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Salinity tolerance requires coordinated responses encompassing salt exclusion in roots and tissue/cellular compartmentation of salt in leaves. We investigated the possible control points for salt ions transport in roots and tissue tolerance to Na+ and Cl– in leaves of two contrasting mungbean genotypes, salt‐tolerant Jade AU and salt‐sensitive BARI Mung‐6, grown in nonsaline and saline (75 mM NaCl) soil. Cryo‐SEM X‐ray microanalysis was used to determine concentrations of Na, Cl, K, Ca, Mg, P, and S in various cell types in roots related to the development of apoplastic barriers, and in leaves related to photosynthetic performance. Jade AU exhibited superior salt exclusion by accumulating higher [Na] in the inner cortex, endodermis, and pericycle with reduced [Na] in xylem vessels and accumulating [Cl] in cortical cell vacuoles compared to BARI Mung‐6. Jade AU maintained higher [K] in root cells than BARI Mung‐6. In leaves, Jade AU maintained lower [Na] and [Cl] in chloroplasts and preferentially accumulated [K] in mesophyll cells than BARI Mung‐6, resulting in higher photosynthetic efficiency. Salinity tolerance in Jade AU was associated with shoot Na and Cl exclusion, effective regulation of Na and Cl accumulation in chloroplasts, and maintenance of high K in root and leaf mesophyll cells. Summary statement: Salinity tolerance in mungbean is related to its ability to intercept Na and Cl in roots, thereby reducing Na and Cl transport to shoot, effectively regulate Na and Cl accumulation in chloroplasts, and maintain high K in root and leaf mesophyll cells. [ABSTRACT FROM AUTHOR]

Halophytes accumulate and sequester high concentrations of salt in vacuoles while maintaining lower levels of salt in the cytoplasm. The current data on cellular and subcellular partitioning of salt in halophytes are, however, limited to only a few dicotyledonous C3 species. Using cryo‐scanning electron microscopy X‐ray microanalysis, we assessed the concentrations of Na, Cl, K, Ca, Mg, P and S in various cell types within the leaf‐blades of a monocotyledonous C4 halophyte, Rhodes grass (Chloris gayana). We also linked, for the first time, elemental concentrations in chloroplasts of mesophyll and bundle sheath cells to their ultrastructure and photosynthetic performance of plants grown in nonsaline and saline (200 mM NaCl) conditions. Na and Cl accumulated to the highest levels in xylem parenchyma and epidermal cells, but were maintained at lower concentrations in photosynthetically active mesophyll and bundle sheath cells. Concentrations of Na and Cl in chloroplasts of mesophyll and bundle sheath cells were lower than in their respective vacuoles. No ultrastructural changes were observed in either mesophyll or bundle sheath chloroplasts, and photosynthetic activity was maintained in saline conditions. Salinity tolerance in Rhodes grass is related to specific cellular Na and Cl distributions in leaf tissues, and the ability to regulate Na and Cl concentrations in chloroplasts. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizal plants trade plant‐assimilated carbon for soil nutrients with their fungal partners. The underlying mechanisms, however, are not fully understood. Here we investigate the exchange of carbon for nitrogen in the ectomycorrhizal symbiosis of Fagus sylvatica across different spatial scales from the root system to the cellular level.We provided 15N‐labelled nitrogen to mycorrhizal hyphae associated with one half of the root system of young beech trees, while exposing plants to a 13CO2 atmosphere. We analysed the short‐term distribution of 13C and 15N in the root system with isotope‐ratio mass spectrometry, and at the cellular scale within a mycorrhizal root tip with nanoscale secondary ion mass spectrometry (NanoSIMS).At the root system scale, plants did not allocate more 13C to root parts that received more 15N. Nanoscale secondary ion mass spectrometry imaging, however, revealed a highly heterogenous, and spatially significantly correlated distribution of 13C and 15N at the cellular scale.Our results indicate that, on a coarse scale, plants do not allocate a larger proportion of photoassimilated C to root parts associated with N‐delivering ectomycorrhizal fungi. Within the ectomycorrhizal tissue, however, recently plant‐assimilated C and fungus‐delivered N were spatially strongly coupled. Here, NanoSIMS visualisation provides an initial insight into the regulation of ectomycorrhizal C and N exchange at the microscale. [ABSTRACT FROM AUTHOR]

The calcifuge habit of plants is commonly explained in terms of high soil pH and its effects on nutrient availability, particularly that of phosphorus (P). However, most Proteaceae that occur on nutrient‐impoverished soils in south‐western Australia are calcifuge, despite their ability to produce cluster‐roots, which effectively mobilize soil P and micronutrients. We hypothesize that the mechanism explaining the calcifuge habit in Proteaceae is their sensitivity to P and calcium (Ca), and that soil‐indifferent species are less sensitive to the interaction of these nutrients. In this study, we analyzed growth, gas‐exchange rate, and chlorophyll fluorescence of two soil‐indifferent and four calcifuge Hakea and Banksia (Proteaceae) species from south‐western Australia, across a range of P and Ca concentrations in hydroponic solution. We observed Ca‐enhanced P toxicity in all analyzed species, but to different extents depending on distribution type and genus. Increasing P supply enhanced plant growth, leaf biomass, and photosynthetic rates of soil‐indifferent species in a pattern largely independent of Ca supply. In contrast, positive physiological responses to increasing [P] in calcifuges were either absent or limited to low Ca supply, indicating that calcifuges were far more sensitive to Ca‐enhanced P toxicity. In calcifuge Hakeas, we attributed this to higher leaf [P], and in calcifuge Banksias to lower leaf zinc concentration. These differences help to explain these species' contrasting sensitivity to Ca‐enhanced P toxicity and account for the exclusion of most Proteaceae from calcareous habitats. We surmise that Ca‐enhanced P toxicity is a major factor explaining the calcifuge habit of Proteaceae, and, possibly, other P‐sensitive plants. [ABSTRACT FROM AUTHOR]

Summary: Endemism and rarity have long intrigued scientists. We focused on a rare endemic and critically‐endangered species in a global biodiversity hotspot, Grevillea thelemanniana (Proteaceae).We carried out plant and soil analyses of four Proteaceae, including G. thelemanniana, and combined these with glasshouse studies. The analyses related to hydrology and plant water relations as well as soil nutrient concentrations and plant nutrition, with an emphasis on sodium (Na) and calcium (Ca).The local hydrology and matching plant traits related to water relations partially accounted for the distribution of the four Proteaceae. What determined the rarity of G. thelemanniana, however, was its accumulation of Ca. Despite much higher total Ca concentrations in the leaves of the rare G. thelemanniana than in the common Proteaceae, very few Ca crystals were detected in epidermal or mesophyll cells. Instead of crystals, G. thelemanniana epidermal cell vacuoles contained exceptionally high concentrations of noncrystalline Ca. Calcium ameliorated the negative effects of Na on the very salt‐sensitive G. thelemanniana. Most importantly, G. thelemanniana required high concentrations of Ca to balance a massively accumulated feeding‐deterrent carboxylate, trans‐aconitate.This is the first example of a calcicole species accumulating and using Ca to balance accumulation of an antimetabolite. [ABSTRACT FROM AUTHOR]

In contrast to the situation in plants inhabiting most of the world's ecosystems, mycorrhizal fungi are usually absent from roots of the only two native vascular plant species of maritime Antarctica, Deschampsia antarctica and Colobanthus quitensis. Instead, a range of ascomycete fungi, termed dark septate endophytes (DSEs), frequently colonise the roots of these plant species. We demonstrate that colonisation of Antarctic vascular plants by DSEs facilitates not only the acquisition of organic nitrogen as early protein breakdown products, but also as non‐proteinaceous d‐amino acids and their short peptides, accumulated in slowly‐decomposing organic matter, such as moss peat. Our findings suggest that, in a warming maritime Antarctic, this symbiosis has a key role in accelerating the replacement of formerly dominant moss communities by vascular plants, and in increasing the rate at which ancient carbon stores laid down as moss peat over centuries or millennia are returned to the atmosphere as CO2. [ABSTRACT FROM AUTHOR]

The Jurien Bay dune chronosequence in south‐western Australia's biodiversity hotspot comprises sites differing in nutrient availability, with phosphorus (P) availability declining strongly with increasing soil age. We have explored the exceptionally high photosynthetic P‐use efficiency (PPUE) of Proteaceae in this region, triggering the question what the PPUE of co‐occurring species in other families might be along the Jurien Bay chronosequence.We explored how traits associated with PPUE, photosynthetic nitrogen (N)‐use efficiency (PNUE) and leaf respiration might converge along the chronosequence, and whether Proteaceae and non‐Proteaceae species differ in leaf traits associated with nutrient use.Seven to 10 species were sampled at three sites differing in nutrient availability (ranging from N‐ to P‐limited). Measurements of leaf light‐saturated photosynthesis and dark respiration were integrated with measurements of total N and P concentration in both mature and senesced leaves, and leaf mass per unit area (LMA).Contrary to what is known for other chronosequences, rates of photosynthesis and respiration did not decrease with increasing soil age and LMA along the Jurien Bay chronosequence. However, they increased when expressed per unit leaf P. Both N and P were used much more efficiently for photosynthesis on nutrient‐poor sites, in both Proteaceae and non‐Proteaceae species. Proteaceae had the fastest rate of photosynthesis per unit leaf P, followed by species that preferentially allocate P to mesophyll cells, rather than epidermal cells.Synthesis. Our results show that with declining soil P availability, photosynthetic P‐use efficiency of all investigated species from different families increased. Plants growing on the oldest, most nutrient‐impoverished soils exhibited similar rates of CO2 exchange as plants growing on more nutrient‐rich younger soils, and extraordinarily high photosynthetic P‐use efficiency. This indicates convergence in leaf traits related to photosynthetic nutrient use on severely P‐impoverished sites. [ABSTRACT FROM AUTHOR]

Crops with improved uptake of fertilizer phosphorus (P) would reduce P losses and confer environmental benefits. We examined how P‐sufficient 6‐week‐old soil‐grown Trifolium subterraneum plants, and 2‐week‐old seedlings in solution culture, accumulated P in roots after inorganic P (Pi) addition. In contrast to our expectation that vacuoles would accumulate excess P, after 7 days, X‐ray microanalysis showed that vacuolar [P] remained low (<12 mmol kg−1). However, in the plants after P addition, some cortex cells contained globular structures extraordinarily rich in P (often >3,000 mmol kg−1), potassium, magnesium, and sodium. Similar structures were evident in seedlings, both before and after P addition, with their [P] increasing threefold after P addition. Nuclear magnetic resonance (NMR) spectroscopy showed seedling roots accumulated Pi following P addition, and transmission electron microscopy (TEM) revealed large plastids. For seedlings, we demonstrated that roots differentially expressed genes after P addition using RNAseq mapped to the T. subterraneum reference genome assembly and transcriptome profiles. Among the most up‐regulated genes after 4 hr was TSub_g9430.t1, which is similar to plastid envelope Pi transporters (PHT4;1, PHT4;4): expression of vacuolar Pi‐transporter homologs did not change. We suggest that subcellular P accumulation in globular structures, which may include plastids, aids cytosolic Pi homeostasis under high‐P availability. We examined clover roots after inorganic phosphorus (Pi) addition. Although vacuolar P concentration was unchanged, unexpectedly, P accumulated in intracellular globular structures and genes similar to plastid envelope Pi transporters were up‐regulated. The structures likely aid cytosolic Pi homeostasis. [ABSTRACT FROM AUTHOR]

Summary: Many Proteaceae are highly phosphorus (P)‐sensitive and occur exclusively on old nutrient‐impoverished acidic soils (calcifuge), whilst a few also occur on young calcareous soils (soil‐indifferent) that are higher in available calcium (Ca) and P. Calcium increases the severity of P‐toxicity symptoms, but its underlying mechanisms are unknown. We propose that Ca‐enhanced P toxicity explains the calcifuge habit of most Proteaceae.Four calcifuge and four soil‐indifferent Proteaceae from South‐Western Australia were grown in hydroponics, at a range of P and Ca concentrations.Calcium increased the severity of P‐toxicity symptoms in all species. Calcifuge Proteaceae were more sensitive to Ca‐enhanced P toxicity than soil‐indifferent ones. Calcifuges shared these traits: low leaf zinc concentration ([Zn]), low Zn allocation to leaves, low leaf [Zn]:[P], low root : shoot ratio, and high seed P content, compared with soil‐indifferent species.This is the first demonstration of Ca‐enhanced P toxicity across multiple species. Calcium‐enhanced P toxicity provides an explanation for the calcifuge habit of most Proteaceae and is critical for the management of this iconic Australian family. This study represents a major advance towards an understanding of the physiological mechanisms of P toxicity and its role in the distribution of Proteaceae. [ABSTRACT FROM AUTHOR]

Phosphorus (P)‐deficiency symptoms are known for Lupinus species grown in calcareous soil, but we do not know if this is due to high calcium (Ca) availability or low P availability in the soil. To address this problem, we explored both the effects of Ca and its interaction with P on nutrient status and growth of three Lupinus species. Two Ca‐sensitive genotypes (Lupinus angustifolius L. P26723 and Lupinus cosentinii Guss. P27225) and two Ca‐tolerant genotypes (L. angustifolius L. cv Mandelup and Lupinus pilosus Murr. P27440) were grown hydroponically at two P (0.1 and 10 μM) and three Ca (0.1, 0.6 and 6 mM) levels. Leaf symptoms and biomass were recorded, whole leaf and root nutrient concentrations were analysed, and leaf cellular P and Ca concentrations were determined. Phosphorus‐deficiency symptoms were only observed in the Ca‐sensitive genotypes. Among all the genotypes in this study, the Ca‐tolerant L. pilosus showed an ability to maintain stable leaf Ca and P concentrations whereas the Ca‐tolerant L. angustifolius cv Mandelup did not maintain a stable whole leaf Ca concentration, but maintained a low cytosolic Ca2+ concentration through effective Ca compartmentation. However, the two Ca‐sensitive genotypes, L. angustifolius P26723 and L. cosentinii, did not exhibit an ability to maintain a stable whole leaf Ca concentration or effectively compartmentalize Ca. Therefore, having the capacity to maintain a stable whole leaf Ca concentration or effectively compartmentalizing Ca in leaves are likely critical for Lupinus species to be Ca tolerant. [ABSTRACT FROM AUTHOR]

Abstract: To study mechanism underpinning the calcifuge habit of some Lupinus species, especially under low‐phosphorus (P) conditions, Lupinus species that were likely to respond differently to calcium (Ca) availability were assembled, and the sensitivity to Ca under a low‐P supply was assessed. Seven Lupinus species (9 genotypes, L. albus L. cv Kiev, L. albus L. P26766, L. angustifolius L. cv Mandelup, L. angustifolius L. P26723, L. luteus L. cv Pootalong, L. hispanicus ssp. bicolor Boiss. and Reut. P22999, L. pilosus Murr. P27440, L. cosentinii Guss. P27225, and L. atlanticus Gladst. P27219) were grown hydroponically at 10 or 6000 μM Ca. Leaf symptoms, gas exchange and biomass were recorded; leaf and root nutrient concentrations were analysed, and the leaf cell types in which Ca and P accumulated were determined using elemental X‐ray microanalyses. Calcium toxicity was demonstrated for L. angustifolius P26723, L. hispanicus ssp. bicolor. P22999, and L. cosentinii P27225, whereas the other species were tolerant of a high Ca supply under low‐P conditions. In addition, genotypic differences in Ca toxicity were found within L. angustifolius. Most Ca accumulated in the mesophyll cells in all species, whereas most P was located in epidermal cells. [ABSTRACT FROM AUTHOR]

Summary: Plants allocate nutrients to specific leaf cell types, with commelinoid monocots preferentially allocating phosphorus (P) to the mesophyll and calcium (Ca) to the epidermis, whereas the opposite is thought to occur in eudicots. However, Proteaceae from severely P‐impoverished habitats present the same P‐allocation pattern as monocots. This raises the question of whether preferential P allocation to mesophyll cells is a phylogenetically conserved trait, exclusive to commelinoid monocots and a few Proteaceae, or a trait that has evolved multiple times to allow plants to cope with very low soil P availability. We analysed the P‐allocation patterns of 16 species from 10 genera, eight families and six orders within three major clades of eudicots across different P‐impoverished environments in Australia and Brazil, using elemental X‐ray mapping to quantitatively determine leaf cell‐specific nutrient concentrations. Many of the analysed species showed P‐allocation patterns that differed substantially from that expected for eudicots. Instead, P‐allocation patterns were strongly associated with the P availability in the natural habitat of the species, suggesting a convergent evolution of P‐allocation patterns at the cellular level, with P limitation as selective pressure and without a consistent P‐allocation pattern within eudicots. Here, we show that most eudicots from severely P‐impoverished environments preferentially allocated P to their mesophyll. We surmise that this preferential P allocation to photosynthetically active cells might contribute to the very high photosynthetic P‐use efficiency of species adapted to P‐impoverished habitats. [ABSTRACT FROM AUTHOR]

Abstract: Plants allocate nutrients to specific leaf cell types; eudicots are thought to predominantly allocate phosphorus (P) to epidermal/bundle sheath cells. However, three Proteaceae species have been shown to preferentially allocate P to mesophyll cells instead. These Proteaceae species are highly adapted to P‐impoverished habitats, with exceptionally high photosynthetic P‐use efficiencies (PPUE). We hypothesized that preferential allocation of P to photosynthetic mesophyll cells is an important trait in species adapted to extremely P‐impoverished habitats, contributing to their high PPUE. We used elemental X‐ray mapping to determine leaf cell‐specific nutrient concentrations for 12 Proteaceae species, from habitats of strongly contrasting soil P concentrations, in Australia, Brazil, and Chile. We found that only species from extremely P‐impoverished habitats preferentially allocated P to photosynthetic mesophyll cells, suggesting it has evolved as an adaptation to their extremely P‐impoverished habitat and that it is not a family‐wide trait. Our results highlight the possible role of soil P in driving the evolution of ecologically relevant nutrient allocation patterns and that these patterns cannot be generalized across families. Furthermore, preferential allocation of P to photosynthetic cells may provide new and exciting strategies to improve PPUE in crop species. [ABSTRACT FROM AUTHOR]

Oxygen deficiency associated with soil waterlogging adversely impacts root respiration and nutrient acquisition. We investigated the effects of O2 deficiency and salinity (100 mM NaCl) on radial O2 concentrations and cell-specific ion distributions in adventitious roots of barley ( Hordeum vulgare)., Microelectrode profiling measured O2 concentrations across roots in aerated, aerated saline, stagnant or stagnant saline media. X-ray microanalysis at two positions behind the apex determined the cell-specific elemental concentrations of potassium (K), sodium (Na) and chloride (Cl) across roots., Severe O2 deficiency occurred in the stele and apical regions of roots in stagnant solutions. O2 deficiency in the stele reduced the concentrations of K, Na and Cl in the pericycle and xylem parenchyma cells at the subapical region. Near the root apex, Na declined across the cortex in roots from the aerated saline solution but was relatively high in all cell types in roots from the stagnant saline solution., Oxygen deficiency has a substantial impact on cellular ion concentrations in roots. Both pericycle and xylem parenchyma cells are involved in energy-dependent K loading into the xylem and in controlling radial Na and Cl transport. At root tips, accumulation of Na in the outer cell layers likely contributed to reduction of Na in inner cells of the tips. [ABSTRACT FROM AUTHOR]

The reproductive phase in chickpea ( C icer arietinum L.) is affected by salinity, but little is known about the underlying cause. We investigated whether high concentrations of Na + and Cl- in the reproductive structures influence reproductive processes. Chickpea genotypes contrasting in tolerance were subjected to 0, 35 or 50 m m NaCl applied to soil in pots. Flower production and abortion, pod number, percentage of empty pods, seed number and size were evaluated. The concentrations of Na+, K+ and Cl- were measured in various plant tissues and, using X-ray microanalysis, in specific cells of developing reproductive structures. Genotypic variation in reproductive success measured as seed yield in saline conditions was associated with better maintenance of flower production and higher numbers of filled pods (and thus seed number), whereas seed size decreased in all genotypes. Despite the variation in reproductive success, the accumulation of Na+ and Cl- in the early reproductive tissues of developing pods did not differ between a tolerant ( Genesis836) and a sensitive ( Rupali) genotype. Similarly, salinity tolerance was not associated with the accumulation of salt ions in leaves at the time of reproduction or in seeds at maturity. [ABSTRACT FROM AUTHOR]

Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed to explore these pathways from the root's vascular bundle to soil microbial communities., Using nanoscale secondary ion mass spectrometry (Nano SIMS) imaging and 13C-phospho- and neutral lipid fatty acids, we traced in-situ flows of recently photoassimilated C of 13 CO2-exposed wheat ( Triticum aestivum) through arbuscular mycorrhiza ( AM) into root- and hyphae-associated soil microbial communities., Intraradical hyphae of AM fungi were significantly 13C-enriched compared to other root-cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co-location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of 13C-photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots., Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes. [ABSTRACT FROM AUTHOR]

Mycorrhiza formation represents a significant carbon ( C) acquisition alternative for orchid species, particularly those that remain achlorophyllous through all life stages. As it is known that orchid mycorrhizas facilitate nutrient transfer (most notably of C), it has not been resolved if C transfer occurs only after lysis of mycorrhizal structures (fungal pelotons) or also across the mycorrhizal interface of pre-lysed pelotons. We used high-resolution secondary ion mass spectrometry ( nanoSIMS) and labelling with enriched 13CO2 to trace C transfers, at subcellular scale, across mycorrhizal interfaces formed by Rhizanthella gardneri, an achlorphyllous orchid. Carbon was successfully traced in to the fungal portion of orchid mycorrhizas. However, we did not detect C movement across intact mycorrhizal interfaces up to 216 h post 13CO2 labelling. Our findings provide support for the hypothesis that C transfer from the mycorrhizal fungus to orchid, at least for R. gardneri, likely occurs after lysis of the fungal peloton. [ABSTRACT FROM AUTHOR]

The ability of plants to compete effectively for nitrogen (N) resources is critical to plant survival. However, controversy surrounds the importance of organic and inorganic sources of N in plant nutrition because of our poor ability to visualize and understand processes happening at the root-microbial-soil interface., Using high-resolution nano-scale secondary ion mass spectrometry stable isotope imaging (Nano SIMS- SII), we quantified the fate of 15N over both space and time within the rhizosphere. We pulse-labelled the soil surrounding wheat ( Triticum aestivum) roots with either [ABSTRACT FROM AUTHOR]

The symbiosis between cnidarians and dinoflagellate algae is not understood at the cell or molecular level, yet this relationship is responsible for the formation of thousands of square kilometres of coral reefs. We have investigated the nature of crystalline material prominent within marine algal symbionts of Aiptasia sp. anemones. This material, which has historically been considered to be calcium oxalate, is shown to be uric acid. We demonstrate that these abundant uric acid stores can be mobilized rapidly, thereby allowing the algal symbionts to flourish in an otherwise N-poor environment. This is the first report of uric acid accumulation by symbiotic marine algae. These data provide new insight and considerations for understanding the physiological basis of algal symbioses, and represent a new and previously unconsidered aspect of N metabolism in cnidarian, and a variety of other, marine symbioses. [ABSTRACT FROM AUTHOR]

Here we demonstrate the technique of nanoscale secondary ion mass spectrometry, utilizing the Cameca NanoSIMS50® ion microprobe, to detect and image the metabolism of an isotopically labeled compound (NaH13CO3) in a biological sample. In particular, we have designed and verified protocols for imaging the subcellular distribution and determining the relative abundance of labeled 13C, within the coral Galaxea fascicularis. Analyses were conducted on 1-μm thick sections of resin-embedded material, using both scanned (mapping) and static (spot analysis) Cs+ primary ion beam of ∼100 nm diameter. Using these samples we establish that NanoSIMS has adequate mass resolution to reliably distinguish 13C from potential isobaric interference by 12C1H and that data extracted from ion maps are comparable to those acquired by spot analyses. Independent of the method of acquisition, ratioing of 13C to the naturally abundant 12C is essential if meaningful data, which can be statistically compared to standard and control samples, are to be obtained. These results highlight the potential of NanoSIMS for intracellular tracking of a variety of organic and inorganic compounds labeled with stable isotopes of C, N, O, S, P, and halogens. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]