Relationships among iron deficit-induced potato callus growth inhibition,Fe distribution,chlorosis, and oxidative stress amplified by reduced antioxidative enzyme activities

Callus cultures were used to investigate and delineate responses of potato to iron (Fe) deficiency conditions over different culture durations. The morphological responses included chlorotic symptoms, reduced fresh weight and area of callus growth on Fe-deficient medium compared to calli grown under Fe sufficient conditions. Biochemically, potato calli under Fe deficit exhibited decreases in chlorophyll and carotenoid contents, reduction in activities of antioxidant enzymes (peroxidase, catalase and ascorbate peroxidase), as well as an increase in ferric chelate reductase (FCR) activity, lipid peroxidation, phenolic production and hydrogen peroxide (H₂O₂) level. Perls staining revealed sparse Fe distribution in Fe-deficient callus cells whereas Fe was widely distributed and intensely stained among numerous actively dividing cells in Fe-sufficient calli. These responses of calli to Fe deficiency were more pronounced with prolonged exposure to such stress leading to severe chlorosis and/or death of cells in chlorosis-susceptible calli but potential chlorosis-tolerant callus cells maintained their greenness and viability. Over a prolonged period in culture, significantly positive correlations were found among callus fresh weight, chlorophyll and carotenoid contents, antioxidant enzyme activities and lipid peroxidation as Fe supplies to the medium was increased. FCR activity was strongly correlated in a negative manner with Fe deficiency, chlorophyll content and peroxidase activity. The responses of calli to Fe supply can serve as reliable indicators for detecting chlorosis tolerance and/or nutrient deficiency stress.     

Ethylene-Induced Chlorosis in the Pathogenesis of Bipolaris sorokiniana Leaf Spot of Poa pratensis

Endogenous ethylene of Poa pratensis leaves infected by Bipolaris sorokiniana was evaluated as a factor in leaf chlorosis during pathogenesis. Detectable increases in endogenous ethylene of leaves of intact plants under normal ambient pressure occurred 12 hours after inoculation and was maximum at 48 hours; from 48 to 96 hours the ethylene progressively decreased. Necrotic lesions surrounded by chlorotic halos occurred on infected leaves between 24 and 48 hours. Midvein chlorosis interconnecting individual lesions and complete chlorosis of all tissues not directly affected by the lesions occurred between 72 and 96 hours, after maximum production of ethylene at 48 hours. The chlorophyll loss in infected leaves by 96 hours was 44% compared with controls.

Subjecting inoculated leaves of intact plants to a controlled atmospheric-environmental system with an atmospheric pressure of 233 millibars and O₂ and CO₂ partial pressures adjusted to approximately that of normal ambient pressure during infection and disease development prevented most midvein chlorosis and complete chlorosis, but did not prevent necrotic lesion or chlorotic halo development. Under the hypobaric conditions, chlorophyll loss during disease development was reduced to 22% compared with controls at 96 hours. The observations suggest that ethylene may function late in pathogenesis of this host-pathogen interaction and is responsible for much of the chlorophyll loss after its maximum production at 48 hours.

     

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.     

EFFECTS OF IRON DEFICIENCY ON ISOCHRYSIS GALBANA (CHRYSOPHYCEAE) AND PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

Cultures of Isochrysis galbana Parks and Phaeodactylum tricornutum Bohlin were grown in iron-limited chemostats. With increasing iron deficiency, photosynthetic rate per cell and assimilation number decreased. The pattern of photosynthesis was also altered; in Fe deficient cells the proportion of ¹⁴C fixed in glycine and serine decreased with an accompanying increase into alanine after 3 min assimilation. Although there was no significant effect of Fe deficiency on the proportion of ¹⁴C incorporated into total amino acids and amides, the percentage of total ¹⁴C fixed in protein increased with increasing Fe deficiency. Cellular levels of chlorophyll a, carotenoids, cytochromes and protein also decreased with increasing Fe deficiency. However, the reduction in chlorophyll a/cell was not as great as that of cytochrorne f₁ and Fe deficient cells therefore showed a marked increase in chlorophyll a:cytochrorne f₁ ratio.     

缺铁和矫治缺铁对梨树叶片结构的影响

通过对不同缺铁黄化程度的酥梨叶片进行解剖结构分析和矫治缺铁后叶片解剖结构的恢复情况的研究,结果表明,缺铁黄化使叶片厚度,叶肉厚度,栅栏组织厚度,栅栏组织／海绵组织的比值均明显下降;栅栏组织细胞排列疏松,细胞变短甚至断裂成块状,叶绿体数量明显减少甚至无,并出现解体细胞;栅栏组织与海绵组织界限模糊,海绵组织细胞排列变密;维管束的导管口径变小,维管束鞘和韧皮部的细胞番红染色加重。进行缺铁黄化矫治后,叶片结构恢复正常。这些结构的变化,可作为梨树缺铁诊断和矫治的指标。     

A physiological study ofTeucrium scorodonia ecotypes which differ in their susceptibility to lime-induced chlorosis and iron-deficiency chlorosis

Summary Edaphic ecotypes ofTeucrium scorodonia have been shown which differ in their susceptibility to lime-induced chlorosis. Plants especially resistant or susceptible to lime-induced chlorosis were found to be similarly resistant or susceptible to iron-deficiency chlorosis. Differences were found in the chlorophyll-iron and dry weight-chlorophyll relationships of the leaves of green and chloroticTeucrium plants, similar effects being produced by growth on a calcareous soil, in iron-deficient culture or by bicarbonate treatment. Chlorotic leaves had less chlorophyll per unit iron but had a greater dry weight per unit chlorophyll than green material. Chlorotic leaves were found to be reduced in both leaf area and dry weight compared with green ones, the reduction in dry weight being the greatest. Common root abnormalities were noted in chlorotic material induced by the above three methods.Evidence was produced which suggested that the difference between chlorosis-resistant and susceptible plants lay in qualitative differences in their iron transport compounds produced within the rootstock. Differential iron uptake was not suggested as a cause of the differences in behaviour. There was, however, evidence of a key role of the root iron pool in population differences in chlorosis susceptibility.Bicarbonate was found to suppress first iron uptake and then iron translocation. A possible causal role of the bicarbonate ion in lime-induced chlorosis was suggested through these effects and through its possible effect on the production of iron-transport compounds.     

Growth at low temperature causes nitrogen limitation in the cyanobacterium Synechococcus sp. PCC 7002

The coloration of cells of the cyanobacterium Synechococcus sp. PCC 7002 changed from normal blue-green to yellow-green when cells were grown at 15° C in a medium containing nitrate as the sole nitrogen source. This change of coloration was similar to a general response to nutrient deprivation (chlorosis). For the chlorotic cells at 15° C, the total amounts of phycobiliproteins and chlorophyll a decreased, high levels of glycogen accumulated, and growth was arithmetic rather than exponential. These changes in composition and growth occurred in cells grown at low (50 μE m^–2 s^–1) as well as high (250 μE m^–2 s^–1) light intensity. After a temperature shift-up to 38° C, chlorotic cells rapidly regained their normal blue-green coloration and normal exponential growth rate within 7 h. When cells were grown at 15° C in a medium containing urea as the reduced nitrogen source, cells grew exponentially and the symptoms of chlorosis were not observed. The decrease in photosynthetic oxygen evolution activity at low temperature was much smaller than the decrease in growth rate for cells grown on nitrate as the nitrogen source. These studies demonstrate that low-temperature-induced chlorosis of Synechococcus sp. PCC 7002 is caused by nitrogen limitation and is not the result of limited photosynthetic activity or photodamage to the photosynthetic apparatus, and that nitrogen assimilation is an important aspect of the low-temperature physiology of cyanobacteria. Received: 24 April 1997 / Accepted: 5 August 1997     

Differential tolerance to iron deficiency of chickpea varieties and Fe resupply effects

The consequences of direct iron deficiency and iron resupply were evaluated during development stages of two Tunisian chickpea varieties (INRAT88 and Chetoui) cultivated in continuously aerated solution with or without 20 muM Fe. The chlorosis score was estimated during culture. Growth parameters, chlorophyll concentration, acidification capacity and Fe concentration were measured every three days during the 21-day treatment. After three weeks of treatment, the chlorosis index was 3-fold higher in Chetoui than in INRAT88, and a considerable decrease of chlorophyll concentration was observed in Chetoui plants since the 6th day of -Fe deprivation. Iron deficiency significantly inhibited whole-plant biomass deposition in both varieties. However, the growth reduction appeared earlier, and was more pronounced in Chetoui than in INRAT88. The whole-plant Fe content decreased dramatically under deficient conditions, and we note an Fe enrichment in shoots at the expense of roots. The sensitivity of Chetoui as compared to INRAT88 was confirmed by the behaviour of resupplied (-Fe/+Fe) plants. In fact, the addition of iron to deficient plants had no significant effect in Chetoui, whereas it led to a total recovery in INRAT88. The capacity of INRAT88 to maintain plant growth and to preserve adequate chlorophyll synthesis under limited iron conditions is related to its better Fe-use efficiency, in addition to its capacity to rapidly recover from this stress.     

Photosynthetic carbon fixation in iron-chlorotic and recovered green sugarcane leaves

Summary Sugarcane var. Co 740 is grown in various parts of Maharashtra (India) and is susceptible to chlorosis due to physiological non-utilization of iron. The physiological disorder is seen over a large area and it results in poor yield. Low sucrose yield can be recovered by foliar sprays of ferrous sulphate. The nonchlorotic and chlorotic leaves were used for the photosynthetic studies. The leaves after ferrous sulphate treatment show an increase in total chlorophyll contents and at the same time show an improved chlorophylla to chlorophyllb ratio which is affected in the chlorotic ones. The recovered green leaves have higher uptake of nitrogen, phosphorus, potassium and iron.¹⁴CO₂ fixation studies for short- and long-term experiments reveal that recovered green leaves can synthesize malate more efficiently and also utilize it for sucrose synthesis more rapidly than in the chlorotic ones. On the contrary more amino acids, reducing sugars and sugar phosphates are synthesized in the chlorotic leaves. There is also an accumulation of citrate, glutamate, and tartrate in the chlorotic leaves. Our results indicate that sucrose synthesis is disturbed in the chlorotic leaves and can be corected byfolia: sprays of ferrous sulphate.     

Effects of the Environment on the Symptom Pattern of Nickel Toxicity in the Oat Plant

Under conditions of nickel toxicity in oats (Avena byzantina),a predisposing condition for the development of chlorosis isinduced in areas of the leaf before emergence from the coleoptileor the enclosing leaf sheath. These areas give rise to chloroticbands which develop on the emerged leaf a little over 24 h afteremergence of the tissue. Alternating light and dark are essentialfor the development of chlorotic bands. The evidence indicatesthat the potentially green tissue is that which is developingunder the coleoptile during the day and emerges later in theday or early in the night, while the potentially chlorotic tissueis that which develops under the coleoptile during the nightand emerges from the top of the coleoptile later in the nightor during the following daylight hours before midday. Plants containing high levels of nickel contain higher levelsof protochlorophyll and lower levels of of chlorophyll thancontrol plants. The visual symptom of nickel toxicity is influenced by the lengthof the light and dark periods. The nature of these effects isdiscussed. Avena byzantina, oat, nickel toxicity symptoms, chlorosis     

The effect of soil moisture on the tolerance of Lupinus pilosus genotypes to a calcareous soil

Commercial narrow-leafed lupins (Lupinus angustifolius L.) grown on calcareous soils commonly display chlorotic symptoms resembling Fe deficiency. The severity of chlorosis increases with concurrent increases in soil moisture content. Our research has indicated that the rough-seeded lupin species, Lupinus pilosus Murr., has a range of adaptation to calcareous soils, from tolerant to intolerant. A pot experiment was conducted comparing a tolerant, a moderately tolerant and a moderately intolerant genotype of L. pilosus. Plants were grown for 35 days in a calcareous soil (50% CaCO₃) at three moisture contents (80%, 100% and 120% of field capacity); the growth was compared with that on a fertile black cracking clay control soil at 70% of field capacity. Visual chlorosis score, chlorophyll meter readings, number of leaves and shoot dry weights were recorded at 14, 21, 28 and 35 days after sowing. Concentrations of chlorophyll, active Fe and nutrients in the youngest fully expanded leaves were also measured. Results showed that increased soil moisture increased the severity of chlorotic symptoms (increased chlorosis score) in all genotypes. The tolerant genotype showed significantly less symptoms than other genotypes at all moisture contents. All genotypes were able to recover from chlorosis symptoms at 80% moisture in the calcareous soil. Chlorosis score negatively correlated with chlorophyll meter readings, chlorophyll concentration and foliar active and total Fe, and Mn concentrations. Visual chlorosis score appeared to be a cost effective, accurate and efficient method enabling classification of the tolerance of genotypes. The chlorotic symptoms were likely to be due to HCO₃ ^- induced nutrient deficiencies or a direct effect of HCO₃ ^- on chlorophyll synthesis. This study indicates that the most probable mechanism of tolerance is related to an ability to prevent uptake of HCO₃ ^- or efficiently sequester it once inside the root which prevents increases in internal pH and transport to the shoots.     

Some Effects of Sodium on Nitrate Assimilation and N(2) Fixation in Anabaena cylindrica

Anabaena cylindrica grown with nitrate required higher levels of sodium (0.4 meq/l NaCl) to prevent chlorosis than when grown without combined nitrogen (0.004 meq/l NaCl). Nitrite accumulated in sodium-deficient cultures containing nitrate. Amounts of nitrite similar to those found in deficient cultures when added to normal cultures resulted in a chlorosis of the cells. Thus loss of chlorophyll was caused by nitrite toxicity.     

Effect of Iron Deficiency Induced Changes on Photosynthetic Pigments,Ribulose-1,5-Bisphosphate Carboxylase,and Photosystem Activities in Field Grown Grapevine (Vitis Vinifera L. cv. Pinot Noir) Leaves

The effect of iron deficiency on photosynthetic pigments, ribulose-1,5-bisphosphate carboxylase (RuBPC), and photosystem activities were investigated in field grown grapevine (Vitis vinifera L. cv. Pinot noir) leaves. The contents of chlorophyll (Chl) (a+b) and carotenoids per unit fresh mass showed a progressive decrease upon increase in iron deficiency. Similar results were also observed in content of total soluble proteins and RuBPC activity. The marked loss of large (55 kDa) and small (15 kDa) subunits of RuBPC was also observed in severely chlorotic leaves. However, when various photosynthetic electron transport activities were analysed in isolated thylakoids, a major decrease in the rate of whole chain (H₂O methyl viologen) electron transport was observed in iron deficient leaves. Such reduction was mainly due to the loss of photosystem 2 (PS2) activity. The same results were obtained when F_v/F_m was evaluated by Chl fluorescence measurements in leaves. Smaller inhibition of photosystem 1 (PS1) activity was also observed in both mild and severely chlorotic leaves. The artificial electron donors, diphenyl carbazide and NH₂OH, markedly restored the loss of PS2 activity in severely chlorotic leaves. The marked loss of PS2 activity was evidently due to the loss of 33, 23, 28-25, and 17 kDa polypeptides in iron deficient leaves.     

LETHAL SYNTHESIS IN CYNODON DACTYLON GROWING IN SOUTHERN AFRICA

Badenhuizen , N. P. (U. Toronto, Ont., Can.), and E. N. Lawson . Lethal synthesis in Cynodon dactylon growing in southern Africa. Amer. Jour. Bot. 49 (2) : 158–167. Illus. 1962.—Both cultivated and wild forms of Cynodon dactylon are characterized in southern Africa by the random production of chlorotic shoots. Some properties of these shoots were typical of chlorotic shoots in general: increase in water and soluble nitrogen content, and inhibition of protein synthesis, chloroplast development and catalase activity. Others, such as sterility and enhanced respiratory activity, were more characteristic of plants treated with streptomycin or amitrol. Allantoin could be demonstrated in the chlorotic shoots and was found to produce chlorosis after being applied to Cynodon plants. Additional characteristics included decreased total and “active” iron content, accompanied by an increase in citric acid. So far, the weight of evidence, including the ultrastructure of the plastids, is not in favor of a mutation, a virus, a fungus, or iron deficiency as the ultimate cause of chlorosis in Cynodon. There appears to be a tendency towards the production of allantoin which may be triggered off more frequently under certain conditions of environment, until a concentration is reached when it irreversibly inhibits stages in the development of the chloroplasts.     

Development of plants from leaf discs of variegatedColeus and its relation to patterns of leaf chlorosis

Summary Leaf discs approximately 8 mm in diameter taken from green and from chlorotic areas of variegated leaves ofColeus were grown in light under sterile conditions in a mineral salt, sucrose, vitamin medium supplemented with auxin and cytokinin. Green shoots, which later formed roots, grew from both green and chlorotic discs in media containing suitable amounts of auxin and cytokinin. None developed in media supplemented with auxin alone or with cytokinin alone. Discs with young plants were transferred to soil. Plants that grew varied widely from those with no chlorosis to those with more chlorosis than the original variety from which the discs were taken. Plants grown from discs taken from green areas of leaves with chlorosis varied in patterns of chlorosis as much as those that grew from discs from chlorotic areas of leaves. This research was supported, in part, by The Conservation and Research Foundation.     

Mapping genetic loci for tolerance to lime-induced iron deficiency chlorosis in grapevine rootstocks (Vitis sp.)

Iron is essential to plants for chlorophyll formation as well as for the functioning of various iron-containing enzymes. Iron deficiency chlorosis is a wide-spread disorder of plants, in particular, of those growing on calcareous soils. Among the different ways to control iron deficiency problems for crops, plant material and especially rootstock breeding is a suitable and reliable method, especially for fruit trees and grapes. The aim of the experiment was to characterize the genetic basis of grapevine chlorosis tolerance under lime stress conditions. A segregating population of 138 F1 genotypes issued from an inter-specific cross between Vitis vinifera Cabernet Sauvignon (tolerant) × V. riparia Gloire de Montpellier (sensitive) was developed and phenotyped both as cuttings and as rootstock grafted with Cabernet Sauvignon scions in pots containing non-chlorosing and chlorosing soils. Tolerance was evaluated by chlorosis score, leaf chlorophyll content and growth parameters of the shoots and roots. The experiments were performed in 2001, 2003 and 2006. The plants analysed in 2006 were reassessed in 2007. The most significant findings of the trial were: (a) the soil properties strongly affect plant development, (b) there are differences in tolerance among segregating genotypes when grown as cuttings or as rootstocks on calcareous soil, (c) calcareous conditions induced chlorosis and revealed quantitative trait loci (QTLs) implicated in polygenic control of tolerance, (d) rootstock strongly contributes to lime-induced chlorosis response, and (e) a QTL with strong effect (from 10 to 25 % of the chlorotic symptom variance) was identified on chromosome 13. This QTL colocalized with a QTL for chlorophyll content (R ² = 22 %) and a major QTL for plant development that explains about 50 % of both aerial and root system biomass variation. These findings were supported by stable results among the different years of experiment. These results open new insights into the genetic control of chlorosis tolerance and could aid the development of iron chlorosis-tolerant rootstocks.     

THE RELATIONSHIP BETWEEN NICKEL-TOXICITY SYMPTOMS AND THE ABSORPTION OF IRON AND NICKEL

During a 70-day experimental period from germination to maturity, the iron content of oat plants that showed symptoms of nickel toxicity changed little, but the nickel content increased rapidly for about 30 days and then decreased slowly. Necrosis varied little with time, while chlorosis increased in severity for 40 days, then decreased until unfolding young leaves were no longer chlorotic. This change in chlorotic symptoms was correlated with the nickel-iron ratio in the plant.
Autoradiographs of leaves from plants supplied with radioactive iron showed that necrotic areas in the leaf matched areas in the autoradiograph having a very low content. Chlorotic areas were found to correspond with areas whose iron content was lower than that of healthy tissue. More iron was found in the veins than in the interveinal tissue, and its distribution was the same whether supplied as ferric citrate or in a chelated form.
The concentration of iron in mature leaves from oat plants growing in a nickel toxic soil was lowest in the necrotic areas of the leaf, suggesting a migration of nutrients out of this dying tissue.     

Occurrence of a high temperature sensitivity of chloroplast ribosome formation in several higher plants

A specific high temperature-induced deficiency of chloroplast ribosome formation, as indicated by the absence of chloroplast rRNA, has been observed in the leaves of light- or dark-grown seedlings of Avena sativa L., Hordeum vulgare L., and Triticum aestivum L. at certain temperatures between 28 and 34 C. While the growth of the leaves (size, morphology, total amino nitrogen content) was little affected by the elevated temperature, chlorophyll accumulation was strongly inhibited, amounting to only 2 to 20% of its content in 22 C-grown leaves which were used as a reference for normal development. The carotenoid contents were also lower but still reached at least 15 to 20% of the corresponding measurements at 22 C. Ribulose-1,5-bisphosphate carboxylase was absent at the higher temperature while NADP-glyceralde-hydephosphate dehydrogenase reached high activities. For the peroxisomal marker enzyme hydroxypyruvate reductase, 30 to 70% of the activity present in 22 C-grown leaves was found in extracts from high temperature-grown leaves. Fumarase reached 1.5- to 4-fold higher activities at the elevated growth temperature than at 22 C. Leaves of Pisum sativum L. were completely chlorotic and deficient of 70S ribosomes at 33 C but simultaneously suffered from a severe general inhibition of their growth. In Zea mays L., a formation of chlorotic leaves was not observed at elevated temperatures.