Non-structural Carbohydrates Research Articles

Contrasting Responses ofTwo Grapevine Cultivars to Drought: The Role ofNon-structural Carbohydrates inXylem Hydraulic Recovery.

Xylem embolism is one of the possible outcomes of decreasing xylem pressure when plants face drought. Recent studies have proposed a role for non-structural carbohydrates (NSCs) in osmotic pressure generation, required for refilling embolized conduits. Potted cuttings of grapevine Grenache and Barbera, selected for their adaptation to different climatic conditions, were subjected to a drought stress followed by re-irrigation. Stem embolism rate and its recovery were monitored in vivo by X-ray micro-computed tomography (micro-CT). The same plants were further analyzed for xylem conduit dimension and NSC content. Both cultivars significantly decreased Ψpd in response to drought and recovered from xylem embolism after re-irrigation. However, although the mean vessel diameter was similar between the cultivars, Barbera was more prone to embolism. Surprisingly, vessel diameter was apparently reduced during recovery in this cultivar. Hydraulic recovery was linked to sugar content in both cultivars, showing a positive relationship between soluble NSCs and the degree of xylem embolism. However, when starch and sucrose concentrations were considered separately, the relationships showed cultivar-specific and contrasting trends. We showed that the two cultivars adopted different NSC-use strategies in response to drought, suggesting two possible scenarios driving conduit refilling. In Grenache, sucrose accumulation seems to be directly linked to embolism formation and possibly sustains refilling. In Barbera, maltose/maltodextrins could be involved in a conduit recovery strategy via the formation of cell-wall hydrogels, likely responsible for the reduction of conduit lumen detected by micro-CT.

Artificial warming affects sugar signals and flavonoid accumulation to improve female willows growth faster than males.

Increasing global warming is severely affecting tree growth and development. However, research on the sex-specific responses of dioecious trees to warming is scarce. Here, male and female Salix paraplesia were selected for artificial warming (an increase of 4°C relative to ambient temperature) to investigate the effects on morphological, physiological, biochemical and molecular responses. The results showed that warming significantly promoted the growth of female and male S. paraplesia, but females grew faster than males. Warming affected photosynthesis, chloroplast structures, peroxidase activity, proline, flavonoids, nonstructural carbohydrates (NSCs) and phenolic contents in both sexes. Interestingly, warming increased flavonoid accumulation in female roots and male leaves but inhibited it in female leaves and male roots. The transcriptome and proteome results indicated that differentially expressed genes and proteins were significantly enriched in sucrose and starch metabolism and flavonoid biosynthesis pathways. The integrative analysis of transcriptomic, proteomic, biochemical and physiological data revealed that warming changed the expression of SpAMY, SpBGL, SpEGLC and SpAGPase genes, resulting in the reduction of NSCs and starch and the activation of sugar signaling, particularly SpSnRK1s, in female roots and male leaves. These sugar signals subsequently altered the expression of SpHCTs, SpLAR and SpDFR in the flavonoid biosynthetic pathway, ultimately leading to the differential accumulation of flavonoids in female and male S. paraplesia. Therefore, warming causes sexually differential responses of S. paraplesia, with females performing better than males.

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.

Physiological and Biochemical Traits of Needles Imply That Understory Light Conditions in the Growing Season May Be Favorable to Pinus koraiensis Trees

Light is often considered the primary factor leading to the regeneration failure of Korean pines (Pinus koraiensis) under the forest canopy. However, studies on the effect of light on Korean pines mainly focus on the use of an artificial sunshade net to control shade; field studies on the canopy are extremely scarce, and the current experimental results are contradictory. For a deeper understanding of the relationship between light conditions and understory Korean pine trees, the conditions of low, middle, high and full light (control) under the forest were tested at 18 years of age. The photosynthetic pigments, chlorophyll fluorescence, non-structural carbohydrate metabolism, antioxidant enzyme activity, and nutrient concentrations of current-year needles from Korean pine trees were measured. From June to September, light intensity and quality decreased under full light, but following leaf fall, understory light conditions improved slightly. As the light conditions improved, the photosynthetic pigments in the needles decreased, but Car/Chl were highest in the needles under full light. All light conditions had a positive correlation with glucose concentrations and Rubisco activity. Full-light needles had the highest APX activity, DPPH scavenging capacity, and proline concentration, as well as higher NPQ and lower Fv/Fm readings. This indicated that full-light Korean pine trees were stressed and inhibited photosynthesis to some extent, while the understory light environment may alleviate stress. The conservative strategy of storing more starch and using less glucose in understory Korean pine trees may be one of the reasons for the observed differences in growth rates among Korean pine trees under varying light conditions. Overall, this study implies that understory light during the growing season is not always unfavorable to 18-year-old Korean pine trees; this means that 18-year-old Korean pine trees still have shade tolerance to some extent and are capable of living under a canopy of deciduous trees.

Genetic variation for bioenergy traits within and among lowland switchgrass (Panicum virgatum L.) crosses

Cellulosic biomass derived from switchgrass can be an alternative source to produce renewable bioenergy. However, bioenergy production from switchgrass is not economically viable unless genotypes with high yield potential and acceptable biofuel quality are available. To identify switchgrass genotypes with good biofuel quality, ten high biomass yielding hybrid populations derived from crosses between two lowland cultivars, Alamo (A) and Kanlow (K), were evaluated in this study. The experiment was planted in 2018 in two field environments, the East Tennessee Research and Education Center, Knoxville, and the Plateau Research and Education Center, Crossville, in a randomized complete block design with two replications per location. Tillers were collected in the Fall of 2020 and 2021, and analyzed for bioenergy traits using the near-infrared reflectance spectroscopy technique. The crosses and their parents were different in bioenergy traits across the environments (locations and years) (P ≤ 0.05). The crosses’ total ethanol yield (EtOH) ranged from 63.5 to 70.4 mg g−1, and the total sugars yield varied from 725 to 737 mg g−1 across the environments. Average cellulose, hemicellulose, lignin, and ash content were 395.8, 333.9, 178.4, and 49.3 mg g−1, respectively. The estimated non-structural carbohydrates were found as good predictors of EtOH (R2 = 0.67) (P ≤ 0.05). The cross, 12A-259 × 12K-247, exhibited high EtOH, high hemicellulose, low lignin, and low ash. Crosses 12A-261 × 12K-245 and 12A-263 × 12K-250 exhibited high cellulose and sugar. These results indicate significant genetic heterogeneity for bioenergy traits within and between these two lowland switchgrass cultivars.

A Moderate Wetting and Drying Regime Combined with Appropriate Nitrogen Application Increases Grain Yield and Nitrogen Use Efficiency in Rice

This study investigated whether and how irrigation regimes interact with nitrogen (N) application rates to mediate the grain yield, N use efficiency (NUE) and water use efficiency (WUE) in rice and to understand the underlying mechanism. A field experiment was conducted with two irrigation regimes, continuously flooded (CF) and alternate wetting and moderate drying (AWMD), and three N application rates, 120 kg ha−1 N (a low N rate, LN), 240 kg ha−1 N (a medium N rate, MN) and 360 kg ha−1 N (a high N rate, HN) in 2021 and 2022. The results showed that the grain yield exhibited the lowest values at the LN, regardless of the irrigation regime, while it was the highest at the MN when the CF regime was adopted. The grain yield was comparable between the MN and HN regarding the AWMD regime. AWMD significantly increased the grain yield, NUE and WUE compared to CF at the same N rate, which was attributed to a higher photosynthetic rate, improved population quality, enhanced nonstructural carbohydrate remobilization from stems to grains during grain filling, and elevated activities of enzymes involved in N assimilation in the roots. The results suggest that an AWMD regime combined with MN treatment could pronounce a synergistic interaction on the grain yield, NUE and WUE in rice by improving root and shoot physiological performances.

Local adaptation to aridity in a widely distributed angiosperm tree species is mediated by seasonal increase of sugars and reduced growth.

Trees in dry climates often have higher concentrations of total non-structural carbohydrates (NSC=starch + soluble sugars) and grow less than conspecifics in more humid climates. This pattern might result from growth being more constrained by aridity than the carbon (C) gain, or reflect local adaptation to aridity, since NSC fuel metabolism and ensure adequate osmoregulation through the supply of soluble sugars (SS), while low growth reduces water and C demands. It has been further proposed that C allocation to storage could come at the expense of growth (i.e., a growth-storage trade-off). We examined whether NSC and growth reflect local adaptation to aridity in Embothrium coccineum (Proteaceae), a species with an exceptionally wide niche. To control for any influence of the phenotypic plasticity on NSC and growth, we collected seeds from dry (500mmyear-1) and moist (> 2500mmyear-1) climates and grew seedlings in a common garden experiment for 3years. We then compared NSC and SS concentrations and pools (i.e., total contents), and the biomass of seedlings at spring, summer, and fall. Seedlings from the dry climate had significantly lower biomass and similar NSC concentrations and pools than seedlings from moist climate, suggesting that reduced growth in arid environments does not result from a prioritization of C allocation to storage but it confers advantages under aridity (e.g., lower transpiration area). Across organs, starch and NSC decreased similarly in seedlings from both climates from spring onward. However, root and stem SS concentrations increased during the growing season, and these increases were significantly higher in seedlings from the dry climate. The greater SS accumulation in seedlings from the dry climate compared to those from the moist climate demonstrates ecotypic differentiation in the seasonal dynamics of SS, suggesting that SS underlie local adaptation to aridity. (298 words).

Optimum Cultivation Model Increased the Grain Yield of Ratoon Rice and Nitrogen Agronomic Efficiency by Improving Root Morphological Traits and Stubble Character of the Main Rice

The present study investigated the effects of different integrated cultivation treatments on the yield, nitrogen agronomic efficiency (AEN), and growth performance of a ratoon rice system. A two-year field experiment was carried out during 2021–2022 using a randomized block design. Cultivation treatments included the farmers’ practice model (control, CK), high-yield and high-efficiency model (T1), enhanced-high-yield and high-efficiency model (T2), and the no-N model (N0). The grain yield, yield components, root traits, and stubble characteristics were determined. The results showed that T2 treatment significantly increased the grain yield and AEN by 53% and 236%, respectively, compared with CK. Similarly, the stubble weight, non-structure carbohydrate contents, and the root attributes were significantly improved under T2 treatment. The correlation analysis suggested that ratoon rice yield and AEN was significantly and positively correlated with root weight (p &lt; 0.01) and the stubble parameters including stubble weight (p &lt; 0.01), starch content (p &lt; 0.01), and soluble sugar content (p &lt; 0.01). Additionally, a significant and positive correlation between root weight and stubble weight (p &lt; 0.05) was determined in our study. Consequently, our work highlights the benefits of integrating planting density, nitrogen/water management, and other practices to achieve high AEN and grain yield of the ratoon rice by improving root trait and stubble characteristics of the main rice.

Light spectrum effects on rocket and lamb's lettuce cultivated in a vertical indoor farming system

Rocket and lamb's lettuce are new leafy vegetables whose consumption in salads is increasing, especially as ready-to-eat products. These plants are often cultivated in greenhouses under artificial light, and are very important due to their pleasant taste, texture, and nutritional value to humans. The present study analyzes the effects of light quality provided by light emitting diodes (LEDs) on the yield and quality of different leafy vegetable species. Lamb's lettuce and rocket plants were grown in the same conditions under 4 light spectrums color fractions (NS-12, AP57, AP673L, and G2) for 27 and 37 days, respectively. Then fresh and dry weight, chlorophyll fluorescence, and chromatic characteristics were determined. The leaf quality of lamb's lettuce and rocket was characterized by measurements of the contents of carbohydrates, organic acids, and amino acids in leaves. Vegetative growth was significantly influenced by light quality and was species-dependent, and treatment with the highest proportion of Red:Blue light (G2) produced the highest fresh weight and maximum efficiency of PSII. The results of the chlorophyll fluorescence parameters were more influenced by the species rather than by the spectrum lights, except for the efficiency of PSII, which was higher in treatments with the lowest Red: Far-red ratio (AP67 and G2). G2 light spectrum reduces chlorophyll and carotenoid content compared to other treatments. Among all the primary metabolites analyzed, non-structural carbohydrates were the most dependent on light quality. Generally, the lights with the greatest effect on the parameters analyzed were those with higher Red:Blue ratios and a higher far-red fraction. No effect of light spectra on glutamate concentration was observed. However, a concentration increase was observed in treatments with a higher proportion of far-red light. Regarding organics acids, the different light spectrums did not affect the concentration of the majority of acids (citrate and malate) in rocket and lamb´s lettuce plants. The spectral composition of light has an influence on the quality and quantity of lamb's lettuce and rocket production. Therefore, each species studied responds differently to the light spectrums.

Diurnal metabolism of energy-cane and sugarcane: A metabolomic and non-structural carbohydrate analysis

Energy-cane is a cross breed between commercial sugarcane and S. spontaneum, a hybrid that has higher fiber content, low sucrose and greater productivity compared to commercial sugarcane hybrids. It has been recently shown that diurnal and seasonal changes impact several physiological characteristics of sugarcane. However, little is known about how the diurnal cycle affects the production of carbohydrates and metabolites in energy-cane. In the present study, we investigate the diurnal cycle of adult sugarcane and energy-cane by analyzing the carbohydrates and metabolites profiles of leaves and internodes. Our results show fluctuations in the soluble sugars content (sucrose, glucose and fructose) and the metabolites profile throughout of day, which indicates different growth strategies and carbon use among these cultivars. In addition, a high concentration of starch was observed in the mature internodes of energy-cane. Some biological pathways related to biomass production, such as the phenylpropanoid pathway, were more active in energy-cane compared to sugarcane. Our results reveal that sugarcane and energy-cane metabolism are different throughout the day, a better understanding of the metabolism of these cultivars opens the possibility of creating more efficient plants through breeding.

The effect of experimental warming on fine root functional traits of woody plants: Data synthesis

Fine root traits are critical to plant nutrition and water uptake, and soil nutrient cycling. The impacts of climate warming on woody plants are predicted to be severe, but the effects on the fine root traits of woody plants remain unclear. To evaluate the effects of warming on fine-root traits of woody plants, we synthesized 431 paired observations of 13 traits from 78 studies. The result showed that warming increased the fine root nitrogen (N) concentration, root mortality, and root respiration, but decreased fine root phosphorus (P) concentration, root C:N and root nonstructural carbohydrates (NSC) concentration. However, warming had no significant effect on fine root biomass, root production and morphological traits. Warming effects on fine root biomass and root diameter decreased with warming magnitude, while root P concentration increased. Moreover, with increasing warming duration, the effect size of specific root length (SRL), root length, root C:N and root NSC increased. The effects size of root biomass, root diameter, root length and root C:N decreased with mean annual temperature (MAT) and mean annual precipitation (MAP) increase. However, the effect size of root N concentration increased with higher MAT and MAP. Furthermore, warming increased the fine root biomass of ectomycorrhiza (ECM) plants, but decreased that of plants associated with arbuscular mycorrhizal (AM) fungi. These results indicate that the effect of warming on fine root traits of woody plants was not only modulated by warming duration and magnitude, but also MAT and MAP. Our findings highlight the differential warming responses to fine root traits of woody plants, which have strong implications for shrubs and tree-dominated ecosystems soil nutrients cycling and carbon stocks.

Nitrogen Addition Alleviates Cadmium Toxicity in Eleocarpus glabripetalus Seedlings

Cadmium (Cd) accumulation in soil is a serious form of heavy metal pollution affecting environmental safety and human health. In order to clarify the tolerance mechanisms to Cd-contaminated soils under N deposition, changes in plant growth, root architecture and physiological characteristics of Eleocarpus glabripetalus seedlings under combined nitrogen (N) and cadmium (Cd) treatments were determined in this study. The results indicated that Cd-induced negative effects inhibited the growth of E. glabripetalus seedlings through increased underground biomass allocation, and affected transpiration and respiratory processes, resulting in a decreased soluble sugars concentration in leaves and non-structural carbohydrates (NSC) in the roots. Root systems might play a major role in Cd absorption. Cd stress restricted the growth of fine roots (&lt;0.5 mm), and affected the uptake of N and P. N addition alleviated the Cd-induced negative effect on plant growth through improving the root system, increasing starch and NSC contents in the roots and increasing total biomass. These findings have important implications for understanding the underlying tolerance mechanisms of Cd pollution under N deposition in arbor species.

Grain yield response to planting date and cutting height of the first crop in rice ratooning

AbstractRice (Oryza sativa L.) ratooning is one of the most essential production strategies to increase grain yield. Field experiments were conducted in southwestern Japan in 2021 and 2022 to determine the effects of planting date and cutting height of the first crop on grain yield. Grain yield of the second crop was higher at early planting date than at late planting date in 2021, but the yield difference was narrowed in 2022. The higher grain yield at early planting date resulted from the higher number of spikelets and percentage of filled spikelets due to the higher stubble nonstructural carbohydrate (NSC) content, leaf area index (LAI), and air temperatures. Grain yield of the second crop was higher at high cutting height than at low cutting height in 2021, but the yield difference was narrowed in 2022. The higher grain yield at high cutting height resulted from the higher number of spikelets due to the higher NSC content and LAI. In the weather conditions, grain yield had a strong positive correlation with the air temperature, which had positive correlations with the number of panicle and percentage of filled spikelets. In the stubble conditions, grain yield had a strong positive correlation with NSC content, which had positive correlations with the number of panicle and percentage of filled spikelets. Therefore, early planting, which secures high air temperatures, and high cutting height, which produces high NSC content, are recommended to increase grain yield of the second crop.

Maca (Lepidium meyenii): In Vitro Evaluation of Rumen Fermentation and Oxidative Stress

The aim of this study was to investigate the chemical composition of three maca (Lepidium meyenii Walp.) ecotypes (yellow, black, and red) and their in vitro fermentation characteristics and antioxidant effects on cow rumen liquor. The three ecotypes were added to a total mixed ratio (TMR) in different doses (0, 150, and 300 mg/g) and incubated in vitro under anaerobic conditions for 120 h. Methane production was recorded after 24 h of incubation. Antioxidant status and degree of lipid peroxidation were also evaluated after 24 and 120 h of incubation with the fermentation liquor. An analysis of the chemical composition showed high concentrations of non-structural carbohydrates in all maca ecotypes, particularly in the yellow ecotypes. Moreover, despite an increase in gas production, it seems that the TMR supplemented with each maca ecotype, particularly at the highest dose, increases the amount of volatile fatty acids and reduces methane production. Finally, the addition of maca can induce an antioxidant effect. Our findings suggest that the three ecotypes of maca are rich in non-structural carbohydrates which affect the in vitro fermentation kinetics and reduce methane production.

Root relative water content is a potential signal for impending mortality of a subtropical conifer during extreme drought stress.

Adaptation to future climates characterized by more frequent severe droughts requires enhanced mechanistic understanding of tree mortality. However, our knowledge of the physiological limits to withstand extreme drought, and how the coordination between water and carbon traits enhances survival, is still limited. Potted seedlings of Pinus massoniana were dehydrated to three target droughts (percentage loss of stem hydraulic conductivity of ca. 50%, 85%, and 100%; PLC50 , PLC85 and PLC100 ) and then relieved from these target droughts by fully rewatering. Predawn and midday water potentials (Ψ), relative water content (RWC), PLC and nonstructural carbohydrates (NSC) were monitored. During drought, Ψ and RWC declined as PLC increased. Root RWC declined more rapidly than other organ RWCs, particularly after PLC50 stress. All organ NSC concentrations were above predrought values. During rewatering, water trait recovery declined as drought increased, with no mortality at PLC50 but 75% mortality at PLC85 . The observed stem hydraulic recovery at PLC50 following rewatering was not correlated to NSC dynamics. Collectively, our results highlighted the primary role of hydraulic failure in Pinus massoniana seedling mortality by assessing mortality threshold and links among water status and water supply. Root RWC can be considered as a potential warning signal of P. massoniana mortality.

Effect of Rootstock on Vineyard Establishment Using Green-Growing Benchgrafts

Demand for vine plant material has increased drastically due to the ongoing expansion of viticulture, and recent widespread replanting efforts. Nurseries and growers are turning to green-grafted vines to meet demand. Unfortunately, most vineyard establishment studies have centered around dormant benchgrafted vines. Thus, little is known regarding the specific establishment trends of green-growing benchgrafts. This study aimed to explore the role rootstock selection has in green-growing benchgraft establishment and development over the first four years post-planting. Vitis vinifera L. cv. Sauvignon blanc was grafted onto multiple rootstocks of varying parentage, including ‘101-14MGT’ (V. riparia × V. rupestris), ‘1103P’ (V. berlandieri × V. rupestris), ‘110R’ (V. berlandieri × V. rupestris), ‘420A MGT’ (V. berlandieri × V. riparia), and ‘Teleki 5C’ (V. berlandieri × V. riparia). The experimental site was organized using a completely randomized design (n = 12) with all vines managed to industry-standard cultural practices. Vines grafted onto 1103P had the largest average trunk diameter (p = 0.0012) and circumference (p &lt; 0.0001) at 22.2 mm and 7.57 cm, respectively. Vines grafted onto 110R had the second-largest trunk circumference at 6.65 cm. Vines grafted onto 110R had the largest concentration of total non-structural carbohydrates at planting at 1.47 g/L, followed by 1103P at 1.25 g/L (p &lt; 0.0001). Total non-structural carbohydrate concentrations in the trunk during dormancy was the highest in 110R at 16.0% total dry weight (p = 0.0008). The larger trunk size and more extensive carbohydrate reserves suggest that green-growing benchgrafts using 110R or 1103P have a higher capacity and likelihood of establishment success.

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.

Whole-Tree Storage of Non-structural Carbohydrates in Apple and Pear Trees on Size-Controlling Rootstocks

Whole-Tree Storage of Non-structural Carbohydrates in Apple and Pear Trees on Size-Controlling Rootstocks

Effect of foliar application of zinc on annual productivity, foliar nutrients, bioactive compounds and oxidative metabolism in pecan

ABSTRACT Pecan nut production is quite commonly limited by zinc (Zn) deficiency. Here, we evaluate the response in terms of the concentrations of non-structural carbohydrates, yield components, foliar nutrient levels and oxidative metabolism in young ‘Western Schley’ pecan nut trees in response to foliar applications of 200 mg · L−1 of Zn as one of the following: ZnSO4, Zn-EDTA, ZnO nanoparticles (NPs) or the proprietary product ‘nitrazinc’ (NZN) (the control). Across two consecutive growing seasons, the spraying of Zn in these various forms helped maintain the foliar concentrations of non-structural carbohydrates, foliar nutrients (total-N, Ca2+ and Mg2+) and the kernel percentage of nuts. Likewise, trees sprayed with ZnSO4 maintained the concentrations of Zn in the leaflets across seasons. On the other hand, Zn-EDTA decreased the concentration of chlorophyll and total carotenoids. In general, leaflets treated with ZnSO4, Zn-EDTA and ZnO NPs reduced their oxidative metabolism. Sources of Zn – such as ZnSO4 – are commercially viable alternatives suitable for increasing the performance of some parameters associated with the yield and quality of nuts in pecan. It would be worthwhile to determine the optimal Zn dose rates for the various pecan cultivars in common use and also to increase our understanding of the physiological and biochemical changes associated with foliar Zn applications.

Differences between tree stem CO2 efflux and O2 influx rates cannot be explained by internal CO2 transport or storage in large beech trees.

Tree stem respiration (RS ) is a substantial component of the forest carbon balance. The mass balance approach uses stem CO2 efflux and internal xylem fluxes to sum up RS , while the oxygen-based method assumes O2 influx as a proxy of RS . So far, both approaches have yielded inconsistent results regarding the fate of respired CO2 in tree stems, a major challenge for quantifying forest carbon dynamics. We collected a data set of CO2 efflux, O2 influx, xylem CO2 concentration, sap flow, sap pH, stem temperature, nonstructural carbohydrates concentrationand potential phosphoenolpyruvate carboxylase (PEPC)capacity on mature beech trees to identify the sources of differences between approaches. The ratio of CO2 efflux to O2 influx was consistently below unity (0.7) along a 3-m vertical gradient, but internal fluxes did not bridge the gap between influx and efflux, nor did we find evidence for changes in respiratory substrate use. PEPC capacity was comparable with that previously reported in green current-year twigs. Although we could not reconcile differences between approaches, results shed light on the uncertain fate of CO2 respired by parenchyma cells across the sapwood. Unexpected high values of PEPC capacity highlight its potential relevance as a mechanism of local CO2 removal, which merits further research.