Root-shoot interactions in mineral nutrition

In this paper four classes of co-operative root-shoot interations are addressed. (I) Nitrogen concentrations in the xylem sap originating from the root and in the phloem sap as exported from source leaves are much lower than those required for growth by apices and developing organs. Enrichment of xylem sap N is achieved by xylem to xylem (X-X) transfer, by which reduced N, but not nitrate, is abstracted from the xylem of leaf traces and loaded into xylem vessels serving the shoot apex. Nitrogen enrichment of phloem sap from source leaves is enacted by transfer of reduced N from xylem to phloem (X-P transfer). Quantitative data for the extent of the contribution of X-X and X-P transfer to the nutrition of young organs of Ricinus communis L. and for their change with time are presented. (II) Shoot and root cooperate in nitrate reduction and assimilation. The partitioning of this process between shoot and root is shifted towards the root under conditions of nitrate- and K-deficiency and under salt stress, while P deficiency shifts nitrate reduction almost totally to the shoot. All four changes in partitioning can be attributed to the need for cation-anion balance during xylem transport and the change in electrical charge occurring with nitrate reduction. (III) Even maintenance of the specificity of ion uptake by the root may – in addition to its need for energy – require a shoot-root interaction. This is shown to be needed in the case of the maintenance of K/Na selectivity under the highly adverse condition of salt stress and absence of K supply from the soil. (IV) Hormonal root to shoot interactions are required in the whole plant for sensing mineral imbalances in the soil. This is shown and addressed for conditions of salt stress and of P deficiency, both of which lead to a strong ABA signalling from root to shoot but result in different patterns of response in the shoot.     

Distribution ofAvena fatua in Czechoslovakia

Avena fatua L., a weedy grass of arable land and an occasional component of ruderal communities, shows uneven distribution over Czechoslovak territory. Compiled in a ?map of historical distribution” the literary and herbarium data suggest a similar pattern of dispersal as at the present time, which is presented in the “map of recent distribution”. Altogether 3124 localitíes, recorded on arable land in Bohemia and Moravia maínly in the period 1967 to 1974, have been listed and statistically evaluated according to various environmental aspects. The present-day distribution ofA. f. remains to be controlled by primary climatic, orographic and soil factors in spite of the profound effects of large-scale field management and weed control. According to its behaviour in Czechoslovakia, the species must be classed as a subthermophyte and subxerophyte dispersed mainly in the planar and colline belt and occupying mainly base-rich soils. The three zones established according to the density of localitíes with respect to the “classes of infestation” coincide well with the new phytogeographical division of western part of Czechoslovakia. Less complete data from the eastern part of the territory revealed similar trends in the species’ distríbution. From the viewpoint of syntaxonomy,A.f. has an optimum ín theSecalietalia, while its occurrence in ruderal communities lies mostly in theSisymbrion.     

Improving crop mineral nutrition

Background

Crops require adequate nutrition for the production of food, fibre and fuel, but soil conditions often limit the ability of crops to acquire mineral nutrients. To address this, mineral nutrients can be applied as inorganic or organic fertilisers to the soil or as liquid fertilisers to foliage. However, production and use of fertilisers can have negative environmental impacts. The articles in this Special Issue illustrate a number of ways to improve nutrient acquisition from the soil and their delivery through foliar application.

Scope

Articles highlighted here include those that discuss ways by which to assess a crop’s requirement for additional mineral elements, ways by which minerals can be supplied more effectively to crops both through roots and shoots, and ways by which the crop itself can be enhanced to acquire more mineral elements.

Conclusions

It is apparent from the information contained in this Special Issue that to improve the ability of crops to acquire mineral elements, a number of strategies are available. However, the success of any one intervention is dependent on how these strategies interact with the environment in which they are deployed and the suitability of the management system for the specific intervention.     

Studies in the mineral nutrition of Japanese mint

Summary This paper presents the results of an experimental enquiry into the effects of phosphorus deficiency and age on the nitrogen metabolism in component parts of mint plants (Mentha arvensis var.piperascens).Estimation of various nitrogenous fractions i.e. ammoniacal, nitrate, amide, rest, total soluble, total insoluble and total nitrogen were made in leaf, stem and root of mint plants, collected from full-nutrient and phosphorus-deficient cultures, at subsequent stages of the life cycle. The outstanding effect of phosphorus deficiency was noted: an increased accumulation of amides resulting in poor formation of proteins which suggested interference in protein synthesis beyond amide stage. Leaf showed maximum percentage of nitrogen in the insoluble form. The stem served as channel for transport and storage and invariably showed high concentration of soluble nitrogen fractions.     

Studies in the mineral nutrition of Japanese mint

Summary The outstanding effects of potassium deficiency on Japanese mint during winter and rainy seasons were marked accumulation of ammonia, amide and nitrate nitrogen with corresponding decrease in protain ntioen indicating arrested protein synthesis at ammonia- and amide formation stages as these fractions showed large proportion in the pool of soluble-N. The accumulation of soluble-nitrogen could be correlated with high respiration rate. Further, potassium-deficient plants had lowe value of rest-N and tootal N in winter and vice a versa in rainy season. In spite of an increased per cent essential oil content (ml/100 g dry weight), the total essential oil production (ml/plant) was low. In general, rainy season plants had higer percentage of essential oil and total oil/plant but showed lower values of all the forms of nitrogen.     

Studies in the mineral nutrition of Japanese mint

Summary Potassium deficiency resulted in a increased accumulation of total phosphorus, inorganic phosphorus and sugar phosphate which suggested some interference in phosphorus metabolism predominantly beyond the sugar phosphate synthesis stage. Roots appeared to be a reservoir for accumulation of various phosphorus fractions of Japanese mint (Mentha arvensis L. var.piperascens).A higher respiration rate under potassium deficiency might be one of the factors to retard the inclusion of inorganic phosphorus into structural components, resulting in poor formation of organophosphorus compounds needed for plant growth and development. In spite of an increased essential oil content (ml/100 g dry weight) in a phosphorus deficient situation, total essential oil production (ml/plant) was low. Foliage growth, essential oil content and respiration was higher between 60 to 80 days and seemed to be associated with a high intensity of enzymatic and metabolic activity, as observed in various phosphorus fractions rising to a very high value after 80 days of crop growth.     

Tree mineral nutrition is deteriorating in Europe

The response of forest ecosystems to increased atmospheric CO₂ is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth‐limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992–2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992–2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO₂, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO₂ emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered.     

Screening Arabidopsis for mutants in mineral nutrition

Arabidopsis thaliana is a small herbaceous plant which is used as a model plant for defining the molecular basis of many plant processes. The advantages of this plant for genetic studies are its small, well-characterized genome, a short life cycle, large seed set and small seed size. The analysis of mutants of this plant has proved useful in understanding basic plant processes. To isolate Arabidopsis mutants in mineral nutrition, we have devised a method of screening based on X-ray fluorescence spectrometry (XRFS) analysis of leaves. We have identified three mutants in P and Mn nutrition after screening over 100 000 seedlings. These mutants show either excessive accumulation of P or Mn in shoots or an inabilty to accumulate normal concentrations of P.     

Effect of aluminium on the mineral nutrition of rice

A study of the effect of increasing aluminium concentration in a dilute nutrient solution on various aspects of the mineral nutrient uptake by the rice plant has shown that aluminium exerts a stimulation on dry matter production and nutrient uptake until a concentration threshold was reached. The value of this threshold was influenced by nutrient solution composition and cultivar. Its location could be calculated by adjusting to the experimental points a rate law from enzyme kinetics on substrate inhibition curve. On the other hand, total uptake of aluminium and its concentration in the tops was a monotonic function of aluminium concentration in the nutrient solution, the effect of which was greatly enhanced by increased phosphate concentration. A sensitive cultivar accumulated more aluminium than a resistant one.The effect of phosphate on the alleviation of aluminium toxicity was slight in the range of concentration studied.Nitrogen uptake either as ammonium or nitrate nitrogen was clearly influenced by aluminium concentration when its instantaneous value was measured by the technique of the continuously flowing culture solution. The ammonium uptake rate of two cultivars different in sensitivity to aluminium was such that the sensitive variety took up less ammonium and acidified less the culture solution flowing through the root sysstem with a residence time of a few hours.Minor elements concentration in the tops of the rice plants did not seem to be greatly influenced by aluminium with the notable exception of manganese, the uptake of which was clearly depressed by increasing aluminium concentration.Attempts were made at using the speciation of the nutrient solutions with or without aluminium complexation by fluoride in order to rank the various ionic forms of aluminium according to their toxicity. It seems that the well-known result of primary toxicity due to the free Al-ion is also true for rice but that some toxicity is associated with the AlSO₄-ion.     

Regulating plant tissue growth by mineral nutrition

The objective of this study was to determine if the growth of sweet orange (Citrus sinensis (L.) Osbeck cv. ‘Valencia’) nonembryogenic callus could be regulated and controlled via the mineral nutrient components of the medium. The 14 salts comprising Murashige and Skoog (MS) basal medium were subdivided into five component groups. These five groups constituted the independent factors in the design. A five-dimensional hypervolume constituted the experimental design space. Design points were selected algorithmically by D-optimality criteria to sample of the design space. Growth of the callus at each design point was measured as % increase of fresh weight at 14 d. An analysis of variance was conducted and a response surface polynomial model generated. Model validation was conducted by mining the polynomial for design points to two regions—“MS-like” growth and MS + 25% growth and comparing callus growth to predicted growth. Five of the eight selected MS-like points and three of the six MS + 25% growth points validated, indicating regions within the design space where growth was equivalent to MS, but the salt combinations were substantially different from MS, and a smaller region where growth exceeded MS by greater than 25%. NH₄NO₃ and Fe were identified as important factors affecting callus growth. A second experiment was conducted where NH₄NO₃ and Fe were varied, thus creating a two-dimensional slice through the region of greatest callus growth and provided increased resolution of the response.     

Modeling optimal mineral nutrition for hazelnut micropropagation

Micropropagation of hazelnut (Corylus avellana L.) is typically difficult because of the wide variation in response among cultivars. This study was designed to determine the required mineral nutrient concentrations for micropropagation of C. avellana cultivars using a response surface design analysis. Driver and Kuniyuki Walnut (DKW) medium mineral nutrients were separated into five factors: NH₄NO₃, Ca(NO₃)₂, mesos (MgSO₄ and KH₂PO₄), K₂SO₄, and minor nutrients (boron, copper, manganese, molybdenum, and zinc) ranging from 0.5× to 2× the standard DKW medium concentrations with 33 treatments for use in modeling. Overall quality and shoot length for all cultivars were influenced by ammonium and nitrate nitrogen, mesos and minors. Reduced Ca(NO₃)₂ improved multiplication while higher amounts increased shoot length for most cultivars. Uptake of nutrients varied among the cultivars. Calcium and magnesium concentrations were greater in the shoots that grew well compared to poorly-growing and control treatments. All five cultivars showed improved growth on some treatments and the models indicated that shoots grown on an optimized medium would be even better. This model indicates that NH₄NO₃, Ca(NO₃)₂, mesos, and minors all had significant effects on hazelnut growth and multiplication and should be optimized in future experiments.     

Effects of sodium on mineral nutrition in rose plants

The effects of sodium (Na⁺) ion concentration on shoot elongation, uptake of ammonium (NH₄⁺) and nitrate (NO₃^?) and the activities of nitrate reductase (NR) and glutamine synthetase (GS) were studied in rose plants (Rosa hybrida cv. “Lambada”). The results showed that shoot elongation was negatively correlated with sodium concentration, although no external symptoms of toxicity were observed. Nitrate uptake decreased at high sodium levels, specifically at 30 meq litre4 of sodium. As flower development was normal under high saline conditions, this could suggest that nitrogen was being mobilised from shoot and leaf reserves. Ammonium uptake was not affected by any of the salt treatments applied probably because it diffuses through the cell membrane at low concentrations. Nitrate reductase activity was reduced by 50% at 30 meq litre 1 compared with control treatment, probably due to a decrease in the free nitrate related to nitrate uptake pattern. None of the salt treatments used affected total leaf GS activity (both chloroplastic and cytosolic isoforms) or leaf NPK mineral contents. Nitrate reductase activity in leaves increased at 10 meq litre^?1 of sodium and GS activity in roots (cytosolic isoform only) followed the same pattern as NR. It is suggested that the activation of both enzymes at low salt level could be attributed to the beneficial effect of increased sulphur in the nutrient solutions.     

Improving in vitro mineral nutrition for diverse pear germplasm

Mineral nutrition in the media used for growth of in vitro plants is often difficult to optimize due to complex chemical interactions of required nutrients. The response of plant tissue to standard growth media varies widely due to the genetic diversity of the plant species studied. This study was designed as the initial step in determining the optimal mineral nutrient requirements for micropropagation of shoot tips from a collection of genetically diverse pear germplasm. Five mineral nutrient factors were defined from Murashige and Skoog salts: NH₄NO₃, KNO₃, mesos (CaCl₂·2H₂0–KH₂PO₄–MgSO₄), micronutrients (B, Cu, Co, I, Mn, Mo, and Zn), and Fe-EDTA. Each factor was varied over a range of concentrations. Treatment combinations were selected using response surface methods. Five pears in three species (Pyrus communis ‘Horner 51,’ ‘Old Home?×?Farmingdale 87,’ ‘Winter Nelis,’ Pyrus dimorphophylla, and Pyrus ussuriensis ‘Hang Pa Li’) were grown on each treatment combination, responses were measured, and each response was analyzed by analysis of variance. The analyses resulted in the identification of the following factors with the single largest effects on plant response: shoot quality (mesos), leaf spotting/necrosis (mesos), leaf size (mesos), leaf color (mesos, NH₄NO₃, and KNO₃), shoot number (NH₄NO₃ and Fe), nodes (NH₄NO₃ and KNO₃), and shoot length (mesos and Fe). Factors with the largest effects (mesos and Fe) were similar among the genotypes. This approach was very successful for defining the appropriate types and concentrations of mineral nutrients for micropropagation of diverse pear genotypes.     

Cadmium effects on mineral nutrition of the Cd-hyperaccumulator Pfaffia glomerata

A plant’s ability to survive in a stressful environment is correlated with its nutritional status, which can be affected by cadmium (Cd) uptake. The present study evaluated the influence of Cd on the concentrations and distributions of nutrients in the roots and shoots of the Cd-hyperaccumulator Pfaffia glomerata (Sprengel) Pedersen. Plantlets were cultivated in nutrient solutions containing increasing Cd concentrations during 20 days under greenhouse conditions, and the concentrations of Cd and essential macro- (N, P, K, Ca, Mg and S) and micro- (Zn, Fe, Mn, Cu) elements in the roots and shoots were subsequently determined. Cd did not affect the plant biomass production. Cd accumulation was found to be higher in roots than in shoots, and influenced the distribution of macro and micro elements in those plants. Despite the high phytotoxicity of this element, our results indicated the existence of Cd-tolerance mechanisms in both nutrient uptake and distribution processes that enabled these plants to survive in Cd-contaminated sites.