Leaf Total Non-structural Carbohydrate Concentration Research Articles

Effects of moderate warming on growth and physiological performance of subtropical saplings in southern China

While studies on temperate species indicate positive correlations between growth and elevated temperature, some observations referring tropical species suggest the opposite, as tropical species operates with more thermally stable climates. In this study, we subjected co-occurring Schima superba Gardn. et Champ., and Ormosia pinnata (Lour.) Merr saplings to infrared heaters in open-top chambers tracking natural temperature variability and measured their growth and physiological responses during a hot summer. Our key findings are (i) Short term warming induced a slight reduction in growth (height and basal stem diameter) of S. superba and O. pinnata saplings, but significantly increased their specific leaf area. (ii) During the warmest period, warming posed a negative and species-specific effect on photosynthetic functioning of these two species, in a manner that stomatal conductance of S. superba, but not of O. pinnata, significantly decreased under warming. The negative impacts of warming on photosynthetic biochemistry were stronger for S. superba compared to O. pinnata. (iii) Warming caused significant reductions in leaf total non-structural carbohydrate concentrations of both species. Species-specific effects of warming were found for leaf carbon (C), nitrogen (N) concentrations and C:N ratios, whereas leaf phosphorus (P) concentrations and N:P ratios were not affected. Higher leaf C concentrations as well as C:N ratios were only detected in legume O. pinnata under warming conditions. Our results demonstrated that climate warming is expected to have adverse and species-specific effects on S. superba and O. pinnata during summer in subtropical China.

Physiological responses of eastern hemlock (Tsuga canadensis) to light, adelgid infestation, and biological control: Implications for hemlock restoration

The rapid loss of eastern hemlock (Tsuga canadensis) in the southern Appalachian Mountains due to hemlock woolly adelgid (Adelges tsugae, HWA) infestation has resulted in substantial changes to ecosystem structure and function. Several restoration strategies have been proposed, including silvicultural treatments that increase incident light in forest understories. We conducted a four-year manipulative field experiment on surviving mid-story hemlock trees to investigate the effects of release from light limitation on HWA infestation and physiological parameters, expecting that higher light levels would improve tree carbon balance. Mixed hardwood forest sites were either previously uninfested with HWA (UN), infested with HWA (I), or infested with HWA and had a history of predatory beetle releases for biological control (I+P). At each site, we identified ten eastern hemlock trees in the mid-story and cut ~15 m radius canopy gaps around half of them while leaving the canopy intact over the other half. We compared short- and long-term indices of carbon gain and stress: leaf net photosynthesis (Anet); leaf fluorescence (Fv/Fm); leaf total non-structural carbohydrate concentration ([TNC]); new shoot growth; HWA density; and basal area growth. We found that trees experienced greater leaf-level stress in gaps and when HWA was actively feeding. Despite being more stressed, trees in gaps fixed 2x more carbon than those in reference conditions. High Anet in the spring translated into high leaf [TNC] in the spring, coinciding with when HWA was actively feeding. Although infested and uninfested trees had similar leaf [TNC] maxima, infestation prevented trees from allocating this carbon to shoot and basal area growth; this was particularly true for reference trees. Greater shoot growth in gap trees translated to greater annual basal area growth—by the end of the study, trees in gaps were growing 9x more than trees in reference conditions, and this was generally regardless of infestation status. In terms of growth and carbon balance, eastern hemlock consistently benefited from the increased light and soil moisture found in gaps; there was inconsistent and rather weak evidence that predator beetles conferred an additional advantage. Our results indicate that silvicultural treatments may improve long-term health and survival of infested trees and that integration of such treatments with existing strategies is worthy of continued exploration.

The influence of exogenously applied 2,4-D and NAA on fruit drop reduction in pummelo cv. Thong Dee

ABSTRACTEffect of 2,4-D and naphthalene acetic acid (NAA) on fruit drop reduction in pummelo cv. Thong Dee was investigated in the pummelo growing areas of Nakhon Pathom province, Thailand. Five similar sized and aged of pummelo trees were selected to set up the experiment. Ten mature branches with the same size from each pummelo tree were randomly selected around the canopy for 2,4-D (20 and 40 mg L−1), NAA (20 and 40 mg L−1) application and control. All treatments were applied to selected pummelo branches 2 times at full bloom and 2 months after fruit set. The results showed that 20 mg L−1 NAA (14.84%) and 40 mg L−1 NAA (12.26%) gave significantly higher percent of fruit retention at 6 months after fruit set. However, leaf total nonstructural carbohydrate concentration analysis showed that 40 mg L−1 2,4-D (104.86 mg g−1) and 20 mg L−1 2,4-D (96.55 mg g−1) gave significantly higher total nonstructural carbohydrate than those in control (78.44 mg g−1). For fruit quality, 40 mg L−1 2,4-D and 20 mg L−1 2,4-D gave the highest peel weight with 435.55 and 358.57 g, respectively, and 40 mg L−1 2,4-D gave the highest peel thickness with 20.25 mm, while 20 mg L−1 NAA gave statistically higher total soluble solid than those in 20 mg L−1 2,4-D and 40 mg L−1 2,4-D. Therefore, 20 mg L−1 of NAA sprayed 2 times at full bloom and 2 month after fruit set effectively reduced fruit drop and increased percentage of fruit retention in pummelo cv. Thong Dee.

Heat waves imposed during early pod development in soybean (Glycine max) cause significant yield loss despite a rapid recovery from oxidative stress.

Heat waves already have a large impact on crops and are predicted to become more intense and more frequent in the future. In this study, heat waves were imposed on soybean using infrared heating technology in a fully open-air field experiment. Five separate heat waves were applied to field-grown soybean (Glycine max) in central Illinois, three in 2010 and two in 2011. Thirty years of historical weather data from Illinois were analyzed to determine the length and intensity of a regionally realistic heat wave resulting in experimental heat wave treatments during which day and night canopy temperatures were elevated 6 °C above ambient for 3 days. Heat waves were applied during early or late reproductive stages to determine whether and when heat waves had an impact on carbon metabolism and seed yield. By the third day of each heat wave, net photosynthesis (A), specific leaf weight (SLW), and leaf total nonstructural carbohydrate concentration (TNC) were decreased, while leaf oxidative stress was increased. However, A, SLW, TNC, and measures of oxidative stress were no different than the control ca. 12 h after the heat waves ended, indicating rapid physiological recovery from the high-temperature stress. That end of season seed yield was reduced (~10%) only when heat waves were applied during early pod developmental stages indicates the yield loss had more to do with direct impacts of the heat waves on reproductive process than on photosynthesis. Soybean was unable to mitigate yield loss after heat waves given during late reproductive stages. This study shows that short high-temperature stress events that reduce photosynthesis and increase oxidative stress resulted in significant losses to soybean production in the Midwest, U.S. The study also suggests that to mitigate heat wave-induced yield loss, soybean needs improved reproductive and photosynthetic tolerance to high but increasingly common temperatures.

ABOVE- AND BELOW-GROUND RESPONSES TO SOIL MOISTURE DEFICITS IN OLIVE

Olive (Olea europaea L.) is characterized by high drought tolerance and adaptability to changing moisture conditions. Root morphological and physiological acclimation is an important component of olive tolerance to drought. The main objective of this experiment was to examine aboveground and belowground growth and physiological responses to drought. Self-rooted olive plants (‘Arbequina’), were grown in splitted rhizoboxes. Plants were exposed either to continuously well watered equally in both halves of the container (WW), continuously deficit irrigated in both halves with 1/3 the quantity of water as the WW treatment (DD), and heterogeneously irrigated with full watering in half the container (Wh) and only partial (1/3) watering in the other side (Dh). Irrigation regimes were maintained for 75 days. Canopy parameters measured were: stem growth rate, photosynthetic activity, stomatal conductance, leaf turgor, osmotic and total water potential and leaf total nonstructural carbohydrate concentration. Root parameters measured were: root respiration, an estimator of metabolic activity and electrolyte leakage, an indicator of root stress. The DD treatment differed significantly from DhWh and WW in all the aboveground parameters showing that drought stress applied to the whole root system was able to reduce plant growth, leaf water potential and leaf gas exchange. Root respiration decreased in the DD treatment and in the dry sector (Dh) of the DhWh treatment. This experiment highlights how roots can respond to drought conditions by reducing metabolism in a localized way. Under low water availability reduction of metabolic activity may contribute to the maintenance of a sustainable costs/benefit ratio. Stress indicators showed higher electrolyte leakage in Dh roots compared to Wh roots, but mainly in fibrous roots older than 38 days. This confirms that olive is a species sensitive to water availability in terms of growth but generally tolerant of water deficits in terms of survival.

Leaf Carbohydrate Concentration Affects Development of Phenolic Compounds in Grape Berries

Carbon supply reduction was used to investigate the relationship between total non-structural carbohydrate (TNSC) concentration in the vegetative tissue and the production of phenolic compounds in the fruit of grapevines. Potted, greenhouse-grown DeChaunac vines were partially defoliated on one of three dates (berry set, veraison, or 7 days pre-harvest) during the growing season. Light environment of the fruit clusters was not affected by defoliation. Seven days following defoliation, half of the vines were destructively harvested for carbohydrate analysis, while the remaining vines were kept for fruit analysis at maturity. Defoliation of vines at berry set and veraison significantly reduced TNSC concentration in the leaf tissue. Partial defoliation of vines at berry set reduced total flavonols by 24%, total anthocyanins by 33%, and total phenolics by 13% in the fruit compared to the control vines. At veraison, partial defoliation of vines reduced total flavonols by 8%, anthocyanins by 43%, and did not affect total phenolics. While flavonol and total phenolic content was not affected by defoliation 7 days prior to harvest, total anthocyanins were increased by 39%, although leaf TNSC concentration was not affected. Concentration of total flavonols and anthocyanins were positively correlated with TNSC in the leaves (r = 0.53 and r = 0.73, respectively) while total phenolic content was not correlated with TNSC. These results indicate that development of anthocyanins and flavonols in fruit is linked to carbohydrate availability from vegetative tissues during berry set and veraison.

Rapid temperature acclimation of leaf respiration rates in Quercus alba and Quercus rubra.

We conducted controlled (chamber) and natural (field) environment experiments on the acclimation of respiration in Quercus alba L. and Quercus rubra L. Three-year-old Louisiana, Indiana and Wisconsin populations of Q. alba were placed in growth chambers and exposed to alternating 5-week periods of cool (20 degrees C mean) and warm (26 degrees C mean) temperatures. We measured respiration rates on fully expanded leaves immediately before and approximately every 2 days after a switch in mean temperature. In a second chamber experiment, 3-year-old potted Q. alba seedlings were exposed to alternating warm (26 degrees C mean) and cool (16 degrees C mean) temperatures at 4-day intervals. Leaf dark respiration rates were measured on days 2, 3 and 4 after each change in temperature. In a third, field-based study, we measured leaf respiration rates in the same three sources of Q. alba and in Arkansas, Indiana and Minnesota sources of Q. rubra before and after a natural 16 degrees C change in mean daily ambient temperature. We observed rapid, significant and similar acclimation of leaf respiration rates in all populations of Q. alba and Q. rubra. Cold-origin populations were no more plastic in their acclimation responses than populations from warmer sites. All geographic sources showed lower respiration rates when measured at 24 degrees C after exposure to higher mean temperatures. Respiration rates decreased 13% with a 6 degrees C increase in mean temperature in the first chamber study, and almost 40% with a 10 degrees C increase in temperature in the second chamber study. Acclimation was rapid in all three studies, occurring after 2 days of exposure to changed temperature regimes. Acclimation was reversible when changes in ambient temperature occurred at 4-day intervals. Respiration response functions, ln(R) = ln(beta0) + beta1T, were statistically different among treatments (cool versus warm, first chamber study) and among sources in a pooled comparison. Pair-wise comparisons indicated statistically significant (P<0.05) differences in cool- versus warm-measured temperature/respiration response functions for Indiana and Wisconsin sources of Q. alba. Log-transformed base respiration rates were significantly lower during periods of higher mean temperatures. Indiana Q. alba showed a significantly higher beta1 when plants were grown at 16 degrees C than when grown at 26 degrees C. Acclimation in Q. alba was unaccompanied by changes in leaf nitrogen concentration, but was associated with a change in leaf total nonstructural carbohydrate concentration. Total nonstructural carbohydrate concentration was slightly, but statistically, lower (13.6 versus 12%, P<0.05) after a 10 degrees C increase in temperature.

Intraspecific variability of phenolic concentrations and their responses to elevated CO 2 in two mediterranean perennial grasses

Intraspecific variability of total phenolic compound concentrations and their responses to elevated CO 2 were studied in two wild Mediterranean perennial grasses, Dactylis glomerata and Bromus erectus. Ten and nine genotypes of each species were grown in climate-controlled naturally-lit glasshouses under plant intergenotypic and interspecific competition for water, light and nutrients. Carbon source–sink balance hypotheses of resource allocation were also tested. Elevated CO 2 induced changes in dry shoot biomass (DM), leaf total non-structural carbohydrate concentrations [TNC] and leaf nitrogen concentrations [N] found in a previous study (New Phytol. 143 (1999) 73) were related to changes in phenolic compound concentrations. Phenolic compound concentrations increased to 15.2% DM in D. glomerata and 86.9% DM in B. erectus under elevated CO 2. These changes were more pronounced when expressed on a structural dry mass basis (DM st). Increases in DM st and [TNC st] and decreases in [N st] were also found according to current resource allocation hypotheses. However, there were no proportional changes between phenolic responses to elevated CO 2 and DM st, [TNC st] and [N st] responses. Phenolic concentrations were highly determined by genetics in both species, but all studied genotypes responded in a similar way to elevated CO 2. Considering the present experimental conditions with plants growing in intraspecific and interspecific competition, the absence of CO 2×genotype interaction would lead to little changes of fitness in terms of antiherbivore chemical defence, and, therefore, to low evolutionary consequences in CBSC under the increasing atmospheric CO 2 concentrations of the next decades.

Short and long-term responses of whole-plant gas exchange to elevated CO 2 in four herbaceous species

Four Mediterranean herbaceous species, the two grasses Bromus madritensis (annual) and B. erectus (perennial), and the two legumes Medicago minima (annual) and M. glomerata (perennial) were grown in glasshouses at two levels of atmospheric CO 2 (350 and 700 μmol mol −1), under non-limiting nutrient conditions. After 6 months of growth, short and long-term responses of whole plant photosynthesis and stomatal conductance to elevated CO 2 were measured, together with changes in leaf total non-structural carbohydrate concentration, leaf nitrogen concentration and specific leaf area. Short-term exposure to elevated CO 2 increased whole plant photosynthesis by 30% on average. However, this stimulation did not persist in the long term, indicating a down-regulation of photosynthesis in plants grown at elevated CO 2. By contrast, stomatal conductance was similarly or more decreased after long-term than after short-term exposure to elevated CO 2. As a result, the short-term effect of CO 2 on instantaneous water use efficiency was conserved in the long-term and the c i/ c a ratio remained nearly constant after both short and long-term exposure to elevated CO 2. Analysis of the main leaf components revealed that when grown at elevated CO 2, leaves of the two grass species showed a large accumulation of total non-structural carbohydrates and a decrease in their nitrogen concentration, while leaf total non-structural carbohydrate and nitrogen concentrations of the two legume species were unaffected by elevated CO 2. Species-specific differences in down-regulation of photosynthesis were positively correlated with the long-term response of stomatal conductance and negatively correlated with changes in total non-structural carbohydrate concentration. This suggests that source–sink relationship may play a role in the control of photosynthetic response to high CO 2 concentration.

Cotton Responses to Shade at Different Growth Stages: Nonstructural Carbohydrate Composition

Photosynthetic irradiance is an important factor affecting cotton (Gossypium hirsutum L.) plant growth, development, lint yield, and fiber quality. A 2‐yr study was conducted to determine the effects of an 8‐d period of shade (63% reduction in photosynthetic photon flux density) at four growth stages [i.e., pinhead square (PHS), first flower (FF), peak flower (PF), and boll development (BD)] leaf photosynthesis, chlorophyll concentration, and nonstructural carbohydrate (hexose, sucrose, and starch) concentrations in leaves, floral bracts, and floral buds of field‐grown cotton plants. At all four growth stages, shade caused a 43 to 55% decrease in leaf photosynthetic rate, and a 14 (on a leaf area basis) or 73% (on a dry weight basis) increase in total chlorophyll concentration, but did not affect leaf dark respiration rate. Starch concentration in leaves and floral bracts decreased sharply under shade, whereas only minor changes in hexose concentration occurred. Shade at the FF and PF stages did not, whereas shade at the BD stage did decrease, the concentration of total nonstructural carbohydrate (TNC) in 20‐d‐old floral buds. Averaged over the four growth stages during the 2 yr, the TNC concentration of shaded cotton decreased 47 to 71% in the leaves, 37 to 48% in the bracts, and 5 to 20% in 20‐d‐old floral buds compared with unshaded control plants. Among the four growth stages, shade at the PF (1994) or BD (1993) stage caused the greatest decrease in leaf TNC concentration; shade at the BD stage resulted in the greatest decrease in the TNC concentrations of bracts and floral buds. Shade during plant reproductive growth significantly reduced leaf photosynthesis and TNC concentrations of field‐grown cotton.

Direct and Indirect Effects of Atmospheric Carbon Dioxide Enrichment on Leaf Respiration of Glycine max (L.) Merr.

Long-term and short-term effects of CO2 enrichment on dark respiration were investigated using soybean (Glycine max [L.] Merr.) plants grown at either 35.5 or 71.0 Pa CO2. Indirect effects, or effects of growth in elevated CO2, were examined using a functional model that partitioned respiration into growth and maintenance components. Direct effects, or immediate effects of a short-term change in CO2, were examined by measuring dark respiration, first, at the CO2 partial pressure at which plants were grown, and second, after equilibration in the reciprocal CO2 partial pressure. The functional component model indicated that the maintenance coefficient of respiration increased 34% with elevated CO2, whereas the growth coefficient was not significantly affected. Changes in maintenance respiration were correlated with a 33% increase in leaf total nonstructural carbohydrate concentration, but leaf nitrogen content of soybean leaves was not affected by CO2 enrichment. Thus, increased maintenance respiration may be a consequence of increased nonstructural carbohydrate accumulation. When whole soybean plants were switched from low CO2 to high CO2 for a brief period, leaf respiration was always reduced. However, this direct effect of CO2 partial pressure was approximately 50% less in plants grown in elevated CO2. We conclude from this study that there are potentially important effects of CO2 enrichment on plant respiration but that the effects are different for plants given a short-term increase in CO2 partial pressure versus plants grown in elevated CO2.