a downstream increase in K c , V f and U; for NH4 + they produced a downstream decrease in K c and V f , and a not well defined pattern for U. We attributed a downstream increase in NO3 ? uptake capacity to an increase in hyporheic exchange and a likely increase in carbon availability. We also found that K c and V f were indirectly related with concentration. Similar evidence of ‘nutrient saturation’ has been reported in other recent studies. Our results suggest that higher-order uptake models might be warranted when scaling NO3 ? uptake across watersheds that are subject to increased nitrogen loading. 相似文献
7.
Rafael de Souza Miranda Juan Carlos Alvarez-Pizarro Celso Marinones Silva Araújo José Tarquinio Prisco Enéas Gomes-Filho 《Acta Physiologiae Plantarum》2013,35(3):841-852
This work aimed to study the regulation of K+/Na+ homeostasis and the physiological responses of salt-treated sorghum plants [Sorghum bicolor (L.) Moench] grown with different inorganic nitrogen (N) sources. Four days after sowing (DAS), the plants were transferred to complete nutrient solutions containing 0.75 mM K+ and 5 mM N, supplied as either NO3 ? or NH4 +. Twelve DAS, the plants were subjected to salt stress with 75 mM NaCl, which was applied in two doses of 37.5 mM. The plants were harvested on the third and seventh days after the exposure to NaCl. Under the salt stress conditions, the reduction of K+ concentrations in the shoot and roots was higher in the culture with NO3 ? than with NH4 +. However, the more conspicuous effect of N was on the Na+ accumulation, which was severely limited in the presence of NH4 +. This ionic regulation had a positive influence on the K+/Na+ ratio and the selective absorption and transport of K+ in the plants grown with NH4 +. Under control and salt stress conditions, higher accumulation of free amino acids and soluble proteins was promoted in NH4 + grown roots than NO3 ? grown roots at both harvesting time, whereas higher accumulation of soluble sugars was observed only at 7 days of salt stress exposure. Unlike the NH4 + grown plants, the gas exchanges of the NO3 ? grown plants were reduced after 7 days of salt stress. These results suggest that external NH4 + may limit Na+ accumulation in sorghum, which could contribute to improving its physiological and metabolic responses to salt stress. 相似文献
8.
Aquaspirillum magnetotacticum strain MS-1 and two nonmagnetic mutants derived from it reduced C2H2 microaerobically but not anaerobically even with NO3 ?. This organism apparently is not capable of NO3 ?-dependent nitrogen fixation. Cells ofA. magnetotacticum reduced C2H2 at rates comparable to those ofAzospirillum lipoferum grown under similar conditions, but much lower than that ofAzotobacter vinelandii grown aerobically. Cells ofA. magnetotacticum in anaerobic cultures lacking NO3 ? did not reduce C2H2 until O2 was introduced. Optimum rates of C2H2 reduction byA. magnetotacticum were obtained at 200 Pa O2. C2H2 reduction was inhibited by more than 1 kPa O2 or 0.2 mM NO3 ? or NH4 +. These results suggest thatA. magnetotacticum fixes N2 only under microaerobic, N-limited conditions. 相似文献
9.
NH4+ and NO3? uptake were measured by continuous sampling with an autoanalyzer. For Hypnea musciformis (Wulfen) Lamouroux, NO3?up take followed saturable kinetics (K2=4.9 μg-at N t?1, Vmax= 2.85 μg- at N, g(wet)?1. h?1. The ammonium uptake data fit a trucatd hyperbola, i.e., saturation was not reach at the concentrations used. NO3? uptake was reduced one-half in the presence of NH4+, but presence of NO3? had no effect on NH4+ uptake. Darkness reduced both NO3? and NH4+ uptake by one-third to one-half. For Macrocystis pyrufera (L) C. Agardh, NO3? uptake followed saturable kinetices: K2=13.1 μg-at N. l?1. Vmax=3.05 μg-at N. g(wet)?1. h?1.NH4+ uptake showed saturable kinetics at concentration below 22 μg-at N l -1 (K2=5.3 μg-at N.1–1, Vmax= 2.38 μg-at N G (wet)?1.h?1: at higher concentration uptake increased lincarly with concentrations. NO3?and NH4+ were taken up simulataneously: presence of one form did not affect uptake of the other. 相似文献
10.
This study aimed to determine the effects of different rootstocks and soilless media on the plant growth and yield of cucumber and on the leaf ion (Na+, Ca++, K+ and Cl?) concentrations. Four commercial rootstocks (TZ148 F1, RS841 F1, Nun9075 F1 and Avar F1) and two local landraces (Local-1 and Local-3 belonging to Cucurbita moschata L.) were used as rootstock and grafted and non grafted plants were tested in three different salinity conditions (2.5 dS m?1, 5.0 dS m?1 and 7.5 dS m?1) on three different soilless media (cocopeat, perlite and rockwool) in spring period under greenhouse conditions. Salinity found to reduce root and shoot dry weight, and yield of plants in all growing media. TZ148, Nun9075 and Local-3 are found to improve tolerance of cucumber plants to saline conditions (5.0 and 7.5 dS m?1) when used as rootstocks. Root and shoot dry weight, yield, Ca++ in leaves and K+/Na+ ratio in leaves were significantly decreased, but Na+ and Cl? concentration in leaves were increased under salt stress. Rootstock potential of Local-3 is also found to be quite good for cucumber under saline conditions. 相似文献
11.
J. C. Alvarez-Pizarro E. Gomes-Filho J. T. Prisco M. F. Grossi-De-Sá O. B. De Oliveira-Neto R. Da Rocha Fragoso 《Biologia Plantarum》2014,58(3):507-514
We studied the influence of inorganic nitrogen sources (NO3 ? or NH4 +) and potassium deficiency on expression and activity of plasma membrane (PM) H+-ATPase in sorghum roots. After 15 d of cultivation at 0.2 mM K+, the plants were transferred to solutions lacking K+ for 2 d. Then, K+ depletion assays were performed in the presence or absence of vanadate. Further, PMs from K+-starved roots were extracted and used for the kinetic characterization of ATP hydrolytic activity and the immunodetection of PM H+-ATPase. Two major genes coding PM H+-ATPase (SBA1 and SBA2) were analyzed by real-time PCR. PM H+-ATPase exhibited a higher Vmax and Km in NH4 +-fed roots compared with NO3 ? -fed roots. The optimum pH of the enzyme was slightly lower in NO3 ? -fed roots than in NH4 +-fed roots. The vanadate sensitivity was similar. The expressions of SBA1 and SBA2 increased in roots grown under NH4 +. Concomitantly, an increased content of the enzyme in PM was observed. The initial rate of K+ uptake did not differ between plants grown with NO3 ? or NH4 +, but it was significantly reduced by vanadate in NH4 +-grown plants. 相似文献
12.
Relationships between induced high leaf intercellular CO2 concentrations, leaf K+ and NO3 ? ion movement and early fruit formation under macronutrient limitation are not well understood. We examined the effects and interactions of reduced K/N input treatments on leaf intercellular CO2, photosynthesis rate, carboxylation and water use efficiency, berry formation as well as leaf/fruit K+, NO3 ? and photosynthate retention of strawberry (Fragaria × ananassa Duch.) to enhance low-input agriculture. The field study was conducted in Nova Scotia, eastern Canada during 2009–2010. The experimental treatments consisted of five K2O rates (0, 6, 12, 18, and 24 kg ha?1) and five N rates (0, 5, 10, 15, and 20 kg ha?1), representing respectively, 0, 25, 50, 75, and 100 % of regular macronutrient recommendations based on the soil testing. The treatments were arranged in a split-plot design with three blocks in the field. The cultivar was ‘Mira’, a June-bearing crop. The results showed that strawberry plants treated with 25 %-reduced inputs could induce significantly higher leaf intercellular CO2 concentrations to improve plant photosynthesis, carboxylation and water use efficiency and translocation of leaf/fruit K+ and dissolved solids, which could advance berry formation by 6 days and produce significantly higher marketable yields (P < 0.05). Higher leaf intercellular CO2 inhibited leaf/fruit NO3 ? ion retention, but this inhibition did not occur in leaf/fruit K+ retention. Linear interactions of the K/N treatments were significant on fruit marketable yields, intercellular CO2, net photosynthesis, leaf transpiration rates, and leaf temperatures (P < 0.05). It was concluded that higher leaf CO2 could enhance plant photosynthesis, promote plant carboxylation and water use efficiency, and advance berry formation, but it could inhibit leaf NO3 ? retention. This inhibition did not find in leaf K+ ion and dissolved solid retention. Overlay co-limitation of leaf intercellular CO2 and translocation of leaf/fruit K+/NO3 ? and total dissolved solids could constrain more fruit formation attributes under full macronutrient supply than reduced inputs. It was suggested that low input would be an optimal and sustainable option for improving small fruit crop physiological development and dealing with macronutrient deficiency challenge. 相似文献
13.
Abstract Changes in the net uptake rate of K+ and in the average tissue concentration of K+ were measured over 14 d in response to changes in root temperature with oilseed rape (Brassica napus L. cv. Bien venu) and barley (Hordeum vulgare L. cv. Atem). Plants were grown in flowing nutrient solutions containing 2.5 mmol m?3 K+ and were acclimatized over 49 d (rape) or 28 d (barley) to low root temperature (5°C) prior to steady–state treatments at root temperatures between 3 °C and 25 °C, with common air temperature. Uptake of K+ was monitored continuously over 14 d and nitrogen was supplied as NH4++ NO?3 or NH+4 or NO?3. Unit absorption rates of K+ increased with time and with root temperature up to Day 4 or 5 following the change in root temperature. Thereafter they usually approached steady-state, with Q10? 2.0 between 7 °C and 17°C, although rates became similar between 7 °C and 13°C. Uptake of K+ by rape plants was invariably greater under NO?3 nutrition compared with NH+4. The percentage K+ in the plant dry matter increased with temperature from 2% at 3 °C to 4% at 25 °C in rape, but there was less effect of temperature on the average concentrations of K+ in the plant fresh weight or plant water content. Concentrations of K+ in the leaf water fraction of rape plants decreased with increasing root temperature, but in barley they increased with increasing root temperature. Concentrations of K+ in the root water fraction were relatively stable with respect to root temperature. The results are discussed in terms of compensatory changes in K+ uptake following a change in root temperature and the relationships between growth, shoot: root ratio and K+ composition of the plant. 相似文献
14.
Combination Effect of NaCl Salinity and Nitrogen Form on Mineral Composition of Sunflower Plants 总被引:2,自引:0,他引:2
The effect of two N-forms (NH4
+ and NO3
–) and NaCl on pattern of accumulation of some essential inorganic nutrients was examined in sunflower (Helianthus annuus L.) cv. Hisun 33. Eight-day-old plants of were subjected for 21 d to Hoagland's nutrient solution containing 8 mM N as NH4
+ or NO3
·, and salinized with and addition of NaCl to the growth medium had no significant effect on total leaf N. However, root N of NH4-supplied plants decreased significantly with increase in NaCl concentration, whereas that of NO3-supplied plants remained unaffected. There was no significant effect of NaCl on leaf or root P, but the NO3-supplied plants had significa concentration of leaf P than that of NH4-supplied plants at varying salt treatments. Salinity of the rooting med did not show any significant effect on Na+ concentrations of leaves or roots of plants subjected to two differen N. NH4-treated plants generally had greater concentrations of Cl– in leaves and roots and lower K+ content in leaves than NO3-supplied plants. Ca2+ concentrations of leaves and roots and Mg2+ concentrations of leaves decreased in NH4-supplied plants due to NaCl, but they remained unaffected in NO3-treated plants. 相似文献
15.
Fu-Cang Zhang Shao-Zhong Kang Fu-Sheng Li Jian-Hua Zhang 《植物学报(英文版)》2007,49(4):455-462
In the present study, we investigated whether growth and main nutrient ion concentrations of cabbage (Brassica campestris L.) could be increased when plants were subjected to different NH4^+/NO3- ratios. Cabbage seedlings were grown in a greenhouse in nutrient solutions with five NH4^+/NO3- ratios (1:0; 0.75:0.25; 0.5:0.5; 0.25:0.75; and 0:1). The results showed that cabbage growth was reduced by 87% when the proportion of NH4^+-N in the nutrient solution was more than 75% compared with a ratio NH4^+/NO3- of 0.5:0.5 35 d after transplanting, suggesting a possible toxicity due to the accumulation of a large amount of free ammonia in the leaves. When the NH4+/NO3- ratio was 0.5:0.5, fresh seedling weight, root length, and H2PO4- (P), K^+, Ca^2+, and Mg^2+ concentrations were all higher than those in plants grown under other NH4^+/NO3- ratios. The nitrate concentration in the leaves was the lowest in plants grown at 0.5: 0.5 NH4^+/NO3-. The present results indicate that an appropriate NH4^+/NO3- ratio improves the absorption of other nutrients and maintains a suitable proportion of N assimilation and storage that should benefit plant growth and the quality of cabbage as a vegetable. 相似文献
16.
Development of Nitrate Reductase Activity in Expanding Leaves of Nicotiana tabacum in Relation to the Concentration of Nitrate and Potassium
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Up to 80% of the total nitrate reductase activity (NRA) determined in vivo in different parts of vegetative tobacco plant (Nicotiana tabacum) was located in the leaves. The NRA reached a peak when a leaf had expanded to 27% of its final weight and 33% of its final area. Thereafter, with advancing expansion and age of the leaf, the activity declined. This pattern of development of NRA during the ontogenesis of leaves was not influenced by raising the supply of NO3− from 3 to 6 milliequivalent per cubic decimeter in the substrate solution. The concentration of NO3− in leaves, stem and root was inversely related to NRA at both NO3− levels. Raising the supply of K+ from 1 to 6 milliequivalent per cubic decimeter at either concentration of NO3− slowed down the development of NRA in the initial stages of expansion, but promoted it subsequently. The peak of the activity which developed in a leaf of 62% of its final area was higher at the higher supply of K+. The higher activity was maintained thereafter in the expanding and in matured and older leaves. It was concluded that NRA and the pattern of its development in expanding leaves is related to the availability of metabolites and their incorporation into enzyme proteins. Both these processes are influenced by: (a) the vertical profile of concentration of K+ in the shoot and (b) the concentration of K+ in a leaf, which depend upon its supply. 相似文献
17.
MAKIKO NAGAI MIWA OHNISHI TAKEO UEHARA MUTSUMI YAMAGAMI EIKO MIURA MAI KAMAKURA AKIRA KITAMURA SHU‐ICHI SAKAGUCHI WATARU SAKAMOTO TERUO SHIMMEN HIDEHIRO FUKAKI ROBERT J. REID TETSURO MIMURA 《Plant, cell & environment》2013,36(10):1826-1837
The concentration of ions in plant cells and tissues is an essential factor in determining physiological function. In the present study, we established that concentration gradients of mobile ions exist in both xylem exudates and tissues within a barley (Hordeum vulgare) primary leaf. For K+ and NO3?, ion concentrations generally decreased from the leaf base to the tip in both xylem exudates and tissues. Ion gradients were also found for Pi and Cl? in the xylem. The hydathode strongly absorbed Pi and re‐translocated it to the rest of the plant, whereas Cl? was extruded. The ion concentration gradients developed early during leaf growth, increased as the tissue aged and remained under both high and low transpiration conditions. Measurement of the expression profiles of Pi, K+ and NO3? transporters along the longitudinal axis of the leaf revealed that some transporters are more expressed at the hydathode, but for most transporters, there was no significant variation along the leaf. The mechanisms by which longitudinal ion gradients develop in leaves and their physiological functions are discussed. 相似文献
18.
Tomato growth was examined in solution culture under constant pH and low levels of NH4+ or NO3?. There were five nitrogen treatments: 20 mmoles m?3 NH4+, 50 mmoles m?3 NO3?, 100 mmoles m?3 NH4+ 200 mmoles m?3 NO3?, and 20 mmoles m?3 NH4++ 50 mmoles m?3 NO3?. The lower concentrations (20 mmoles m?3 NH4+ and 50 mmoles m?3 NO3?) were near the apparent Km for net NH4+ and NO3? uptake; the higher concentrations (100 mmoles m?3 NH4+ and 200 mmoles m?3 NO3?) were near levels at which the net uptake of NH4+ or NO3? saturate. Although organic nitrogen contents for the higher NO3? and the NH4++ NO3? treatments were 22.2–30.3% greater than those for the lower NO3? treatment, relative growth rates were initially only 10–15% faster. After 24 d, relative growth rates were similar among those treatments. These results indicate that growth may be only slightly nitrogen limited when NH4+ or NO3? concentrations are held constant over the root surface at near the apparent Km concentration. Relative growth rates for the two NH4+ treatments were much higher than have been previously reported for tomatoes growing with NH4+ as the sole nitrogen source. Initial growth rates under NH4+ nutrition did not differ significantly (P≥ 0.05) from those under NO3? or under combined NH4++ NO3?. Growth rates slowed after 10–15 d for the NH4+ treatments, whereas they remained more constant for the NO3? and mixed NH4++ NO3? treatments over the entire observation period of 24–33 d. The decline in growth rate under NH4+ nutrition may have resulted from a reduction in Ca2+, K+, and/or Mg2+ absorption. 相似文献
19.
Jingrui Li Zhen Tian Xiaolei Wu Guiyun Lv Wanli Ma Ying Zhang Hongbo Gao 《Plant Molecular Biology Reporter》2018,36(3):530-542
Pakchoi plants were grown in 32 mM NO3? nutrient solution with or without 2.5 mM γ-aminobutyric acid (GABA) to investigate metabolite changes, gene and protein expression levels, and the activities of key enzymes related to nitrate metabolism in the leaves over a period of 0–12 days. High-nitrogen treatment enhanced plant growth and the NO3?, NO2?, NH4+, Gln, and Glu contents in the leaves; promoted the gene and protein expression of nitrate reductase (NR) and glutamate decarboxylase (GAD); and increased the activities of NR, nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT), and GAD. The endogenous GABA concentration in the leaves was enhanced in parallel with the increase in GAD activity. The GABA-treated leaves displayed the greatest increases in the gene and protein expression levels of NR and GAD and in the activities of NR, NiR, GS, GOGAT, and GAD. In addition, accelerated rates of nitrate reduction and assimilation were detected, and these changes occurred concurrently with the observed increases in gene or protein expression and enzyme activity. As a result, the concentrations of NH4+, Gln, Glu, and endogenous GABA were significantly elevated, and the NO3? and NO2? contents were significantly decreased, in GABA-treated leaves compared with plants exposed to nitrogen-rich conditions. Our results reveal a potential positive that GABA may act as a nitrogen source to improve the plant growth and the most prominent effect of decreasing nitrate contents by accelerating NO3? reduction and assimilation. Exogenous GABA plays an important role in reducing the NO3? content of leaves, and thereby improves the ability to harvest leafy vegetables containing higher levels of endogenous GABA. 相似文献
20.
Net rates of NO3? and K+ uptake were compared for oilseed rape (Brassica napus L. cv. Jet neuf), perennial ryegrass (Lolium perenne L. cv. S23), Italian ryegrass (Lolium multiflorum Lam. cv. Augusta) and wheat (Triticum aestivum L. cv. Fen-man) in flowing solution culture during a 4-day sequence of low-low-high-high natural irradiance. Concentrations of NO3? (10 μM) and K+ (2.5 μM) in solutions were maintained automatically and hourly variation in net uptake of these ions was measured. During the 2 days of low irradiance (<1 MJ m?2 day?1) the uptake rates of both ions by all species were low at <1 mmol NO3?, m?2 h?1 and <0.4 mmol K+ m?2 h?1. Uptake increased in each species during the first day of high irradiance (7.90 MJ m?2 day?1) to >4 mmol NO3? m?2 h?1 and >1.4 mmol K+ m?1 h?1. These higher rates were maintained throughout the following night. The lag-time between maximum irradiance and the onset of the highest acceleration in uptake was greater for NO3? (5–8 h) than for K+ (≤1 h) in rape, wheat and Italian ryegrass. Uptake of NO3?, by perennial ryegrass showed an almost constant acceleration for 18 h following maximum irradiance. In all species the measured maximum inflows (uptake rate per unit root length) of both ions were greater than theoretical maximum potential inflows to a non-competing infinite-sink root in soil, by factors of 7 and 36, respectively, for NO3? and K+, averaged over all species. 相似文献