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1.
Root active uptake and remobilization of boron (B) have been accepted as mechanisms contributing to nutrient efficiency under low supply of boron. Here, we examined the existence of these mechanisms in eggplant (Solanum melongena L.) supplied either with luxury (100 μM, B+) or low (7.5 μM, B–) B in the growth medium via semihydroponic cultivation. Boron treatment was marginally not limiting growth thus avoiding side‐effects and impairment of acclimation mechanisms of plants. The induction of a B‐concentrating mechanism was evident in the roots as B concentration in the xylem sap was only decreased by 23% in B– compared to B+ plants, i.e., B– roots concentrated B by a factor of 2.7 relative to the external solution. Leaf B concentration in the B– treatment decreased by 33% and 40% in young fully expanded and mature leaves, respectively. Larger differences were observed in the soluble B fraction that decreased by 65% in mature leaves. However, both total and soluble B concentrations in developing leaves were almost equal for both treatments exhibiting a pattern commonly observed in B‐remobilizing plants. On the other hand, amounts of B export in the phloem sap were small compared to other species in which B is highly mobile. The B export rate from source leaves was slightly increased under low B supply while that of sucrose was not affected. We conclude that the root concentrating mechanism contributes to the alleviation of B deficiency in eggplant under low B supply while B remobilization may also contribute to a lower degree.  相似文献   

2.
Beneficial effects of aluminum (Al) on plant growth have been reported for plant species adapted to acid soils. However, mechanisms underlying the stimulatory effect of Al have not been fully elucidated. The aim of this study was to determine the possible contribution of photosynthesis, antioxidative defense, and the metabolism of both nitrogen and phenolics to the Al‐induced growth stimulation in tea (Camellia sinensis [L.] Kuntze) plants. In hydroponics, shoot growth achieved its maximum at 50 μM Al suply (24 μM Al3+ activity). A more than threefold increase of root biomass was observed for plants supplied with 300 μM Al (125 μM Al3+ activity). Total root length was positively related to root Al concentrations (r = 0.98). Chlorophyll a and carotenoid concentrations and net assimilation rates were considerably enhanced by Al supply in the young but not in the old leaves. Activity of nitrate reductase was not influenced by Al. Higher concentrations of soluble nitrogen compounds (nitrate, nitrite, amino acids) and reduction of protein concentrations suggest Al‐induced protein degradation. This occurred concomitantly with enhanced net CO2‐assimilation rates and carbohydrate concentrations. Aluminum treatments activated antioxidant defense enzymes and increased free proline content. Lowering of malondialdehyde concentrations by Al supply indicates that membrane integrity was not impaired by Al. Leaves and roots of Al‐treated plants had considerably lower phenolic and lignin concentrations in the cell walls, but a higher proportion of soluble phenolics. In conclusion, Al‐induced growth stimulation in tea plants was mediated by higher photosynthesis rate and increased antioxidant defense. Additionally, greater root surface area may improve water and nutrient uptake by the plants.  相似文献   

3.
The growth of ‘Ridge Pineapple’ sweet orange [Citrus sinensis (L.) Osbeck] seedlings and their susceptibility to Phytophthora root rot were studied under contrasting supplies of phosphate (Pi) or Phosphite (Phi). After 10 weeks of repeated applications of nutrient solutions, Phi concentrations were barely detectable in soil. Soil Pi was higher in Phi treatments than in pots that received Pi alone. Seedling growth was greatest when supplied with Pi or Phi separately, but when Pi and Phi were combined, growth was reduced to levels comparable to plants that received no P. Phi was found in both stems and leaves after it was applied to soil supporting the mobility of Phi within the plant. In addition, a small amount of Phi was found in roots after applications of Phi in foliar sprays. Different sources of soil-applied P did not affect the amount of Pi in roots, while the amounts of Pi in leaves were higher in plants that received Phi and Pi combined. Root resistance to Phytophthora root rot of citrus seedlings treated with Phi alone or in combination with Pi was greater than in plants treated with Pi alone, confirming the antifungal effect of Phi.  相似文献   

4.
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5.
In order to study the effect of different growth rates of the shoot apex, i.e. shoot demand, on the remobilization of iron (Fe) from mature (primary) leaves, bean (Phaseolus vulgaris L.) plants were precultured with 8x10‐5 M FeEDTA for four days. Thereafter, plants were grown for another six days at various levels of Fe (0.0, 1.0, and 10.0μM FeEDTA), and simultaneously treated with or without shading of one primary leaf. Dry weight increment of the shoot apex decreased with decreased Fe in the nutrient solution. Shading of one primary leaf decreased total dry weight of plants irrespective of Fe supply, but increased the dry weight of the shoot apex of plants supplied without Fe or with only 1.0μM Fe. In these plants, the concentration of chlorophyll and Fe in the shoot apex corresponded with the treatment effects on dry weight of the shoot apex. Shading induced senescence of the shaded leaf, decreased the content of “active Fe”; (extractable in dilute acid), and also enhanced the remobilization of Fe and copper (Cu) from the shaded leaf. The remobilization of Fe from primary leaves was not related to the severity of chlorosis in the shoot apex (the Fe demand of sink tissue), indicating that only a certain fraction of the total Fe in mature leaves can be remobilized.  相似文献   

6.
Plants frequently accumulate or reserve some organic nitrogenous substances of small molecules, when supplied with inorganic nitrogenous compounds in excess. It is well known that rice plants in the field accumulate asparagine when supplied with ammonium salts in excess. This phenomenon is effectively utilized as a criteria for adequate supply of nitrogen fertilizers in the field (1). Accumulation of asparagine has also been generally recognized among seedlings of various plant species grown with excess ammonium, nitrate or urea (2). With rye grass, glutamine was reported to be accumulated in leaves and sometimes excreted when ammonium sulfate was supplied in excess (3). Arginine is a major free amino acid accumulating in nitrogen fertilized apple trees (4), phosphate-deficient mulberries (5), and potassium deficient rice plants (6). Allantoin is known to be a reserve form of nitrogen in some families of higher plants, notably the Aceraceae, Leguminosae and Boraginaceae (7,8). Thus the form of reserve nitrogen compound differs with different plant species.  相似文献   

7.
The influence of a growth stimulating low Cr III concentration (1.0 μM) on chloroplast ultrastructure, the Fe, Cr, and Mn content of chloroplast extracts, o‐phenantroline extractable leaf Fe, and catalase activity was studied in both Fe‐sufficient and Fe‐deficient bush bean (Phaseolus vulgaris L.) plants. Chromium supply hardly affected the chloroplast ultrastructure of Fe‐sufficient plants but significantly improved chloroplast ultrastructure in Fe‐deficient leaves. Generally, Cr supply did not significantly influence chloroplast Fe‐content, but increased the Fe/Mn ratio in Fe‐deficient chloroplasts. In leaves from Fe‐deficient plants, o‐phenantroline extractable Fe was significantly increased, while catalase activity was not significantly influenced by Cr supply. The possible mechanisms of the beneficial effects of Cr III in Fe‐deficient plants are discussed.  相似文献   

8.
The quality of green tea is highly dependent on the concentration of free amino acids, whose profile is dominated by the unique amino acid theanine (N5‐ethyl‐glutamine). A high quality is associated with a high amino acid–to–catechin ratio, but previous results indicated that excessive chloride (Cl–) supply is detrimental for amino acid accumulation. Several experiments were conducted to investigate the effect of chloride on growth and concentrations of free amino acids in young tea plants. Soil‐grown tea plants supplied with different levels of potassium (K) as K2SO4 or KCl exhibited increased concentrations of free amino acid in young shoots only when supplied with K2SO4, and the negative effect of KCl supply was mainly due to a reduced concentration of theanine. Concentrations of other nutrients in plant tissues were not influenced. The uptake of Cl– and its interaction with nitrogen (N) uptake were further investigated in a second experiment, in which soil‐cultivated tea plants were supplied with varying amounts of Cl–. Chloride application reduced yield of young shoots, and severity of leaf damage was related to the concentration of Cl– in leaves. Nitrogen uptake was reduced by Cl– addition. To verify whether the decrease of free amino acids was simply a result of inhibited NO assimilation, a third experiment was conducted, in which tea plants were NH ‐fed in the absence or presence (equivalent to the NH concentration) of Cl–. Again, concentrations of theanine and total free amino acids in young shoots were reduced by Cl– supply, but changes of the free–amino acid pool did not contribute to the maintenance of charge balance. However, concentration of theanine in roots, where it is synthesized, was not influenced by Cl–. Total N concentrations of roots and mature leaves, uptake rate of NH , and activity of glutamine synthetase in fibrous roots and young leaves were all unaffected by Cl– as well. It is suggested that translocation of theanine from root to shoot and its catabolism in young shoots might be influenced by Cl–.  相似文献   

9.
Bush bean plants (Phaseolus vulgaris L. cv Contender) were grown for twenty days in nutrient solution (pH=5), containing 0.13, 0.3, 0.5 or 0.75 mg 1‐1 Zn as ZnSO4‐7H2O. The plant yield decreased linearly with the increase of the Zn concentration supplied. The phytotoxic threshold content (for 10% growth reduction) was about 486, 242, 95 and 134‐ μg Zn g‐1 for roots, steins, mature primary and trifoliate leaves, and developing leaves, respectively. High inverse correlation coefficients with the Zh concentration supplied were found for the Mn content of all organs, for the P content of roots, and for the Cu and Ca contents of developing leaves. Significant positive relations were found for the Fe, Zn and Cu contents in roots and for the Zn con‐ tents in stems and fully expanded leaves. The ratios of the mineral contents between organs suggest inhibition of uptake of Mn and P, and inhibition of translocation of Fe, Cu and Ca. The relation between dry weight decrease and Zn‐induced nutrient content disorders were discussed.  相似文献   

10.
Effect of Si on alleviation of Mn toxicity of barley (Hordeum vulgare L.) seedlings was investigated with special reference to the effect on Mn microdistribution and peroxidase activity. Manganese treatment was conducted by growing the seedlings in nutrient solutions containing different concentrations of Mn. Silicon treatment was conducted by growing the seedlings in the solutions with or without Si supply. Silicon supply alleviated the necrotic browning in the leaves but did not affect the chlorosis caused by Mn toxicity. Silicon treatment did not appreciably alter the uptake of Mn by the plants. Electron probe X‐ray microanalysis revealed that Mn accumulated in high concentration around the necrotic brown spots and that Si supply prevented the uneven distribution of Mn in the tissues. Increase in the level of Mn supply caused an increase in peroxidase activity in the tissues, and Si supply prvented the increase in peroxidase activity.  相似文献   

11.
Two experiments are described in which tomato plants (Lycopersicon esculentum L. var Ailsa Craig) were grown in water culture supplied with 10–300 μM Mn. Toxicity symptoms associated with a yield reduction were observed only in treatments in excess of 50 μM Mn indicating that this species is relatively tolerant of high Mn supply. Dark brown/black spots appeared first in the cotyledons. Similar symptoms were observed in the leaves, progressively from the oldest leaf. Manganese concentration in the shoot tissues ranged from 286 to 4240 μg. g‐1 dry weight. The high Mn concentration values found in the shoot tissues of the toxic plants indicate that Mn was highly mobile in the xylem as confirmed by xylem sap analysis.

The concentrations of both Ca and Mg were lower in the smaller Mn toxic plants. Not only was uptake of Ca and Mg retarded but so also was the distribution of Ca and Mg to the younger tissues as illustrated by measurements of Ca and Mg concentrations along a leaf age sequence. This is in accord with the cation‐anion balance of the xylem exudates collected from decapitated plants.

Higher cation exchange capacity (CEC) was found in the leaf tissues of toxic plants particularly in the older leaves but similar values of C.E.C were recorded for the younger leaf tissues of both control and toxic plants.  相似文献   

12.
A mutant of Arabidopsis thaliana, bor1-1 (Noguchi et al. 1997: Plant Physiol., 115, 901–916) requires high levels of boron (B) for normal growth. We analyzed the B-deficiency symptoms of bor1-1 mutant plants in detail. A low B supply retarded the growth of the mutant plants more evidently in leaves than in roots. In particular, cell expansion and formation of air spaces were severely impaired by B deficiency in young rosette leaves. Such defects in growth were correlated with the reduced contents of B in leaves. These defects were not observed when a sufficient amount of B was supplied. Uptake experiments with 10B-enriched tracer B demonstrated that B taken up through roots was preferentially transported to young leaves compared to old leaves in the wild-type plants under a low B supply. Such a preferential transport to young leaves was not evident in the mutant plants. In conclusion, our data demonstrated that in A. thaliana plants B is preferentially transported to young organs under a low B supply and that this transport process is controlled at least in part by the BOR1 gene.  相似文献   

13.
缺磷胁迫对黄瓜体内磷运输及再分配的影响   总被引：16，自引：1，他引：15  
本研究用营养液培养法定量地测定并计算了在正常供磷及缺磷后不同时间黄瓜植株体内磷的分布及再运输。缺磷处理５天后,新生叶和根系中的吸磷量明显增加,分别占植株总吸磷量的３６．１％和１３．５％,而相应的正常供磷植株的新生叶和根系中的吸磷量仅分别占植株总吸磷量的２２．４％和６．３４％,而且缺磷植株根系的生长显著快于供磷的植株。缺磷胁迫１０天后,植株地上部生长受到明显抑制,老叶中的磷通过韧皮部运向新生叶以保证新生器官的生长,使新生叶中磷的浓度比老叶中高４７％,但缺磷植株根系中磷的累积量下降不多。本研究还定量证明了即使在正常供磷条件下,随着生长时间的延长,也有大量的磷由老叶运向新叶。不论缺磷与否,植株新生叶和根中磷的浓度都保持最高,但缺磷和供磷植物体中磷的分配模式不同。  相似文献   

14.
The impact of phosphorus (P) deficiency on response of symbiotic N2 fixation and carbohydrate accumulation in soybean (Glycine max [L.] Merr.) to atmospheric CO2 enrichment was examined. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown in growth chambers with controlled atmospheres of 400 and 800 μL CO2 L‐1 and supplied either 1.0 mM‐P (P‐sufficient) or 0.05 mM‐P (P‐deficient) nitrogen (N)‐free nutrient solution. When plants were supplied with sufficient P, CO2 enrichment significantly increased whole plant dry mass (83%), nodule mass (67%), total nitrogenase activity (58%), and N (35%) and P (47%) accumulation at 35 days after transplanting (DAT). Under sufficient P supply, CO2 enrichment significantly increased starch concentrations in nodules compared to the normal atmospheric CO2 treatment. Under normal CO2 levels (400 μL L‐1) nonstructural carbohydrate concentration (starch plus soluble sugar) was significantly higher in leaves of P‐deficient plants than in leaves of P‐sufficient plants in which nonstructural carbohydrate concentration exhibited a strong diurnal pattern. Under deficient P supply whole plant dry mass, symbiotic N2‐fixation parameters, and N and P accumulation were not enhanced by atmospheric CO2 enrichment. Phosphorus deficiency decreased nonstructural carbohydrate accumulation in nodules at the end of a 10‐day period in which functional activity was developing by 86% relative to P‐sufficient controls. While P deficiency elicited significant increases in the nonstructural carbohydrate concentration in leaves, it caused significant decreases in the nonstructural carbohydrate concentration in nodules over the diurnal cycle from 30 to 31 DAT. Collectively, these results indicate that the lack of a symbiotic N2‐fixation response to atmospheric CO2 enrichment by P‐deficient plants may be related to the decreased carbohydrate status of nodules.  相似文献   

15.
The aim of this study was to induce symptoms of zinc deficiency and Zn excess and to relate the generation of reactive oxygen species (ROS) and the altered cellular redox environment to the effects of Zn stress in mulberry (Morus alba L.) cv. Kanva‐2 plants. The antioxidative responses of Zn‐stressed mulberry plants were studied by determining malondialdehyde content (MDA, a measure of lipid peroxidation) as indicator of oxidative damage and the ratio of dehydroascorbate (DHA) to ascorbic acid (AsA) as an index of the cellular redox state. The Zn‐deficiency effects appeared as faint paling and upward cupping of the young emerging leaves. The paling intensified with time, and affected leaves finally developed necrotic spots. At advanced stage of Zn deficiency, newly emerged leaves were spindle‐shaped, pale, and small in size. Apart from their stunted appearance, the plants supplied excess Zn did not show any specific visible symptom. Leaf water status of mulberry plant was affected in Zn‐stressed plants. Deficient leaves had decreased water potential (Ψ) and specific water content (SWC), contained less tissue Zn, less chloroplastic pigments, and high tissue Fe and Mn concentrations. However, excess supply of Zn was found to increase Ψ and decrease tissue Fe. Both hydrogen peroxide and MDA accumulated in leaves of Zn‐stressed plants. While the concentration of DHA did not vary in Zn‐deficient leaves, it was increased in leaves of plants supplied excess Zn. The ratio of the redox couple (DHA to AsA) was increased both in Zn‐deficient or Zn‐excess plants. The activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), peroxidase (EC 1.11.1.7), and ascorbate peroxidase (EC 1.11.1.11) increased in Zn‐stressed plants. The results suggest that deficiency or excess of Zn aggravates oxidative stress through enhanced generation of ROS and a disturbed redox homeostasis in mulberry plants.  相似文献   

16.
评价4个茶树品种的氟吸收富集能力差异,为有效降低茶叶中氟含量和茶叶生产中推广低氟品种提供参考依据。以前期初选出的4个不同氟含量茶树品种的一年生无性系茶苗为材料,采用溶液培养的方法,研究各品种的短期吸收动力学参数差异、 氟吸收累积动态及累积能力差异。结果表明,在低氟浓度生长环境下,茶树对氟的吸收符合Michaelis-Menten动力学方程Vi=VmaxCi/（Km+Ci）描述,表现出主动吸收过程,茶树各部位对氟的吸收累积能力表现为成熟叶根茎; 随着氟浓度的增加,茶树对氟的吸收逐渐表现出了明显的被动吸收现象。茶树各部位对氟的吸收累积能力表现为成熟叶茎根;中茶102品种对氟的吸收累积能力及对氟的耐受性与中茶108相比有较大的差异,中茶108对氟具有比较稳定的低吸收累积特性,而中茶102则对氟表现出了较强的吸收累积特性,龙井43与乌牛早则介于两者之间。中茶108具有稳定的低氟吸收累积特性,可以作为低氟品种推广。  相似文献   

17.
The ability of plants to utilize P efficiently is important for crops growing in P‐deficient soils or on soils with a high P‐fixing capacity. The purpose of this work was to investigate early physiological changes which occur when wheat (Triticum aestivum L.) seedlings were grown under P‐deficient conditions. Wheat plants were grown in a greenhouse and watered with nutrient solution containing or lacking P. During the interval 12 to 18 days after planting, the dry weight of wheat seedlings was similar regardless of P treatment, although the P‐deficient plants had a greater proportion of the total plant weight in the roots. Sixteen days after planting, the roots and leaves of P‐deficient plants had only 20 to 30% the P content of P‐sufficient plants. After 16 days, plants grown under P stress had 41% more p‐nitrophenol phosphatase activity and 70% more β‐glucosidase activity in shoot homogenates than was found in P‐sufficient plants. Changes in both enzyme activities may be involved in the mobilization of plant resources during the early stages of P‐deficient growth.  相似文献   

18.
In order to study the iron (Fe) distribution pattern in bean plants with different Fe nutritional status, french bean (Phaseolus vulgaris L.) seedlings were precultured in a complete nutrient solution with 8x10‐5 M FeEDTA for five days. Thereafter, plants were further supplied with 8x10‐5 M FeEDTA (Fe‐sufficient) or with only 2x10‐6 M FeEDTA (Fe‐deficient) for another eight days. At this stage, the Fe‐deficient plants had much lower chlorophyll contents and lower dry weight of the leaves but higher reducing capacity of the roots compared with the Fe‐sufficient plants. For studies on short‐term distribution of Fe, the Fe‐sufficient plants were supplied 8x10‐5 M 59FeEDTA (specific activity 9.9 GBq/mol) and the Fe‐deficient plants 1x106 M 59FeEDTA (specific activity 98.8 GBq/mol). The plants were harvested after 4 and 24 hours. Despite a much lower supply of 59FeEDTA/(factor 80), the Fe‐deficient plants took up significantly more 59Fe but translocated less to the shoots (14.6% after 24 h) compared with the Fe‐sufficient plants (29.4% after 24 h). However, regardless of the Fe nutritional status of the plants, the majority of 59Fe was translocated in the primary leaves. Our results demonstrate a similar distribution patterns of root‐derived 59Fe in the shoots of Fe‐sufficient and Fe‐deficient plants, and thus, no preferential direct translocation of Fe to the shoot apex in the Fe‐deficient plants.  相似文献   

19.
The result of intensive agriculture in cities is the decline in crop yields and depletion of the resource base. The aims of this study were to assess effects of nitrogen (N) or phosphorus (P) fertilization on bioavailable aluminum (Al) and their contribution on Al and nutrient uptake in Hibiscus sabdariffa. A pot experiment was led to supply a tropical soil with N and P fertilizers. P amendment decreased Al in soil solution, not N amendment. Fertilizers had effects on Al and nutrient uptake in roots and leaves of Hibiscus sabdariffa. The results also showed that the uptake of Al and nutrients depends on Al in soil solution or N supply or P supply. Only P uptake in roots and leaves was explained by combined effects of a nutrient supply × exchangeable Al. Furthermore, P supply does not limit the translocation of Al in shoots of plants in acid soils.  相似文献   

20.
Cabbage plants (B. oleracea L. var. capitata L.) were grown for 37 days in culture solutions containing 4 levels (0, 0.5, 5, 25 ppm) of beryllium or strontium with a low or high supply (20 or 200 ppm) of calcium, and the effects of the cations supplied on the growth of the plants were studied.

The total dry weights of the plants decreased successively with increasing levels of Be and Sr in the culture solution, concurrfnt with an increase in the contents of each cation in the plants. The decrease in the yield (dry weight of inner leaves) was most pronounced in the Be treatment with the low Ca supply. The critical contents of Be and Sr which resulted in a 50% decrease in the yield due to the excess injury were estimated to be about 0.0006 and 0.4% on a dry basis in the outer leaves and 0.3 and 0.4% in the roots, respectively, regardless of the Ca supply.  相似文献   

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