The Mobility of Manganese in the Wheat Plant: I. Redistribution and Follar Application

The distribution of manganese in wheat plants grown in solutionculture has been studied. Manganese supply from the medium wasso arranged that early leaves received sufficient for normalfunction but subsequent growth was severely restricted by deficiencyof the element. Under these conditions little or no redistributionwithin the plant was observed, so that the early leaves retainedmost or all of their manganese, and remained healthy. When manganesewas applied externally to the second leaves of deficient plantsa small but significant amount was translocated to the growingpoints. The effect was slightly enhanced by repeated rewettingof the treated leaves, but the amount moved was still smallin relation to that applied and to the requirement of the plants.It appears that manganese is not readily transported by thephloem under these conditions, but this does not wholly accountfor the ability of some leaves to retain critical levels whena state of deficiency exists at the growing points. Possiblemechanisms for this effect are discussed.     

Redistribution of Potassium, Calcium, Magnesium, and Manganese in the Plant

The extent of redistribution in apple was described by calculating the fruit/leaf ratio of the cation content. It was found that the redistribution diminishes in the sequence K > Mg > Ca ～ Mn. These results are more or less in agreement with those found elsewhere. Investigations were made to see whether it was possible to account for the differences in redistribution by the phloem by means of the solubility of these cations in the sieve tube sap. As model plants Yucca flaccida and Ricinus communis were used, plants from which it was possible to obtain phloem sap in a rather pure state. It was found that the addition of potassium and magnesium as a chloride in the usual investigated range of concentrations did not give precipitation. With calcium and manganese, however, a precipitate soon occurred. Manganese was demonstrated to be less soluble than calcium. For Ricinus the maximum amount of calcium and manganese the sieve tube sap could contain before precipitation set in was higher than for Yucca sap. The results confirm the possibility that the redistribution of the different cations in the plant can be related inter alia to their solubility in the sieve tube sap. It was also found that the calcium in the phloem sap is present in ionic condition. Thus the normal laws of solubility should be applicable.     

Translocation and Metabolism of Endosperm-Applied [2-C] Indoleacetic Acid in Etiolated Avena sativa L. Seedlings

The role of free indole-3-acetic acid (IAA) in the endosperm of Avena sativa L. seedlings was investigated to determine its contribution to free IAA in the shoot. [2-¹⁴C]IAA was injected into the endosperm of darkgrown seedlings and the transport and metabolism of the [¹⁴C]-labeled compounds determined. It was concluded that translocation of free IAA directly from the endosperm is probably not a significant source of free IAA in the shoot, mainly because even small amounts of [¹⁴C]IAA introduced into the endosperm were rapidly metabolized. This suggested that, in Avena, free IAA does not normally exist in the liquid endosperm.     

Manganese Redistribution by Calcium-stimulated Vesicle Trafficking Bypasses the Need for P-type ATPase Function

Regulation of intracellular ion homeostasis is essential for eukaryotic cell physiology. An example is provided by loss of ATP2C1 function, which leads to skin ulceration, improper keratinocyte adhesion, and cancer formation in Hailey-Hailey patients. The yeast ATP2C1 orthologue PMR1 codes for a Mn²⁺/Ca²⁺ transporter that is crucial for cis-Golgi manganese supply. Here, we present evidence that calcium overcomes the lack of Pmr1 through vesicle trafficking-stimulated manganese delivery and requires the endoplasmic reticulum Mn²⁺ transporter Spf1 and the late endosome/trans-Golgi Nramp metal transporter Smf2. Smf2 co-localizes with the putative Mn²⁺ transporter Atx2, and ATX2 overexpression counteracts the beneficial impact of calcium treatment. Our findings suggest that vesicle trafficking promotes organelle-specific ion interchange and cytoplasmic metal detoxification independent of calcineurin signaling or metal transporter re-localization. Our study identifies an alternative mode for cis-Golgi manganese supply in yeast and provides new perspectives for Hailey-Hailey disease treatment.     

Redistribution of Manganese in Maturing Lupin us angustifolius cv. Illyarrie in Relation to Levels of Previous Accumulation

The retranslocation of Mn from pools of pre-accumulation todeveloping seed of Lupinus angustifolius was examined in growthchamber and field experiments. In the growth chamber experiment, plants (cv. Illyarrie) weregrown in sand containing Mn at 18 levels of supply from low(15 fig Mn kg"1) to luxury (12800 fig Mn kg{small tilde}l).At 90 d, sand was washed from the roots and the plants weregrown to maturity in nutrient solution in the absence of Mn.At sequential harvests, the plants were divided into a numberof fractions and were analysed for Mn to determine changes inthe amount of Mn contained in each component. Plants (cv. Marri)were also grown in the field at a Mn deficient site with andwithout added Mn, and similar harvests and observations weremade. Manganese moved readily from roots, stems and petioles to developingsinks, including seeds via pods. Retranslocation of Mn preventedthe appearance of Mn deficient seed (‘split seed’)in plants which had accumulated sufficient Mn prior to the omissionof Mn supply. The mode of Mn transport is discussed, and itsconveyance to seed in phloem, mediated by transfer cells, issuggested. The identification of pools of Mn accumulation fromwhich Mn may retranslocate presents a basis on which tests prognosticof impending Mn deficiency in maturing lupins may be developed.Stem is favoured as the tissue on which to base such tests. No Mn translocated to developing seed sinks from mature, oreven senescing lupin leaves. The cause appears to be that Mnis poorly loaded into the phloem of leaves although much wasfound to be leachable. About 40 per cent of leaf Mn was extractablewith water, more (approx. 70 per cent) with dilute ethylenediamine tetraacen’c acid but little (approx. 14 per cent)with N7>Jdimethyl formamide along with other cell contents.The form of Mn in leaves is discussed.     

Evolution of Multilocus Genetic Structure in Avena Hirtula and Avena Barbata

Avena barbata, an autotetraploid grass, is much more widely adapted than Avena hirtula, its diploid ancestor. We have determined the 14-locus genotype of 754 diploid and 4751 tetraploid plants from 10 and 50 Spanish sites, respectively. Allelic diversity is much greater in the tetraploid (52 alleles) than in the diploid (38 alleles): the extra alleles of the tetraploid were present in nonsegregating heteroallelic quadriplexes. Seven loci were monomorphic for the same allele (genotypically 11) in all populations of the diploid: five of these loci were also monomorphic for the same allele (genotypically 1111) in all populations of the tetraploid whereas two loci each formed a heteroallelic quadriplex (1122) that was monomorphic or predominant in the tetraploid. Seven of the 14 loci formed one or more highly successful homoallelic and/or heteroallelic quadriplexes in the tetraploid. We attribute much of the greater heterosis and wider adaptedness of the tetraploid to favorable within-locus interactions and interlocus (epistatic) interactions among alleles of the loci that form heteroallelic quadriplexes. It is difficult to account for the observed patterns in which genotypes are distributed ecogeographically except in terms of natural selection favoring particular alleles and genotypes in specific habitats. We conclude that natural selection was the predominant integrating force in shaping the specific genetic structure of different local populations as well as the adaptive landscape of both the diploid and tetraploid.     

Metabolism of diclofop-methyl in cell cultures of Avena sativa and Avena fatua

The metabolism of the herbicide, diclofop-methyl (methyl-2-[4-(2', 4'-dichlorophenoxy) phenoxy]propanoate), in cell suspension cultures of Avena sativa L. (cv. Garry) and in callus of Avena fatua L. (transferred to liquid) was determined as a function of time (8 h to about 3 weeks) and was compared to previous metabolism data from intact plants. A. fatua metabolized ¹⁴C-labeled diclofop-methyl more rapidly than A. sativa, but the metabolites formed were similar if not identical. Within 2 days, approximately 50% of the total ¹⁴C recovered was in A. fatua cells whereas less than 15% was in A. sativa cells. In older cultures of A. fatua, the amounts of ¹⁴C in the cells and in the medium were about 45% each; 10 to 12% was in the non-extractable cell residue. The ¹⁴C recovered from A. sativa cells increased to a maximum of about 35% at 7 days and then slowly decreased to about 18% by 21 days, whereas the ¹⁴C in the medium of A. sativa decreased to about 60% at 7 days and then increased to over 75% by 21 days. The nonextractable ¹⁴C residue was 5% or less even after 21 days. Major metabolites in methanolic extracts of cells of both A. sativa and A. fatua were diclofop (2-[4-(2', 4'-dichlorophenoxy)phenoxy] propanoate), diclofop hydroxylated at an undetermined position on the 2,4-dichlorophenyl ring (ring OH-diclofop), and conjugates of diclofop and ring-OH diclofop.     

四倍体大燕麦与六倍体裸燕麦的受精作用和胚胎发育

用石蜡切片法,对四倍体大燕麦（Avena magna L.）和六倍体裸燕麦（Avena nuda L.）杂交的受精作用和胚胎发育进行了观察。结果表明,六倍体裸燕麦花偻在四倍体大燕麦柱头上萌发良好,花粉管可顺利长入花柱和胚囊,观察的168个四倍体大燕麦子房中,2.38%发生了双受精,产生了胚和胚乳;1.79%发生了单卵受精,只产生胚乳而无胚;总受精率为5.36%;成胚率为4.17%。由于胚乳的缺管或发育异常及败育,最终难以获得有生活力的种子,为四倍体大燕麦和六倍体裸燕麦杂交提供了细胞胚胎学证据。     

The Phototropic Responses of Avena Coleoptiles

Macleod, K., Firn, R. D. and Digby, J. 1986. The phototropicresponses of Avena coleoptiles.—J. exp. Bot. 37: 542–548. A number of studies of the elongation rate changes causing phototropismhave been made but the findings of different groups have notbeen entirely Consistent. Studies of oat coleoptile phototropismin response to first-positive and second-positive doses indicatethat no single pattern of elongation rate changes causes phototropismeven in a single species. The relative effect of phototropicstimulation on the elongation rate at the shaded or the illuminatedside of coleoptiles subject to unilateral illumination dependson physiological state of the cell-for instance its positionin the elongation zone or whether it has been given red lightrecently. Models of phototropism will have to account for sucha diversity of phototropic responses. The importance of makingfull elongation rate measurements has once again been demonstrated. Key words: Phototropism, first-positive, second-positive, phytochrome, coleoptile, elongation rate     

Induction of Manganese Superoxide Dismutase by Nuclear Translocation and Activation of SIRT1 Promotes Cell Survival in Chronic Heart Failure

Oxidative stress plays a pivotal role in chronic heart failure. SIRT1, an NAD⁺-dependent histone/protein deacetylase, promotes cell survival under oxidative stress when it is expressed in the nucleus. However, adult cardiomyocytes predominantly express SIRT1 in the cytoplasm, and its function has not been elucidated. The purpose of this study was to investigate the functional role of SIRT1 in the heart and the potential use of SIRT1 in therapy for heart failure. We investigated the subcellular localization of SIRT1 in cardiomyocytes and its impact on cell survival. SIRT1 accumulated in the nucleus of cardiomyocytes in the failing hearts of TO-2 hamsters, postmyocardial infarction rats, and a dilated cardiomyopathy patient but not in control healthy hearts. Nuclear but not cytoplasmic SIRT1-induced manganese superoxide dismutase (Mn-SOD), which was further enhanced by resveratrol, and increased the resistance of C2C12 myoblasts to oxidative stress. Resveratrol''s enhancement of Mn-SOD levels depended on the level of nuclear SIRT1, and it suppressed the cell death induced by antimycin A or angiotensin II. The cell-protective effects of nuclear SIRT1 or resveratrol were canceled by the Mn-SOD small interfering RNA or SIRT1 small interfering RNA. The oral administration of resveratrol to TO-2 hamsters increased Mn-SOD levels in cardiomyocytes, suppressed fibrosis, preserved cardiac function, and significantly improved survival. Thus, Mn-SOD induced by resveratrol via nuclear SIRT1 reduced oxidative stress and participated in cardiomyocyte protection. SIRT1 activators such as resveratrol could be novel therapeutic tools for the treatment of chronic heart failure.     

The Redistribution of Assimilate in Field-grown Winter Wheat

The long- and short-term movement of carbon in a field cropof winter wheat was investigated with the radioactive tracercarbon-14. The flag leaves of individual plants assimilateda pulse of ¹⁴CO₂ and the plant parts were assayed subsequently.Groups of plants were pulse-labelled four times during the mainperiod of growth—twice before and twice after anthesis.Plants were harvested and assayed twice weekly after labellingand the time-course of the changes in the amount of ¹⁴C recoveredfrom the leaves, stems and ears was observed for each groupof plants. Concurrently with these long-term studies, otherwheat plants were pulse-labelled, then harvested and assayed24 h later. The partitioning of ¹⁴C between leaves, stem, earand in some cases roots, was measured over the period from thestart of stem elongation to the end of grain filling. Two distinct types of relocation of carbon were observed. Carbonassimilated early in the growth of the plant and used in thegrowth of new leaves was seen to be partly relocated to theear. Carbon assimilated 8 d after anthesis was partly storedin the stem, and 15 d later relocated to the ear. This relocationcorresponded to a decrease in stem dry mass seen in growth analysis.Little other change in the ¹⁴C content of the plants occurred,suggesting that most respiration used current rather than storedassimilate. Key words: Carbon assimilate, redistribution, wheat     

The Thermodynamics of Short-distance Translocation in Plants

Flux equations derived from the thermodynamics of irreversibleprocesses are applied to calculations on the probable pathwayof short-distance translocation through non-vascular tissue.The Onsager theory predicts that a significant fraction of wateris transported over short distances via an extracellular (cellulosecell wall) pathway. It is suggested that the Onsager equationsare more comprehensive than other equations previously used,and the Onsager theory is found to support an increasing bodyof evidence for an extracellular pathway. Using the values of the Onsager coefficients measured in isolatedNitella cell walls, it is shown that an electrical gradientof I.5 mV/cm will cause the same water flux through cell wallsas a pressure gradient of I atm/cm. It is suggested that electricalgradients can contribute significantly to short-distance trans-location.     

The Foliar Uptake and Translocation of Caesium

A study has been made of the foliar uptake and translocationof caesium-137 by pea plants which have been grown for a periodin either the light or the dark. Keeping plants in the darkreduces both processes, and also reduces the proportion of mobilecaesium which is transported downwards. Other experiments involved darkening only parts of the plantand also the use of various metabolic inhibitors. These showedthat the reduction in foliar uptake and translocation in thedark was connected with changes in the carbohydrate metabolismof the leaf to which the caesium was applied. They further suggestedthat a metabolically controlled process was involved in thetransfer of caesium from the mesophyll into the phloem of theleaf veins. Changes in the distribution of caesium were alsogoverned in some way by changes in the carbohydrate metabolismof the ‘source’ leaf.     

The evolution pattern of rDNA ITS in Avena and phylogenetic relationship of the Avena species (Poaceae: Aveneae)

Ribosomal ITS sequences are commonly used for phylogenetic reconstruction because they are included in rDNA repeats, and these repeats often undergo rapid concerted evolution within and between arrays. Therefore, the rDNA ITS copies appear to be virtually identical and can sometimes be treated as a single gene. In this paper we examined ITS polymorphism within and among 13 diploid (A and C genomes), seven tetraploid (AB, AC and CC genomes) and four hexaploid (ACD genome) to infer the extent and direction of concerted evolution, and to reveal the phylogenetic and genome relationship among species of Avena. A total of 170 clones of the ITS1-5.8S-ITS2 fragment were sequenced to carry out haplotype and phylogenetic analysis. In addition, 111 Avena ITS sequences retrieved from GenBank were combined with 170 clones to construct a phylogeny and a network. We demonstrate the major divergence between the A and C genomes whereas the distinction among the A and B/D genomes was generally not possible. High affinity among the A(d) genome species A. damascena and the ACD genome species A. fatua was found, whereas the rest of the ACD genome hexaploids and the AACC tetraploids were highly affiliated with the A(l) genome diploid A. longiglumis. One of the AACC species A. murphyi showed the closest relationship with most of the hexaploid species. Both C(v) and C(p) genome species have been proposed as paternal donors of the C-genome carrying polyploids. Incomplete concerted evolution is responsible for the observed differences among different clones of a single Avena individual. The elimination of C-genome rRNA sequences and the resulting evolutionary inference of hexaploid species are discussed.     

The Intercellular Spaces of the Avena Coleoptile

In the transverse sections of fresh Avena coleoptile certain intercellular spaces are transparent, others are dark. The transparent spaces represent the result of water-logging of the originally water-lined air passages. The dark spaces are lined with a plastic lipid-containing membrane which can be impregnated with melted paraffin. In the living tissue this membrane can be cut transversely and the cut sections presumably seal off the gas inside thus causing the dark interfacial refraction. Because of the high permeability of lipids to carbon dioxide and the virtual impermeability to oxygen and nitrogen, there is a reason to believe that the lipid-lined spaces are filled with gas rich in carbon dioxide, and the lipid membrane may function as a regulator of the diffusion pressure of this gas.