Changes in net proton release by roots of intact maize plants after local nutrient supply in a split root system

The effect of local nutrient supply to maize roots (Zea mays L. cv. Blizzard) on net proton release was studied using the split root technique (SRNS, SRCa) to compare plants that were cultivated with their roots completely in either nutrient solution (NS) or 0.1 mM CaSO₄ (Ca). Roots in NS released more protons than roots in Ca. This higher net proton release was associated with significantly higher ATP concentrations in the root tissue. Higher net proton release and ATP concentrations were also observed after a 4 h lag phase when 20 μM abscisic acid were exogenously applied to roots in 0.1 mM CaSO₄. It is suggested that higher metabolic activity in roots supplied with nutrients increased ATP concentrations and thus the substrate supply of the plasma membrane H⁺ ATPase. When only half of the root system was supplied with nutrient solution with the other half bathed in 0.1 mM CaSO₄, the roots in the SRNS compartment released significantly higher amounts of protons relative to the NS control plants. Conversely, roots in the SRCa compartment showed net proton uptake in contrast to the roots of control plants in 0.1 mM CaSO₄ which significantly acidified the root medium. These differences in proton release by roots in the split root system and control roots could not be explained in terms of differences in ATP concentrations. It is therefore suggested that an internal signal may lead to a modification of the plasma membrane H⁺ ATPase as shown earlier during plant adaptation to low pH in the root medium.     

Calcium (45Ca2+) efflux from sorghum root tips

Sorghum [Sorghum bicolor (L.) Moench. cv GP‐10] root tips (1‐cm) were exposed to ⁴⁵Ca²⁺ for 1 hr. Root tips were washed in 0.01M EDTA for 5, 10, 15, 30, and 60 min. Calcium (⁴⁵Ca²⁺) remaining in the roots decreased on a T_1/2 = 12–13 minutes scale, which represents Ca²⁺‐ATPase activity in the GP‐10 root tips (1‐cm).     

Adenosine diphosphatase and adenosine triphosphatase activities of maize tonoplast‐enriched vesicles

Microsomal fraction enriched with tonoplast vesicles was obtained from maize root (Zea mays L. FRB 73) by sucrose step gradient centri‐fugation. The vesicles contained an adenosine diphosphatase (ADPase) activity as determined by the hydrolysis of Mg‐ADP. The ADPase and adenosine triphospha‐tase (ATPase) of the fraction have different sensitivities toward several modifiers. ADPase activity was not sensitive to nitrate, N,N'‐dicyclohexylcarbodiimide (DCCD), diethylstilbestrol (DES), and azide, but partially sensitive to vanadate and molybdate. In contrast, ATPase was very sensitive to nitrate, DCCD, and DES, but not to vanadate, azide, and molybdate. The presence of 2'‐or (3')‐trinitrophenol adenosine 5'‐diphosphate (TNP‐ADP) significantly reduced ADPase activity but not that of the ATPase activity. On the other hand, the addition of TNP‐ATP abolished ATPase activity but not the ADPase activity. Since the influence of these modifiers to the activities are different, the binding and the hydrolysis of ADP and ATP in maize tonoplast vesicles may occur at different sites.     

EDDS对印度芥菜Cu积累的影响及与P-ATPase的关系研究

通过水培的方法研究了可降解螯合剂EDDS对印度芥菜对Cu积累的影响,分析了根系中与Cu主动排出有关的P型ATPase的活性及其基因表达。结果表明:根系中Cu的积累量随外界浓度的升高而升高,但Cu在茎杆与叶片中的积累量则变化不大。随着外加EDDS浓度的增加,根、茎、叶中的Cu的积累量均出现下降的趋势。上述结果表明,根系以Cu离子为主要的吸收形式,而不是EDDS-Cu。通过对印度芥菜根系细胞膜上P型ATPase活性及基因表达分析后发现,不加EDDS时,随着外界Cu浓度的升高,ATPase活性增强,而当Cu达到16μmol L-1时出现降低的趋势。但是,ATPase活性随着外加EDDS的浓度增加而降低,这是因为EDDS降低了外界的Cu活度。RT-PCR分析结果表明,该ATPase的基因(BjHMA)在转录水平上的表达与活性变化一致。由于P型ATPase的作用是将Cu排出细胞,因此上述结果说明,其活性大小以及转录水平的变化受到外界Cu离子活度的影响,在一定的范围内可以调节植物对Cu的积累。     

Role of Plasmalemma H+ ATPase in Sugar Retention by Roots of Intact Maize and Field Bean Plants

Net release and net uptake of sugars by roots of intact maize (Zea mays cv. Blizzard) and field bean (Vicia faba L. cv. Alfred) were studied at micromolar external sugar concentrations that are relevant to the rhizosphere. Besides various sugars not further characterized there was net release of glucose, fructose, sucrose, arabinose, ribose, and galactose. The net release of these sugars into the root medium (0.1 mM CaSO₄) was stimulated by the protonophore CCCP (10 μM), the sulfhydryl reagent NEM (300 μM), the specific inhibitor of plasmalemma H⁺ ATPase vanadate (0.5 mM), and by the inhibitor of the glucose carrier phlorizin (2 mM). Net uptake of glucose, fructose, and arabinose from 10 μM external concentrations was inhibited by these substances. Stimulation of net release and inhibition of net uptake was most pronounced for glucose. Sucrose added to the root medium was hydrolyzed by invertase activity leading to glucose and fructose uptake by roots. It is concluded that the retention of sugars by plant roots is not only determined by plasmalemma permeability but is also controlled by the H⁺ electrochemical gradient established by ATPase activity (retrieval mechanism). The proton gradient drives a sugar/H⁺ cotransport system that is selective for glucose but may also transport other sugars, particularly in the absence of glucose.     

Separation of tonoplast vesicles enriched in atpase and pyrophosphatase activity from maize roots

Continuous sucrose gradient (15–35%) centrifugation of maize (Zea mays L.) root microsomal membranes yielded two well‐separated fractions of tonoplast vesicles located between 19–21% (Peak I) and 25–26% sucrose (Peak II). Marker enzyme analyses indicated that both fractions were essentially free from plasma membrane, mitochondria and Golgi contaminations. The adenosine triphosphate (ATP) supported proton transport activity was found in both Peak I and Peak II with a 70 to 30% distribution. The pyrophosphatase (PP_;) supported proton transport activity was found only in Peak II. Both hydrolytic activities assumed a bell shape pH dependency with pH optimum at 6.5–7.5 and at 6.5–8.5 for ATPase and PP_; ase, respectively. The K_m of the ATPase and PP_iase, at their respective optimal pH, was found to be 1.2 mM and 0.02 mM, respectively. Both ATPase and PPjase activities were strongly inhibited by N.N'‐dicyclohexylcarbodiimide (DCCD) and diethylstilbestrol (DES) but not by molybdate. Peak I contained nitrate‐sensitive and vanadate‐insensitive ATP hydrolysis activity. In addition to catalyzing the nitrate and vanadate‐insensitive hydrolysis of PP; Peak II also contained some minor ATP hydrolysis activity that was sensitive to vanadate and nitrate. The results indicate that H⁺‐ATPases and H⁺‐PP_fase occur different populations of tonoplast vesicles from corn roots.     

Changes of H+ pumps of tonoplast vesicle from wheat roots in vivo and in vitro under aluminum treatment and effect of calcium

Wheat seedlings were treated with 0.1 mM Al for 7 days. Tonoplast vesicles were isolated from apical segments of roots and activities of H⁺‐ATPase and H⁺‐PPase measured. Compared with the control, 0.1 mM Al increased H⁺‐ATPase activity and decreased H⁺‐PPase activity. High external supply of calcium (Ca) (5 mM) diminished the extent of the stimulation of H⁺‐ATPase activity and alleviated the reduction of H⁺‐PPase activity under Al treatment. However, 0.1 mM Al treatment in vitro resulted in the inhibition of H⁺‐ATPase activity with the decrease of Vmax and Km for ATP. In vitro treatment with 0.1 mM Al also decreased the H⁺‐PPase activity, but increased the Km for PPi.     

Effect of placement of coated urea fertilizer on root growth and rubidium uptake activity in soybean plant

Abstract

We reported in the previous paper (Takahashi et al. 1991) that the deep placement of slow release N fertilizer (coated urea) contributed to a stable increase of soybean (Glycine max L. Merr.) yield. In the previous study we observed that the deep placement of coated urea did not depress appreciably the nitrogen fixation by root nodules although fertilizer N was efficiently utilized. We assumed that the N absorbed from the roots in the deep layers did not cause nodule senescence, contributed to the maintenance of the leaf activity during the maturation stage, and that the increase in the availability of carbohydrate and N improved seed production. In the current report the effects of placement of coated urea fertilizer on the root growth and activity were studied by measuring the root dry weight and Rb absorption activity.     

The changes in physiological and biochemical traits of Tibetan wild and cultivated barley in response to low phosphorus stress

Low phosphorus (LP) limits crop growth and productivity in the majority of arable lands worldwide. Here, we investigated the changes in physiological and biochemical traits of Tibetan wild barleys (Hordeum vulgare L. ssp. spontaneum) XZ99 (LP tolerant), XZ100 (LP sensitive), and cultivated barley ZD9 (moderately LP tolerant) under two phosphorus (P) levels during vegetative stage. These genotypes showed considerable differences in the change of biomass accumulation, root/shoot dry weight ratio, root morphology, organic acid secretion, carbohydrate metabolism, ATPase (Adenosine triphosphatase) activity, P concentration and accumulation under LP in comparison with CK (control) condition. The higher LP tolerance of XZ99 is associated with more developed roots, enhanced sucrose biosynthesis and hydrolysis of carbohydrate metabolism pathway, higher APase (Acid phosphatase) and ATPase activity, and more secretion of citrate and succinate in roots when plants are exposed to LP stress. The results prove the potential of Tibetan wild barley in developing barley cultivars with high tolerance to LP stress and understanding the mechanisms of LP tolerance in plants.     

Effect of Iron Deficiency on RNA and Protein Synthesis in Cucumber Roots

Abstract

Strategy I is a multifaceted mechanism developed by plants to overcome iron deficiency. Beyond the main responses based on the Fe(III) reduction and rhizosphere acidification, there are other morphological, physiological, and biochemical responses that enable plants belonging to this class to respond in a more complex way to iron starvation. Most of these responses are catalyzed by enzymes, so the synthesis of mRNA and protein must occur rapidly to support these changes. Increase in the Fe(III) reductase and H⁺‐ATPase activities at the plasma membrane level, increase in some respiration enzymes and of phosphoenolpyruvate carboxylase (PEPC) are well acknowledged. In this paper we provide more direct evidence that both RNA and protein synthesis are increased under Fe deficiency and that the protein synthesis machinery is better developed in this condition. This hypothesis seems to be sustained also by the greater availability of free aminoacids and in particular of aspartate and glutamate in Fe deficient plant roots.     

Does H+ pumping by plasmalemma ATPase limit leaf growth of maize (Zea mays) during the first phase of salt stress?

In the first phase of salt stress, growth of plants is impaired mainly by osmotic stress. To elucidate the effect of NaCl salinity on elongation growth of maize leaves in the first phase of salt stress, we investigated the effect of NaCl on gene expression and activity of the plasmalemma H⁺ ATPase of elongating leaves of maize (Zea mays L.). Treatment of maize plants with 125 mM NaCl for 3 d decreased leaf growth relative to control plants (1 mM NaCl). Whereas H⁺ ATPase hydrolytic activity was unaffected, the ability of the H⁺ ATPase to establish a pH gradient was strongly reduced. Total mRNA of plasmalemma H⁺ ATPase was slightly increased. However, mRNA of the ATPase isoform MHA1 was significantly reduced and ATPase isoform MHA4 was strongly increased at the mRNA level. Synthesis of total H⁺ ATPase protein was unchanged as revealed by western blot. The results indicate that reduced pumping of H⁺ ATPase in leaf plasmalemma under salt stress may be caused by a switch to gene expression of the specific isoform MHA4, which shows inferior H⁺‐pumping efficiency in comparison to isoforms expressed under control conditions. We propose that reduced H⁺ pumping of plasmalemma H⁺ ATPase is involved in the reduction of leaf growth of maize during the first phase of salt stress.     

Effect of sodium chloride stress on the plasma membrane ATPase of barley roots: Probable cause for decrease in ATPase activity

The regulation of plasma membrane ATPase activity by salt stress was investigated in barley roots. The plasma membrane fractions were prepared from the roots treated with or without 200 mM sodium chloride (NaCl) for one day. After salt treatment, ATPase activity reduced by 20 to 30% as compared with that of control roots. No significant changes in the content of total phospholipid and sterol were detected in the plasma membrane fraction by salt stress. After extraction of most of the phospholipids in the plasma membrane vesicles with a solution containing 1% (W/V) octylglucoside and 1% (W/V) Triton X‐100, the ATPase activity in salt‐stressed roots was lower than that of control roots. After reconstitution of detergent‐extracted protein into liposome, the reduction of ATPase activity by salt stress did not recover. Based on immunoblott analysis, the relative amount of H⁺‐ATPase in plasma membrane fraction prepared, from NaCl‐stressed roots was smaller than that of control roots. These results indicate that the reduction of H⁺‐ATPase activity by salt stress was caused by the decrease in the amount of H⁺‐ATPase rather than the modification of ATPase.     

Root phosphatase activity of sorghum genotypes grown with organic and inorganic sources of phosphorus 1

Abstract

Relatively insoluble sources of phosphorus (P) may require solubilization, and organic P (P_o) may require hydrolysis to inorganic P (P_i) before P can be readily absorbed by plants roots. The mechanisms for these processes, however, are unknown. Root phosphatase (Pase) activity was measured to assess its relationships to P uptake by seven sorghum [Sorghum bicolor (L.) Moench] genotypes grown with P_o (ethylammonium phosphate, glycerophosphate, and phenylphosphate) and P_i (KH₂PO₄, calcium tribasic phosphate, calcium pyrophosphate, aluminum phosphate, and ferric phosphate) in nutrient solutions in a greenhouse.

Plants grown with P_o had lower root Pase activities than plants grown with P_i NB9040 and SC369–3–1JB (tolerant to low levels of P) had lower root Pase activities than CK60‐Korgi and SC33–9–8‐E4 (sensitive to low levels of P), with the other genotypes having intermediate root Pase activities. Higher root Pase activity was associated with lower root P concentrations, but Pase activity was not related to dry matter yield of roots. In experiments where genotypes were grown three weeks with KH₂PO₄ before being transferred to other sources of P, within four days root Pase activity patterns were similar to those for plants grown initially in the particular P_o or P_i compound. Root Pase activity of sorghum plants appeared to be an indicator of P status or P deficiency stress in the plants, and not associated with making P_o or P_i compounds more available for plant use.     

Erythrosine B influence on sorghum root curvature and wheat leaf rust germling use of extracellular lipids

Root curvature response to unilaterally applied calcium (Ca²⁺) in agar was inhibited 81% by erythrosine B (EB) (10 nM) in sorghum [Sorghum bicolor (L.) Moench.] cv Funk G522DR, 70% in cv SC283, and 11% in cv SC574. EB (10 nM) is reported to totally inhibit Ca²⁺‐ATPase, while 10–50 μM EB is required to inhibit H⁺‐ATPase. Therefore, differences in relative concentrations of Ca²⁺‐ATPase and H+‐ATPase exist in the root plasma membranes (PM) of the three cultivars. Carbon dioxide (¹⁴CO₂) production from glycerol‐tri‐(1‐¹⁴C)‐palmitate by wheat (Triticum aestivum L.) leaf rust (Puccinia recondita Rob. ex Desm.) urediospore germlings was inhibited 85% by EB (10 nM).     

CO-INOCULATION OF SOYBEAN (GLYCINE MAX) WITH ACTINOMYCETES AND BRADYRHIZOBIUM JAPONICUM ENHANCES PLANT GROWTH,NITROGENASE ACTIVITY AND PLANT NUTRITION

The aim of this study was to determine the potential of the endophytic actinomycetes that produce plant growth promoters used as co-inoculants with Bradyrhizobium japonicum to promote the growth of soybean. These endophytes exhibited the potential to enhance plant growth, nitrogenase activity of root nodules and plant nutrient uptake. Co-inoculum of B. japonicum with Nocardia alba conferred the maximum yield of root and shoot dry weight. All single-inoculated actinomycetes strains had the ability to enhance plant growth. Noc. alba and Nonomuraea rubra increased total plant dry weight up to 2.14-fold and 2.11-fold, respectively, when compared to the uninoculated controls. Co-inoculations of B. japonicum with each of Noc. alba, Non. Rubra, and Actinomadura glauciflava increased acetylene reduction activity up to 1.7 to 2.7-fold. For plant mineral composition, all of co-inoculation treatments significantly increased the nutrient levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) within a soybean plant.     

Nitrogen metabolism in Nicotian a rustica L. grown with molybdenum. I. vegetative development

Abstract

The effect of 1 ppm of molybdenum on nitrate reductase (EC 1.6.6.1.3) and nitrite reductase (EC 1.7.7.1) activity, and the nitrate, nitrite, ammonium, total nitrogen, total protein content on vegetative development of Nicotiana rustica L. was studied. This molybdenum supply increased the ammonium and nitrite content in leaves and the protein content in the root. Variations in enzymatic activity was not observed. The vegetative stage was shorter in the plants grown with this molybdenum supply.     

In vivo nitrate reductase activity in carex pseudocyperus L.: The influence of nitrate ‐ ammonium concentration ratios and correlation with growth

Abstract

The influence of the nitrate nutritional status and increasing ammonium concentrations on the nitrate reductase activity of shoots and roots of Carex pseudocyperus L. was investigated. The activity of this enzyme was correlated with the relative growth rates of the plant. Nitrate reductase activity was determined by a modified in vivo test (1). A specially developed test system allowed a large amount of samples to be handled easily.

The optimization procedure of the incubation buffers led to different assay conditions for the shoot and the root, respectively. Enzyme activity in the shoot was dependent on the length of the incubated leaf pieces. Incubation had to take place under dark, anaerobic conditions.

Enzyme activity was influenced by an evident diurnal rhythm with an optimum six hours after starting illumination, so that harvesting occurred always at that day time.

Increasing nitrate concentrations of up to 2.5mM NO₃‐ in the nutrient solution induced an increasing nitrate reductase activity in the shoot. The enzyme activity of the root was already fully induced at 1mM NO₃ ^?. A nitrate concentration above 5mM NO₃ ^? inhibited enzyme activity in shoots as well as in roots. The addition of increasing amounts of ammonium to a solution containing 2mM NO₃ ^? led to a significant inhibition of the enzyme activity in both parts of the plant.

Relative growth rates of the shoot, as a function of increasing nitrate concentrations in the nutrient solution, were highly positively correlated to the corresponding nitrate reductase activity, but only a slight, negative correlation was observed between these two parameters in the root.     

Sulfur deficiency of rice plants in the Lower Volta area,Ghana

Abstract

It is well known that stem nodules are formed on the aerial parts of Aeschynomene spp. and Sesbania rostrata grown in the field (Yatazawa and Yoshida 1979; Dreyfus and Dommergues 1981; Yoshida et al. 1985). We have reported that stem nodules were successfully formed by inoculation of Rhizobium isolates derived from both stem and root nodules of A. indica (Yoshida et al. 1985; Sasakawa et al. 1986). The specific activity of nitrogen fixation in stem nodules is comparable to that of root nodules (Sasakawa et al. 1986; Sasakawa 1990). A red pigment, which suggests the presence of leghemoglobin, was detected in stem nodules as well as in root nodules (Yatazawa and Yoshida 1979; Yatazawa and Susilo 1980; Sasakawa et al. 1986).     

Effect of Iron and Auxins on Peroxidase Activity and Rooting Performance of Three Citrus Rootstocks In Vitro

Abstract

The effects of FeCl₃, Fe‐EDDHA and Fe‐EDTA as iron sources at 5.6 ppm, as well as their combined effect with the auxins IBA and α‐NAA on rooting capacity and total peroxidase activity of three Citrus rootstocks (Swingle Citrumelo, C. taiwanica, and C. aurantium) in vitro were studied for eight weeks. No root or callus formation was observed in the presence of IBA independently of the Fe source, or in the absence of Fe in the culture medium independently of the hormone used. Low rooting percentage obtained by FeCl₃, while the best results were obtained using Fe‐EDDHA as Fe source. The time of root appearance was also influenced by the different sources of Fe as well as by the kind of the rootstock. In the presence of Fe‐EDTA plantlets survived for four weeks and then died. Total peroxidase activity declined sharply shortly before root appearance, but the decline was less pronounced shortly before callus formation (in some cases of FeCl₃ treatment).     

Mineral Content and Root Respiration of In Vitro Grown Kiwifruit Plantlets Treated with Two Humic Fractions

ABSTRACT

In vitro grown kiwifruit (Actinidia deliciosa, Liang and Ferguson) plantlets were treated with two humic fractions distinguished by two different relative molecular mass and characterized through their elemental composition and ¹³Carbon (C) nuclear magnetic resonance. The effects exerted on plant growth, root morphology, and nutrition were evidenced by means of leaves and roots mineral content, root respiration, and nitrate reductase activity. The two humic substances differentially influenced the studied parameters. The lower molecular fraction humic substance, endowed with a higher content of phenolic and carboxylic groups, caused an enhanced content of micro- and macro-elements, together with a higher root respiration at lower concentrations (0.5–1 mg C L^{? 1}). The high molecular fraction humic substance, needed higher concentrations (> 5 mg C L^{? 1}) in order to achieve similar effects. This fraction also caused major changes on root morphology. The ability to improve micronutrient assimilation, in particular iron, confirmed the agronomic importance of humic substances on soil fertility.