The Effect of c-Fos Demethylation on Sodium Fluoride-induced Apoptosis in L-02 Cells

Magnesium (Mg) deficiency has been reported to affect plant photosynthesis and growth, and cerium (Ce) was considered to be able to improve plant growth. However, the mechanisms of Mg deficiency and Ce on plant growth remain poorly understood. The main aim of this work is to identify whether or not Mg deprivation affects the interdependent nitrogen and carbon assimilations in the maize leaves and whether or not Ce modulates the assimilations in the maize leaves under Mg deficiency. Maize plants were cultivated in Hoagland’s solution. They were subjected to Mg deficiency and to cerium chloride administration in the Mg-present Hoagland’s media and Mg-deficient Hoagland’s media.After 2 weeks,we measured chlorophyll (Chl) a fluorescence and the activities of nitrate reductase (NR), sucrose-phosphate synthase(SPS), and phosphoenolpyruvate carboxylase (PEPCase)in metabolic checkpoints coordinating primary nitrogen and carbon assimilations in the maize leaves. The results showed that Mg deficiency significantly inhibited plant growth and decreased the activities of NR, SPS, and PEPCase and the synthesis of Chl and protein. Mg deprivation in maize also significantly decreased the oxygen evolution, electron transport,and efficiency of photochemical energy conversion by photosystem II (PSII). However, Ce addition may promote nitrogen and carbon assimilations, increase PSII activities,and improve maize growth under Mg deficiency. Moreover,our findings would help promote usage of Mg or Ce fertilizers in maize production.     

Iron availability in plant tissues-iron chlorosis on calcareous soils

The article describes factors and processes which lead to Fe chlorosis (lime chlorosis) in plants grown on calcareous soils. Such soils may contain high HCO₃ ^- concentrations in their soil solution, they are characterized by a high pH, and they rather tend to accumulate nitrate than ammonium because due to the high pH level ammonium nitrogen is rapidly nitrified and/or even may escape in form of volatile NH₃. Hence in these soils plant roots may be exposed to high nitrate and high bicarbonate concentrations. Both anion species are involved in the induction of Fe chlorosis.Physiological processes involved in Fe chlorosis occur in the roots and in the leaves. Even on calcareous soils and even in plants with chlorosis the Fe concentration in the roots is several times higher than the Fe concentration in the leaves. This shows that the Fe availability in the soil is not the critical process leading to chlorosis but rather the Fe uptake from the root apoplast into the cytosol of root cells. This situation applies to dicots as well as to monocots. Iron transport across the plasmamembrane is initiated by Fe^III reduction brought about by a plasmalemma located Fe^III reductase. Its activity is pH dependent and at alkaline pH supposed to be much depressed. Bicarbonate present in the root apoplast will neutralize the protons pumped out of the cytosol and together with nitrate which is taken up by a H⁺/nitrate cotransport high pH levels are provided which hamper or even block the Fe^III reduction.Frequently chlorotic leaves have higher Fe concentrations than green ones which phenomenon shows that chlorosis on calcareous soils is not only related to Fe uptake by roots and Fe translocation from the roots to the upper plant parts but also dependent on the efficiency of Fe in the leaves. It is hypothesized that also in the leaves Fe^III reduction and Fe uptake from the apoplast into the cytosol is affected by nitrate and bicarbonate in an analogous way as this is the case in the roots. This assumption was confirmed by the highly significant negative correlation between the leaf apoplast pH and the degree of iron chlorosis measured as leaf chlorophyll concentration. Depressing leaf apoplast pH by simply spraying chlorotic leaves with an acid led to a regreening of the leaves.     

Iron deficiency in peach trees: effects on leaf chlorophyll and nutrient concentrations in flowers and leaves

The effects of iron deficiency on the leaf chlorophyll concentrations and on the macro- (N, P, K, Ca and Mg) and micro-nutrient (Fe, Mn, Zn and Cu) composition of flowers (at full bloom) and leaves (60 and 120 days after full bloom) of field-grown peach (Prunus persica L. Batsch) trees were investigated. Flowers and leaves were taken and analysed from fifty individual trees. Our data indicate that large decreases in leaf chlorophyll concentration were found at the beginning of the season in control trees, possibly associated to a dilution effect by leaf growth, that were later followed by leaf chlorophyll concentration increases. Leaf Fe chlorosis apparently results from two different processes, the dilution of leaf Chl caused by growth and the subsequent inability to produce and/or stabilize new Chl molecules in the thylakoid membrane. Iron chlorosis did not change the seasonal change patterns of any of the nutrients studied. In Fe-deficient trees the K concentration and the K/Ca ratio were high not only in leaves but also in flowers, indicating that this is a characteristic of Fe-deficient plant tissue in the whole fruit tree growing season. Flower Fe concentrations were well correlated with the degree of chlorosis developed later in the season by the trees, suggesting that flower analysis could be used for the prognosis of Fe deficiency in peach.     

Effects of nitric oxide and Fe supply on recovery of Fe deficiency induced chlorosis in peanut plants

The effects of nitric oxide (NO) and/or iron (Fe) supplied to Fe deficient plants have been investigated in peanut (Arachis hypogaea L.) grown in Hoagland nutrient solution with or without Fe. Two weeks after Fe deprivation, recovery was induced by addition of 250 μM sodium nitroprusside (SNP, a NO donor) and/or 50 μM Fe (Fe-EDTA) to the Fe deprived (-Fe) nutrient solution. Activities of antioxidant enzymes, leaf chlorophyll (Chl), and active Fe content decreased, whereas activities of H⁺-ATPase, ferric-chelate reductase (FCR), nitrate reductase, and nitric oxide synthase and NO production increased in Fe deficient plants, consequently an Fe chlorosis symptom appeared obviously. In contrast, these symptoms disappeared gradually after two weeks with NO and/or Fe supply, which caused an increases in leaf Chl and active Fe content, especially following by co-treatment with NO and Fe to values found in Fe sufficient plants. Increased activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and decreased accumulation of reactive oxygen species (H₂O₂, O ₂ ^?? ) and malondialdehyde enhanced the ability of resistance to oxidative stress. Supplied NO alone had the obvious effect on increased NO production and on activity of H⁺-ATPase and FCR, whereas root length and root/shoot ratio were most effectively increased by Fe supplied alone. Co-treatment with NO and Fe did the best effects on recovery peanut chlorosis symptoms by significantly increased Chl and available Fe content and adjusted distribution of Fe and other mineral elements (Ca, Mg, and Zn) in both leaves and roots.     

Activated oxygen and antioxidant defences in iron-deficient pea plants

Iron (Fe) deficiency in pea leaves caused a large decrease (44–62&) in chlorophyll a, chlorophyll b and carotenoids, and smaller decreases in soluble protein (18&) and net photosynthesis (28&). Catalase, non-specific peroxidase and ascorbate peroxidase activities declined by 51& in young Fe-deficient leaves, whereas monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase activities remained unaffected. Ascorbate peroxidase activity was highly correlated (r²= 0. 99, P < 0. 001) with the Fe content of leaves, which allows its use as an indicator of the Fe nutritional status of the plant. Fe deficiency resulted in an increase of CuZn-superoxide dismutase but not of Mn-superoxide dismutase. The content of ascorbate decreased by only 24& and those of reduced and oxidized glutathione and vitamin E did not vary. The low-molecular-mass fraction of Fe-sufficient leaves contained 30–65 μg (g dry weight)^?1 Mn. This concentration was 15–60 times greater than that of Fe and Cu in the same fraction, and was further enhanced (1. 5- to 2. 5-fold) by Fe deficiency without causing Mn toxicity. The concentration of catalytic Fe, that is, of Fe active for free radical generation, was virtually zero and that of catalytic Cu did not change with severe Fe deficiency. Because catalytic metals mediate lipid and protein oxidation in vivo, the above findings would explain why oxidatively damaged lipids and proteins do not accumulate in Fe-deficient leaves.     

Low CO(2) Prevents Nitrate Reduction in Leaves

The correlation between CO₂ assimilation and nitrate reduction in detached spinach (Spinacia oleracea L.) leaves was examined by measuring light-dependent changes in leaf nitrate levels in response to mild water stress and to artificially imposed CO₂ deficiency. The level of extractable nitrate reductase (NR) activity was also measured. The results are: (a) In the light, detached turgid spinach leaves reduced nitrate stored in the vacuoles of mesophyll cells at rates between 3 and 10 micromoles per milligram of chlorophyll per hour. Nitrate fed through the petiole was reduced at similar rates as storage nitrate. Nitrate reduction was accompanied by malate accumulation. (b) Under mild water stress which caused stomatal closure, nitrate reduction was prevented. The inhibition of nitrate reduction observed in water stressed leaves was reversed by external CO₂ concentrations (10-15%) high enough to overcome stomatal resistance. (c) Nitrate reduction was also inhibited when turgid leaves were kept in CO₂-free air or at the CO₂-compensation point or in nitrogen. (d) When leaves were illuminated in CO₂-free air, activity of NR decreased rapidly. It increased again, when CO₂ was added back to the system. The half-time for a 50% change in activity was about 30 min. It thus appears that there is a rapid inactivation/activation mechanism of NR in leaves which couples nitrate reductase to net photosynthesis.     

Effects of Exogenous Salicylic Acid on Alleviating Chlorosis Induced by Iron Deficiency in Peanut Seedlings (Arachis hypogaea L.)

The effects of salicylic acid (SA) on alleviating chlorosis induced by iron (Fe) deficiency in peanut seedlings (Arachis hypogaea L.) were studied by investigating the symptoms, plant growth, chlorophyll concentrations, soluble Fe concentration, Fe distribution in subcellular, and antioxidant enzymes. Fe deficiency caused serious chlorosis and inhibited growth of peanut seedlings, and dramatically decreased the soluble Fe concentration and chlorophyll concentration. Furthermore, ion balance was disturbed. The addition of 50, 100, and 250 μM SA significantly increased the absorption of Fe from the cell wall to cell organelles and the soluble fraction, enhanced the Fe concentration in cell organelles, Fe activation and chlorophyll concentrations in leaves, ameliorated the inhibition of Ca, Mg, and Zn absorption induced by Fe deficiency, alleviated the chlorosis induced by Fe deficiency and promoted plant growth. The accumulation of reactive oxygen species (ROS) is dramatically increased in peanut seedlings exposed to Fe deficiency, and resulted in lipid peroxidation, which was indicated by accumulation of malondialdehyde (MDA). The application of 50, 100, and 250 μM SA significantly decreased the level of ROS and MDA concentrations, and significantly increased the activities of superoxide dismutase, peroxidase, and catalase in peanut seedlings exposed to Fe deficiency. The addition of 100 μM SA had the best effect on alleviating chlorosis induced by Fe deficiency, whereas the addition of 500 μM SA had no significant effect under Fe deficiency.     

Activity of ascorbate-dependent H2O2-scavenging enzymes and leaf chlorosis are enhanced in magnesium- and potassium-deficient leaves, but not in phosphorus-deficient leaves

The effect of phosphorus (P), potassium (K), and magnesium (Mg)deficiency on the development of leaf symptoms (chlorosis andnecrosis) and activities of ascorbate-dependent H₂O₂ scavengingenzymes (ascorbate peroxidase, monodehydroascorbate reductase,dehydroascorbate reductase, and glutathione reductase) was studiedin bean (Phaseolus vulgans) plants over a 12 d period of growthin nutrient solution. With increasing plant age Mg- and K-deficientleaves developed severe interveinal chlorosis and, accordingly,chlorophyll concentrations were reduced. However, in P-deficientleaves neither chlorosis nor necrosis appeared; the leaves remaineddark green and even at an advanced stage of P deficiency, chlorophyllconcentrations were still higher than those of control plants.In K- and, particularly, Mg-deficient leaves with an increasein severity of leaf chlorosis, activity of ascorbate-dependentH₂O₂- scavenging enzymes was progressively increased. In contrast,in P-deficient leaves, as in leaves of the control plants, activityof H₂O₂-scavenging enzymes remained at a low level over the12 d period. Accordingly, compared with P-deficient and controlplants, Mg- and K-deficient leaves with elevated anti-oxidativepotential showed much higher resistance to chlorophyll destructionby the herbicide paraquat. Elevated levels of H₂O₂-scavengingenging enzymes in Mg- and K-deficient leaves indicate a higherproduction of H₂O₂ and related toxic O₂ species. It Is suggestedthat in Mg- and K-deficient leaves, utilization of photoreductantsin CO₂ fixation is restricted because of impaired export andthus accumulation of photosynthates. This disturbance mightlead to enhanced photoreduction of molecular O₂ to toxic O₂species causing chlorophyll destruction (chlorosis), a processwhich is not important in P-deficient leaves where export ofsucrose is not affected. Key words: Bean, hydrogen peroxide detoxification, leaf chlorosis, magnesium nutrition, oxygen activation, phosphorus nutrition, potassium nutrition     

Adaptations of Photosynthetic Electron Transport,Carbon Assimilation,and Carbon Partitioning in Transgenic Nicotiana plumbaginifolia Plants to Changes in Nitrate Reductase Activity

Transgenic Nicotiana plumbaginifolia plants that express either a 5-fold increase or a 20-fold decrease in nitrate reductase (NR) activity were used to study the relationships between carbon and nitrogen metabolism in leaves. Under saturating irradiance the maximum rate of photosynthesis, per unit surface area, was decreased in the low NR expressors but was relatively unchanged in the high NR expressors compared with the wild-type controls. However, when photosynthesis was expressed on a chlorophyll (Chl) basis the low NR plants had comparable or even higher values than the wild-type plants. Surprisingly, the high NR expressors showed very similar rates of photosynthesis and respiration to the wild-type plants and contained identical amounts of leaf Chl, carbohydrate, and protein. These plants were provided with a saturating supply of nitrate plus a basal level of ammonium during all phases of growth. Under these conditions overexpression of NR had little impact on leaf metabolism and did not stimulate growth or biomass production. Large differences in photochemical quenching and nonphotochemical quenching components of Chl a fluorescence, as well as the ratio of variable to maximum fluorescence, (FV/FM), were apparent in the low NR expressors in comparison with the wild-type controls. Light intensity-dependent increases in nonphotochemical quenching and decreases in FV/FM were greatest in the low NR expressors, whereas photochemical quenching decreased uniformly with increasing irradiance in all plant types. Nonphotochemical quenching was increased at all except the lowest irradiances in the low NR expressors, allowing photosystem II to remain oxidized on its acceptor side. The relative contributions of photochemical and nonphotochemical quenching of Chl a fluorescence with changing irradiance were virtually identical in the high NR expressors and the wild-type controls. Zeaxanthin was present in all leaves at high irradiances; however, at high irradiance leaves from the low NR expressors contained considerably more zeaxanthin and less violaxanthin than wild-type controls or high NR expressors. The leaves of the low NR expressors contained less Chl, protein, and amino acids than controls but retained more carbohydrate (starch and sucrose) than the wild type or high NR expressors. Sucrose phosphate synthase activities were remarkably similar in all plant types regardless of the NR activity. In contrast phosphoenolpyruvate carboxylase activities were increased on a Chl or protein basis in the low NR expressors compared with the wild-type controls or high NR expressors. We conclude that large decreases in NR have profound repercussions for photosynthesis and carbon partitioning within the leaf but that increases in NR have negligible effects.     

Foliar fertilization to control iron chlorosis in pear (Pyrus communis L.) trees

The effectiveness of foliar fertilization to re-green chlorotic leaves in iron-deficient pear trees has been studied. Trials were made to assess the influence of (i) the level of Fe deficiency, (ii) the leaf surface treated (adaxial or abaxial), and (iii) two different surfactants, L-77 and Mistol. Treatments were ferrous sulphate alone, ascorbic, citric and sulphuric acids, applied either alone or in combination with ferrous sulphate, Fe-DTPA and water as a control. Solutions were applied with a brush and leaves were treated twice each year. None of the treatments caused a full recovery from Fe deficiency chlorosis. Treatments containing Fe caused the largest re-greening effects, and FeSO₄ had a similar re-greening effect to Fe(III)-DTPA. Increases in leaf Chl were more pronounced with abaxial leaf surface applications and in severely deficient leaves. Using Fe(III)-DTPA in foliar sprays does not seem to be justified, since their effects are not better than those of FeSO₄. The joint use of Fe(III)-DTPA and L-77 and that of FeSO₄ and citric acid do not seem to be suitable. With a single foliar application, FeSO₄ combined with acids gave slightly better results than FeSO₄ alone. Acidic solution applications without Fe may be effective in alleviating chlorosis in some cases, especially in the case of citric acid. In the current state of knowledge, foliar fertilization cannot offer yet a good alternative for full control of Fe chlorosis, although its low environmental impact and cost make this technique a good complementary measure to soil Fe-chelate applications and other chlorosis alleviation management techniques. Abbreviations: Chl – chlorophyll; EDDCHA – ethylenediamine di(5-carboxy-2-hydroxyphenylacetic) acid; EDDHA – ethylenediamine di(o-hydroxyphenylacetic) acid; EDDHMA – ethylenediamine di(o-hydroxy-p-methylphenylacetic) acid; EDDHSA – ethylenediamine di(2-hydroxy-5-sulfophenylacetic) acid     

Nitrate reductase activity and chlorophyll content in sun leaves of subtropical Australian closed-forest (rainforest) and open-forest communities

Summary A study of the sun leaves of two closed-forest (rainforest) and eight open-forest communities in subtropical southeast Queensland, Australia, showed that a large number of pioneer woody species in closed-forests had high levels of nitrate reductase (EC 1.6.6.1), whereas only a few herbaceous species in the open-forests showed high levels. There was a continuously declining gradient in nitrate reductase activity from pioneer to mature-forest species in all communities, associated with a decrease in Leaf Specific Area. The level of nitrate reductase activity was lower in certain plant families (including sclerophyllous monocotyledons, small-leaved composites and legumes), but still showed the same general relationship with Leaf Specific Area. The decrease in Leaf Specific Area is associated with an increase in both the dry weight: fresh weight ratio and the chlorophyll a: chlorophyll b ratio of the leaves. Three groups of plants can be recognised by nitrate reductase activity plotted against water content (% fresh weight) of their leaves-(1) pioneer, (2) mature-forest and (3) semi-sclerophyllous species. As the proportion of cytoplasm to structural tissue (indicated by water content) in leaves increases, there is a continuous increase in (a) nitrate reductase activity (b) total chlorophyll (per unit dry weight) (c) the proportion of chlorophyll b to chlorophyll a and (b) chloroplastic isoform of glutamine synthetase. These attributes are associated with high nitrogen content in the leaves and high photosynthetic potentials, resulting in rapid growth rates of pioneer species.     

Cadmium and zinc induced chlorosis in Indian mustard [<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czern] involves preferential loss of chlorophyll <Emphasis Type="Italic">b</Emphasis>

Plants of Indian mustard (Brassica juncea) were treated with either 50 μM Cd, 250 μM Zn, or 25 μM Cd+125 μM Zn and the progression of chlorosis in the mature leaves monitored. As relative chlorophyll (Chl) contents in the mature leaves decreased to 75, 50, and 25 % relative to controls, both mature and young leaves were harvested and the Chl pools extracted. The metal treatments caused a greater loss of Chl b than Chl a. As mature leaves underwent progressive chlorosis, the young leaves displayed a characteristic over-greening, due largely to increased content of Chl b. However, as the young leaves began to experience chlorosis, a greater loss of Chl b was also observed. Thus during metal induced chlorosis, there is a preferential turnover of the Chl b pool in mature and young leaves.     

Effects of iron chlorosis and iron resupply on leaf xylem architecture, water relations, gas exchange and stomatal performance of field-grown peach (Prunus persica)

There is increasing evidence suggesting that iron (Fe) deficiency induces not only leaf chlorosis and a decline of photosynthesis, but also structural changes in leaf morphology, which might affect the functionality of leaves. In this study, we investigated the effects of Fe deficiency on the water relations of peach ( Prunus persica (L.) Batsch.) leaves and the responses of previously chlorotic leaves to Fe resupply via the root or the leaf. Iron deficiency induced a decline of maximum potential photosystem II (PSII) efficiency (F _V/F _M), of rates of net photosynthesis and transpiration and of water use efficiency. Iron chlorosis was associated with a reduction of leaf xylem vessel size and of leaf hydraulic conductance. In the course of the day, water potentials in chlorotic leaves remained higher (less negative) than in green leaves. In chlorotic leaves, normal stomatal functioning was disturbed, as evidenced by the lack of opening upon withdrawal of external CO₂ and stomatal closure after sudden illumination of previously darkened leaves. We conclude that the Fe deficiency induced limitations of xylem conductivity elicited a water saving strategy, which poses an additional challenge to plant growth on high pH, calcareous soils. Fertilisation with Fe improved photosynthetic performance but the proper xylem structure and water relations of leaves were not fully restored, indicating that Fe must be available at the first stages of leaf growth and development.     

氮素形态和铁营养对玉米苗期生长及体内铁分布的影响

以玉米(Zea mays)品种‘豫玉-22’为材料,采用营养液培养方法,研究了低铁和正常供铁条件下供应不同形态氮素对玉米苗期生长及体内铁分布的影响。结果表明:(1)与低铁介质相比,常铁介质增加了各氮素处理玉米幼苗的株高、地上部干重、全株干重,降低了根冠比,其中硝态氮处理表现得尤其突出;与供应硝态氮(NO3--N)相比,增施铵态氮(1/2 NO3--N 1/2 NH4 -N,NH4 -N)能明显促进低铁介质中玉米生长,但在常铁介质下作用不明显。(2)相比于低铁介质,正常供铁显著提高了相应处理玉米新叶叶绿素含量及净光合速率;2种供铁介质中,NH4 -N处理的新叶叶绿素含量以及净光合速率均高于其它氮素处理。(3)相比于低铁介质,正常供铁处理总体上增加了玉米各部分活性铁含量和全铁含量,对NO3--N处理的新叶活性铁含量增加尤其明显;2种供铁介质中,NH4 -N均有利于提高新叶活性铁含量和植株地上部全铁含量。(4)玉米新叶活性铁含量不仅与其叶绿素含量显著正相关(r=0.979**),也与叶片净光合速率显著正相关(r=0.950**)。研究发现,供铁状况显著影响玉米新叶的叶绿素含量及其净光合速率且与供氮形态存在互作;供应铵态氮有利于提高缺铁条件下玉米新叶活性铁含量,增强玉米植株的光合能力,进而促进其正常生长。     

Manganese Toxicity in Sugarcane Plantlets Grown on Acidic Soils of Southern China

Ratoon sugarcane plantlets in southern China have suffered a serious chlorosis problem in recent years. To reveal the causes of chlorosis, plant nutrition in chlorotic sugarcane plantlets and the role of manganese (Mn) in this condition were investigated. The study results showed that the pH of soils growing chlorotic plantlets ranged from 3.74 to 4.84. The symptoms of chlorosis were similar to those of iron (Fe) deficiency while the chlorotic and non-chlorotic plantlets contained similar amount of Fe. Chlorotic plantlets had 6.4-times more Mn in their leaf tissues compared to the control plants. There was a significantly positive correlation between Mn concentration in the leaves and the exchangeable Mn concentration in the soils. Moreover, leaf Mn concentration was related to both seasonal changes in leaf chlorophyll concentration and to the occurrence of chlorosis. Basal stalks of mature sugarcanes contained up to 564.36 mg·kg^-1 DW Mn. Excess Mn in the parent stalks resulted in a depress of chlorophyll concentration in the leaves of sugarcanes as indicated by lower chlorophyll concentration in the leaves of plantlets emerged from basal stalks. Ratoon sugarcane plantlets were susceptible to chlorosis due to high Mn accumulation in their leaves (456.90–1626.95 mg·kg^-1 DW), while in planted canes chlorosis did not occur because of low Mn accumulation (94.64–313.41mg·kg^-1 DW). On the other hand, active Fe content in chlorotic plantlets (3.39 mg kg^-1 FW) was only equivalent to 28.2% of the concentration found in the control. These results indicate that chlorosis in ratoon sugarcane plantlets results from excessive Mn accumulated in parent stalks of planted cane sugarcanes grown on excessive Mn acidic soils, while active Fe deficiency in plantlets may play a secondary role in the chlorosis.     

驳枝对早花烟草成熟期间叶中叶绿素含量、硝酸还原酶和淀粉酶活性的影响

对早花烟草驳枝后,其成熟期间中部和上部叶中叶绿素（Ch1）含量和硝酸还原酶（NR）活性下降,下部叶则增高,成熟后期的上部叶中淀粉酶（AM）活性明显增强。经驳枝的烟草,中、上部叶烘烤后叶中淀粉、氮和烟碱含量下降,下部叶中的淀粉含量无明显变化。