Production Ecophysiology of Hungarian Green Pepper Under Elevated Air CO2 Concentration

SUMMARY

Production, dry matter (including reproductive) allocation, photosynthesis, transpiration, water use efficiency and carbon and nitrogen responses of a Hungarian sweet pepper (Capsicum annum L.) under continuous elevated CO₂ concentrations are reported. Plants were grown in open top chambers under a temperate-continental climate in Hungary from plantation at ambient (350 μmol mol^?1) and elevated (700 μmol mol^?1) CO₂ concentrations. The CO₂ assimilation responses of the green pepper plants grown in high CO₂ from plantation until final harvest reflected down-regulation of their photosynthesis. The integrated and combined effect of the increased net CO₂ assimilation rate and the unchanged rate of transpiration resulted in higher WUE at elevated CO₂ concentrations in the high CO₂ plants than in the control ones grown at ambientCO₂. However, the improved water use efficiency in the high CO₂ plants was not followed by an acclimation in C-trans-location and C-allocation to the reproductive organs in the required degree. This was reflected in a slightly increased overall plant production and higher reproductive allocation, but was not accompanied by an increased fresh or dry berry mass production. The acclimation discussed may be of advantage for plant growth in a high CO₂ environment with restricted water availability. We did not find worthy statistical difference between the yield mass of the control and elevated CO₂, although the dry matter production parameters of the high CO₂ plants had statistically not significantly higher values.     

The Effect of Elevated Atmospheric CO2 Concentration on Two Populus Clones Grown in a FACE System

SUMMARY

Two poplar clones, hybrid Populus deltoides Bartr. Ex Marsh X Populus nigra L. (Populus xeuramericana), clone I-214, and Populus deltoides, clone Lux, were grown from hardwood cuttings for one growing season in either ambient (360 μmol mol^?1) or elevated (560 μmol mol^?1) [CO₂] in FACE-systemrings at Rapolano Terme (Siena, Italy). Both clones I-214 and Lux exhibited a higher aboveground bio-mass, photosynthesis at light saturation and instantaneous transpiration efficiency (ITE) in CO₂-enriched air. The elevated [CO₂]-induced responses of clone I-214 included increased investment in branch and leaf biomass, and enhanced stem volume. The elevated [CO₂]-induced responses of clone Lux included an increase in the number of branches (and foliage area). Indication of photosynthetic acclimation under elevated [CO₂] was found during the early morning, but only in clone I-214. Stomatal conductance decreased under elevated [CO₂] particularly in clone Lux. Clone differences in response to elevated [CO₂] should be taken in account when planning future poplar plantations in forecast warmer and drier Mediterranean sites.     

Effects of elevated atmospheric CO2 concentration on morphology of leaf blades in Chinese yam

ABSTRACT

The effects of elevated carbon dioxide concentration on the morphology of leaf blades in two Chinese yam lines under different temperature conditions were determined. Plants were grown under two [CO₂] levels, ambient (about 400 µmol mol^?1) and elevated (ambient + 200 µmol mol^?1) in the daytime, and two mean air temperature regimes, approximately ambient temperature (22.2°C) and high temperature (25.6°C). The palisade layer was thicker under elevated [CO₂] than under ambient [CO₂] in both temperature regimes, and the whole yam leaf blade was thicker under elevated [CO₂] than under ambient [CO₂] in the approximately ambient temperature regime. The numbers of chloroplasts per palisade cell and spongy cell as well as per unit profile area of palisade cell, number of starch grains per chloroplast, profile area of the starch grain, and starch-to-chloroplast area ratio in both palisade and spongy cells were higher under elevated [CO₂] than under ambient [CO₂] in both temperature regimes. Furthermore, the stomatal density on the abaxial side of the leaf blade in Chinese yam was greater under elevated [CO₂] than under ambient [CO₂] under both temperature regimes, and stomatal-pore length was higher under elevated [CO₂] than under ambient [CO₂] in the approximately ambient temperature regime. These results indicate that elevated [CO₂] positively affects the photosynthetic apparatus. The results of this study provide information for understanding the response characteristics of the leaf blade under elevated [CO₂] and a possible explanation for the positive photosynthetic responses of Chinese yam to elevated [CO₂] in our previous study.

List of Abbreviations:[CO₂]: carbon dioxide concentration     

Effects of elevated CO2 concentration on growth and photosynthesis of Chinese yam under different temperature regimes

Chinese yam (‘yam’) was grown at different carbon dioxide concentrations ([CO₂]), namely, ambient and elevated (ambient + 200 μmol mol^?1), under low- and high-temperature regimes in summer and autumn, separately. For comparison, rice was also grown under these conditions. Mean air temperatures in the low- and high-temperatures were respectively 24.1 and 29.1 °C in summer experiment and 20.2 and 24.9 °C in autumn experiment. In summer experiment, yam vine length, leaf area, leaf dry weight (DW), and total DW were significantly higher under elevated [CO₂] than ambient [CO₂] in both temperature regimes. Additionally, number of leaves, vine DW, and root DW were significantly higher under elevated [CO₂] than under ambient [CO₂] in the low-temperature regime. In autumn experiment, tuber DW was significantly higher under elevated [CO₂] than under ambient [CO₂] in the high-temperature regime. These results demonstrate that yam shows positive growth responses to elevated [CO₂]. Analysis of variance revealed that significant effect of [CO₂] × air temperature interaction on yam total DW was not detected. Elevated-to-ambient [CO₂] ratios of all growth parameters in summer experiment were higher in yam than in rice. The results suggest that the contribution of elevated [CO₂] is higher in yam than in rice under summer. Yam net photosynthetic rate was significantly higher under elevated [CO₂] than under ambient [CO₂] in both temperature regimes in summer. Elevated [CO₂] significantly affected on the rate in yam but not in rice in both experiments. These findings indicate that photosynthesis responds more readily to elevated [CO₂] in yam than in rice.     

Physio-morphological Studies of F1 Hybrids in Rice (Oryza sativa L.): Photosynthetic ability and yield

Summary

Photosynthetic ability in terms of CO₂ exchange rate and leaf area, dry matter accumulation (dry weight) and other important growth components along with yield and yield contributing characters in two F₁ hybrids of Akebono × Chiyonishiki (A × C) and Zenith × Akebono (Z × A) were studied. The photosynthetic rate at the flowering stage was lower than that at the panicle initiation stage in all the inbred parent cultivars and F₁ hybrids. Heterosis in photosynthetic rate was higher at the panicle initiation stage than that at the flowering stage. Pre-anthesis leaf area in the F₁ hybrid was significantly larger than that in the parent cultivars. However, the post- anthesis decline in leaf area was more rapid in the F₁ hybrids than in the parent cultivars and its magnitude was the highest in the F₁ hybrid of Z × A which was tall having long and curved panicles. Pre-anthesis dry matter accumulation in both hybrids was significantly higher in the F₁ plants than the parental cultivars, but post-anthesis dry matter accumulation in the F₁ hybrid was lower than the mid-parental value in Z × A. The degree of heterosis in grain yield varied with the hybrid combination, an average heterosis being 1.03. Heterosis in grain yield was closely associated with heterosis in harvest index.     

Impacts of early-season square abscission on the growth and yield of transgenic Bt cotton under elevated CO2

A field study was carried out to quantify the compensation capacity of Bacillus thuringiensis (Bt)-transgenic cotton to simulated damage by manually removing squares during the early growing season in 2004 and 2005 in combination with CO₂ levels (ambient CO₂ and elevated CO₂). Treatments included: initial squares were wholly (100%) removed manually for 1 week (i.e., SR1 treatment) and for 2 consecutive weeks (i.e., SR2 treatment). Plant leaf area was measured every 2 weeks, and plant root, stem, leaf, shatters, boll dry weight and lint yield and maturity were measured at harvest. Significantly higher leaf area per plant was observed on each sampling date for SR1 and SR2 treatments compared with control (SR0) treatment in 2004 and 2005 under elevated CO₂. Significantly higher lint yield and maturity were observed for SR0, SR1 and SR2 treatments under elevated CO₂ in 2004 and 2005. CO₂ concentration and square removal significantly affected plant lint yield and maturity. Moreover, the interaction between CO₂ concentration × square removal had a significant effect on plant leaf dry weight, lint yield and maturity. Our results indicated that transgenic cotton plants can compensate for the manual removal of 100% of the initial squares for 1 and 2 weeks under ambient and elevated CO₂.     

Effects of atmospheric CO2 concentration and defoliation on the growth of Themeda triandra

The effects of elevated atmospheric carbon dioxide (CO₂) concentration (700 μmol mol^?1) on defoliated (three clippings at 3‐week intervals) and undefoliated plants were determined for the C₄ grass Themeda triandra, Forsk. The elevated CO₂ concentration significantly increased leaf regrowth following defoliation, and total leaf production was greatest in this treatment. Shoot biomass of undefoliated plants was also increased under the elevated CO₂ concentration treatment. The primary effect of the elevated CO₂ concentration in both defoliated and undefoliated plants was an increase in individual leaf length and mass of dry matter, linked to a higher leaf water content and increased photosynthetic rates at the canopy level. Photosynthetic down‐regulation at the leaf level occurred, but this was compensated for by increased assimilation rates and greater canopy leaf area at the elevated CO₂ concentration. Increases in leaf and sheath growth of defoliated plants in the elevated CO₂ concentration treatment were lost following a final 3‐week reversion to ambient CO₂ concentration, but occurred in plants exposed to the elevated CO₂ concentration for the final 3‐week period only. In conclusion, elevated atmospheric CO₂ concentration increases shoot growth via increased leaf extension, which is directly dependent on stimulation of concurrent photosynthesis. CO₂ responsiveness is sustained following moderate defoliation but is reduced when plants experience reduced vigour as a result of maturation or high frequency of defoliation.     

Increase in Atmospheric CO2 and Ambient Temperatures in the North

SUMMARY

Crop production in the North is constrained by a short growing season, spring and autumn frosts, long winters with deep snow cover and low temperatures during the growing season. Increase in concentration of atmospheric CO₂ and other greenhouse gases, and the subsequent increase in ambient temperatures could benefit crop production in countries located in the North, including Finland. However, longer growing seasons, milder winters and higher growing season temperatures could increase the occurrence of pests and pathogens, and ultimately decrease crop yields and the net income of farmers. Benefits to be gained from increased tillering and higher numbers of grains per unit area resulting from elevated CO₂ levels might be smaller than expected in countries like Finland, where the uniculm growth habit of cereals is maintained by the long days that characterise the growing season.     

The Effect of Elevated Levels of Carbon Dioxide on Potato Crops

SUMMARY

Experiments, which have investigated the effect of elevated concentrations of atmospheric CO₂ on the physiology, growth and yield of potato (Solanum tuberosum L.), are reviewed. These studies were conducted in controlled environment chambers, in glasshouses, in open top field chambers as well as using free air carbon dioxide (FACE) exposure systems. In general, photosynthesis is stimulated by elevated CO₂ initially although long-term exposure leads to acclimation. The stomata of potato leaves partially close in response to elevated CO₂ and starch granules build up in the chloroplasts. Although above- and below-ground biomass production is stimulated, accelerated senescence limits growth towards the end of the growing season exposure to elevated CO₂ stimulates tuber yield, the magnitude of which depends on agronomic practise, cultivar choice and growing conditions. The beneficial effects of elevated CO₂ may be reduced by interaction with other components of climate change, such as drought stress. Modelling of the effects of climate change on potato yield has predicted an increase in yields in northern Europe with little change in central and southern Europe. It is suggested that further research is needed to understand the reasons for photosynthetic acclimation, field trials are also needed to understand and quantify the interaction between elevated CO₂ and drought stress.     

Eclipse Effects on CO2 Profile within and above Sorghum Canopy

Abstract

We analyzed the effects of a partial solar eclipse (22 July 2009) on microclimate including vertical gradients of CO₂ concentrations ([CO₂]), so called [CO₂] profile, in a mature sorghum canopy. Together with CO₂ measurement, major photosynthetic drivers of microclimate, light intensity, temperature and atmospheric H₂O concentration ([H₂O]) were also measured simultaneously at the same place and height. [CO₂] at 6.0, 3.2, 2.1, 1.4, 0.7, 0 m above the ground (canopy height was 3.2 m) increased by 5.8, 4.8, 9.0, 7.8, 6.4, 7.6μmol mol-¹, respectively, from 1 hour before the eclipse maximum to the eclipse maximum, during which theincident solar radiation above the canopy dropped by 1473 μmol photons m-² s-¹. However, it declined by 3.4, 10.6, 10.8, 6.0, 5.4, and 5.8μmol mol-¹, respectively, from the eclipse to 1 hour later,during which the incident radiation increased by 1350μmol photons m-² s-¹. The [CO₂] profile during the eclipse was uniform except for higher [CO₂] near the ground. Comparative analysis of theeffect of light intensity on the microclimate during the eclipse-induced light decreasing phase (ELDP) and eclipse-induced light increasing phase (ELIP) revealed that [CO₂], [H₂O], temperature and relative humidity (RH) are significantly correlated with the light intensity above the canopy in a nearly linear fashion. Furthermore it indicated that detected less light-reacted canopy photosynthesis at a higher layer within the canopy during ELIP might be due to slower response of stomatal opening (than closing) to the light intensity above the canopy.     

Impact of elevated CO2 concentration on inter-subspecific hybrid rice cultivar Liangyoupeijiu under fully open-air field conditions

Hybrid rice cultivar plays an important role in rice production system due to its high yield potential and resistance to environmental stress. Quantification of its responses to rising CO₂ concentration ([CO₂]) will reduce our uncertainty in predicting future food security and assist in development of adaptation strategies. Using free air CO₂ enrichment (FACE), we measured seasonal changes in growth and nitrogen (N) uptake of an inter-subspecific hybrid rice cultivar Liangyoupeijiu grown under two levels of [CO₂] (ambient and elevated by 200 μmol mol⁻¹) and two levels of N fertilization in 2005–2006. Average across the 2 years, FACE increased crop growth rate similarly by 22%, 24% and 23% in the periods from transplanting to panicle initiation (PI), PI to heading and heading to maturity, which was mainly attributed to an increase in green leaf area index rather than the greater net assimilation rate. Grain yield increased greatly under FACE as a result of similar contributions by panicle number per unit area, grain number per panicle and individual grain yield. Final aboveground N acquisition showed a 10.4% increase under FACE, which resulted from enhanced N uptake at both vegetative and reproductive growth stages. Compared with previous FACE studies on final productivity of two inbred japonica cultivars, inter-subspecific hybrid cultivar appears to profit more from elevated [CO₂], which mainly resulted from its greater enhancement in photosynthetic production during reproductive growth due to a lack of N limitations late in the season.     

High-temperature-tolerant mungbean (Vigna radiata L.) lines produce better yields when exposed to higher CO2 levels

Increasing global air temperatures, along with rising CO₂ levels, are causing concerns about reducing available freshwater resources and altering cropping patterns. They may influence overall growth and production pattern of crop plants. These likely changes would become major limiting factors for future sustainable food production largely in the tropics and subtropics. Thus, understanding physiological responses hold the key to determining the functional relationship between the environment and crop performance. We explore here the impact of rising CO₂ on the growth and yield traits of a few selected high-temperature (HT)-tolerant mungbean lines, which we earlier screened for HT tolerance using a physiological assay under managed growth conditions. The HT-tolerant lines grown under elevated CO₂ levels (550 and 700 μL L^?1) showed a considerable improvement in growth rates (13.5%, 67.8%, and 46.5% in plant height, leaf area, and total dry matter, respectively) and pod and seed yield (48.7% and 31.7%, respectively), compared to local checks under the same environments. Interestingly, the symptoms of accelerated pod maturity were also observed in most of these lines. The outcome of the study would undoubtedly open up opportunities for increased yield potentials of legumes under the conditions of the warming climate and elevated levels of carbon dioxide.     

Effect of CO2 Concentration,Temperature and N Fertilization on Biomass Production of Soybean Genotypes Differing in N Fixation Capacity

Abstract

We tested the hypothesis that elevated CO₂ concentration [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype that has a higher nitrogen (N) fixation capacity. Furthermore, we analyzed theinteractive effects of N fertilization, temperature and [CO₂] on biomass production. Three genetically related genotypes: Enrei (normally-nodulating genotype), Kanto 100 (supernodulating genotype), and En1282 (non-nodulating genotype) were grown in pots, with or without N fertilizer for two years (2004, 2005). They were then subjected to two different [CO₂] (ambient and elevated (ambient + 200 ?mol mol-¹)) × two temperature regimes (low,high (low + 4~5ºC)). Top dry weight at maturity was the greatest in the elevated [CO₂] × high temperature regime, irrespective of genotype and N fertilization. The [CO₂] elevation generally enhanced N acquisition and dry matter production during the vegetative growth stage, and the enhancement was more pronounced in the nodulating genotypes (Enrei and Kanto 100) than in the non-nodulating genotype (En1282), indicating that N supply through N fixation contributes to elevated [CO₂]-induced biomass production in soybean. However, the relative responsiveness ofbiomass production to elevated [CO₂] was not necessarily higher in the supernodulating genotype than the normally-nodulating genotype. The N utilization efficiency to produce biomass was inferior in the supernodulating genotype than in the normally-nodulating and non-nodulating genotypes. These results did not fully verify the hypothesis that elevated [CO₂]-induced enhancement of biomass production of soybean is greater in a genotype with a higher N fixation capacity.     

Screening of High kcat Rubisco among Poaceae for Improvement of Photosynthetic CO2 Assimilation in Rice

Abstract

The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a major limitation of photosynthetic CO₂ assimilation in C₃ plants. In order to find useful Rubisco for improvement of photosynthesis in rice under elevated CO₂, we analyzed the catalytic turnover rate (k_cat) of Rubisco in Poaceae including C₃ alpine plants, C₃ cold-resistant plants and C₄ plants. Rubisco in these plants showed 1.1- to 2.8-fold higher k_cat than that in rice. However, the most of high k_cat Rubisco also showed a higher km for CO₂ (Kc) than that of rice, indicating that increase in k_cat led to decrease in the affinity for CO₂. Rubisco in Festuca ovina, Phleum pratense and Sorghum bicolor showed relatively high k_cat to Kc. Although the k_cat of Rubisco in F. ovina and P. pratense was not so high (1.5-1.6 fold relative to rice), the Kc was comparable to that in rice and the amino acid sequence of RbcL shared higher identity to that in rice than that in S. bicolor. By contrast, Rubisco of S. bicolor showed considerably high k_cat (2.5-fold relative to rice), which is considered to be the most important factor for improvement of photosynthesis. In our estimation, the expression of high k_cat Rubisco of F. ovina and S. bicolor in rice could significantly enhance CO₂ assimilation at Ci of 50 Pa, the level assumed to be reached by the middle of this century.     

Effects of elevated CO2 concentration on bulbil germination and early seedling growth in Chinese yam under different air temperatures

The present study investigated the effects of elevated carbon dioxide concentration ([CO₂]) and air temperature on the germination of seed bulbils and the seedling vigour of two Chinese yam lines. Plants were grown under two [CO₂] levels, ambient and elevated (ambient + 200 μmol mol^?1), and two mean air temperature regimes, 22.2 °C (ambient + 1.4 °C) and 25.6 °C (ambient + 5.2 °C). Elevated [CO₂] did not affect bulbil germination under both air temperature regimes. During the early growth stage, the dry weight (DW) of leaves, vines, shoots, roots, belowground parts (roots + tubers) and whole plants were higher under elevated [CO₂] than ambient [CO₂] for both lines under the low- and high-temperature regimes. The values of vigour indexes (index I = germination % × seedling length and index II = germination % × seedling DW) were also higher under elevated [CO₂] than ambient [CO₂] for both lines. These results indicated that Chinese yam seedlings respond positively to elevated [CO₂] during the early growth stage. The above:belowground DW ratios were lower under elevated [CO₂] than ambient [CO₂] in seedlings with very small new tubers for both yam lines, indicating that elevated [CO₂] strongly affected the root growth in the early growth stage. The DWs of post-treatment seed bulbils were higher in the elevated [CO₂] under both air temperature regimes. The results showed that Chinese yam used a smaller amount of the reserves in seed bulbils under elevated [CO₂] than under ambient [CO₂].     

CO2 Enrichment Effects on Forage and Grain Nitrogen Content of Pasture and Cereal Plants

SUMMARY

Increasing atmospheric CO₂ concentrations [CO₂] have the potential to enhance growth and yield of agricultural plants. Con-comitantly plants grown under high [CO₂] show significant changes of the chemical composition of their foliage and of other plant parts. Particularly, high [CO₂] result in a decrease of plant nitrogen (N) concentration, which may have serious consequences for crop quality. This presentation summarizes the results of a variety of CO₂ enrichment studies with pasture plants (Lolium spp., Trifolium repens) and cereal species (Triticum aestivum, Hordeum vulgare) which were conducted at our laboratory under different growth and CO₂ exposure conditions ranging from controlled environment studies to investigations under free air carbon dioxide enrichment (FACE). With the exception of clover in all experiments a CO₂-induced decline of forage and grain N concentration was observed. The magnitude of this reduction differed between species, cultivars, management conditions (N fertilization) and CO₂ exposure conditions. No unambiguous evidence was obtained whether N fertilization can contribute to meet the quality requirements for cereals and grass monocultures with respect to tissue N concentrations in a future high-CO₂ world. As shown in the FACE experiments current application rates of N fertilizers are inadequate to achieve quality standards.     

Limited Increase of Agricultural Soil Carbon and Nitrogen Stocks Due to Increased Atmospheric CO2 Concentrations

SUMMARY

Increased atmospheric concentrations of CO₂ may lead to increases in agricultural soil carbon and nitrogen storage, but the impact is likely to be small and is uncertain due to limitations in other resources (e.g., nutrients, water) and interactions with climatic changes. Since only a small percentage of carbon added to the soil becomes stabilised, the impact of CO₂ fertilisation of crops is considered to be very small compared to deliberate efforts to increase soil carbon by improved agricultural management. Even if agricultural soil carbon stocks are increased, carbon credits cannot be claimed under the Kyoto Protocol since the increases are not directly human-induced, a condition which must be met in order for any carbon sink to be included in emission reduction targets.     

Climate Change and CO2 Effects on Productivity of Danish Agricultural Systems

SUMMARY

Scenarios of climate change for Denmark suggest increases in annual mean temperature of 1 to 4°C by the end of the 21st century with an associated increase in rainfall of approximately 10%. The climatic warming and the associated increase in atmospheric CO₂ concentration will increase the productivity of agricultural crops. The increase may be slightly higher for indeterminate species, such as grass and other fodder crops, compared with cereals and other determinate species, where the duration of growth depends on temperature and daylength. The full benefits of the climatic warming requires adaptation in crop management, which at the individual crop level means changes in sowing dates, i.e., later sowings for winter cereals and earlier sowings for spring cereals. Some crop substitution will probably occur. On dairy farms more cereals will be grown due to higher productivity of the grasslands, which frees up some land for grain production. On sandy loam and loam soils spring cereals may become slightly more favorable and winter cereals slightly less favorable.     

Intracellular position of mitochondria and chloroplasts in bundle sheath and mesophyll cells of C3 grasses in relation to photorespiratory CO2 loss

In C₃ plants, photosynthetic efficiency is reduced by photorespiration. A part of CO₂ fixed during photosynthesis in chloroplasts is lost from mitochondria during photorespiration by decarboxylation of glycine by glycine decarboxylase (GDC). Thus, the intracellular position of mitochondria in photosynthetic cells is critical to the rate of photorespiratory CO₂ loss. We investigated the intracellular position of mitochondria in parenchyma sheath (PS) and mesophyll cells of 10 C₃ grasses from 3 subfamilies (Ehrhartoideae, Panicoideae, and Pooideae) by immunostaining for GDC and light and electron microscopic observation. Immunostaining suggested that many mitochondria were located in the inner half of PS cells and on the vacuole side of chloroplasts in mesophyll cells. Organelle quantification showed that 62–75% of PS mitochondria were located in the inner half of cells, and 62–78% of PS chloroplasts were in the outer half. In mesophyll cells, 61–92% of mitochondria were positioned on the vacuole side of chloroplasts and stromules. In PS cells, such location would reduce the loss of photorespiratory CO₂ by lengthening the path of CO₂ diffusion and allow more efficient fixation of CO₂ from intercellular spaces. In mesophyll cells, it would facilitate scavenging by chloroplasts of photorespiratory CO₂ released from mitochondria. Our data suggest that the PS cells of C₃ grasses have already acquired an initial structure leading to proto-Kranz and further C₃–C₄ intermediate anatomy. We also found that in the Pooideae, organelle positioning in PS cells on the phloem side resembles that in mesophyll cells.