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1.
A method has been developed to consistently induce increases in root ferric chelate reductase activity in the fruit tree rootstock GF 677 (Prunus amygdalopersica) grown under iron (Fe) deficiency. Clonal GF 677 plants were grown hydroponically in a growth chamber with 0 or 90 μM Fe(III)‐EDTA. Root ferric chelate reductase activity was measured in vivo using BPDS. Plants grown without Fe developed visible symptoms of chlorosis and had lower root ferric chelate reductase activities than those grown with Fe. Root ferric chelate reductase activities were 0.1–1.9 and 0.6–5.3 nmol of Fe reduced per gram of fresh mass and minute, respectively, in Fe‐deficient and sufficient plants. However, when plants grown without Fe for several days were resupplied with 180 μM of Fe(III)‐EDTA, FC‐R activities increased within 1 day. The FC‐R values after Fe resupply were 20‐fold higher than those found in Fe‐deficient plants and 5‐fold higher than those found in the Fe‐sufficient controls. After three days of the Fe treatments the FC‐R activities had decreased again to the control values. The reduction of Fe was localized at the subapical root zone. In the conditions used we have found no decreases of the nutrient solution pH values, indicating that this type of response is not strong enough to be detected in peach tree rootstocks. Also, no major changes in root morphology have been found in response to Fe deficiency. This ferric chelate reductase induction protocol may be used in screening assays to select rootstock genotypes tolerant to Fe chlorosis.  相似文献   

2.
In soil, iron (Fe) solubility depends on complex interactions between Fe minerals and organic matter, but very little is known about plant availability of Fe present in Fe oxides associated with humic substances. For this purpose, this study investigates the effect of Fe mineral crystallinity in the presence of humic acids (HA) on Fe availability to plants. Four Fe–HA mineral coprecipitates were prepared, either in the presence or absence of oxygen, i.e., two goethite (G)‐HA samples containing large amounts of Fe as nanocrystalline goethite and ferrihydrite mixed phases, and two magnetite (M)‐HA samples containing crystalline magnetite. Bioavailability studies were conducted in hydroponic systems on cucumber plants (Cucumis sativus L.) grown under Fe deficient conditions and supplied with the Fe–HA coprecipitates containing goethite or magnetite. Results showed that plants grown in the presence of Fe–HA coprecipitates exhibited a complete recovery from Fe deficiency, albeit less efficiently than plants resupplied with Fe‐chelate fertilizer used as control (Fe‐diethylene triamine penta acetic acid, Fe‐DTPA). However, the supply with either G‐ or M–HA coprecipitates produced different effects on plants: G–HA‐treated plants showed a higher Fe content in leaves, while M–HA‐treated plants displayed a higher leaf biomass and SPAD (Soil–Plant Analysis Development) index recovery, as compared to Fe‐DTPA. The distribution of macronutrients in the leaves, as imaged by micro X‐ray fluorescence (µXRF) spectroscopy, was different in G–HA and M–HA‐treated plants. In particular, plants supplied with the poorly crystalline G–HA coprecipitate with a lower Fe/HA ratio showed features more similar to those of fully recovered plants (supplied with Fe‐DTPA). These results highlight the importance of mineral crystallinity of Fe–HA coprecipitates on Fe bioavailability and Fe uptake in hydroponic experiments. In addition, the present data demonstrate that cucumber plants can efficiently mobilize Fe, even from goethite and ferrihydrite mixed phases and magnetite, which are usually considered unavailable for plant nutrition.  相似文献   

3.
Limited data are available on the physiological responses of leaves from fruiting trees to magnesium (Mg) deficiency. Magnesium deficiency–induced effects on photosystem II (PSII) photochemistry in leaves of fruiting (Citrus reticulate cv. Ponkan) trees were assessed by the chlorophyll a fluorescence (OJIP) transient. Magnesium deficiency decreased leaf CO2 assimilation and carbohydrates, but had no effect on intercellular CO2 concentration. Activity of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) and concentrations of Chlorophyll (Chl) and carotenoids (Car) decreased to a lesser extent than CO2 assimilation. Chlorophyll a fluorescence transient from Mg‐deficient leaves had increased O step and decreased P step, accompanied by positive ΔL, ΔK, ΔJ, and ΔI bands. Magnesium deficiency decreased maximum quantum yield of primary photochemistry (Fv/Fm), quantum yield of electron transport from Q<$>_A^‐<$> to the photosystem I (PSI) end electron acceptors (φR0), maximum amplitude of IP phase and total performance index (PItot, abs), but increased deactiviation of oxygen‐evolving complex (OEC) and energy dissipation. Magnesium‐deficient leaves had higher or similar activities of antioxidant enzymes except for lower catalase (CAT) activity, higher or similar concentrations of antioxidant metabolites, and a higher ratio of Car : Chl. Magnesium‐deficiency did not affect concentration of malondialdehyde (MDA) and ratios of ascorbate (ASC) to ASC + dehydroascorbate (DHA) and reduced glutathione (GSH) to GSH + oxidized glutathione (GSSG). In conclusion, Mg deficiency–induced impairment of the whole photosynthetic electron transport chain may be the main factor contributing to decreased CO2 assimilation. Enhanced energy dissipation and antioxidant metabolism provide sufficient protection to Mg‐deficient leaves against photo‐oxidative damage.  相似文献   

4.
To determine the effect of boron (B) deficiency on biomass, reproductive yield, metabolism, and alterations in seed reserves of chickpea (Cicer arietinum L.) cv. ‘13.G‐256,’ plants were grown in refined sand until maturity at deficient (0.033 mg L?1) and adequate (0.33 mg L?1) B, supplied as boric acid (H3BO3). Boron‐deficient plants exhibited visible deficiency symptoms in addition to reduced number of pods and seeds, resulting in lowered biomass and economic yield. Boron deficiency lowered the concentration of B in leaves and seeds, photosynthetic pigments (leaves), Hill reaction activity, starch (in leaves and seeds), and proteins and protein N (in seeds), whereas phenols, sugars (in leaves and seeds), and nonprotein N (in seeds) were elevated. Specific activity of peroxidase (POX) increased in leaves and pod wall and decreased in seeds, while activity of acid phosphate and ribonuclease were stimulated in leaves, seeds, and pod wall in B‐deficient chickpea.  相似文献   

5.
The effect of prolonged sulfur (S) deficiency on photosynthesis and S‐containing compounds in leaves of rapeseed (Brassica napus L.) plants, grown in nutrient solution, was studied under greenhouse conditions. The rate of photosynthetic activity and stomatal conductance of water and CO2 in treated plants decreased significantly after 3 months of treatment. The total chlorophyll content decreased after one month of S deprivation, after which it remained constant. The total S. content and both the water‐soluble and non‐protein soluble S fractions in the leaves showed a marked decrease. Whereas, the total protein soluble S remained unaffected during the period of observation. In the treated plants, the content of two major S compounds, e.g., cysteine and glutathione, were as a result of deprivation, although in the control it showed a trend to increase. Sulfur deficiency also decreased appreciably the activity of ATP sulfurylase. After the three‐month period of S deprivation, this enzymatic activity was about four times lower than that in the control plants. The data reported in this paper suggested that plants grown under S deficiency were capable of adjusting their S metabolism to maintain a sufficient protein and glutathione synthesis by lowering their photosynthetic activity.  相似文献   

6.
《Journal of plant nutrition》2013,36(10):2205-2228
ABSTRACT

Chlorosis in crops grown on calcareous soil is mainly due to iron (Fe) deficiency and can be alleviated by leaf application of soluble Fe2+ or diluted acids. Whether chlorosis in indigenous plants forced to grow on a calcareous soil is also caused by Fe deficiency has, however, not been demonstrated. Veronica officinalis, a widespread calcifuge plant in Central and Northern Europe, was cultivated in two experiments on acid and calcareous soils. As phosphorus (P) deficiency is one of the major causes of the inability of many calcifuges to grow on calcareous soil we added phosphate to half of the soils. Leaves in pots with the unfertilized and the P-fertilized soil, respectively, were either sprayed with FeSO4 solution or left unsprayed. Total Fe, P, and manganese (Mn) in leaves and roots and N remaining in the soil after the experiment were determined. In a second experiment, no P was added. Leaves were either sprayed with FeSO4 or with H2SO4 of the same pH as the FeSO4 solution. Degree of chlorosis and Fe content in leaves were determined. Calcareous soil grown plants suffered from chlorosis, which was even more pronounced in the soils supplied with P. Newly produced leaves were green with Fe spray but leaves that were chlorotic before the onset of spraying did not totally recover. H2SO4 spray even increased chlorosis. This demonstrated that chlorosis was due to Fe deficiency. As total leaf Fe was similar on acid and calcareous soil, it was a physiological Fe deficiency, caused by leaf tissue immobilization in a form that was not metabolically “active”. Iron in the leaves was also extracted by 1,10-phenanthroline, an Fe chelator. In both experiments, significant differences between leaves from acid and calcareous soil were found in 1,10-phenanthroline extractable Fe but not in total leaf Fe, when calculated on a dry weight basis. Differences in 1,10-phenanthroline extractable Fe were more pronounced when calculated per unit dry weight than calculated per leaf area, whereas the opposite condition was valid for total leaf Fe.  相似文献   

7.
The photosynthetic pigment composition of chlorotic leaves of Citrus limon L. cv. Verna, grown in the field under iron deficiency conditions was determined. A Fe‐polyflavonoid was used as fertilizer to control iron chloro‐ sis. The photosynthetic pigment content and the chlorophyllase activity were determined at 20 day intervals during the deficiency recovery period and compared to untreated similar material. The corresponding differences among treated and untreated control material were analyzed. Iron application increased the levels of all pigments, but the extent of the increase depended on the pigment affected. The chlorophylls/carotenoids and ß‐carotene/xantophylls ratios were increased as chlorosis diminished. A multivariance analysis was performed with the data obtained which revealed that chlorophyll a and ß‐carotene had the highest correlation coefficient. The chlorophyllase activity did not show significant changes, but it was lower in the treated leaves than in the untreated control leaves during all the sampling cycle.  相似文献   

8.
Some plants respond to Fe‐deficiency stress by inducing Fe‐solubilizing reactions at or near the root surface. In their ability to solubilize Fe, dicotyledonous plants are more effective than monocotyledonous plants. In this study we determined how representative plants differ in their response when subjected to Fe‐deficiency stress in a calcareous soil and in nutrient solutions. Iron‐inefficient genotypes of tomato, soybean, oats, and corn all developed Fe chlorosis when grown in soil, whereas Fe‐efficient genotypes of these same species remained green. The same genotypes were grown in complete nutrient solutions and then transferred to nutrient solutions containing N (as NO3 ‐) and no Fe.

The T3238 FER tomato (Lycopersican esculentum Mill.) Fe‐efficient) was the only genotype that released significant amounts of H from the roots (the pH was lowered to 3.9) and concomitantly released reductants. Under similar conditions, Hawkeye soyhean [Glycine max (L.) Merr.] released reductants but the solution pH was not lowered. Both Fe‐inefficient and Fe‐efficient genotypes of oats (Avena sativa L.) and corn (Zea mays L.) released insufficient H or reductant from their roots to solubilize Fe; as a result, each of these genotypes developed Fe‐deficiency (chlorosis).

The marked differences observed among these genotypes illustrate the genetic variability inherent within many plant species. A given species or genotype may accordingly not be adapted to a particular soil. Conversely, a given species or genotype may be found (or developed) that is precisely suited for a particular soil. In this event, the need for soil amendments may be reduced or eliminated.  相似文献   

9.
《Journal of plant nutrition》2013,36(10-11):1985-1996
Abstract

A field experiment was carried out in a drip‐irrigated orchard of Clementine (Citrus clementina Ort. ex. Tan) grafted on Troyer citrange (C. sinensis × Poncirus trifoliata) rootstock located in the Valencian Citrus area (Spain). The trees received a single iron (Fe) EDDHA (ethylene diamine diorthohydroxyphenyl acetate) rate (3 g Fe tree?1) supplied in different application frequencies from April to September (8‐, 4‐, 2‐, or 1‐week intervals). Leaf chlorophyll (Chl) concentrations were estimated every month by using an SPAD‐502 meter. The foliar contents of Fe were also evaluated with time. Mineral composition of leaves, total Chl concentration, yield, and fruit quality were also evaluated at the end of the assay. SPAD readings, Chl, N, K, Mg, Fe, and Mn concentration in leaves increased as a result of Fe application. The concentration of Zn, however, significantly decreased in comparison to the control trees. Iron treatment increased yield and some of the fruit quality parameters, like total juice, sugar, and acid contents. Iron application frequency had not a consistent effect on the concentrations of macro and micronutrients in leaves, yield, and fruit quality. The highest values of SPAD readings and the leaf Chl content were obtained when Fe was applied at 4‐week intervals along the year. These results suggest that soil Fe‐EDDHA application with a moderate frequency could be recommended to the Citrus farmers in the area for a more rational Fe application along the growth cycle in Citrus orchards.  相似文献   

10.
A typical symptom of iron (Fe) deficiency in plants is yellowing or chlorosis of leaves. Heavy metal toxicity, including that of zinc (Zn), is often also expressed by chlorosis and may be called Fe chlorosis. Iron deficiency and Zn toxicity were evaluated in soybean (Glycine max [L.] Merr.) at two levels each of Zn (0.8 and 40 μM), Fe (0 and 20 μM), and sulfur (S) (0.02 and 20 mM). Reduction in dry matter yield and leaf chlorosis were observed in plants grown under the high level of Zn (toxic level), as well as in the absence of Fe. Zinc toxicity, lack of Fe, and the combination of these conditions reduced dry matter yield to the same extent when compared to the yield of the control plants. The symptoms of Zn toxicity were chlorosis in the trifoliate leaves and a lack of change in the orientation of unifoliate leaves when exposed to light. The main symptoms of Fe deficiency were chlorosis in the whole shoot and brown spots and flaccid areas in the leaves. The latter symptom did not appear in plants grown with Fe but under Zn toxicity. It seems that Fe deficiency is a major factor impairing the growth of plants exposed to high levels of Zn. Under Zn toxicity, Fe and Zn translocation from roots to shoots increased as the S supply to the plants was increased.  相似文献   

11.
Young maize plants, grown hydroponically, were supplied with different amounts (7.5, 0.75, 0.15, 0.075, and 0 mg Fe/L) of iron (Fe). At 14, 21, and 28 days, parameters characterizing growth and photosynthesis were determined. Iron‐deficiency resulted in significant changes in biomass accumulation and distribution between vegetative organs as well as changes in the content of chlorophyll a, chlorophyll b, and the carotenoids. The photosynthetic rate per leaf area was decreased. Part of 14C incorporated in low molecular compounds was increased and the share of amino acids and organic acids in them was increased. Plants supplied with 1/10th of the optimum Fe required partially adapted to the Fe deficiency. Plants with visual symptoms of Fe deficiency showed some peculiarities as compared to those plants severely Fe‐deficient.  相似文献   

12.
A greenhouse pot experiment was conducted with peanuts (Arachis hypogaea L., Fabceae) to evaluate iron compound fertilizers for improving within-plant iron content and correcting chlorosis caused by iron deficiency. Peanuts were planted in containers with calcareous soil fertilized with three different granular iron nitrogen, phosphorus and potassium (NPK) fertilizers (ferrous sulphate (FeSO4)–NPK, Fe–ethylendiamine di (o-hydroxyphenylacetic) (EDDHA)–NPK and Fe–citrate–NPK). Iron nutrition, plant biomass, seed yield and quality of peanuts were significantly affected by the application of Fe–citrate–NPK and Fe–EDDHA–NPK to the soil. Iron concentrations in tissues were significantly greater for plants grown with Fe–citrate–NPK and Fe–EDDHA–NPK. The active iron concentration in the youngest leaves of peanuts was linearly related to the leaf chlorophyll (via soil and plant analyzer development measurements) recorded 50 and 80 days after planting. However, no significant differences between Fe–citrate–NPK and Fe–EDDHA–NPK were observed. Despite the large amount of total iron bound and dry matter, FeSO4–NPK was less effective than Fe–citrate–NPK and Fe–EDDHA–NPK to improve iron uptake. The results showed that application of Fe–citrate–NPK was as effective as application of Fe–EDDHA–NPK in remediating leaf iron chlorosis in peanut pot-grown in calcareous soil. The study suggested that Fe–citrate–NPK should be considered as a potential tool for correcting peanut iron deficiency in calcareous soil.  相似文献   

13.
The unique ability of dried plant residues Azolla to adsorb iron (Fe) was employed to formulate and test an organic Fe biofertilizer. A simplified experimental system was established to examine the effectiveness of Fe‐enriched Azolla as a source of Fe for the remedy of Fe‐deficient plants. The optimal Fe‐enrichment level needed to achieve a complete recovery of starved plant by the Fe‐Azolla complex was tested using a bioassay system of hydroponically grown cucumbers. Dried Azolla plants were mixed a with a solution of ferrous sulfate (FeSO4) at pH 2.0, rinsed, and dried to form organic, compact material containing 4% (w/w) Fe bound to Azolla. The Fe‐Azolla complex was applied to the nutrient solutions of Fe‐deficient cucumber seedlings. Growth rates and development measurements as well as chlorophyll and the Fe‐containing catalase activity tests have been performed. The effect of the slowly released Fe in correcting Fe deficiency were followed for three weeks and compared with the efficiency of additions of several synthetic Fe chelates. Iron‐starved plants exhibited fast regreening of the chlorotic interveinal tissues after the addition of Fe‐Azolla complex to the nutrient solutions. Iron starvation decreased the activity of catalase. Iron‐treated‐starved plants exhibited recovery of catalase activity compared to the low level activity measured untreated Fe‐starved plants. Iron‐enriched Azolla treatment was found equivalent to Fe‐EDTA and Fe‐EDDHA. This study is the first step in our research program aimed to establish the application of Fe‐enriched Azolla as a bioagent for the benefit of Fe‐deficient crops.  相似文献   

14.
A symptom called leaf‐oranging, indicating a deficiency of many nutrients, occurs in paddy rice (Oryzasativa L.) when production expands into some upland soils. Rice (Gui Chou cv.) was grown in culture pots in a flooded, weathered, upland soil (Nacogdoches) and compared to rice growth in a flooded soil currently used for paddy rice production (Dacosta) in Texas to understand the soil and plant factors involved in leaf‐oranging. Fertilizer rates of 0, 10, and 100 mg N/kg as (NH4)2SO4 were applied to each soil along with phosphorus (P) and potassium (K) fertilizer. The orange Leaf Index (OLI), a measure of leaf‐oranging, was determined weekly and increased to 60–70% for plants grown in the upland soil but its progression was delayed by higher N treatments. No leaf‐oranging was observed in the paddy soil. The soil evoking leaf‐oranging was low in silicon (Si) and high in iron (Fe). In addition, analysis of leaves from these plants showed 19–25% higher leaf ammonium‐nitrogen (NH4‐N), 9–137% higher manganese (Mn) levels and lower total N:NH4 concentration compared to normal rice leaves four weeks after transplanting. This inferred that leaf‐oranging probably was associated with some degree of NH4‐N toxicity and antagonism with K. Leaf‐oranging was also associated with low calcium (Ca) assimilation or Ca uptake inhibition because of the heavy Fe‐oxide coating of the roots of the affected rice plants. In this experiment, leaf‐oranging was not associated with toxic levels of Fe or Mn.  相似文献   

15.
Iron deficiency decreases the amount of photosynthetic pigments in higher plants, and also results in characteristic changes in the relative photosynthetic pigment composition. Iron deficient plants exhibit a relative increase in xanthophylls, largely attributable to pigments within the xanthophyll cycle, violaxanthin, antheraxanthin, and zeaxanthin. Furthermore, the xanthophyll cycle functions in Fe‐deficient plants, but not in other yellow, carotenoid enriched‐materials, such as etiolated or senescing leaves. When Fe‐deficient leaves are illuminated, part of the violaxanthin is converted into antheraxanthin and zeaxanthin. When Fe‐deficient leaves are placed in the dark, the cycle reverts back to violaxanthin. In this paper we present further data on this cycle and discuss the possible relevance of pigment changes as an alternative mechanism for the dissipation of excess energy. The possibility of using characteristic pigment changes as a tool for monitoring Fe status in higher plants is discussed.  相似文献   

16.
In the present study, plant traits related to the photosynthetic capacity at the whole plant level were compared during grain filling in two maize genotypes with different nitrogen (N) efficiency. The plants were grown in a greenhouse in large root containers and supplied either with suboptimal or optimal rates of N fertilizer. Suboptimal N supply reduced total plant biomass at maturity (47 days (d) after flowering) by 29 % for the efficient genotype and by 36 % for the inefficient genotype. Suboptimal N supply reduced leaf growth of both genotypes. The reduction of leaf area was less severe in the N‐efficient genotype, despite of lower N content in the leaves. This indicates lower sensitivity of leaf growth towards internal N limitation in the efficient genotype. At low N supply, the green leaf area per plant gradually decreased after flowering in both genotypes, because of loss of chlorophyll during leaf senescence. The rate of net photosynthesis per unit leaf area (A) was reduced at low in comparison with high N supply. The ratio of A/leaf N content or leaf chlorophyll content was higher in the efficient genotype, indicating more efficient utilization of internal N for photosynthesis. At the end of grain filling, low N supply led to enhanced intercelluar CO2 concentrations (Ci) in the leaves, indicating limitation of CO2 assimilation by carboxylation rather than by stomatal resistance. The N deficiency‐induced increase of Ci was less pronounced in the efficient genotype. Furthermore, higher photosynthetic rate of the efficient genotype at suboptimal N supply was associated with lower contents of reducing sugars and sucrose in the leaves, whereas starch content was higher than in the inefficient genotype. The ability to avoid excessive sugar accumulation in the leaves under N deficiency might be related to higher photosynthetic N efficiency.  相似文献   

17.
To assess the genetic variability of peanut (Arachis hypogaea L.) in tolerance to iron (Fe) deficiency, spectral and photosynthetic parameters of 12 peanut cultivars were determined. The results showed that peanut exhibit significant variations in spectral and photosynthetic parameters within cultivars in response to Fe deficiency. The 12 peanut cultivars were separated into three groups, which include (i) a Fe-deficient tolerant cultivar (‘Zhenghong 3’), (ii) a Fe-deficient sensitive cultivar (‘Huayu 22’), and (iii) ten intermediate cultivars. Iron deficiency caused an increase in root biomass, root/shoot ratio, structure independent pigment index and intercellular carbon dioxide (CO2) concentration, but resulted in a decrease in net photosynthetic rate (Pn), quantum yield of PS II photochemistry (Fv/Fm), effective quantum yield of PS II (ΦPS II), photochemical reflectance index, red edge point, and chlorophyll normalized difference index. Iron deficiency-induced decline in net photosynthetic rate may be resulted from the reduction of photosynthetic pigment contents and inhibition of PSII photochemistry.  相似文献   

18.
《Journal of plant nutrition》2013,36(10-11):2111-2121
Abstract

The finding that the methionine is the sole precursor of the mugineic acid family phytosiderophores induced us to evaluate whether sulfur assimilation pathway has a role in plant response to Fe deficiency. Maize plants were grown for 10 days in nutrient solution (NS) containing 80 µM Fe in the presence (+S) or absence (?S) of sulfate. After removing the root extraplasmatic iron pool, half of the plants of each treatment (+S and ?S) were transferred to a new Fe deficient NS (0.1 µM final Fe concentration) (?Fe). The remaining plants of each pre‐culture condition (+S and ?S) were transferred to a new NS containing 80 µM Fe (+Fe). Leaves were collected 4 and 24 hours from the beginning of Fe deprivation period and used for chemical analysis and enzyme assays. Results showed that iron content in the leaves was lower in plants grown in S‐deficiency than in those grown in the presence of the macro‐nutrient. Iron deprivation produced an increase in the level of SH compounds in both nutritive conditions (+S and ?S). These observations are suggestive of some relationship between S nutrition and Fe uptake. For this reason, we next investigated the influence of Fe availability on S metabolism through the evaluation of changes in ATPs and OASs activity, the first and the last enzyme of S assimilation pathway respectively. Results showed that S‐starvation increased the activity of both enzymes, but this effect disappeared in plants upon Fe deficiency suggesting that S metabolism is sensitive to Fe availability. Taken together these evidences suggest that S metabolism is sensitive to soil Fe‐availability for plant nutrition and support the hypothesis of S involvement in plant response to Fe deprivation.  相似文献   

19.
Abstract

Experiments were conducted using different NO3 –/NH4 + ratios to determine the effects of these sources of N on mineral element uptake by sorghum [Sorghum bicolor (L.) Moench] plants grown in nutrient solution. The NO3 –/NH4 + ratios in nutrient solution were 200/0, 195/5, 190/10, and 160/40 mg N L–1. Nutrient solutions were sampled daily and plants harvested every other day during the 12‐day treatment period.

Moderately severe Fe deficiencies were observed on leaves of plants grown with 200/0 NO3 –/NH4 + solutions, but not on the leaves of plants grown with the other NO3 –/NH4 + ratios. As plants aged, less Fe, Mn, and Cu were translocated from the roots to leaves and leaf/root ratios of these elements decreased dramatically in plants grown with 200/0 NO3 –/NH4 + solutions. Extensive amounts of Fe, Mn, and Cu accumulated in or on the roots of plants grown with 200/0 NO3 –/NH4 + solutions. Manganese and Cu may have interacted strongly with Fe to inhibit Fe translocation to leaves and to induce Fe deficiency. As the proportion of NH4 + in solution increased, K, Ca, Mg, Mn, and Zn concentrations decreased in the leaves, and Ca, Mg, Mn, and Cu concentrations decreased in roots. Potassium and Zn tended to increase in roots as NH4 + in solution increased.  相似文献   

20.
Cool white fluorescent (CWF) light reduces Fe3+ to Fe2+ while low pressure sodium (LPS) light does not. Cotton plants grown under CWF light are green, while those yrown under LPS light develop a chlorosis very similar to the chlorosis that develops when the plants are deficient in iron (Fe). It could be that CWF light (which has ultra violet) makes iron more available for plant use by maintaining more Fe2+ in the plant. Two of the factors commonly induced by Fe‐stress in dicotyledonous plants‐‐hydroyen ions and reductants released by the roots‐‐were measured as indicators of the Fe‐deficiency stress response mechanism in M8 cotton.

The plants were grown under LPS and CWF light in nutrient solutions containing either NO3‐N or NH4‐N as the source of nitrogen, and also in a fertilized alkaline soil. Leaf chlorophyll concentration varied significantly in plants grown under the two light sources as follows: CWF+Fe > LPS+Fe > CWF‐Fe ≥ LPS‐Fe. The leaf nitrate and root Fe concentrations were significantly greater and leaf Fe was generally lower in plants grown under LPS than CWF light. Hydrogen ions were extruded by Fe‐deficiency stressed roots grown under either LPS or CWF light, but “reductants”; were extruded only by the plants grown under CWF light. In tests demonstrating the ability of light to reduce Fe3+ to Fe2+ in solutions, enough ultra violet penetrated the chlorotic leaf of LPS yrown plants to reduce some Fe3+ in a beaker below, but no reduction was evident through a yreen CWF grown leaf.

The chlorosis that developed in these cotton plants appeared to be induced by a response to the source of liyht and not by the fertilizer added. It seems possible that ultra violet liyht could affect the reduction of Fe3+ to Fe2+ in leaves and thus control the availability of this iron to biological systems requiring iron in the plant.  相似文献   

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