Heiner E. Goldbach

Boron in plant and animal nutrition

This book comprises the contributions of the international workshop Boron 2001 which was aimed at gathering all relevant information on recent developments in boron research in soils, plants, animal and men over the past years. Review articles and original contributions deal with both applied and basic aspects in this area, comprising topics such as methods for B determination, the physiological functions of boron in plant and animal metabolism, including use of 10B for diagnostic purposes and cancer treatment. Genetic and molecular aspects of boron efficiency and tolerance to toxic levels in plants and the early physiological reactions to boron deprivation are further important topics of this volume. The role of boron for reproductive development is dealt with in further contributions. Furthermore, improved methods for the diagnosis of the available boron status in soils, plants appropriate timing and leaf fertilizer application are addressed. Special emphasis is given in the contributions to highlight the most recent developments in the aforementioned areas.

Rapid response reactions of roots to boron deprivation

Upon B removal from the nutrient solution, several response reactions of root cells can be measured within minutes. These include: reduction of cell wall elasticity modulus e, increase of hydraulic conductivity, reduced activity of plasmalemma-bound inducible (NADH) reductase, (smaller) changes of the membrane potential, and liberation of Ca2+ (apoplastic and membrane-bound). The B most demanding (root) tissues are epidermal and outer cortical cells of the extension zone, xylem vessels, and root hair tips. Deprivation of B leads to morphological changes which can be noticed within hours to days, including browning of tissues, growth inhibition, death of apical meristems, and lack of root hairs. How the primary response reaction(s) lead to the expression of visible symptoms, however, is not yet clear. The present review summarizes rapid responses to B deprivation and shows several possibilities how primary might be linked to secondary reactions, including cytoskeleton-mediated responses. Schnelle Reaktionen von Wurzeln auf Bor-Mangel Nach Umsetzen auf ein B-Mangelmedium konnen verschiedene Reaktionen von Wurzelzellen innerhalb von Minuten beobachtet werden, wie z.B. Verringerung des Zellwandelastizitatsmoduls e, Zunahme der hydraulischen Leitfahigkeit, verringerte Plasmalemma-gebundene induzierbare (NADH) Reduktaseaktivitat, (kleinere) Anderungen des Membranpotenzials und eine Freisetzung von apoplastischem und membrangebundenem Ca2+. Die Wurzelgewebe mit dem hochsten B-Bedarf scheinen die epidermalen und auseren Rindenzellen der Streckungszone, Xylem und Wurzelhaarspitzen zu sein. B-Entzug fuhrt zu morphologischen Anderungen, die innerhalb von Stunden und Tagen sichtbar werden, wie Gewebeverbraunung, Wachstumshemmung und Absterben apikaler Meristeme, sowie Fehlen von Wurzelhaaren. Wie die raschen Reaktionen zur (sekundaren) Auspragung von Mangelsymptomen fuhren, ist jedoch noch nicht klar. In dieser Ubersicht werden rasche Reaktionen auf B-Entzug zusammengefasst und Moglichkeiten zur Verknupfung primarer und sekundarer Reaktionen diskutiert.

Advances in plant and animal boron nutrition

Boron is one of the essential micronutrients for higher plants growth and development, and more and more studies have been conducted to establish boron as an essential element in animals and humans. This book reviews all aspects of boron research in recent years and is based on the Third International Symposium on all Aspects of Plant and Animal Boron Nutrition which was held in Wuhan, P.R. China in 2005. This includes B sorption mechanisms in soils, deficiency and toxicity of B, B fertilizer application and basic research on the physiology and molecular biology of plant B nutrition, and nutritional function of B in animals and humans. This book is aimed at scientists, and Masters or Ph. D. students focusing on boron research field. It will also provide managers involved in agricultural production with an important reference to recent developments in boron nutrition research.

A miniaturized curcumin method for the determination of boron in solutions and biological samples

Methods for the determination of boron require either sophisticated and expensive equipment (e.g. ICP-OES or ICP-MS) or a relatively large sample volume (e.g. spectrophotometric methods). A modified and miniaturized spectrophotometric curcumin method is presented which allows the determination of boron in sample volumes of 50—150 μl with a detection limit of 0.010 mg B l1. The calibration curve is linear up to a concentration of 3 mg B l1. Interferences with other ions are eliminated by extraction of boron with 2-ethyl-1,3-hexanediol in chloroform. Simultaneously, enrichment of boron in the sample can be performed within the same extraction step. Results show good reproducibility with a relative standard deviation of 15% at B concentrations between 0.05 and 0.40 mg B l—1. In different types of solutions, recovery of added boron was in the range of 98 to 99%. For several plant materials containing from 18 to 58 μg B (g dw)1, an overall relative standard deviation of 4.5% was established. So far, the method has been successfully applied to determine boron in waters, nutrient solutions, different plant parts (roots, stems and leaves) as well as in phloem sap and apoplastic washing fluid of several plant species. Eine miniaturisierte Curcumin-Methode zur Bestimmung von Bor in Losungen und in biologischen Proben Methoden der Bor-Bestimmung erfordern entweder teure und aufwendige Technik (z. B. ICP-OES oder ICP-MS) oder aber ein relativ groses Probenvolumen (z. B. Spektrophotometrische Methoden). Es wird eine modifizierte und miniaturisierte spektrophotometrische Curcumin-Methode vorgestellt, mit der Bor in Probenvolumina von 50—100 μl mit einer Nachweisgrenze von 0,010 mg B l1 bestimmt werden kann. Die Kalibriergerade ist bis zu einer Konzentration von 3 mg B l1 linear. Storende Einflusse anderer Ionen werden durch Extraktion mit 2-Ethyl-1,3-Hexandiol in Chloroform eliminiert. Zugleich kann mit der Extraktion eine Bor-Anreicherung der Probe erfolgen. Die Ergebnisse sind gut reproduzierbar mit einer relativen Standardabweichung von 1—5% bei B-Konzentrationen zwischen 0,05 und 0,40 mg B l1. In verschiedenen Losungen betrug die Wiederfindung zugegebenen Bors 98 bis 99%. Fur unterschiedliche Pflanzenmaterialien mit einem B-Gehalt zwischen 18 und 58 μg B (g TS)1 wurde in allen Fallen die relative Standardabweichung mit rund 4.5% bestimmt. Die Methode wurde bisher erfolgreich zur B-Bestimmung in Wasser, Nahrlosungen, verschiedenen Pflanzenteilen (Wurzeln, Sprosachsen, Blattern) sowie in Phloemsaft und apoplastischer Waschflussigkeit mehrerer Pflanzenarten angewendet.

The possible role of aerosols on stomatal conductivity for water vapour

Summary Stomatal conductance, which controls both the exchange of water vapour and CO 2 , is thought to be strictly determined by stomatal aperture. However, water transport processes might be modified by deposition of hygroscopic salts on the leaf surface. For this reason, simultaneous measurements of gas exchange and stomatal aperture were performed on Sambucus nigra leaves before and after treatment with sub-micrometer NaNO 3 aerosol. Aerosol treatment of the leaves led to higher transpiration, which was particularly pronounced at small apertures, leading to an enhancement of minimum leaf conductance between 45 and 90%. CO 2 -uptake of Sambucus leaves was not enhanced by aerosol treatment, and consequently water use efficiency decreased at small stomatal apertures. Artificial leaves consisting of small water reservoirs tapped with filter membranes also showed an increase in evaporation after aerosol treatment, which indicates a mainly physical explanation for the findings with Sambucus leaves. Absorption and desorption of water by salt deposits due to changing thickness of the laminar sublayer and entering turbulent elements -‘bursts’- is suggested to be a possible explanation of the results. The cyclic elementary process, condensation and evaporation of water on the leaf surface, was observed microscopically under changing boundary layer conductance at 50% relative humidity (RH). Hygroscopic particles might therefore act as intermediate short-term storage or as primary evaporation sites after liquid water transport along films of salt solution through stomatal pores. A dynamic model describes the effects of cycles of short-term storage of salts. Possible consequences for plant water relations are discussed. Wasserdampf- und CO 2 -Austausch von Blattern werden durch die stomatare Leitfahigkeit reguliert, welche bislang als eine Funktion alleine der Spaltoffnungsweite gesehen wurde. Hygroskopische Salze auf der Blattoberflache konnten diese eindeutige Beziehung aufgrund ihrer Wechselwirkung mit Wasser(dampf) beeinflussen. Aus diesem Grund wurden gleichzeitig Gasaustausch und Spaltoffnungsweiten an Blattern von Holunder ( Sambucus nigra ) gemessen. Die Ergebnisse dieser Messungen vor und nach Bespruhung der Blatter mit NaNO 3 -Aerosol wurden verglichen. Nach der Aerosolbehandlung war die Transpiration signifikant erhoht. Die relative Zunahme war bei kleinen Offnungsweiten besonders stark und die mimimale Leitfahigkeit erhohte sich um 4590%. Dagegen stieg die CO 2 -Aufnahme der Sambucus -Blatter durch die Aerosolbehandlung nicht an, wodurch sich bei kleinen Spaltoffnungsweiten eine geringere Wassernutzungseffizienz ergab. Auch fur Modellblatter (kleine mit Membranfiltern verschlossene Wassergefase) wurde nach Aerosolbehandlung ein Verdunstungsanstieg gemessen, was auf eine uberwiegend physikalische Ursache der Ergebnisse an Sambucus hindeutet. Die Ursache konnte in der wiederholten Ab- und Desorption von Wasser an den Salzablagerungen liegen und auf Veranderungen der Grenzschichtdicke und das Eindringen von Turbulenzelementen (“bursts”) in die Grenzschicht zuruckgehen. Der elementare Zyklus, Kondensation und Evaporation von Wasser auf der Blattoberflache bei sich andernder Grenzschichtleitfahigkeit, wurde bei 50% relativer Feuchte mikroskopisch beobachtet. Analog konnten hygroskopische Partikel als kurzzeitige Zwischenspeicher fungieren oder, nach dem Transport flussigen Wassers entlang von Filmen aus Salzlosung durch die Spaltoffnungen, als primare Verdunstungsorte wirken. Ein dynamisches Modell beschreibt die Wirkung wiederholter kurzzeitiger Speicherung durch das Salz. Die mogliche Bedeutung der Ergebnisse fur den pflanzlichen Wasserhaushalt wird diskutiert.

Physico-chemical properties of plant cuticles and their functional and ecological significance

Most aerial plant surfaces are covered with a lipid-rich cuticle, which is a barrier for the bidirectional transport of substances between the plant and the surrounding environment. This review article provides an overview of the significance of the leaf cuticle as a barrier for the deposition and absorption of water and electrolytes. After providing insights into the physico-chemical properties of plant surfaces, the mechanisms of foliar absorption are revised with special emphasis on solutes. Due to the limited information and relative importance of the leaf cuticle of herbaceous and deciduous cultivated plants, an overview of the studies developed with Alpine conifers and treeline species is provided. The significance of foliar water uptake as a phenomenon of ecophysiological relevance in many areas of the world is also highlighted. Given the observed variability in structure and composition among, for example, plant species and organs, it is concluded that it is currently not possible to establish general permeability and wettability models that are valid for predicting liquid-surface interactions and the subsequent transport of water and electrolytes across plant surfaces.

Ligands of boron in Pisum sativum nodules are involved in regulation of oxygen concentration and rhizobial infection

Boron (B) is an essential nutrient for N(2)-fixing legume-rhizobia symbioses, and the capacity of borate ions to bind and stabilize biomolecules is the basis of any B function. We used a borate-binding-specific resin and immunostaining techniques to identify B ligands important for the development of Pisum sativum-Rhizobium leguminosarum 3841 symbiotic nodules. arabinogalactan-extensin (AGPE), recognized by MAC 265 antibody, appeared heavily bound to the resin in extracts derived from B-sufficient, but not from B-deficient nodules. MAC 265 stained the infection threads and the extracellular matrix of cortical cells involved in the oxygen diffusion barrier. In B-deprived nodules, immunolocalization of MAC 265 antigens was significantly reduced. Leghaemoglobin (Lb) concentration largely decreased in B-deficient nodules. The absence of MAC 203 antigens in B-deficient nodules suggests a high internal oxygen concentration, as this antibody detects an epitope on the lipopolysaccharide (LPS) of bacteroids typically expressed in micro-aerobically grown R. leguminosarum 3841. However, B-deprived nodules did not accumulate oxidized lipids and proteins, and revealed a decrease in the activity of the major antioxidant enzyme ascorbate peroxidase (APX). Therefore, B deficiency reduced the stability of nodule macromolecules important for rhizobial infection, and for regulation of oxygen concentration, resulting in non-functional nodules, but did not appear to induce oxidative damage in low-B nodules.

Nutrient interactions of alley cropped Sorghum bicolor and Acacia saligna in a runoff irrigation system in Northern Kenya

In a runoff irrigation system in Northern Kenya, we studied the nutrient interactions of sole cropped and alley cropped Sorghum bicolor (L.) Moench and Acacia saligna (Labill.) H.L. Wendl. The trees were pruned once before the cropping season and the biomass was used as fodder for animals. The nutrient contents in leaf tissue, soil and soil solution were monitored and the uptake of applied tracers (15N, Sr) was followed. The grain yield of alley cropped sorghum was similar to or slightly higher than in monoculture and did not decrease near the tree-crop interface. Foliar N and Ca contents of the crop were higher in the agroforestry combination than in monoculture, corresponding to higher soil N and Ca contents. Soil solution and soil mineral N dynamics indicate an increase of N under the tree row and unused soil N at the topsoil in the alley of the sole cropped trees as well as below 60 cm depth in the crop monoculture. The N use efficiency of the tree+crop combination was higher than the sole cropped trees or crops. Competition was observed for Zn and Mn of both tree and crop whereas for Ca only the tree contents decreased. P, K, Mg and Fe dynamics were not affected by alley cropping at our site. The lower uptake of applied Sr by trees in alley cropping compared to those of the monoculture stand suggested a lower competitiveness of the acacia than sorghum, which did not show lower Sr contents when intercropped. The study showed the usefulness of combining soil and plant analyses together with tracer techniques identifying nutrient competition, nutrient transfer processes and the complementary use of soil nutrients, as the main features of the tree-crop combination.

Early effects of boron deficiency on physical cell wall parameters, hydraulic conductivity and plasmalemma-bound reductase activities in young C. pepo and V. faba roots

Rapid effects of boron (B) starvation were investigated in squash (Cucurbita pepo) and bean (Vicia faba) roots. A transitory decrease of the cell wall elastic modulus (e) and a concomitant increase of the cell hydraulic conductivity up to fourfold have been observed by measurement with the cell pressure probe. This is in line with a putative role of B in determinating the cell wall physical parameters by the formation of cross links in the pectate fraction.

Boron Toxicity: the Importance of Soluble Boron

The function of boron in plants has often been associated with cell wall bound insoluble boron. This was mainly due to the fact that B-related nutritional disorders clearly lead to a structural damage of the cell wall, and that the cell wall bound B-RGII-complex has been isolated and characterized in detail. However, more and more evidence indicates that other functions of B are important in plants, which can not be related to cell wall bound B-RGII. Rapid reactions under B deficiency, effects of B toxicity, and, most important of all, the observed essentiality of B for animals (Eckert, 1998, Eckert and Rowe, 1999), can not be explained by a structural function of B in the cell wall. Since animals do not have a pectin-rich cell wall, other B forms, e.g. free or loosely bound B, must be involved in those reactions.