共查询到20条相似文献，搜索用时 31 毫秒
1.
《Journal of plant nutrition》2013,36(10-11):2231-2242
Abstract Radioactively labeled iron (59Fe) was used to study iron retranslocation from mature leaves of Broad bean (Vicia faba L. var. Scirocco). Our experiments offered the possibility to detect and quantify the translocation of foliar applied iron by imaging technique in combination with tissue analysis. 59Fe labeled solution was placed as a droplet onto the leafs upper surface of intact plants. Distribution of 59Fe was analyzed after 0.5 h up to 2 days. Iron was translocated acropetally (towards the tip of the treated leaf) as well as basipetally. Movement in the apical direction was predominant, amounting to about 65% of 59Fe translocated from the application site. About 35% of 59Fe were transported basipetally, corresponding to absolute amounts of 2.8–53.6 pmol h?1. After 30 min, it was detectable in the petiole, which included a translocation of 20 mm basipetal from the application site. A mean of 15% of the iron retranslocated from a leaflet was detected in non‐treated leaflets of the same leaf. This iron was supposed to have been exchanged from the phloem into the xylem pathway, probably within the petiole. When the loading rate into the phloem was estimated on basis of the sum of retranslocated 59Fe per time and per area of the leaf treated, a range of 0.031–2.21 pmol h?1 mm?2 (mean: 0.62 pmol h?1 mm?2) was obtained. This was not sufficient to meet an estimated demand for iron in the growing terminal bud, but could cover about 25% of it. In conclusion, average iron retranslocation from leaves of Fe‐sufficient plants was not large enough to meet the iron demand of the growing shoot. This was not due to a limitation in iron availability for transport, as an excess amount of iron was supplied which was not biologically bound, but a limitation due to transport facilities, probably in the phloem, seemed to be more likely in this case. 相似文献
2.
Maturing wheat grains represent major sinks for solutes in the phloem, while the xylem sap entering the ear is mainly delivered to the glumes. Nutrients and assimilates transported in the phloem may either be exported from source organs or loaded into the sieve tubes by a xylem‐to‐phloem transfer in the stem. The transfer of zinc from xylem to phloem in the peduncle of wheat was investigated by feeding radiolabelled zinc into the cut xylem of detached shoots. The label accumulated in grains of shoots with an intact phloem but not in those steam‐girdled below the ear. These findings indicate that zinc fed in low concentrations (0.1 ‐ 10 μM) entered the ear mainly via the phloem. After feeding high zinc concentrations (100 ‐1000 μM), the label was mainly retained in the stem and steam‐girding below the ear was rather ineffective. These results led to the conclusion that at these high concentrations zinc was still eliminated from the xylem sap, but loaded only in a minor percentage into the phloem. The interactions between the two long distance transport systems may play an important role in the regulation of zinc transport to the maturing grains of cereals. 相似文献
3.
Reiko Nishiyama Keitaro Tanoi Shuichi Yanagisawa 《Soil Science and Plant Nutrition》2013,59(5):750-755
Zinc (Zn) is an essential nutrient for human beings, and most Zn intake occurs through vegetables or cereals such as rice (Oryza sativa L.) grains. Recently, we detected Zn as well as cadmium, which may be partitioned to rice grains, in the phloem saps from the uppermost internodes of rice and in the xylem saps from the cut stems at early grain-filling. To quantify Zn transport to the grains via the phloem and xylem, a mathematical model previously developed for cadmium transport to rice grains was applied. We examined the translocation of zinc into the grains of rice plants at early grain-filling by feeding zinc-65 (65Zn) via a root-bathing medium, through culm cuts above and below the flag-leaf nodes, and through the flag leaves. The estimate made using the mathematical model and experimental data for three types of 65Zn transport suggests that the grain Zn may be accumulated predominantly via the phloem through two means of transport, phloem transport of stored Zn from the leaves and, more importantly, xylem-to-phloem transfer at the nodes from Zn as it is being absorbed. The Zn transport via the phloem to the grains is more selective than that of cadmium, a non-nutrient element, as also evidenced by the greater transport of cadmium to the glumes via the xylem. 相似文献
4.
硅对向日葵水分利用效率的影响 总被引：7，自引：2，他引：7
以向日葵(Helianthus.annuus.L.cv.G101)为试验材料,研究了硅对营养液培养的向日葵生长和水分利用效率的影响。结果表明,施硅显著增加向日葵的水分利用效率,对向日葵生物量、叶面积的影响不大,却使最大展开叶的SPAD值显著增加;施硅显著降低了向日葵叶片背面的蒸腾速率以及叶片导度,而对叶片正面的蒸腾速率和叶片导度影响不大。同时,施硅向日葵木质部汁液的流速显著降低,体内硅含量增加。表明叶片蒸腾速率、叶片导度、木质部汁液流速的降低是硅提高向日葵水分利用效率的主要原因。 相似文献
5.
Long distance transport of sodium in bean plants In 8–10 days old bean plants Na+ (22Na) has been applied to either a certain root zone, the stem, or the base and tip respectively of a primary leaf and the long distance transport of Na+ was studied in the following 12–48 h. The long distance transport of Na+ applied to the root zone 9–12 cm behind the tip was strongly restricted towards the shoot and hardly detectable towards the root tip (phloem transport). Presence of K+ in the surrounding solution strongly increased the Na+ efflux from the roots. After leaf application within 48 h 30–40% of the absorbed Na+ had been translocated out of the leaf in direction of the root where, from the basal root zones, intensive Na+ efflux took place. This Na+ efflux was hardly affected by presence of K+ in the external medium and was usually more than 10% of the Na+ taken up by the leaves. From the Na+ taken up by the hypocotyl within 12 h more than 25% had been released from the basal root zones into the nutrient solution. Less than 1% of the Na+ applied either to the leaf or the stem was translocated towards the shoot apex. Separation of the hypocotyl into cortex and stele at the end of the experiment demonstrated the high capacity of the stele for Na+ accumulation. Within the hypocotyl the transfer of Na+ from the stele to the cortex and the phloem seems to be a rapid process whereas the release of Na+ from the phloem into the stele is obviously very restricted. The long distance transport of Na+ within the phloem of the shoot is strictly basipetal and very efficient. Low Na+ contents of bean leaves are therefore the result of several regulating mechanisms: K+ stimulated Na+ efflux in the roots, restricted long distance transport in the xylem due to high Na+ accumulation in the stele, Na+ pumps at the phloem in stem and leaves for phloem loading of Na+, and finally strictly basipetal retranslocation of Na+ in the phloem into the roots and efflux into the solution from basal root zones. 相似文献
6.
超积累植物吸收重金属的生理及分子机制 总被引：87，自引：2，他引：87
超积累植物从根际吸收重金属 ,并将其转移和积累到地上部 ,这一过程包括跨根细胞质膜运输、从根表皮细胞向中柱的横向运输、从根系的中柱薄壁细胞装载到木质部导管、木质部长途运输、从木质部卸载到叶细胞 (跨叶细胞膜运输 )、跨叶细胞的液泡膜运输等主要环节和调控位点。本文就近十年来这方面的研究进展作一综述 相似文献
7.
用营养液培养方法研究了在不同供铁条件下不同形态N和韧皮部烫伤对玉米苗期韧皮部Fe运输的影响。结果表明,韧皮部烫伤提高了玉米根系Fe的再利用,降低了初生叶中Fe的再利用,尤其在缺Fe条件下这种作用更明显,提高和降低的幅度更大。韧皮部烫伤还降低了伤流总量,增加了Fe的浓度。在供应铵态N的条件下,Fe的韧皮部运输比供应硝态N条件下有显著增加,Fe的再利用明显提高。 相似文献
8.
《Journal of plant nutrition》2013,36(8):1457-1470
Abstract The influence of silicon (Si) on water use efficiency (WUE) in maize plants (Zea mays L. cv. Nongda108) was investigated and the results showed that plants treated with 2 mmol L?1 silicic acid (Si) had 20% higher WUE than that of plants without Si application. The WUE was increased up to 35% when the plants were exposed to water stress and this was accounted for by reductions in leaf transpiration and water flow rate in xylem vessels. To examine the effect of silicon on transpiration, changes in stomata opening were compared between Si-treated and nontreated leaves by measuring transpiration rate and leaf resistance. The results showed that the reduction in transpiration following the application of silicon was largely due to a reduction in transpiration rate through stomata, indicating that silicon influences stomata movement. In xylem sap of plants treated with 2 mmol L?1 silicic acid, the Si concentration was 200-fold higher, while the Ca concentration which is mainly determined by the transpiration rate, was 2.5-fold lower than that of plants grown without Si. Furthermore, the water flow rate in xylem vessels of plants with and without Si was compared. Flow rate in plants with 2 mmol L?1 Si was 20% lower than that without Si, which was accounted for by the increased affinity for water in xylem vessels induced by silica deposits. These results demonstrated the role of Si in improving WUE in maize plants. 相似文献
9.
Iron is attractive to plant physiologists since J. Sachs has proven in 1868 the essentiality and the possible leaf uptake of Fe. It lasted about 100 years before the principal processes for Fe mobilization in the rhizosphere were discovered and classified as two distinct strategies for Fe acquisition. During the 80's and 90's of the last century the uptake of Fe2+ and FeIII-phytosiderophores by specific transporters in strategy I- and strategy II-plants, respectively, were postulated without any application of the new approaching molecular techniques. In the following decade, the various transporters for Fe uptake by roots, such as AtIRT1 in Arabidopsis or ZmYS1 in maize and their possible regulation were characterized. In the following years with fast developing molecular approaches further Fe trans ortsrs were genetically described with often only vague physiological functions. In view of a plant nutritionist, besides uptake processes by roots, the following transport processes within the respective target tissue have to be considered by molecular biologists in more detail: 1) radial transfer of Fe from the root cortex through the endodermis, 2) xylem loading in roots, 3) transfer of Fe from xylem to phloem via transfer cells, 4) phloem loading with Fe in source leaves and retranslocation to sink organs, and 5) remobilization and retranslocation via the phloem during senescence of perennial plants. The importance of these various specific transport processes for a well-regulated Fe homeostasis in plants and new strategies to identify and characterize proteins involved in Fe transport and homeostasis will be discussed. 相似文献
10.
磷对不同玉米品种生长、体内磷循环和分配的影响 总被引：5，自引：2，他引：3
以杂交玉米蠡玉16和冀单28为供试作物,采用供高磷（250 mol/L）和低磷（5 mol/L）营养液的石英砂培养方法,研究2个玉米品种的各器官干重和磷积累与分配、体内磷在木质部和韧皮部中的循环、流动及磷的吸收和利用效率。结果表明,与供高磷处理相比,低磷处理的2个玉米品种各营养器官的干重、磷含量和木质部中运输的磷量显著降低; 而磷在体内韧皮部的再循环显著增加,并且玉米各部位叶片活化出的磷主要是通过韧皮部循环至根中后,再经过木质部向上部新生叶运输的; 体内光合产物与磷向上部叶的运输是不同步的过程。低磷时,与冀单28相比,蠡玉16的根冠比高010,整株干重和磷含量增加269%和120%,磷吸收和利用效率提高121%和133%,木质部总磷向上部叶运输的比例高306%。说明低磷条件下,磷高效玉米品种生物量大是由于具有较大的根冠比,木质部中更大比例的磷被分配到上部新生叶以及其具有较高的磷吸收和利用效率。 相似文献
11.
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
12.
Kensuke Tanaka Shu Fujimaki Toru Fujiwara Tadakatsu Yoneyama 《Soil Science and Plant Nutrition》2013,59(2):311-313
To obtain direct evidence for the translocation of cadmium (Cd) via the phloem, we measured the Cd concentrations in the phloem sap of 5-week-old rice plants (Oryza sativa L. cv. Kantou) treated with a nutrient solution containing Cd. The phloem sap was collected from the leaf sheaths through the cut ends of stylets of the brown planthopper (Nilaparvata lugens Stål.). Cd concentrations in the phloem sap from the plants treated with 10 and 100 µM Cd for 3 d were 4.6 ± 3.4 and 17.7 ± 9.8 µM, respectively. Detection of Cd in the phloem sap indicated that Cd was translocated via sieve tubes in rice plants. Cd concentrations in the xylem exudate collected from the cut basis of the leaf sheaths of the plants treated with 10 and 100 µM Cd for 3 d were 18.9 ± 6.4 and 64.2 ± 14.6 µM, respectively. Cd concentrations in the phloem sap were significantly lower than those in the xylem exudate, indicating that Cd is not concentrated during the transfer from xylem to phloem. To our knowledge, this is the first determination of Cd concentrations in the phloem sap of plants, and the first direct proof that Cd is translocated via sieve tubes in rice plants. 相似文献
13.
U. Schwertmann 《植物养料与土壤学杂志》1973,134(1):68-69
Investigations on translocation of magnesium (28Mg) in sunflower plants. 1. The translocation and retranslocation of Mg respectively 28Mg in sunflower plants of different age have been investigated. The focus of this investigation was on the influence of the composition of the uptake solution and the age of plants on the uptake of Mg respectively 28Mg through the roots or through the leaves and on Mg translocation (distribution). 2. After sunflower plants were grown in Mg-deficient 1/2-Hoagland solution Mg in the plants were redistributed. The Mg in the roots, stems, cotyledons, primary and secondary leaves was retranslocated to the youngest leaves. 3. In isolated, secondary-rooted sunflower shoots grown in Mg-deficient solution, plant Mg was retranslocated into the new roots and into the youngest shoots. 4. The 28Mg-uptake from the 0,2 mM MgSO4 solution was usually higher than from the 1/10-Hoagland solution. The composition of the uptake solution had little influence on the distribution of 28Mg. Independent of the age plants had the highest 28Mg content in the young and the lowest in the old leaves. 5. Root uptake of 28Mg resulted in a more uniform distribution in the plant than leaf uptake. The old leaves had a higher 28Mg content by root uptake than by leaf uptake of 28Mg. This is probably influenced by transpiration, in combination with the xylem transport of 28Mg after root uptake, which differs from leaf uptake and translocation in basipetal direction. 6. With increased age of plants, the content of 28Mg/10 gr. fresh weight decreased and the difference in content between the parts of plant was higher. The decrease of Mg content in the oldest leaves was the highest. 7. The results showed that Mg was transportable in the phloem. The magnitude and the direction of Mg transport was determined as primarily through the assimilation stream, which is coupled with Mg transport in plants. 相似文献
14.
Abstract Copper absorption by roots or leaf and transport to other parts were followed in 9‐days old bean (Phaseolus vulgaris L. cv. Vaghya) seedlings. Translocation was also measured in 4 cm segments of the stem. It was found that larger amount of Cu was retained in the roots and Cu was more mobile through phloem than through xylem, as indicated by the data on translocation from root and leaf. Bean plants were found to translocate more Cu to the stem than to other parts. Kinetic analysis of absorption by excised roots and stem segments revealed that the roots have a maximum uptake capacity and high affinity for Cu. 相似文献
15.
Effect of external and internal factors on the calcium content of paprika and bean fruits In water culture experiments with paprika and bean plants the effect of Ca supply, transpiration and growth rate on the Ca content of the fruits has been studied. A 10-fold increase in Ca supply only slightly increased the Ca content. The Ca content of the paprika fruits was increased considerably at high transpiration rates of either the whole shoot or the single fruit. High transpiration also increased the Mg content but had no effect on the K content. In bean high transpiration rates only increased the Ca content in the early stages of fruit development. The ratio of Ca translocation versus water loss by transpiration sharply declined during fruit growth in both species. In paprika the highest ratio (μg Ca/ml) in the fruits corresponded with the ratio in the leaves. In bean fruits, however, this ratio distinctly exceeded that of fully developed leaves. At high transpiration rates of the shoot 20% of the Ca (45Ca) injected into the fruit were translocated out of the fruit. At low transpiration rates of the shoot the corresponding value was below 1%. Most of all the growth rate of the fruits affected the Ca content. With increasing growth rate the Ca transport into the fruits was hardly altered which in turn led to a sharp decrease of the Ca content per unit dry weight. The results support the idea of the Ca transport into the fruit via the xylem. This Ca transport — i.e. also the Ca content of the fruit — is regulated and is also to be influenced by direct or indirect alterations of the water transport in the xylem. 相似文献
16.
Satoshi Yamada Atsushi Takeoka Masuo Yamanouchi 《Soil Science and Plant Nutrition》2013,59(4):969-974
Detached leaves of several crop plants were cultured in a nutrient solution containing 32P, and the 32P mobility between and within organs was investigated. The results obtained were as follows: 1) In soybean and adzuki bean, 32P was well distributed all over the leaf blade and petiole within 24 h after 32P absorption, though the transfer of 32P from the leaf vein to the mesophyll varied among the varieties. 2) In rice, 32P reached the middle or proximal part of the leaf blade within 48 h after 32P absorption. The gradient of 32P density decreased distally. 3) In maize and pumpkin, a small amount of 32P reached the leaf blade; in maize, the gradient of 32P density was similar to that in rice, though 32P was retained in the whole petiole in pumpkin. Besides transpiration, 32P transfer from xylem to mesophyll and structures of leaf tissues could be considered to regulate the 32P mobility. 相似文献
17.
18.
Soodabeh Bastani 《Soil Science and Plant Nutrition》2013,59(3):254-263
ABSTRACTIn order to compare plants’ response to phosphorus (P) application through roots and leaves, oilseed rape (Brassica napus L. cv. Hayola) plants were cultivated until vegetative or reproductive stages and were pretreated with an adequate (+P) or low (?P) supply of P. Thereafter, these plants were treated with 0.3 mM P as sodium dihydrogen phosphate (NaH2PO4) either through roots (root application, RA) or leaves (leaf application, LA). Shoot biomass was observed to be suppressed under ?P conditions at both stages, whereas root growth was comparatively improved in ?P plants at the vegetative stage but not at the reproductive stage. Both RA and LA were able to compensate for the growth of vegetative shoot and roots at both stages; however, LA reduced P and dry matter partitioning into the fruits. At the vegetative stage, recovery of applied P was similar between RA and LA treatments, and was extensive in ?P plants compared with the +P ones. At the reproductive stage, in contrast, significantly lower recovery of P was observed likely due to the lower capacity of leaves for P absorption and/or their lower re-translocation ability through the phloem. Data of P utilization efficiency showed that ?P plants, at both vegetative and reproductive stages, efficiently use leaf-applied P for biomass production when compared with the +P plants. Activity of acid phosphatase was sharply inhibited by RA in ?P plants, whereas it was preferably increased by LA in both +P and ?P plants. Results indicated that under P-deficiency conditions, plants had higher ability to utilize foliar-applied P, and in contrast to RA, LA may enable plants for a continuous higher capacity of P uptake from P-deficient soil; however, RA was superior to LA in terms of fruit growth. 相似文献
19.
《Soil Science and Plant Nutrition》2013,59(6):717-725
Abstract Until now, the real-time uptake and movement of manganese (Mn), an essential plant nutrient, has not been documented in plants. In this study, the real-time translocation of Mn in barley (Hordeum vulgare L. cv. Ehimehadaka no. 1) was visualized using the positron-emitting tracer 52Mn and a positron-emitting tracer imaging system (PETIS). PETIS allowed the non-destructive monitoring of Mn translocation in barley under various conditions. In all cases, 52Mn first accumulated in the discrimination center (DC) at the basal portion of the shoot, suggesting that this region may play an important role in Mn distribution in graminaceous plants. Manganese-deficient barley showed greater translocation of 52Mn from roots to shoots than did Mn-sufficient barley, demonstrating that Mn deficiency causes enhanced Mn uptake and loading into vascular bundles. In contrast, the translocation of 52Mn from roots to shoots was suppressed in Mn-excess barley. In these plants, the uptake of Mn may be suppressed or Mn may accumulate in the intercellular organelles of root cells, resulting in low rates of Mn translocation to shoots. In Mn-sufficient barley, the dark treatment did not suppress the translocation of 52Mn to the youngest leaf, suggesting that the translocation of Mn to the youngest leaf is independent of the transpiration stream. When 52Mn was supplied to the cut end of an expanded leaf, 52Mn was transported to the DC within 27 min and then retranslocated to roots and other leaves. Our results show that the translocation of Mn from the roots to the DC depends passively on water flow, but actively on the Mn transporter(s). 相似文献
20.
The first objective of this study was to search for a possible correlation between accumulation of calcium (Ca), potassium (K), and magnesium (Mg) and fruit transpiration in developing apricot (Prunus armeniaca L.) fruit. Secondly, the work aimed to determine the significance of transpirational flux on Ca nutrition. We hypothesized that if the fruit transpiration is the determining factor of Ca accumulation (phloem‐immobile element) then the import of Ca would be suppressed by restriction of fruit water loss, while the import of phloem‐mobile nutrients (i.e., K and Mg) would not be. To test this hypothesis, the seasonal changes of transpiration and of Ca, K, and Mg concentration/accumulation were assessed in fruits left to naturally transpire or under restricted transpiration (bagged fruits). Fruit transpiration was measured on detached fruits using a portable gas‐exchange equipment (ADC‐LCA4, ADC BioScientific Ltd, Hoddesdon, England). Results demonstrated that 83% of total fruit Ca content was gained within the first 4 weeks after fruit‐set, and that Ca import ceased concomitantly to a reduction of transpiration. In spite of the limitation of fruit transpiration, Ca entered the nontranspiring fruits, and its concentration was about 45% of that in control fruits suggesting that other factor(s) operated for Ca accumulation. This study provides the evidence that fruit transpiration accounted for 55% of total Ca that entered a fruit. We conclude that optimal soil Ca availability and apportioning to the fruit during the early 4 weeks of growth are essential to sustain the fruit demand of this nutrient and that some cultural practices (e.g., summer pruning, irrigation) should be tested as possible tools to improve fruit Ca nutrition via increasing fruit transpiration. 相似文献