Sodium nitrate effect on development of neurological deficiency in rats after semi-global brain ischemia

Dose-dependent effects of sodium nitrate (NaNO₃) on the dynamics of neurological disorders after brain ischemia induced by bilateral occlusion of the common carotid artery were investigated in rats of the Wistar line. NaNO₃ at 50 and 500 mg/1000 g decreased mortality rates and neurological disorders. NaNO₃ at 5 mg/1000 g had no effect.     

The effect of source,concentration and time of application of nitrogen on the growth,nodulation and nitrogen fixation ofLotus pedunculatus andTrifolium repens

Summary Studies under growth cabinet conditions investigated the effect of source and concentration of nitrogen and timing of nitrogen application on the growth and nitrogen fixation byLotus pedunculatus cv. Maku andTrifolium repens cv. S184. KNO₃, NaNO₃ and NH₄NO₃ were added at transplanting at the following rates: 3.33, 7.78 and 13.33 mg N/plant. KNO₃ was added at 3.33 and 7.78 mg N/plant at 0, 6, 12, 18, 24 or 30 days after transplanting.Lotus shoot weight increased with all increasing nitrogen sources but clover only responded to KNO₃ and NaNO₃. The root weight of both species increased with increasing KNO₃ and NH₄NO₃. The percentage increase in lotus and clover shoot growth was greater than that of root growth when KNO₃ was added within a week of transplanting. Increases in growth by both species resulted from added nitrogen except with lotus when NaNO₃ was applied where increased nitrogen fixation also contributed to increased growth.Weight and number of effective nodules on both species were increased with 3.33 mg N per plant as KNO₃ but nitrogen fixation was not affected. Addition of 13.33 mg N as NaNO₃ reduced weight and number of effective nodules in both species and also nitrogen fixation by lotus.KNO₃ increased growth and nodulation of both species when applied within one week after transplanting. Nodulated lotus plants responded to KNO₃ by increasing growth but not nodulation.KNO₃ appeared to affect infection and development of nodules on lotus and may affect the growth of existing nodules on clover.     

The effect of nitrate and nitrous oxide on hydrogen and methane accumulation in anaerobically-incubated soils

Summary The effect of KNO₃ and N₂O on the accumulation of CH₄, H₂ and denitrification products in two North Dakota soils during anaerobic incubation at 30°C was studied by means of gas chromatography. KNO₃ and N₂O (500 ppm N) reduced the rate of accumulation of CH₄ by a Tetonka soil regardless of whether the soil was in an air-dried condition or had been pre-incubated and actively producing CH₄ prior to the treatment application. Both KNO₃ and N₂O completely suppressed H₂ accumulation by the remoistened air-dried soil; no H₂ either in the presence or absence of added KNO₃ or N₂O was accumulated by the pre-incubated Tetonka soil subsequent to the treatment application. KNO₃ (250 ppm N) reduced the rate of accumulation of CH₄ by a Cavour loam during anaerobic incubation. No H₂ was accumulated by this soil during anaerobic incubation. At equivalent K⁺ concentrations, KNO₃ suppressed CH₄ accumulation by the Tetonka and Cavour soils to a greater extent than did KCl.     

Variable Effects of Nitrate on ATP-Dependent Proton Transport by Barley Root Membranes

The effects of NO₃⁻ and assay temperature on proton translocating ATPases in membranes of barley (Hordeum vulgare L. cv California Mariout 72) roots were examined. The membranes were fractionated on continuous and discontinuous sucrose gradients and proton transport was assayed by monitoring the fluorescence of acridine orange. A peak of H⁺-ATPase at 1.11 grams per cubic centimeter was inhibited by 50 millimolar KNO₃ when assayed at 24°C or above and was tentatively identified as the tonoplast H⁺-ATPase. A smaller peak of H⁺-ATPase at 1.16 grams per cubic centimeter, which was not inhibited by KNO₃ and was partially inhibited by vanadate, was tentatively identified as the plasma membrane H⁺-ATPase. A step gradient gave three fractions enriched, respectively, in endoplasmic reticulum, tonoplast ATPase, and plasma membrane ATPase. There was a delay before 50 millimolar KNO₃ inhibited ATP hydrolysis by the tonoplast ATPase at 12°C and the initial rate of proton transport was stimulated by 50 millimolar KNO₃. The time course for fluorescence quench indicated that addition of ATP in the presence of KNO₃ caused a pH gradient to form that subsequently collapsed. This biphasic time course for proton transport in the presence of KNO₃ was explained by the temperature-dependent delay of the inhibition by KNO₃. The plasma membrane H⁺-ATPase maintained a pH gradient in the presence of KNO₃ for up to 30 minutes at 24°C.     

NH4 + and NO3 − requirement for wheat somatic embryogenesis

The influence of three nitrogen salts: NH₄NO₃, KNO₃ and NH₄Cl on wheat in vitro cultures was investigated. Both NO ₃ ⁻ and NH ₄ ⁺ ions were indispensable for proliferation of embryogenic calli and development of wheat somatic embryos. It is possible to obtain wheat somatic embryos when the medium is enriched with NH₄NO₃ only as a source of inorganic nitrogen. The results of the statistical analysis showed that the level of NH₄NO₃ and KNO₃ in the medium had a great influence on the efficiency of somatic embryogenesis. We observed tendency that calli on media containing 50 mM NH₄NO₃ and 0 to 20 mM KNO₃ turned out to be more embryogenic than on control MS medium. High concentrations of KNO₃- 100 mM inhibited somatic embryogenesis, while 100 mM NH₄NO₃ did not. The level of total N did not have significant influence on wheat somatic embryogenesis. Ratio NO ₃ ⁻ :NH ₄ ⁺ also turned out to be not substantial. We observed that mutual connection of concentration levels between NH₄NO₃ and KNO₃ and between NH₄Cl and KNO₃ was more important. The efficiency of somatic embriogenesis obtained in the experiment with NH₄Cl and KNO₃ was significantly lower than in experiment with NH₄NO₃ and KNO₃.     

The Effect of Inorganic Salts on the Senescence of Dianthus caryophyllus Flowers

Certain inorganic salts like KNO₃, KCl, K₂SO₄, Ca(NO₃)₂ and NH₄NO₃ extend longevity of cut carnation flowers. The effect of KNO₃ was studied in some detail. There is an osmotic adjustment in response to KNO₃ treatment. The osmotic concentration change occurred in the external as well as in the internal compartments. The osmotic concentration change in the external compartment is well correlated with extension of longevity. The effect of KNO₃ on the sensitivity to ethylene, and its significance in delaying senescence is discussed.     

The effects of KNO3 concentration in callus induction medium for wheat anther culture

KNO₃ concentration was found to significantly affect the anther culture of wheat (Triticum aestivum L.). When KNO₃ was increased from 0 to 15 mM (in cultivar Jinghua 1) or from 10 to 15 mM (in cultivars 2531-10, Xiaoyan 759 and Norin 10), the callus induction frequency increased significantly. When KNO₃ was increased further above 20 mM, the callus induction frequency decreased significantly in all the tested cultivars. The subsequent frequency of green plantlet regeneration increased significantly, and the ratio of green to albino regenerants increased sharply when KNO₃ concentration increased. Further experiments found that the decrease of callus induction frequency in the medium with too much KNO₃ might be caused by NO₃ ^- ion alone, while the effect of KNO₃ on green plantlet regeneration might be caused by both K⁺ and NO₃ ^- ions, and that the effects of NO₃ ^- concentration were independent of NH₄ ⁺ concentration in the medium.     

Apigenin-7-O-β-D-(-6'-p-coumaroyl)-Glucopyranoside Treatment Elicits Neuroprotective Effect against Experimental Ischemic Stroke

Stroke is the major cause of permanent disability and mortality in China. Apigenin-7-O-β-D-(-6''''-p-coumaroyl)-glucopyranoside (APG) is a glycoside subtype of apigenin and has the antioxidant activity; however, whether and how it plays a neuroprotective role following cerebral ischemia remains unknown. In present study, we adopted the oxygen glucose/reperfusion model in PC12 cells, bilateral common carotid artery occlusion model in C57B6 mice and middle cerebral artery occlusion model in SD rats to observe the therapeutic effects of APG on ischemic stroke. We also discussed the underlying mechanism. Treatment with 0.4 μg/ml or 0.8 μg/ml APG promoted cell viability and proliferation, reduced LDH release and apoptotic cell death levels in PC12 cells. Treatment with 50 mg/kg or 100 mg/kg APG at 30 minutes after reperfusion improved neurological outcomes in vivo, as demonstrated by elevation of neurological scores in both mice and rats. It also increased the number of survival neurons in mice and reduced infarct volume in rats. APG also increased the contents of Mn-SOD and the phosphorylation level of STAT3, elevated the antioxidant activity and reduced oxidative productions. These findings revealed a neuroprotective effect of APG, which possibly induced by the STAT3 phosphorylation-mediated Mn-SOD up-regulation.     

Partial Carotid Occlusion as Treatment for Intracranial Internal Carotid Aneurysms

A study was undertaken to investigate the possibility of using partial carotid occlusion instead of complete carotid ligation for the treatment of intracranial internal carotid aneurysms with a view to avoiding such complications of the latter procedure as neurological deficit resulting from cerebral ischemia, and ascending thrombus formation. The beneficial effect of carotid ligation has been explained by the interruption of pulsatile flow which can cause rupture of an aneurysm by resonance phenomena. Studies on blood flow in the aorta in dogs, as well as in a human carotid artery in vivo and in vitro, showed that the same object could be achieved by the use of constriction by a Poppen clamp. This changed the pulsatile blood flow to a relatively non-pulsatile state with slight diminution in mean flow. Partial occlusion of the common carotid artery is recommended for those cases of intracranial aneurysm in which complete carotid occlusion would not likely be tolerated.     

Growth and physiological characteristics of wasabi plantlets cultured by photoautotrophic micropropagation at different temperatures

Iranian seedless barberry is a very recalcitrant species in in vitro culture which does not show appropriate growth on standard culture media. Response surface methodology was employed to evaluate the effects of changing macronutrients concentrations on establishment and proliferation phases. KNO₃ and NH₄NO₃ macronutrients at 0.3 to 1.5?×?MS medium levels and CaCl₂, MgSO₄ and KH₂PO₄ macronutrients in a range of 0.5 to 1.5?×?MS medium concentrations were tested in a response surface design with 30 treatments. Many significant interactions were found among the macronutrients. High concentrations of KNO₃, NH₄NO₃ and CaCl₂ improved the growth rate in the establishment phase. The growth rate in media containing high KNO₃ and low CaCl₂ was high. Reduced concentrations of CaCl₂ and KNO₃ decreased hyperhydricity. The greatest hyperhydricity was induced when both NH₄NO₃ and CaCl₂ were used at 1.5?×?MS level. The number of hooked leaves decreased as KH₂PO₄ increased and MgSO₄ reduced. In the proliferation phase, there were many significant interactions among the macronutrients. Increased concentration of NH₄NO₃ and reduced concentration of KH₂PO₄ improved the growth rate. Proliferation rate increased in media containing high concentration of KNO₃ and low to moderate concentrations of NH₄NO₃. The greatest production of new tissues and organs was seen in media with high KNO₃ and moderate to high CaCl₂. High concentration of NH₄NO₃ and low concentration of KH₂PO₄ also increased production of new tissues and organs. No shoot apical meristem was seen when CaCl₂ level was high and KNO₃ level was low. Formation of shoot apical meristem required high KH₂PO₄ concentration and low CaCl₂ concentration. Finally, low concentration of KNO₃ and low to moderate concentrations of NH₄NO₃ increased phenol exudation.

     

Effect of plant growth regulators and different nitrogen sources on NADP-isocitrate dehydrogenase activity of radish cotyledons

NADP-isocitrate dehydrogenase (NADP-ICDH) activity of radish (Raphanus sativus L.) seedlings pretreated with various plant growth regulators: KiN, GA, and ABA and different nitrogen sources viz. KNO₃, NH₄Cl and NH₄NO₃ in light and dark was investigated. ICDH activity was significantly higher in light than in dark; addition of different nitrogen sources reduced it to a greater extent in NO₃ supplementation. Among hormonal treatment only KiN showed slight promotion with KNO₃ and NH₄NO₃. On the other hand in light KNO₃ and/or NH₄NO₃ promoted ICDH activity and among hormones, KiN significantly promoted the activity in KNO₃ and NH₄NO₃ supplemented seedlings while ABA was effective in NH₄CL. It is suggested that in non-photosynthetic tissues, NADP-ICDH provides both reductant and carbon skeleton for glutamate synthesis.     

Seed germination in Chenopodium album L.: further evidence for the dependence of the effects of growth regulators on nitrate availability

Abstract Chenopodium album L. plants, grown under controlled environmental conditions on different levels of soil nitrate, produced seeds with proportionately different NO^?₃ contents. Regardless of the endogenous NO^?₃ content, few seeds germinated in water or upon treatment with KNO₃. Ethylene promoted germination, and the extent of germination was positively correlated with the endogenous seed NO^?₃ content. Combined application of ethylene and KNO₃ in the dark had a synergistic effect on NO^?₃ -deficient seed. The synergism between ethylene and KNO₃ was attributable to the NO^?₃ moiety of the nitrate salt. Ethylene and light showed moderate synergism in seeds with low or high endogenous nitrate. Addition of nitrate, however, masked the interaction between ethylene and light. Gibberellic acid₄₊₇ (GA₄₊₇) or red light, each alone or combined with KNO₃, had little effect on germination. When applied together in the dark, ethylene and GA₄₊₇ synergistically enhanced the germination of NO^?₃-deficient seed. The combined effects of the two hormones on this seed were further enhanced by the addition of KNO₃. There was no synergism between ethylene and GA₄₊₇ in NO^?₃-rich seed. These interactions among GA₄₊₇, ethylene and KNO₃ were not affected by light. The results confirm and further elaborate our earlier finding that the sensitivity of C. album seeds to ethylene may depend on nitrate availability.     

Effects of different N-sources on growth,nutritional status,chlorophyll content,and photosynthetic parameters of shoots of the apple rootstock MM 106 cultured <Emphasis Type="Italic">in vitro</Emphasis>

The effects of five different N-sources (KNO₃ + NH₄NO₃ = control, KNO₃, NH₄NO₃, NH₄H₂PO₄, L-alanine) on growth, nutritional status, chlorophyll (Chl) content, and photosynthetic parameters of the apple rootstock MM 106 shoots cultured in vitro were investigated. In comparison to all the other treatments, control explants grown on a MS medium containing KNO₃ + NH₄NO₃ had the highest fresh mass, Chl content, net photosynthetic rate, transpiration rate, and stomatal conductance.     

Role of potassium and malate in nitrate uptake and translocation by wheat seedlings

Wheat seedlings (Triticum vulgare) treated with 1 mm KNO₃ or NaNO₃, in the presence of 0.2 mm CaSO₄, were compared during a 48-hour period with respect to nitrate uptake, translocation, accumulation and reduction; cation uptake and accumulation; and malate accumulation. Seedlings treated with KNO₃ absorbed and accumulated more nitrate, had higher nitrate reductase levels in leaves but less in roots, accumulated 17 times more malate in leaves, and accumulated more of the accompanying cation than seedlings treated with NaNO₃. Within seedlings of each treatment, changes in nitrate reductase activity and malate accumulation were parallel in leaves and in roots. Despite the great difference in malate accumulation, leaves of the KNO₃-treated seedlings had only slightly greater levels of phosphoenolpyruvate carboxylase than leaves of NaNO₃-treated seedlings. NADP-malic enzyme levels increased only slightly in leaves and roots of both KNO₃- and NaNO₃-treated seedlings. The effects of K⁺ and Na⁺ on all of these parameters can best be explained by their effects on nitrate translocation, which in turn affects the other parameters. In a separate experiment, we confirmed that phosphoenolpyruvate carboxylase activity increased about 2-fold during 36 hours of KNO₃ treatment, and increased only slightly in the KCl control.     

Spontaneous Super-Swarming Derivatives of Azospirillum brasilense Sp245 have Different DNA Profiles and Behavior in the Presence of Various Nitrogen Sources

Azospirillum brasilense swims in liquid environments and swarms in semisolid media. Five variants of A. brasilense Sp245, Sp245.P1–Sp245.P5, which swarmed faster than Sp245 in a semisolid malate–salt medium, have been isolated. In Sp245.P1–Sp245.P4, a new megaplasmid was revealed instead of an indigenous 85-MDa plasmid (p85). By polymerase chain reactions (PCR) with primers to the segments of p85 important for proper bacterial motility/flagellation and for dissimilatory nitrite and NO reduction, that DNA of p85 was found retained by all the variants. In ERIC- and RAPD-PCR, microdiversity between the total DNAs of Sp245 and its variants was detected. Interstrain differences in growth characteristics in liquid peptone–succinate–salt medium with KNO₃ or KNO₂ and in KNO₂ production/consumption were revealed. Although all the variants swam and swarmed faster than Sp245 in the medium supplemented with NH₄Cl or KNO₃, not all of them could do so in MPSS with KNO₂.     

Effect of nitrate on water transfer across roots of nitrogen pre-starved maize seedlings

The addition of 10 mM KNO₃ to the solution bathing the roots of young nitrogen-starved seedlings of Zea mays L. enhanced root water transfer within 15 h, compared with 10 mM KCl addition. The free exudation flux was 2.2–3.9 times higher in excised KNO₃-treated roots than in KCl-treated ones. Cryo-osmometry data for xylem sap suggested that, compared with chloride, nitrate treatment increased the steady solute flux into the xylem, but did not modify the osmotic concentration of sap. Root growth was not significantly modified by nitrate within 15 h. Root hydraulic conductances were measured by using either hydrostatic-pressure or osmotic-gradient methods. During hydrostatic experiments, the conductance (k_p), which is thought to refer mainly to the apoplasmic pathway, was 1.6 times larger in KNO₃-than in KCl-treated plants. From experiments in which polyethylene glycol (PEG) 8000 was used as external osmolyte, osmotic conductances (k_s) were found to be smaller by 5–20 times than k_p for the two kinds of plants. The KCl-treated roots were characterized by a low k_s which was the same for influx or efflux of water. By contrast, KNO₃-treated roots exhibited two distinct conductances k_s1 and k_s2, indicating that influx of water was easier than efflux when the water flow was driven by the osmotic pressure gradient. Infiltration of roots with KNO₃ solution supported the idea that nitrate might enhance the efficiency of the cell-to-cell pathway. The low k_s value of KCl-treated roots and the existence of two contrasting k_s values (k_s1 and k_s2) for KNO₃-treated roots are discussed in terms of reversible closing of water channels.     

改良线栓法大鼠大脑中动脉阻塞模型的建立

目的对大鼠大脑中动脉阻塞（MCAO）再灌注模型进行改良,通过比较再灌注24h时大鼠神经功能评分、梗死率、模型制作时间、成功率和死亡率等指标评价改良线栓法大鼠MCAO再灌注模型的有效性。方法12只SD大鼠随机分为对照和模型两组,对照组采用分离结扎翼腭动脉,从颈外动脉插入线栓至大脑中动脉。模型组采用不分离结扎翼腭动脉,从颈总动脉分叉处插入线栓至大脑中动脉。阻断大脑中动脉血供2h后将线栓拔出实现再灌注。于再灌注24h时观察脑组织组织病理学改变,计算比较两组大鼠神经功能评分、模型制作时间、模型成功率和死亡率以及鼠脑切片TTC染色测量脑梗死率。结果两组MCAO模型在再灌注24h后大鼠神经功能评分、梗死率、模型成功率和死亡率等方面没有显著差异;模型组的模型制作时间显著少于对照组（P〈0．05）。结论采用不分离结扎翼腭动脉,由颈总动脉插入线栓的改良线栓法是稳定和可靠的MCAO造模方法。     

Ecophysiological effects of light quality and nitrate on seed germination in species from Western Australia

Germination occurs usually in response to multiple environmental cues. Seeds with the ecophysiological ability to simultaneously sense the previous presence of fire and appropriate levels of temperature, light and soil nitrate could restrict germination to postfire, winter and competition-free microhabitats, where the potential for seedling survival is enhanced. Germination responses of 16 species with a range of life forms, fire responses and seed weights were determined under controlled conditions of 15°C temperature, a 12 h light cycle, exposure to 1 g L^?1 nitrate solution, and six conditions of light quality (white, blue, yellow, red, far-red light and darkness). Germination in Oenothera stricta, a weedy naturalized ephemeral, and two small-seeded indigenous Asteraceae species of mulga woodlands, Leucochrysum fitzgibbonii and Craspedia sp., were enhanced by white, yellow or red light compared with germination achieved in the dark, or under far-red or blue light. In red light, KNO₃ further enhanced germination of these positively photoblastic species. The germination response of Trachyandra divaricata, a naturalized herb of sandy, seaside locations, and several native jarrah forest legumes (four Acacia species, Bossiaea aquifolium, Gompholobium marginatum and Sphaerolobium vimineum) proved to be negatively photoblastic. Of these seven negatively photoblastic herb and shrub species, exposure to KNO₃ overcame the inhibition of light only in the resprouter species, Acacia lateriticola. In the serotinous, negatively photoblastic tree species, Corymbia calophylla and Eucalyptus marginata, KNO₃ seemed to be required before the negative response to light exposure was recorded. A dose–curve experiment on two positively photoblastic and three negatively photoblastic species indicated that although KNO₃ exposure affected germination in all species, different concentrations of KNO₃ (0, 0.5, 1, 2, and 5 g L^?1) produced different levels of response. Detailed studies with additions of KNO₃ (1 g L^?1) and the growth hormone, gibberellic acid (GA₃; 50 mg L^?1), showed that increased germination percentages of the positively photoblastic species, Oenothera stricta, occurred in the light, but blocking endogenous gibberellic synthesis with paclobutrazol, or adding exogenous GA₃ or KNO₃ had no effect on the light-induced germination levels. In the negatively photoblastic species Trachyandra divaricata, additions of KNO₃ and GA₃ had no influence on the germination inhibition induced by exposure to light nor did blocking endogenous GA synthesis. The 16 species growing naturally in Western Australia, Australia show a range of germination responses to environmental conditions, but depending on their natural habitat, the ecophysiology of each species appears to be optimized for subsequent seedling survival.     

Enhanced In Vitro Plantlet Regeneration from Mature Embryo-derived Primary Callus of a Basmati Rice Cultivar Through Modification of Nitrate-nitrogen and Ammonium-nitrogen Concentrations

Mature-embryo derived primary calli of the basmati rice (Oryza sativa L.) cv Karnal Local showed significant enhancement in in vitro green-plantlet regeneration efficiency through modification of nitrogen content of the callusing medium. Using KNO₃ as the source of nitrate nitrogen and (NH₄)₂SO₄ as the source of ammonium nitrogen, forty-five media combinations involving 9 levels of KNO₃ (0–40 mM) and 5 concentrations (0–6.5 mM) of (NH₄)₂SO₄ were examined. The highest frequency of plantlet regeneration (100%) and a maximum number of green-plantlets (～ 7) per embryo-derived primary callus was obtained in calli derived from the medium having 35 mM KNO₃ and 5 mM (NH₄)₂SO₄. Higher concentrations of KNO₃ and/or (NH₄)₂SO₄ showed a decline in the regeneration efficiency. It was also observed that although the nitrogen content of the callus induction medium had a profound effect on the regenerability of the callus, the nitrogen composition of the regeneration medium also affected it significantly.     

Effect of nitrates and sucrose on the induction of nitrate reductase in etiolated seedling leaves from selected barley genotypes in darkness

The parental genotypes, cv. Aramir and R567 line, as well as the selected DH lines C23, C47/1, C41 and C55, growing in darkness differed significantly in the level of NR activity in crude leaf extracts independently of nitrate concentration in the medium. The highest activity of the enzyme was found in the line C23. When plants grew on the medium with 0.5 mM KNO₃, NR activity in that genotype was almost 10-fold higher than in the parents and lines C41, C55 and also 3.5-fold higher than in the line C47/1. An increase of nitrate concentration in the medium to 10 mM caused a significant increase of NR activity in all the genotypes under study. In the line C23 this enzyme activity was only 20% lower than that found previously in the green leaves of that genotype in light. NR from the leaves of C23 and C41 lines was thermally unstable under in vitro conditions. This enzyme in the leaf extracts from the line C23 was characterized by a considerably lower unstability. The lines DH C23 and C41 growing in the dark on the medium with 0.5 mM KNO₃ did not differ in nitrate accumulation in leaves, whereas a larger nitrate content was found in the leaves of the line C41 when it grew on the medium with 10 mM KNO₃. Independently of nitrate concentration in the medium, leaves of the line C23 were found to have a higher sucrose content than those of the line C41. Excised, etiolated leaves of barley treated with 0.5 and 10 mM KNO₃ in dark under conditions favorable to transpiration had a low NR activity. Leaf treatment with a solution containing 10 mM KNO₃ + 0.2 M sucrose caused, on the average, a 13-fold increase of NR activity in comparison to leaves treated only with 10 mM KNO₃ and about a 6-fold increase of this enzyme in comparison to leaves treated with 0.5 mM KNO₃ + 0.2 M sucrose.