High thermal acclimation potential of both photosynthesis and respiration in two lowland Plantago species in contrast to an alpine congeneric

Thermal acclimation of photosynthesis and respiration can enable plants to maintain near constant rates of net CO₂ exchange, despite experiencing sustained changes in daily average temperature. In this study, we investigated whether the degree of acclimation of photosynthesis and respiration of mature leaves differs among three congeneric Plantago species from contrasting habitats [two fast‐growing lowland species (Plantago major and P. lanceolata), and one slow‐growing alpine species (P. euryphylla)]. In addition to investigating some mechanisms underpinning variability in photosynthetic acclimation, we also determined whether leaf respiration in the light acclimates to the same extent as leaf respiration in darkness, and whether acclimation reestablishes the balance between leaf respiration and photosynthesis. Three growth temperatures were provided: constant 13, 20, or 27°C. Measurements were made at five temperatures (6–34°C). Little acclimation of photosynthesis and leaf respiration to growth temperature was exhibited by P. euryphylla. Moreover, leaf masses per area (LMA) were similar in 13°C‐grown and 20°C‐grown plants of the alpine species. In contrast, growth at 13°C increased LMA in the two lowland species; this was associated with increased photosynthetic capacity and rates of leaf respiration (both in darkness and in the light). Alleviation of triose phosphate limitation and increased capacity of electron transport capacity relative to carboxylation were also observed. Such changes demonstrate that the lowland species cold‐acclimated. Light reduced the short‐term temperature dependence (i.e. Q₁₀) of leaf respiration in all three species, irrespective of growth temperature. Collectively, our results highlight the tight coupling that exists between thermal acclimation of photosynthetic and leaf respiratory metabolism (both in darkness and in the light) in Plantago. If widespread among contrasting species, such coupling may enable modellers to assume levels of acclimation in one parameter (e.g. leaf respiration) where details are only known for the other (e.g. photosynthesis).     

Seasonal changes in temperature and nutrient control of photosynthesis, respiration and growth of natural phytoplankton communities

1. To investigate the influence of elevated temperatures and nutrients on photosynthesis, respiration and growth of natural phytoplankton assemblages, water was collected from a eutrophic lake in spring, summer, autumn, winter and the following spring and exposed to ambient temperature and ambient +2, +4 and +6 °C for 2 weeks with and without addition of extra inorganic nutrients. 2. Rates of photosynthesis, respiration and growth generally increased with temperature, but this effect was strongly enhanced by high nutrient availability, and therefore was most evident for nutrient amended cultures in seasons of low ambient nutrient availability. 3. Temperature stimulation of growth and metabolism was higher at low than high ambient temperature showing that long‐term temperature acclimation of the phytoplankton community before the experiments was of great importance for the measured rates. 4. Although we found distinct responses to relatively small temperature increases, the interaction between nutrient availability, time of the year and, thus, ambient temperature was responsible for most of the observed variability in phytoplankton growth, photosynthesis and respiration. 5. Although an increase in global temperature will influence production and degradation of organic material in lakes, the documented importance of ambient temperatures and nutrient conditions suggests that effects will be most pronounced during winter and early spring, while the remaining part of the growth season will be practically unaffected by increasing temperatures.     

Energy metabolism of Plantago lanceolata, as affected by change in root temperature

The long and short term metabolic effects of a shift in root temperature was investigated in Plantago lanceolata L. with special reference to the role of the cyanide resistant alternative pathway in root respiration. After a 10-day period of growth at a 13°C root temperature, a decrease in root as well as shoot growth was observed, compared to control plants grown continuously at 21°C. Apart from an increase in shoot soluble and insoluble sugar level, no changes in metabolism were found, neither in root respiration, shoot photosynthesis, nor in root sugar and plant protein level.
Decreasing the root temperature from 21 to 13°C gave several clear short term changes in metabolism. Within one hour a decrease in cytochrome chain activity of the roots was found together with an increase in activity of the alternative chain. After 24 h a recovery to the initial level of both chains was observed. An increase in root temperature from 13 to 21°C gave an immediate increase in activity of both respiratory chains that was still present 24 h after the switch.
It is concluded that the activity of the alternative respiratory pathway in the root is strongly affected by a sudden temperature change in the root environment. This pathway acts in a way which is described by 'the energy overflow model'. The presence of the alternative electron transport pathway should be taken into account in determinations of the respiratory Q₁₀. Moreover, the length of time between the temperature change and respiration measurements is an important factor.     

Growth temperature influences the underlying components of relative growth rate: an investigation using inherently fast- and slow-growing plant species

We examined the effect of growth temperature on the underlying components of growth in a range of inherently fast‐ and slow‐growing plant species. Plants were grown hydroponically at constant 18, 23 and 28 °C. Growth analysis was conducted on 16 contrasting plant species, with whole plant gas exchange being performed on six of the 16 species. Inter‐specific variations in specific leaf area (SLA) were important in determining variations in relative growth rate (RGR) amongst the species at 23 and 28 °C but were not related to variations in RGR at 18 °C. When grown at 18 °C, net assimilation rate (NAR) became more important than SLA for explaining variations in RGR. Variations in whole shoot photosynthesis and carbon concentration could not explain the importance of NAR in determining RGR at the lower temperatures. Rather, variations in the degree to which whole plant respiration per unit leaf area acclimated to the different growth temperatures were responsible. Plants grown at 28 °C used a greater proportion of their daily fixed carbon in respiration than did the 18 and 23 °C‐grown plants. It is concluded that the relative importance of the underlying components of growth are influenced by growth temperature, and the degree of acclimation of respiration is of central importance to the greater role played by NAR in determining variations in RGR at declining growth temperatures.     

Acclimation of the respiration/photosynthesis ratio to temperature: insights from a model

Based on short-term experiments, many plant growth models – including those used in global change research – assume that an increase in temperature stimulates plant respiration (R) more than photosynthesis (P), leading to an increase in the R/P ratio. Longer-term experiments, however, have demonstrated that R/P is relatively insensitive to growth temperature. We show that both types of temperature response may be reconciled within a simple substrate-based model of plant acclimation to temperature, in which respiration is effectively limited by the supply of carbohydrates fixed through photosynthesis. The short-term, positive temperature response of R/P reflects the transient dynamics of the nonstructural carbohydrate and protein pools; the insensitivity of R/P to temperature on longer time-scales reflects the steady-state behaviour of these pools. Thus the substrate approach may provide a basis for predicting plant respiration responses to temperature that is more robust than the current modelling paradigm based on the extrapolation of results from short-term experiments. The present model predicts that the acclimated R/P depends mainly on the internal allocation of carbohydrates to protein synthesis, a better understanding of which is therefore required to underpin the wider use of a constant R/P as an alternative modelling paradigm in global change research.     

Relation between relative growth rate, endogenous gibberellins, and the response to applied gibberellic acid for Plantago major

Relationships between relative growth rate (RGR), endogenous gibberellin (GA) concentration and the response to application of gibberellic acid (GA₃) were studied for two inbred lines of Plantago major L., which differed in RGR. A4, the fast-growing inbred line, had a higher free GA concentration than the slow-growing W9, as analyzed by enzyme immunoassay. GA₃ application increased total plant weight and RGR₃ particularly for the slow-growing line. Chlorophyll a content and photosynthetic activity per unit leaf area were decreased, while transpiration rate was unaffected by GA₃ application. The increase in RGR by GA₃ application was associated with an increased leaf weight ratio; specific leaf area and percentage of dry matter in the leaves were only temporarily affected. Root respiration rate per unit dry weight was unaffected.
The correlation between low RGR, low GA concentration and high responsiveness to applied GA₃ supports the contention that gibberellins are involved in the regulation of RGR. However, the transient influence of GA₃ application on some growth components suggests the involvement of other regulatory factors in addition to GA.     

Thermal acclimation of leaf and root respiration: an investigation comparing inherently fast- and slow-growing plant species

We investigated the extent to which leaf and root respiration (R) differ in their response to short‐ and long‐term changes in temperature in several contrasting plant species (herbs, grasses, shrubs and trees) that differ in inherent relative growth rate (RGR, increase in mass per unit starting mass and time). Two experiments were conducted using hydroponically grown plants. In the long‐term (LT) acclimation experiment, 16 species were grown at constant 18, 23 and 28 °C. In the short‐term (ST) acclimation experiment, 9 of those species were grown at 25/20 °C (day/night) and then shifted to a 15/10 °C for 7 days. Short‐term Q₁₀ values (proportional change in R per 10 °C) and the degree of acclimation to longer‐term changes in temperature were compared. The effect of growth temperature on root and leaf soluble sugar and nitrogen concentrations was examined. Light‐saturated photosynthesis (A_sat) was also measured in the LT acclimation experiment. Our results show that Q₁₀ values and the degree of acclimation are highly variable amongst species and that roots exhibit lower Q₁₀ values than leaves over the 15–25 °C measurement temperature range. Differences in RGR or concentrations of soluble sugars/nitrogen could not account for the inter‐specific differences in the Q₁₀ or degree of acclimation. There were no systematic differences in the ability of roots and leaves to acclimate when plants developed under contrasting temperatures (LT acclimation). However, acclimation was greater in both leaves and roots that developed at the growth temperature (LT acclimation) than in pre‐existing leaves and roots shifted from one temperature to another (ST acclimation). The balance between leaf R and A_sat was maintained in plants grown at different temperatures, regardless of their inherent relative growth rate. We conclude that there is tight coupling between the respiratory acclimation and the temperature under which leaves and roots developed and that acclimation plays an important role in determining the relationship between respiration and photosynthesis.     

On the developmental dependence of leaf respiration: responses to short- and long-term changes in growth temperature

Using measurements of leaf respiratory O(2) uptake (R), we investigated whether immature and mature Arabidopsis thaliana (ecotype Columbia) leaves differed in their response to temperature. Confocal microscopy (using plants with mitochondrially targeted green fluorescent protein [GFP]) was used to determine whether ontogenetic changes in R are associated with concomitant changes in mitochondrial morphology/abundance. Comparisons were made of warm-grown (25/20°C) leaves, warm-grown leaves shifted to cold (5°C) for 10 days, and cold-developed leaves. Short-term Q(10) values and the ability to cold-acclimate were determined. In warm-grown plants, rates of R per mass were highest in immature leaves, decreasing as leaves developed. Moreover, although mitochondrial size (5.6-6.5 μm(3)) remained constant during development, mitochondrial number per μm(3) declined from 0.01 to 0.003 as leaves expanded (i.e., mitochondrial density decreased). Immature and mature leaves did not differ in Q(10) values but did differ in their ability to cold-acclimate. Whereas mature leaves had clear evidence of cold acclimation (e.g., when measured at 25°C, R was highest in cold-developed leaves), young leaves had none. Collectively, the results highlight the changes in rates of R, mitochondrial density, and biomass allocation associated with leaf development and that changes in respiratory flux associated with acclimation only take place within mature tissues.     

Cross-species amplification of primers developed from Plantago major and P. intermedia in two Hawaiian Plantago species from the section Plantago

Thirty-nine primers, developed from the sister species Plantago major and P. intermedia, were tested in two Hawaiian Plantago species from the section Plantago. Eight primers were polymorphic, of which three were published earlier, and five are new ones presented here. Amplification and polymorphism levels appeared to be high in these Hawaiian species. These markers will be valuable for further mating system and evolutionary studies in species from the section Plantago that are closely related to P. major and P. intermedia.     

Acclimation of photosynthesis and respiration is asynchronous in response to changes in temperature regardless of plant functional group

Gas exchange, fluorescence, western blot and chemical composition analyses were combined to assess if three functional groups (forbs, grasses and evergreen trees/shrubs) differed in acclimation of leaf respiration (R) and photosynthesis (A) to a range of growth temperatures (7, 14, 21 and 28 degrees C). When measured at a common temperature, acclimation was greater for R than for A and differed between leaves experiencing a 10-d change in growth temperature (PE) and leaves newly developed at each temperature (ND). As a result, the R : A ratio was temperature dependent, increasing in cold-acclimated plants. The balance was largely restored in ND leaves. Acclimation responses were similar among functional groups. Across the functional groups, cold acclimation was associated with increases in nonstructural carbohydrates and nitrogen. Cold acclimation of R was associated with an increase in abundance of alternative and/or cytochrome oxidases in a species-dependent manner. Cold acclimation of A was consistent with an initial decrease and subsequent recovery of thylakoid membrane proteins and increased abundance of proteins involved in the Calvin cycle. Overall, the results point to striking similarities in the extent and the biochemical underpinning of acclimation of R and A among contrasting functional groups differing in overall rates of metabolism, chemical composition and leaf structure.     

The effect of an elevated atmospheric CO2 concentration on growth, photosynthesis and respiration of Plantago major

The effect of an elevated atmospheric CO₂ concentration on growth, photosynthesis and root respiration of Plantago major L. ssp. major L. was investigated. Plants were grown in a nutrient solution in growth chambers at 350 and 700 μl I⁻¹ CO₂ during 7 weeks. The total dry weight of the Co₂-enriched plants at the end of this period was 50% higher than that of control plants. However, the relative growth rate (RGR) was stimulated only during the first half of the growing period. The transient nature of the stimulation of the RGR was not likely to be due to end-product inhibition of photosynthesis. It is suggested that in P. major , a rosette plant, self-shading causes a decline in photosynthesis and results in an increase in the shoot: root ratio and a decrease in RGR. CO₂-enriched plants grow faster and cosequently suffer more from self-shading. Corrected for this ontogenetic drift, high CO₂ concentrations stimulated the RGR of P. major throughout the entire experiment.     

Seasonal changes in the contribution of root respiration to total soil respiration in a cool-temperate deciduous forest

A trenching method was used to determine the contribution of root respiration to soil respiration. Soil respiration rates in a trenched plot (R _trench) and in a control plot (R _control) were measured from May 2000 to September 2001 by using an open-flow gas exchange system with an infrared gas analyser. The decomposition rate of dead roots (R _D) was estimated by using a root-bag method to correct the soil respiration measured from the trenched plots for the additional decaying root biomass. The soil respiration rates in the control plot increased from May (240–320 mg CO₂ m^–2 h^–1) to August (840–1150 mg CO₂ m^–2 h^–1) and then decreased during autumn (200–650 mg CO₂ m^–2 h^–1). The soil respiration rates in the trenched plot showed a similar pattern of seasonal change, but the rates were lower than in the control plot except during the 2 months following the trenching. Root respiration rate (R _r) and heterotrophic respiration rate (R _h) were estimated from R _control, R _trench, and R _D. We estimated that the contribution of R _r to total soil respiration in the growing season ranged from 27 to 71%. There was a significant relationship between R _h and soil temperature, whereas R _r had no significant correlation with soil temperature. The results suggest that the factors controlling the seasonal change of respiration differ between the two components of soil respiration, R _r and R _h.     

Cytochrome and alternative pathway respiration in white spruce (Picea glauca) roots. Effects of growth and measurement temperature

Interactions between growth temperature and measurement temperature were examined for their effects on white spruce [ Picea glauca (Moench) Voss] root respiration. Total dark respiration rates increased with measurement temperature and were unaffected by growth temperature. Partitioning of respiratory electron flow between the cytochrome and alternative pathways was also unaffected by growth temperature. The proportion of respiration mediated by the alternative pathway was constant at measurement temperatures between 4°C and 18°C, but was increased at higher temperatures. Changes in alternative pathway activity were paralleled by changes in capacity, and the alternative pathway was almost fully engaged at all temperatures. Roots grown at low temperature displayed higher carbohydrate levels than roots grown at higher temperatures, but respiration rate was unaffected. Spruce root respiration did not appear to acclimate to growth temperature, and the alternative pathway was not preferentially engaged at low temperature.     

氮过量吸收对地肤暗呼吸速率及相对生长速率的影响

为研究N过量吸收对植物生长的作用,以耐盐植物地肤(Kochia scoparia)作为研究对象,设置3个不同的施N处理,测量了不同生长时期的N含量、暗呼吸速率、生物量和相对生长速率(RGR)。结果表明:在N过量吸收的情况下,多余的N对暗呼吸速率并没有显著的影响,导致了暗呼吸中N的利用效率变低;单位质量暗呼吸速率与相对生长速率(RGR)有很好的线性相关,并且直线的斜率和截距并不受氮素过量吸收的影响,表明单位质量暗呼吸速率与RGR的关系不受施氮水平的影响;暗呼吸速率与总N的异速关系中,幂指数的大小与施N量相关,施N量越大对应的幂指数越小。     

The influence of increasing growth temperature and CO2 concentration on the ratio of respiration to photosynthesis in soybean seedlings

Using controlled environmental growth chambers, whole plants of soybean, cv. ‘Clark’, were examined during early development (7–20 days after sowing) at both ambient (≈ 350 μL L^–1) and elevated (≈ 700 μL L^–1) carbon dioxide and a range of air temperatures (20, 25, 30, and 35 °C) to determine if future climatic change (temperature or CO₂ concentration) could alter the ratio of carbon lost by dark respiration to that gained via photosynthesis. Although whole-plant respiration increased with short-term increases in the measurement temperature, respiration acclimated to increasing growth temperature. Respiration, on a dry weight basis, was either unchanged or lower for the elevated CO₂ grown plants, relative to ambient CO₂ concentration, over the range of growth temperatures. Levels of both starch and sucrose increased with elevated CO₂ concentration, but no interaction between CO₂ and growth temperature was observed. Relative growth rate increased with elevated CO₂ concentration up to a growth temperature of 35 °C. The ratio of respiration to photosynthesis rate over a 24-h period during early development was not altered over the growth temperatures (20–35 °C) and was consistently less at the elevated relative to the ambient CO₂ concentration. The current experiment does not support the proposition that global increases in carbon dioxide and temperature will increase the ratio of respiration to photosynthesis; rather, the data suggest that some plant species may continue to act as a sink for carbon even if carbon dioxide and temperature increase simultaneously.     

Respiration as a percentage of daily photosynthesis in whole plants is homeostatic at moderate, but not high, growth temperatures

Here, we investigated the impact of temperature on the carbon economy of two Plantago species from contrasting habitats. The lowland Plantago major and the alpine Plantago euryphylla were grown hydroponically at three constant temperatures: 13, 20 and 27 degrees C. Rates of photosynthetic CO(2) uptake (P) and respiratory CO(2) release (R) in shoots and R in roots were measured at the growth temperature using intact plants. At each growth temperature, air temperatures were changed to establish short-term temperature effects on the ratio of R to P (R/P). In both species, R/P was essentially constant in plants grown at 13 and 20 degrees C. However, R/P was substantially greater in 27 degrees C-grown plants, particularly in P. euryphylla. The increase in R/P at 27 degrees C would have been even greater had biomass allocation to roots not decreased with increasing growth temperature. Short-term increases in air temperature increased R/P in both species, with the effects of air temperature being most pronounced in 13 degrees C-grown plants. We conclude that temperature-mediated changes in biomass allocation play an important role in determining whole-plant R/P values, and, while homeostasis of R/P is achieved across moderate growth temperatures, homeostasis is not maintained when plants are exposed to growth temperatures higher than usually experienced in the natural habitat.     

Impact of temperature on the relationship between respiration and nitrogen concentration in roots: an analysis of scaling relationships, Q10 values and thermal acclimation ratios

* The impact of nitrogen (N) supply on the temperature response of root respiratory O(2) uptake (R) was assessed in several herbaceous species grown in solution culture. Warm-grown (25 : 20 degrees C, day:night) plants differing in root N concentration were shifted to 13 : 8 degrees C for 7 d to cold-acclimate. * Log-log plots of root R vs root N concentration both showed that R increased with increasing tissue N concentration, irrespective of the growth temperature. Although the regression slopes of the log-log plots did not differ between the warm-grown and cold-acclimated plants, cold-acclimated plants did exhibit a higher y-axis intercept than their warm-grown counterparts. This suggests that cold acclimation of root R is not entirely dependent on cold-induced increases in tissue N concentration and that scaling relationships (i.e. regression equations fitted to the log-log plots) between root R and N concentration are not fixed. * No systematic differences were found in the short-term Q(10) (proportional change in R per 10 degrees C change in temperature), or degree of cold acclimation (as measured by the proportional difference between warm- and cold-acclimated roots) among roots differing in root N concentration. The temperature response of root R is therefore insensitive to tissue N concentration. * The insensitivity of Q(10) values and acclimation to tissue N concentration raises the possibility that root R and its temperature sensitivity can be predicted for a range of N supply scenarios.