Nitrogen nutrition effects on δC of plant respired CO are mostly caused by concurrent changes in organic acid utilisation and remobilisation.

Nitrogen (N) nutrition impacts on primary carbon metabolism and can lead to changes in δC of respired CO. However, uncertainty remains as to whether (1) the effect of N nutrition is observed in all species, (2) N source also impacts on respired CO in roots and (3) a metabolic model can be constructed to predict δC of respired CO under different N sources. Here, we carried out isotopic measurements of respired CO and various metabolites using two species (spinach, French bean) grown under different NH :NO ratios.

Light-emitting diode combined with humic acid improve the nutritional quality and enzyme activities of nitrate assimilation in rocket (Eruca sativa (Mill.) Thell.).

Belonging to the Brassicaceae family, rocket (Eruca sativa (Mill.) Thell.), is considered to be a nitrate-accumulating leafy vegetable.

Structure and activity of a novel robust peroxidase from Alkanna frigida cell culture.

Demands for peroxidases (POX)s with diverse physicochemical properties have steadily grown as more applications of POXs are demonstrated. Plants are among the best sources of versatile POXs, and plant biotechnology, as an agricultural hassle-free technology, promises to circumvent the limitations of natural resource exploitation and to address the demands. Following this trend, it was shown that POX production steadily increased during the 31-day subculture of Alkanna frigida (from Boraginaceae) callus on Murashige-Skoog medium containing 2,4-dichlorophenoxyacetic acid (10 M) and kinetin (10 M).

Nitrate and ammonium differ in their impact on δC of plant metabolites and respired CO from tobacco leaves.

The carbon isotopic composition (δC) of foliage is often used as proxy for plant performance. However, the effect of vs. supply on δC of leaf metabolites and respired CO is largely unknown.

Effects of Potassium Fertilization on Oil Palm Fruit Metabolism and Mesocarp Lipid Accumulation.

Potassium fertilization is commonly practiced in oil palm () plantations to increase yield. However, its effects on fruit oil content and composition are not well documented. Here, we conducted bunch, metabolomics, and oil composition analyses in two contrasting crosses ( × and × ) grown under different K fertilization conditions.

Stomatal and non-stomatal limitations are responsible in down-regulation of photosynthesis in melon plants grown under the saline condition: Application of carbon isotope discrimination as a reliable proxy.

Salinity is one of the most severe environmental stresses limiting agricultural crop production worldwide. Photosynthesis is one of the main biochemical processes getting affected by such stress conditions. Here we investigated the stomatal and non-stomatal factors during photosynthesis in two Iranian melon genotypes "Ghobadlu" and "Suski-e-Sabz", as well as the "Galia" F1 cultivar, with an insight into better understanding the physiological mechanisms involved in the response of melon plants to increasing salinity.

The validity of carbon isotope discrimination as a screening criterion for grain yield in two barley landraces under deficit irrigation with saline water in southern Tunisia.

Arid and semiarid regions with rain shortage and scarce good quality water must make use of low-quality water for irrigation. Consequently, improved plant cultivars for use in these areas should show adaptation capacities to confer drought and salt resistance and allow the cultivation under limited water availabiltiy. The present study was conducted to determine the effect of deficit irrigation with saline water on two local barley landraces, "Karkeni" and "Bengardeni".

Pyrrolizidine Alkaloids-Free Extract from the Cell Culture of Lithospermum officinale with High Antioxidant Capacity.

The benefits of Lithospermum officinale has encouraged people to continue using its extract (CAS 90063-58-4) in both medicinal and cosmetic industries despite the fact that chemical analysis confirms the presence of pyrrolizidine alkaloids (PAs) in the extract. While the cultivation of L. officinale takes, at least, 2 years to produce usable crops, its callus culture proliferated 8.

Genotypic differences in physiological and biochemical responses to salinity stress in melon (Cucumis melo L.) plants: Prospects for selection of salt tolerant landraces.

Melon (Cucumis melo L.) is one of the most important horticultural crops in Iran often cultivated in arid and semiarid regions of the country with salinity problems. The objective of this work was to better understand the mechanisms of physiological and biochemical responses to salinity stress of five Iranian melon landraces "Samsuri", "Kashan", "Khatouni", "Suski-e-Sabz", and "Ghobadlu" from different geographical origins, and "Galia" F1 cultivar.

Intraspecific variability of carbon isotope discrimination and its correlation with grain yield in safflower: prospects for selection in a Mediterranean climate.

The goals of the present study were to obtain a first estimate of intraspecific variability of carbon isotope discrimination (Δ) in safflower, a thistle-like herbaceous plant, and to determine the statistical relationship between Δ and grain yield as well as its components in a collection of 45 accessions of different origins. Grain yield and aboveground biomass, harvest index, average grain weight, and Δ (measured on the bulk leaf organic matter) were investigated in experimental field conditions. A large variability was noted for all traits but a principal component analysis (PCA) allowed to identify several homogeneous groups of accessions.

Changes and their possible causes in δ13C of dark-respired CO2 and its putative bulk and soluble sources during maize ontogeny.

The issues of whether, where, and to what extent carbon isotopic fractionations occur during respiration affect interpretations of plant functions that are important to many disciplines across the natural sciences. Studies of carbon isotopic fractionation during dark respiration in C3 plants have repeatedly shown respired CO2 to be (13)C enriched relative to its bulk leaf sources and (13)C depleted relative to its bulk root sources. Furthermore, two studies showed respired CO2 to become progressively (13)C enriched during leaf ontogeny and (13)C depleted during root ontogeny in C3 legumes.

Natural (13) C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern.

Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet.

Changes in δ(13)C of dark respired CO2 and organic matter of different organs during early ontogeny in peanut plants.

Carbon isotope composition in respired CO2 and organic matter of individual organs were measured on peanut seedlings during early ontogeny in order to compare fractionation during heterotrophic growth and transition to autotrophy in a species with lipid seed reserves with earlier results obtained on beans. Despite a high lipid content in peanut seeds (48%) compared with bean seeds (1.5%), the isotope composition of leaf- and root-respired CO2 as well as its changes during ontogeny were similar to already published data on bean seedlings: leaf-respired CO2 became (13)C-enriched reaching -21.

Opposite carbon isotope discrimination during dark respiration in leaves versus roots - a review.

In general, leaves are (13) C-depleted compared with all other organs (e.g. roots, stem/trunk and fruits).

Biotic and abiotic factors affecting the delta(13)C of soil respired CO(2) in a Mediterranean oak woodland.

The flux (R(s)) and carbon isotopic composition (delta(13)C (Rs)) of soil respired CO (2) was measured every 2 h over the course of three diel cycles in a Mediterranean oak woodland, together with measurements of the delta(13)C composition of leaf, root and soil organic matter (delta(13)C (SOM)) and metabolites. Simulations of R(s) and delta(13)C (Rs) were also made using a numerical model parameterised with the SOM data and assuming short-term production rates were driven mainly by temperature. Average values of delta(13)C (Rs) over the study period were within the range of root metabolite and average delta(13)C (SOM) values, but enriched in (13)C relative to the bulk delta(13)C of leaf, litter, and roots and the upper soil organic layers.

On the 13C/12C isotopic signal of day and night respiration at the mesocosm level.

While there is currently intense effort to examine the (13)C signal of CO(2) evolved in the dark, less is known on the isotope composition of day-respired CO(2). This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c(i)/c(a) effect) from respiratory effect (production of CO(2) with a different delta(13)C value from that of net-fixed CO(2)) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO(2)].

On the resilience of nitrogen assimilation by intact roots under starvation, as revealed by isotopic and metabolomic techniques.

The response of root metabolism to variations in carbon source availability is critical for whole-plant nitrogen (N) assimilation and growth. However, the effect of changes in the carbohydrate input to intact roots is currently not well understood and, for example, both smaller and larger values of root:shoot ratios or root N uptake have been observed so far under elevated CO(2). In addition, previous studies on sugar starvation mainly focused on senescent or excised organs while an increasing body of data suggests that intact roots may behave differently with, for example, little protein remobilization.

Changes in 13C/12C of oil palm leaves to understand carbon use during their passage from heterotrophy to autotrophy.

The carbon isotope composition of leaf bulk organic matter was determined on the tropical tree Elaeis guineensis Jacq. (oil palm) in North Sumatra (Indonesia) to get a better understanding of the changes in carbon metabolism during the passage from heterotrophy to autotrophy of the leaves. Leaf soluble sugar (sucrose, glucose and fructose) contents, stomatal conductance and dark respiration, as well as leaf chlorophyll and nitrogen contents, were also investigated.

Consistent patterns in leaf lamina and leaf vein carbon isotope composition across ten herbs and tree species.

Wide-spread post-photosynthetic fractionation processes deplete metabolites and plant compartments in (13)C relative to assimilates to varying degrees. Fragmentation fractionation and exchange of metabolites with distinct isotopic signatures across organ boundaries further modify the patterns of plant isotopic composition. Heterotrophic organs tend to become isotopically heavier than the putative source material as a result of respiratory metabolism.

Kinetic 12C/13C isotope fractionation by invertase: evidence for a small in vitro isotope effect and comparison of two techniques for the isotopic analysis of carbohydrates.

The natural (13)C/(12)C isotope composition (delta(13)C) of plants and organic compounds within plant organs is a powerful tool to understand carbon allocation patterns and the regulation of photosynthetic or respiratory metabolism. However, many enzymatic fractionations are currently unknown, thus impeding our understanding of carbon trafficking pathways within plant cells. One of them is the (12)C/(13)C isotope effect associated with invertases (EC 3.

Preparation of starch and soluble sugars of plant material for the analysis of carbon isotope composition: a comparison of methods.

Starch and soluble sugars are the major photosynthetic products, and their carbon isotope signatures reflect external versus internal limitations of CO(2) fixation. There has been recent renewed interest in the isotope composition of carbohydrates, mainly for use in CO(2) flux partitioning studies at the ecosystem level. The major obstacle to the use of carbohydrates in such studies has been the lack of an acknowledged method to isolate starch and soluble sugars for isotopic measurements.

Carbon stable isotope ratio of phloem sugars in mature pine trees throughout the growing season: comparison of two extraction methods.

The study presents a comparison of two phloem sugar extraction methods. The amount of phloem sugar extracted and the carbon isotope composition (delta(13)C) of the total extracts and of the main phloem compounds separated by high-performance liquid chromatography (sucrose, glucose, fructose and pinitol) are compared. These two phloem sap extraction methods are exudation in distilled water and a new method using centrifugation, which avoids the addition of any solvent.

Is there any 12C/13C fractionation during starch remobilisation and sucrose export in potato tubers?

The delta(13)C (carbon isotope composition) variations in respired CO(2), total organic matter, proteins, sucrose and starch have been measured during tuber sprouting of potato (Solanum tuberosum) in darkness. Measurements were carried out both on tubers and on their growing sprouts for 23 days after the start of sprout development. Sucrose was slightly (13)C-depleted compared with starch in tubers, suggesting that starch breakdown was associated with a small isotope fractionation.