Leaf Non-structural Carbohydrate Content Research Articles

Physiological factors contribute to increased competitiveness of grass relative to sedge, forb and legume species under different N application levels

In alpine grasslands, increased N deposition is increasing the dominance of grasses relative to other functional types according to our previous study Shen et al. (2022). However, the mechanisms that drive this compositional change are not fully understood. We measured the effects of 4–6 years' N addition to simulate N deposition at rates of 0 (CK), 8 (N1), 24 (N2), 40 (N3), 56 (N4), and 72 (N5) kg N ha−1 year−1 on dominant representatives of four functional types, Leymus secalinus (grass), Carex capillifolia (sedge), Potentilla multifidi (non-leguminous forb), and Medicago ruthenica (legume), in the alpine grassland on the Qinghai-Tibetan Plateau (QTP). In-situ experiment showed that N addition increased aboveground biomass in L. secalinus but had negative or neutral effects on aboveground biomass in the other species. Consistent with this finding, N addition increased net photosynthesis, chlorophyll content, and rubisco activity in L. secalinus with less positive effects on the other species. Nitrogen addition increased leaf N content in L. secalinus and C. capillifolia and reduced leaf non-structural carbohydrate content in all four species. In L. secalinus, the highest N addition rate (N5) reduced MDA content, a marker of oxidative stress, by enhancing antioxidant enzyme activity. Overall, our findings suggested that physiological factors can contribute to increased competitiveness of grass relative to sedge, forb and legume species under high N application levels. The rapid growth of this grass species reduces resource availability to non-grass species, increasing its dominance in the alpine meadow.

Transient Effects of Snow Cover Duration on Primary Growth and Leaf Traits in a Tundra Shrub.

With the recent climate warming, tundra ecotones are facing a progressive acceleration of spring snowpack melting and extension of the growing season, with evident consequences to vegetation. Along with summer temperature, winter precipitation has been recently recognised as a crucial factor for tundra shrub growth and physiology. However, gaps of knowledge still exist on long-living plant responses to different snowpack duration, especially on how intra-specific and year-to-year variability together with multiple functional trait adjustments could influence the long-term responses. To fill this gap, we conducted a 3 years snow manipulation experiment above the Alpine treeline on the typical tundra species Juniperus communis, the conifer with the widest distributional range in the north emisphere. We tested shoot elongation, leaf area, stomatal density, leaf dry weight and leaf non-structural carbohydrate content of plants subjected to anticipated, natural and postponed snowpack duration. Anticipated snowpack melting enhanced new shoot elongation and increased stomatal density. However, plants under prolonged snow cover seemed to compensate for the shorter growing period, likely increasing carbon allocation to growth. In fact, these latter showed larger needles and low starch content at the beginning of the growing season. Variability between treatments slightly decreased over time, suggesting a progressive acclimation of juniper to new conditions. In the context of future warming scenarios, our results support the hypothesis of shrub biomass increase within the tundra biome. Yet, the picture is still far from being complete and further research should focus on transient and fading effects of changing conditions in the long term.

Glycolate catabolic bypass pathway integration in rice could be effective in lowering photorespiratory rate with modulating starch content and grain quality

Photorespiration, which is prevalent under higher temperature and arid conditions, significantly affects crop productivity by reducing yields up to 50% in C3 crops like rice under severe stress conditions. This is primarily attributed to a reduction in net photosynthetic rate (PN). Rice flag leaf photosynthesis is the primary supplier of sugar to the maturing spikelets after anthesis. This study evaluated the grain quality traits and starch content of the wild type (WT) and transgenic rice generated by introducing Escherichia coli (E. coli) glycolate catabolic pathway bypassed (GCPB) through agrobacterium mediated transformation. Leaf soluble protein, photosynthetic CO2 assimilation rate, leaf non-structural carbohydrate content, grain quality traits such as hulling and milling percentages, head rice recovery, water uptake, volume expansion, alkali spreading value, gel consistency, grain breadth, grain starch content and amylose content were affected to a great extent in GCPB transgenic plants (T4). This study indicates the possible role of photorespiratory bypass mechanism in the regulation of source-sink communication, starch biosynthesis and grain quality in rice.

Spatial variability in carbon- and nitrogen-related traits in apple trees: the effects of the light environment and crop load.

Photosynthetic carbon assimilation rates are highly dependent on environmental factors such as light availability and on metabolic limitations such as the demand for carbon by sink organs. The relative effects of light and sink demand on photosynthesis in perennial plants such as trees remain poorly characterized. The aim of the present study was therefore to characterize the relationships between light and fruit load on a range of leaf traits including photosynthesis, non-structural carbohydrate content, leaf structure, and nitrogen-related variables in fruiting ('ON') and non-fruiting ('OFF') 'Golden Delicious' apple trees. We show that crop status (at the tree scale) exerts a greater influence over leaf traits than the local light environment or the local fruit load. High rates of photosynthesis were observed in the ON trees. This was correlated with a high leaf nitrogen content. In contrast, little spatial variability in photosynthesis rates was observed in the OFF trees. The lack of variation in photosynthesis rates was associated with high leaf non-structural carbohydrate content at the tree level. Taken together, these results suggest that low carbon demand leads to feedback limitation on photosynthesis resulting in a low level of within-tree variability. These findings provide new insights into carbon and nitrogen allocations within trees, which are heavily dependent on carbon demand.

Responses of leaf traits to low temperature in an evergreen oak at its upper limit

AbstractLow temperature is a major driver of the upper distributional limits of subtropical evergreen broadleaved forests in East Asia. The eco‐physiology of evergreen broadleaved trees at the upper limits could respond to both lower winter temperature and lower averaged annual temperature that covary with elevation. To analyze these responses, we assessed the variations in leaf chemical traits of Cyclobalanopsis gracilis with seasonality and along elevation in the ecotone from subtropical to temperate climate, and analyzed the relationships between traits of mature leaves and temperature. The study showed that the mass‐based nonstructural carbohydrate (NSC) content reached the highest level across elevations during winter; however, the winter NSC content did not differ between elevations. For mature leaves, leaf dry mass per area (LMA) tended to be higher approaching the upper limit. The leaf carbon to phosphorus ratio (C/P) showed an increasing trend with decreasing temperature, as did leaf carbon to nitrogen ratio (C/N) to some extent. The mass‐based P content showed a decreasing trend approaching the upper limit, whereas area‐based P content showed no significant variation. Our main results indicate that leaf NSC content is highest at all elevations in winter, and individuals at high elevations have high LMA and high nutrient use efficiency. The results suggest that for C. gracilis, an increasing leaf NSC results in a baseline protection to cope with cold in winter, which, at higher elevations is supplemented with increasing LMA and nutrient use efficiency to cope with associated low‐temperature stress.

Photosynthetic and Respiratory Responses of Two Bog Shrub Species to Whole Ecosystem Warming and Elevated CO2 at the Boreal-Temperate Ecotone

Peatlands within the boreal-temperate ecotone contain the majority of terrestrial carbon in this region, and there is concern over the fate of such carbon stores in the face of global environmental changes. The Spruce and Peatland Response Under Changing Environments (SPRUCE) facility aims to advance the understanding of how such peatlands may respond to such changes, using a combination of whole ecosystem warming (WEW; +0, 2.25, 4.5, 6.75 and 9 °C) and elevated CO2 (eCO2; +500 ppm) treatments in an intact bog ecosystem. We examined photosynthetic and respiration responses in leaves of two ericaceous shrub species--leatherleaf (Chamaedaphne calyculata (L.) Moench) and bog Labrador tea (Rhododendron groenlandicum (Oeder) Kron & Judd)--to the first year of combined eCO2 and WEW treatments at SPRUCE. We surveyed the leaf N content per area (Narea), net photosynthesis (AST) and respiration (RD25) at 25°C and 400 ppm CO2 and net photosynthesis at mean growing conditions (AGR) of newly emerged, mature and overwintered leaves. We also measured leaf non-structural carbohydrate content (NSC) in mature leaves. The effects of WEW and eCO2 varied by season and species, highlighting the need to accommodate such variability in modeling this system. In mature leaves, we did not observe a response to either treatment of AST or RD25 in R. groenlandicum, but we did observe a 50% decrease in AST of C. calyculata with eCO2. In mature leaves under eCO2, neither species had increased AGR and both had increases in NSC, indicating acclimation of photosynthesis to eCO2 may be related to source-sink imbalances of carbohydrates. Thus, productivity gains of shrubs under eCO2 may be lower than previously predicted for this site by models not accounting for such acclimation. In newly emerged leaves, AST increased with WEW in R. groenlandicum, but not C. calyculata. Overwintered leaves exhibited a decrease in RD25 for R. groenlandicum and in AST for C. calyculata with increasing WEW, as well as an increase of AGR with eCO2 in both species. Responses in newly emerged and overwintered leaves may reflect physiological acclimation or phenological changes in response to treatments.

Differences in physiological traits and resistances of Alternanthera philoxeroides after herbivory by generalists and specialists

Many researchers have surveyed damages caused by natural enemies of invasive plants in both native and introduced ranges to test the enemy release hypothesis. In this study, we report our findings on the physiological and morphological impacts of a co-evolved specialist insect (Agasicles hygrophila) and two generalist insects (Atractomorpha sinensis and Hymenia recurvalis) in introduced ranges on an invasive plant, Alternanthera philoxeroides, in both field trials and controlled environments. The resistance of A. philoxeroides against the generalists and the specialist was also studied. We obtained consistent results in both the field trials and the controlled treatments: both the generalists and the specialist decreased leaf biomass, photosynthesis, leaf nitrogen content, and total leaf non-structural carbohydrate content in A. philoxeroides. However, the specialist decreased leaf mass, photosynthesis, and leaf nitrogen content more acutely than the generalists. Moreover, A. philoxeroides increased both leaf lignin and cellulose concentrations upon the generalists’ attack but only increased cellulose concentration in response to the specialist. Our results showed that even under the same population density, the co-evolved specialists from original ranges caused more severe morphological and physiological damage to A. philoxeroides than the generalists in introduced ranges. This revealed that invasive plants released some herbivory stress before their co-evolved specialists were introduced, which may contribute to the superior performance of invasive plants in introduced regions.

Differences in Physiological Traits and Resistances of Alternanthera philoxeroides after Herbivory by Generalists and Specialists

Many researchers have surveyed damages caused by natural enemies in invasive plants in both native and introduced ranges to testing enemy release hypothesis. Although the physiological impact of natural enemies on invasive plants is important, little research has been conducted to compare the impacts between generalists and specialists. In this study, we report our findings on the physiological and morphological impacts of a native specialist insect (Agasicles hygrophila) and two generalist insects (Atractomorpha sinensis and Hymenia recurvalis) in introduced ranges on an invasive plants Alternanthera philoxeroides in both field trials and controlled environments. Resistances of A. philoxeroides against the generalists and the specialist were also studied. We obtained consistent results in both the field trials and the controlled treatments. Both the generalists and the specialist decreased leaf biomass, photosynthesis, leaf nitrogen content and total leaf non-structural carbohydrate content in A. philoxeroides. However, the specialist decreased leaf mass, photosynthesis, and leaf nitrogen content more acutely than the generalists. Moreover, A. philoxeroides increased both leaf lignin and cellulose concentrations upon the generalists’ attack, but only increased cellulose concentration in response to the specialist. Our results revealed that even under the same population density, the specialists from native ranges caused more severe morphological and physiological damages on A. philoxeroides than the generalists in introduced ranges. Which magnified the consequence of invasive plants suffered lower richness and abundance of natural enemy and contributed to superior performance of invasive plants in introduced regions.

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae.

Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows. A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7°C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8°C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology. Six years of experimental warming resulted in reductions in nectar volume per floret (64·7% of control), floret number per capitulum (8·7%) and capitulum number per plant (32·5%), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90% in nectar production per unit area. The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant-pollinator interactions and plant reproduction via induction of allocation shifts for plants growing in communities subject to asymmetric warming.

Season effects on leaf nitrogen partitioning and photosynthetic water use efficiency in mango

The key parameters of photosynthetic capacity (maximum carboxylation rate (V(cmax)), electron transport capacity (J(max)) and dark respiration rate (R(d))) and the slope (m) of the stomatal conductance model of Ball et al. [Progress in photosynthetic research, Martinus Nijhoff, Dordrecht, 1987] were measured for a whole growing season in fully expanded leaves of 12-year-old mango trees cv. Cogshall in La Réunion island. Leaf nitrogen partitioning into carboxylation (P(c)) and bioenergetic (P(b)) pools were computed according to the model of Niinemets and Tenhunen [Plant Cell Environ 1997;20: 845-66]. V(cmax), J(max), R(d), P(c) and P(b) remained relatively stable over the whole study period, with the exception of the period of linear fruit growth when J(max), R(d) and P(b) were slightly lower, and leaf non-structural carbohydrate content higher. During the pre-floral and floral periods, m decreased by more than 50%, indicating an increase in photosynthetic water use efficiency and m increased again during the period of linear fruit growth. Our results show that, in tropical orchard conditions characterized by mild seasonal climatic changes and non-limiting water supply, leaf nitrogen partitioning is rather stable. Our results also advocate for more studies on the effect of phenology on m and photosynthetic water use efficiency, which is of paramount importance for building coupled biochemical models of photosynthetic carbon assimilation.

Trinexapac-ethyl Does Not Increase Total Nonstructural Carbohydrate Content in Leaves, Crowns, and Roots of Tall Fescue

Turfgrass growth regulators (TGRs) are an effective means of reducing vertical shoot growth and the production of clippings of tall fescue (Festuca arundinacea Schreb.). Recently, using TGRs has been suggested as a way to acclimate or precondition turfgrass to stress conditions, possibly through total nonstructural carbohydrate (TNC) accumulations and altered TNC partitioning. The TNC may accumulate in response to growth suppression associated with the TGR application. The objective of this study on tall fescue was to determine the effect of a single trinexapac-ethyl (TE) application on tissue weight and on TNC concentration and weight in leaves, crowns, and roots when sampled 6 to 7 weeks following TE application. This sampling time was chosen to coincide with the 28- to 56-day callback schedule that professional lawn care personnel follow when working with tall fescue. In 1995, a high level of turfgrass maintenance was used, consisting of N applications at 49 kg·ha-1 per month and two mowings per week, while in 1996 a moderate level was used, consisting of N applications at 24 kg·ha-1 per month and one mowing per week. Though TE provided reasonable inhibition of clipping growth for a 4-week period during both years, we observed no increase in tissue weight or in TNC concentration or weight in leaves, crowns, and roots when sampled 6 to 7 weeks after treatment. Chemical name used: [4(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] (trinexapac-ethyl).

Leaf non-structural carbohydrates and leaf dry weight per area in three altitudinal populations ofEspeletia schultzii WEDD

The leaf non-structural carbohydrate (NSC) content and total non-structural carbohydrate content (TNC) were measured on a dry weight basis and on a leaf area basis in three altitudinal (3100, 3550 and 4200 m a.s.l.) populations ofE. schultzii. The values of leaf dry weight per area (LWA) increase with altitude. The leaf non-structural carbohydrate content (expressed as g/kg dry weight) does not show statistically significant difference among populations, but the values expressed on an area basis (g/m2) show a statistically significant increase with altitude. Significant correlations were observed between LWA and TNC (r 2=0.65); insoluble carbohydrate (r 2=0.78); total soluble carbohydrate (r 2=0.53); reducing sugars (r 2=0.47) expressed on area basis. Correlations between LWA and NSC for any fraction and TNC on a dry weight basis were not significant. It appears that along this altitudinal gradient the leaf area is more affected than the leaf dry weight. Since the NSC is known to play a role in the freezing tolerance of plants, the results indicate that the freezing tolerance does not change among the populations along the gradient.