Distribution Of Non-structural Carbohydrates Research Articles

Distribution of Non-Structural Carbohydrates and Root Structure of Plantago lanceolata L. under Different Defoliation Frequencies and Intensities.

Plantago lanceolata L. (plantain) increases herbage dry matter (DM) production and quality during warm and dry conditions due to its deep roots and drought tolerance and reduces nitrogen losses in grazing systems compared to traditional pastures. However, plantain density usually declines after the third growing season, mainly due to defoliation management. The effects of defoliation frequency and intensity on water-soluble carbohydrate (WSC) reserves and below-ground plant responses need further research to optimize grazing strategies for improved productivity and sustainability of grazing systems. Our study investigated the effects of defoliation frequencies (15, 25, and 35 cm of extended leaf length, ELL) and intensities (5 and 8 cm of residual heights) on morphological traits and WSC concentrations in plantain biomass under controlled environmental conditions. Defoliation frequency significantly influenced morphological and chemical characteristics and biomass distribution more than residual height. Less frequent defoliations promoted above-ground herbage DM production, reproductive stems, and root biomass. Root architecture showed adaptations in response to defoliation frequency, optimizing resource acquisition efficiency. Frequent defoliation reduced high molecular weight WSC concentrations in leaves, affecting regrowth capacity and DM mass. A defoliation frequency of 25 cm ELL (~15 days) balances herbage production and root development, promoting long-term pasture sustainability.

Shrubs have a greater influence on the nonstructural carbohydrates of desert mosses along precipitation decreased

Biological soil crusts and the mosaic distribution of vascular plants have become an important landscape feature on the desert surface owing to limited water. The desert shrub, as one of the best-known vascular plants, exerts a notable influence on multiple facets, encompassing the growth and development of biological soil crusts as well as the coverage, biomass, physiology, and biochemical properties of mosses. Therefore, to comprehend how plants react and adapt to drought conditions, it is necessary to investigate the concentration and allocation patterns of nonstructural carbohydrates (NSCs). Nevertheless, the phenomenon still remains unclear whether the influence of shrubs on biological soil crusts follows any pattern concerning the alteration in precipitation gradients on a broader spatial scale. In this investigation, Syntrichia caninervis was gathered from two distinct microenvironments within the Gurbantunggut Desert spanning the gradient of natural precipitation. The aim was to examine the reaction of NSCs within S. caninervis to the presence of shrubs under varying precipitation circumstances. The amount of total NSCs and their components in S. caninervis were determined by the shrub effect, mean annual precipitation (MAP), and mean annual temperature (MAT). The presence of shrubs led to a remarkable rise in the content of fructose, starch, and total NSCs in S. caninervis, but a decline in the ratio of soluble sugar to starch. Nonetheless, variations were observed in the overall NSCs content, the individual constituents of NSCs, and the proportion of soluble sugars to starch within S. caninervis across diverse microenvironments and sampling locations. The content of total NSC and its components, as well as the ratio of soluble sugar to starch, substantially increased with a decrease in MAP (negative correlation) in S. caninervis. Conversely, they significantly decreased as MAT decreased (positive correlation). With the amplifying MAP, the disparities in these parameters (total NSC content, its components, and the ratio of soluble sugar to starch) between two distinct microhabitats diminished gradually, whereas these disparities progressively intensified with rising mean annual temperature (MAT). The outcomes derived from the structural equation model (SEM) underscored the direct and indirect influence of climate and the presence of shrubs influenced the content of NSCs directly or indirectly by enhancing soil nutrients. As a conclusion, the impact of shrub presence, followed by mean annual precipitation (MAP), had the most notable effect on NSCs in S. caninervis. Consequently, despite the observed spatial pattern in NSCs content, shrubs emerged as the most critical factor, in speaking of their effect continuous raising with the declining MAP. These findings provide new insights into the mechanisms of NSCs distribution and stress resistance in desert moss in different microhabitats.

Effects of Drought Stress on Non-Structural Carbohydrates in Different Organs of Cunninghamia lanceolata.

The Chinese fir Cunninghamia lanceolata (Lamb.) Hook. is an important timber conifer species in China. Much has been studied about Chinese fir, but the distribution of non-structural carbohydrates (NSCs) among different organs (needles, branch, stem, and roots) under drought stress remains poorly understood. In this study, we used one-year-old C. lanceolata plantlets to evaluate the effects of simulated drought under four water regimes, i.e., adequate water or control, light drought, moderate drought, and severe drought stress corresponding to 80%, 60%, 50%, and 40%, respectively of soil field maximum capacity on various NSCs in the needles, branch, stem and roots. The degree and duration of drought stress had significant effects on fructose, glucose, sucrose, soluble sugar, starch, and NSC content in various organs (p < 0.05). Fructose content increased in stem xylem, stem phloem, and leaves. Glucose and sucrose content declined in stem and branch xylem under light drought stress and moderate drought stress, and increased under severe drought stress conditions. Soluble sugars content declined, and starch content increased in leaf and branch phloem, but the latter could not compensate for soluble sugar consumption in the whole plant, and therefore, total NSCs decreased. Correlation analysis showed that a significant positive correlation existed in the soluble sugar content between leaves and roots, and between xylem and phloem in the stems and branches. Chinese fir appears to have different NSCs distribution strategies in response to drought stress, viz., allocating more soluble sugars to fine roots and increasing starch content in the needles, as well as ensuring osmosis to prevent xylem embolism. Our study may broaden the understanding of the various mechanisms that Chinese fir and other plants have to enhance their tolerance to drought stress.

Correlation between Non-Structural Carbohydrates and C:N:P Stoichiometric Ratio of Haloxylon ammodendron under Different Water–Salt Gradients

Growth is restricted by both water and phosphorus (P), and balancing the relationship between non−structural carbohydrates (NSCs) and carbon: nitrogen: phosphorus (C:N:P) is essential for Haloxylon ammodendron to adapt to arid habitats. The survival and growth strategies of the dominant species H. ammodendron in a desert ecosystem were examined in order to better serve the restoration of degraded ecosystems and desertification control. Three water and salt gradients (high water and high salinity, medium water and salinity, and low water and low salinity) in the Aibi Lake Reserve were selected. We analyzed the accumulation and distribution of NSCs in the assimilation branches and secondary branches of H. ammodendron and the changes in the measurement ratio characteristics of C:N:P, as well as the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) content. The results showed that: (1) With the decrease of soil water and salt content, the basal diameter, plant height, crown area, and NSC content of H. ammodendron significantly decreased. This morphological adjustment in the aboveground part is similar to a “self thinning” behavior, aimed at reducing transpiration area and balancing carbon distribution in the body. The carbon accumulation in the body helps the H. ammodendron to resist the dual stresses of drought and salt. (2) With the decrease of water and salt content, the C content of assimilating branches increased significantly, while there was no significant change in secondary branches. However, the N and P content of both branches decreased significantly, and the N: P of both branches was greater than 16, indicating that it was mainly limited by P. (3) The NSC of the two branches was significantly negatively correlated with C, and significantly positively correlated with N and P, and there was a strong positive correlation between the assimilation branches NSC: C: P and NSC: C: P. The synthesis and accumulation of NSC of H. ammodendron were influenced by the content and relationship of C, N, and P, and the abundance of P content transported by the root system to the aboveground portion may have an important and decisive role in regulating nutrient balance and non-structural carbon dynamics.

Intrinsic morphology and spatial distribution of non-structural carbohydrates contribute to drought resistance of two mulberry cultivars.

Drought is one of the most adverse environmental stresses limiting plant growth and productivity. However, the underlying mechanisms regarding non-structural carbohydrates (NSCs) metabolism in source and sink organs are still not fully elucidated in woody trees. Saplings of mulberry cultivars Zhongshen1 and Wubu were subjected to a 15-day progressive drought stress. NSCs levels and gene expressions involved in NSCs metabolism were investigated in roots and leaves. The growth performance and photosynthesis, leaf stomatal morphology, and other physiological parameters were also analyzed. Under well-watered conditions, Wubu had higher root-to-shoot ratio (R/S) with higher NSCs in leaves than roots, while Zhongshen1 exhibited lower R/S with higher NSCs in roots than leaves. Under drought stress, Zhongshen1 showed decreased productivity and increased concentrations of proline, abscisic acid, reactive oxygen species and activities of antioxidant enzymes, while Wubu sustained comparable productivity and photosynthesis. Interestingly, drought resulted in decreased levels of starch and slightly increased soluble sugars in leaves of Wubu, accompanied by notable downregulation of starch-synthesizing genes and upregulation of starch-degrading genes. The similar patterns in NSCs levels and relevant gene expressions were also observed in roots of Zhongshen1. Concurrently decreased soluble sugars and unchanged starch in roots of Wubu and leaves of Zhongshen1 were found. However, the gene expressions of starch metabolism in roots of Wubu were unaltered, but in leaves of Zhongshen1 the starch metabolism was largely activated. These findings revealed that intrinsic R/S and the spatial distribution of NSCs in roots and leaves concomitantly contributed to drought resistance in mulberry.

Effect of Ectomycorrhizal Fungi on the Drought Resistance of Pinus massoniana Seedlings.

Studies on the dynamics of non-structural carbohydrates (NSCs) play an important role in understanding the mechanisms of plant responses to drought stress. The objective of this study was to assess the influence of ectomycorrhizal fungi (ECMF) on the content and distribution of NSCs in Pinus massoniana seedlings under different drought intensities and to further explore the possible mechanism by which ECMF enhances the stress resistance of host plants. We conducted a pot experiment using P. massoniana seedlings that were inoculated (M) or non-inoculated (NM) with Suillus luteus (Sl) under well-watered, moderate, and severe drought stress conditions. The results showed that drought significantly reduced the photosynthetic capacity of P. massoniana seedlings and inhibited their growth rate. P. massoniana could respond to different degrees of drought stress by increasing the accumulation of NSCs and increasing WUE. However, compared with well-watered treatment, NSCs consumption began to appear in the roots of NM due to the decrease in starch content under severe drought, whereas NSCs content in M seedlings was higher than that in the well-watered treatment, showing that the ability to maintain C balance was higher in M seedlings. Compared with NM, inoculation with Sl increased the growth rate and biomass of roots, stems, and leaves under moderate and severe drought. In addition, Sl can also improve the gas exchange parameters (net photosynthetic rate, transpiration rate, intercellular CO2 concentration and stomatal conductance) of P. massoniana seedlings compared with NM seedlings, which was conducive to the hydraulic regulation of seedlings and improved their C fixation capacity. Meanwhile, the content of NSCs in M seedlings was higher. Moreover, the soluble sugar content and SS/St ratio of leaves, roots, and whole plants were higher under drought stress after Sl inoculation, indicating that Sl could also change the C distribution mode, regulate more soluble sugar to respond to drought stress, which was conducive to improving the osmotic adjustment ability of seedlings, and providing more available C sources for plant growth and defense. Overall, inoculation with Sl could enhance the drought resistance of seedlings and promote their growth under drought stress by improving NSCs storage, increasing soluble sugar distribution, and improving the plant water balance of P. massoniana seedlings.

Characterization of the Polar Profile of Bacon and Fuerte Avocado Fruits by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry: Distribution of Non-structural Carbohydrates, Quinic Acid, and Chlorogenic Acid between Seed, Mesocarp, and Exocarp at Different Ripening Stages.

Avocado fruit growth and development, unlike that of other fruits, is characterized by the accumulation of oil and C7 sugars (in most fruits, the carbohydrates that prevail are C6). There are five essential carbohydrates which constitute 98% of the total content of soluble sugars in this fruit; these are fructose, glucose, sucrose, d-mannoheptulose, and perseitol, which together with quinic acid and chlorogenic acid have been the analytes under study in this work. After applying an efficient extraction procedure, a novel methodology based on hydrophilic interaction liquid chromatography coupled to mass spectrometry was applied to determine the levels of these seven substances in tissues─exocarp, seed, and mesocarp─from avocado fruits of two different varieties scarcely studied, Bacon and Fuerte, at three different ripening stages. Quantitative characterization of the selected tissues was performed, and the inter-tissue distribution of metabolites was described. For both varieties, d-mannoheptulose was the major component in the mesocarp and exocarp, whereas perseitol was predominant in the seed, followed by sucrose and d-mannoheptulose. Sucrose was found to be more abundant in seed tissues, with much lower concentrations in avocado mesocarp and exocarp. Quinic acid showed a predominance in the exocarp, and chlorogenic acid was exclusively determined in exocarp samples.

Effects of moisture and humic acid on the metabolism of oat fructans

To provide theoretical guidance and technical support for oat production in dry farming area, we exa-mined the effects of moisture and humic acid (HA) on the accumulation and distribution of non-structural carbohydrates (NSC) in different organs of oat, as well as the mechanism of sugar metabolism and grain weight formation of oat. Two oat cultivars, 'Mengnong Dayan 1' and 'Neiyan 5', were used as experimental material. HA and clean water (CK) were foliar sprayed under dry framing (without irrigation) and limited irrigation (irrigated twice at jointing and heading stage). The dynamics of NSC components in stems, leaves and panicles, as well as the changes of carbon metabolism-related enzyme activities at different growth stages of oats after flowering were measured. Results showed that the trend of the contents of NSC in stems, leaves and panicles, in both two oat cultivars increased firstly and then decreased with the prolong of post-anthesis time. The contents of NSC in different organs were similar between two oat cultivars. Under irrigation treatment, the fructan content in panicle for Mengnong Dayan 1 of HA was higher than that of CK, with magnitude of enhancement being significantly greater than that corresponding treatment under dry farming. Under irrigation condition, the fructan, invertase activities in leaves and grain weight per panicle for Mengnong Dayan 1 of HA were increased by 27.1%, 30.6% and 55.9% compared with CK, respectively. Further, the increase trend under irrigation was stronger than that under dry farming condition. For Mengnong Dayan 1, the 1000-grain weight and grain weight per panicle were positively correlated with the content of fructan in leaves. In conclusion, the synergistic effect of moisture and humic acid could effectively regulate the accumulation of oat fructans and the activities of carbon metabolic enzymes, consequently promoting the formation of yield.

Analysis of Non-Structural Carbohydrate in Relation with Shoot Elongation of Rice under Complete Submergence

Regulation of non-structural carbohydrates (NSCs) are important for plants in response to submergence. In this study, the difference in non-structural carbohydrates in relation with shoot elongation between Sub1A and non-Sub1A rice genotypes was investigated. Two rice genotypes, namely Inpari30 (Sub1A genotype) and IR72442 (non-Sub1A genotype), were submerged completely for 6 days and re-aerated by lowering water level up to stem base for 6 days of post submergence. In addition, non-submerged plants (control) was treated with water level up to stem base during the experiment. Photosynthesis rate decreased in both submerged Inpari30 and IR72442 genotypes 71% and 96% lower than their control, respectively. Submerged IR72442 declined Fv/Fm 15.6% lowest than its control and both control and submerged Inpari30. Investigation of the distribution of starch and soluble sugar content in plant organs suggested that shoot elongation of non-Sub1A genotype led to starch and sugar consumption that distributed faster to the new developed organ during submergence. In contrast, Sub1A genotype of Inpari30, which did not exhibit shoot elongation and showed slower NSCs distribution during submergence, performed better on post submergence by maintaining NSCs and distributing to the new developed organ faster than IR72442. These results suggest that Sub1A genotype managed elongation and NSCs during submergence more efficiently than non-Sub1A genotype.

Distribution of non-structural carbohydrates in the vegetative organs of upland rice

ABSTRACT Rice is one of the main foods consumed by half of the world’s population. The rice crop requires plenty of water, but upland rice is cultivated in a non-flooded environment, although its productivity is lower than that of lowland rice. Rice grains mostly consist of starch, which is synthesized from the non-structural carbohydrates imported from the vegetative organs. The long-term storage of carbohydrates plays a remarkable role in maintaining the supply of photoassimilates during grain filling if photosynthesis does not meet energy demand. Therefore, the dynamics of non-structural carbohydrates is central to the productivity of rice crops. The present study aimed to determine the non-structural carbohydrate content and soluble carbohydrate profiles in different vegetative organs of upland rice of the genotype BRS Esmeralda. The content was determined at the end of vegetative development. The identification and quantification of carbohydrates were performed by high-performance anion-exchange chromatography with pulsed amperometric detection. Fully expanded leaf blades, expanding leaf blades, and expanding stems exhibited the soluble carbohydrate content of 59.7, 53.3, and 52.3 mg g-1 DM, respectively. The stem was found to be the main organ for the long-term storage of non-structural carbohydrates, wherein the starch content was 36.1 mg g-1 DM. It also contained soluble carbohydrates such as glucose, fructose, and sucrose. The non-structural carbohydrates were found in low amounts in the roots, showing that this organ does not store long-term carbohydrates.

Driving Forces Analysis of Non-structural Carbohydrates for Phragmites australis in Different Habitats of Inland River Wetland

Habitat variation in non-structural carbohydrates (NSC) reflects the resource allocation trade-offs for clonal plants, and its driving force analysis embodies the ecological adaptation strategy of clonal plants to heterogeneous environments. In this paper, the reed (Phragmites australis) in the northwestern inland wetlands of China, as a typical example of clonal plants, was used as the research object. The content and distribution of NSC in reeds and their response characteristics to soil environmental factors were compared under three different environmental gradients with wet, salt marsh and desert habitats. The results showed: (1) the content of NSC and starch gradually increased and the content of soluble sugar gradually decreased from wetland to desert habitats, and the ratio of soluble sugar to starch increased significantly (p &lt; 0.05), which demonstrated that reeds converted more NSC into starch to adapt to harsh environments as the environment changed. (2) Reeds tended to invest more NSC in underground architectures to achieve survival and growth with the increase in environmental stress, providing the evidence that NSC were transferred from leaf to rhizome, and root, stem and rhizome received more soluble sugar investment. The ratio of soluble sugar to starch of reed stem and rhizome increased significantly with the increasing content of soluble sugar and the decreasing content of starch, and more starch was converted into soluble sugar to resist the harsh environment. (3) Soil water, soil bulk density and salinity were the main driving forces for the NSC content and the distribution characteristics of reeds using the relative importance analysis. The study results clarified the habitat variation law, and the main environmental driving forces of NSC for reeds in inland river wetlands, which provided the significant references for enriching the ecology research theory of clonal plants and protection measures in the fragile and sensitive wetlands in arid regions.

Unfolding Non-structural Carbohydrates from Sapling to Dying Black Locust on China’s Loess Plateau

Non-structural carbohydrates (NSC) play important roles in metabolic processes of plants and represent important functional traits in plant adaptation to the external environment. However, there are few reports concerning intra-annual NSC distribution in temperate deciduous forests, especially for the purpose of comparison among different stand ages on China’s Loess Plateau. Here, NSC allocation dynamics with age ring-porous black locust tree was determined for the growing (May) and dormant (November) seasons over the period from sapling to dying trees—defined as a completely defoliated tree with dried branches in the growing season. It was noted that regardless of tree age, NSC concentration was highest in coarse roots [16.4 g per 100 g of dry mass (16.4% DM)] and stems (15.1% DM). At the tree level, NSC concentration was highest (14.3% DM) in a 30-year-old stand in November and lowest (4.1% DM) in dying stands in May. The pool of NSC at tree level was highest (25.2 kg DM per tree) in 30-year-old stands in November and lowest (0.13 kg DM per tree) in sapling stands in May. The concentration of NSC was significantly lower in May than in November for all tree ages, organs, and biochemical components. The results underscored the importance of NSC in plant growth on China’s Loess Plateau. It also provided a useful insight into the dynamics of NSC from sapling to dying broadleaved tree species.

芦芽山林线华北落叶松径向变化季节特征

利用点状树木径向变化记录仪对芦芽山林线树种华北落叶松树木茎干的径向变化进行了一年的连续观测,分析了华北落叶松茎干径向日变化规律及茎干累积变化的季节动态。结果表明:华北落叶松茎干日变化在温暖季和寒冷季存在着相反的变化模式。在温暖季,茎干径向日变化归因于空气温度导致树木蒸腾作用强度的日变化而使茎干组织水分发生变化;在寒冷季,茎干径向日变化主要是因为空气温度通过热力学原理导致的"茎干冻融作用"。华北落叶松年内茎干径向变化存在4个不同阶段:1)春季茎干水分恢复期,2)夏季茎干快速增长期,3)秋季茎干脱水收缩期,4)冬季茎干相对稳定期。在不同阶段,影响华北落叶松茎干径向变化的环境因子并不一致。土壤温度为生长季中控制华北落叶松茎干径向生长的主导因子。;The treeline, which is defined as the upper limit of altitudinal tree distribution, is one of the most conspicuous vegetation boundaries worldwide. Treeline environments are generally characterized by harsh climatic conditions, which restrict tree growth and metabolic functions. Tree growth at the treeline is very sensitive to environmental changes, and it may be immediately influenced by small changes to limiting factors. Therefore, tree growth at the treeline can be used as an amplifier of external environmental changes, which has important implications for global climate change research. Fine resolution studies of tree radial variation on short temporal scales can be useful for exploring the interplay of the main physical variables that trigger the radial variation. From 19 Oct. 2008 to 17 Oct. 2009, we continuously monitored the stem radial variation of <em>Larix principis-rupprechtii</em> trees using point dendrometers, at the treeline of the Luya Mountains, in Shanxi, northern China. Our results showed that there were two reverse daily variation patterns in the warm and cold seasons, which were related to the daily transpiration rates and daily stem freeze-thaw cycles, respectively. In the warm seasons, the diurnal stem variation pattern was resolved into three phases: (1) radius contraction, (2) radius expansion, and (3) radius increment. Generally, during daytime, when tree transpiration exceeded water absorption, stem diameters usually decreased, and stem expansion occurred at night because of greater water absorption by the roots compared with water loss due to transpiration. In our study, a wide range of stem radius variations occurred during the stem freeze-thaw cycles during the cold seasons when the air temperature fluctuated around -5℃. The course of the cumulative radial variation during the year showed similarities among individuals representing the characteristic seasonal patterns. The average net stem radial increment of <em>Larix principis-rupprechtii</em> during the growing season was (2014.1±240.5) μm. Annual stem radial variation of <em>Larix principis-rupprechtii</em> was divided into four distinct periods: (1) spring stem rehydration, (2) summer stem rapid growth, (3) autumn stem dehydration contraction, and (4) winter stem stagnation. During different growth periods, the major environmental factors controlling stem radial variation were different. During the first period, the large radial increments were due to stem tissue rehydration by root pressure in early spring, and soil water content became the crucial environmental factor influencing stem radius variation. During the period of rapid stem growth in the summer, soil temperature was the major determining factor. Low soil temperature can inhibit net photosynthesis of <em>Larix principis-rupprechtii</em>, distribution of non-structural carbohydrates in the stem, and root activity and water uptake. The third period was characterized by the cessation of increments accompanied by dehydration of stem cells. These changes accompanied the declines in temperature and soil water content. Changes occurring in the cambia likely allow for over-wintering, which may be a survival strategy to avoid frost damage during cold winter conditions. During the fourth period, <em>Larix principis-rupprechtii </em>entered the dormancy stage and the stem remained relatively stable. It was observed that fluctuations in the radius of<em> Larix principis-rupprechtii</em> were mainly related to the changes in air temperature.

Radial distribution of non-structural carbohydrates in Malaysian teak

Non-structural carbohydrates are primary compounds whose distribution in the wood affects its properties. During the two last decades, a high variability of natural durability of plantation teak wood properties has been found with consequences for industry and consumers. In order to further investigate chemical traits for natural durability in Malaysian teak, we studied the radial distribution of main non-structural carbohydrates (NSC) from the sapwood to the inner heartwood. NSC were analysed by thin layer chromatography coupled to an enzymatic method. The main NSC were starch, glucose, fructose and sucrose. Stachyose and raffinose were also detected. Starch was the major NSC while sucrose was the less abundant. NSC were highly accumulated in sapwood and decreased drastically in heartwood. In our sampling, NSC distribution patterns were the same between trees but were different on a quantitative point of view. Our results suggested that NSC were stored as reserve materials in the sapwood and then were used in the sapwoodheartwood boundary for metabolic activities during heartwood formation process. Their involvement in heartwood formation was discussed.Keywords: Tectona grandis, sapwood, heartwood, non-structural carbohydrates, starch.

SEASONAL CARBOHYDRATE AND TOTAL NITROGEN DISTRIBUTION IN ROSE PLANTS: DEVELOPMENTAL AND GROWTH IMPLICATIONS

SEASONAL CARBOHYDRATE AND TOTAL NITROGEN DISTRIBUTION IN ROSE PLANTS: DEVELOPMENTAL AND GROWTH IMPLICATIONS

Non-structural carbohydrate composition of long-day onion in vitro

SummaryBulb formation in onion (Allium cepa L.) is strongly influenced by environmental factors, particularlyby light via photosynthesis and daylength. Dry-matter content (DM) in an onion bulb varies between 6 and 25%. Of this, 60–80% is made up of non-structural carbohydrates (NSC). This study compared the relative influence of genetics and environment on the concentration and composition in NSC of onion bulbs. The effects of clonal genotype, light spectrum quality and sucrose concentration in the culture medium were investigated in vitro on a long-day onion type. NSC analyses were performed enzymatically and by HPLC on growing material. Fructans characterized the basal tissues, and the sucrose content in the medium influenced the NSC distribution of the onion tissues. Bulb induction by supplementary incandescent light stimulated fructan accumulation in basal tissues. The high DM clones stored fructans faster and at higher concentrations than the low DM ones. They expressed a higher potential for fructan sink or biosynthesis. A similar biochemical composition in vitro as field-grown bulbs resulted from the light spectrum quality of light.

Formation of heartwood substances in the stemwood of Robinia pseudoacacia L. II. Distribution of nonstructural carbohydrates and wood extractives across the trunk

The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (>1 μmol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.

Effect of Light Level on Dinitrogen Fixation and Carbohydrate Distribution in Virginia Peanuts1

The peanut (Arachis hypogaea L.) is an important grain legume world‐wide, yet the N2 fixation capabilities of this crop have received minimal attention. An experiment was conducted to study the effects of radiant flux on peanut growth, N2 fixation, and the distribution of nonstructural carbohydrates among plant parts during vegetative and early‐reproductive growth stages. Two Virginia‐type cultivars, NC4 and NC6, were grown in controlled‐environment chambers under average photon flux treatments of 230 and 650 µimol photon m−2 s−1. Plants grown under the higher irradiance accumulated three times more dry matter, fixed three times more N2, and had greater reproductive potential than plants under the low irradiance. The greater fixation in plants under high light was attributed to an increased effective nodule mass in those plants and not to a greater efficiency of nodules to fix N2. There were no significant cultivar differences for dry matter or N accumulation, although NC4 was always slightly higher than NC6. Concentrations of nonstructural carbohydrates in peanut tissues varied depending on the growth stage. The content of carbohydrates in root, stem, and leaf tissues was greater in high‐light plants, compared with plants under low light. Within the high‐light treatment, carbohydrate content was greatest in tissues of NC4 plants. Carbohydrate concentration in nodules was not significantly different between light treatments.