Differences in acclimation to elevated growth CO2 (700 µmol mol-1, EC) and elevated temperature (ambient +4 °C, ET) in successive leaves of wheat were investigated in field chambers. At a common measurement CO2, EC increased photosynthesis and the quantum yield of electron transport (Φ) early on in the growth of penultimate leaves, and later decreased them. In contrast, EC did not change photosynthesis, and increased Φ at later growth stages in the flag leaf. Contents of chlorophyll (Chl), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO), and total soluble protein were initially higher and subsequently lower in penultimate than flag leaves. EC decreased RuBPCO protein content relative to soluble protein and Chl contents throughout the development of penultimate leaves. On the other hand, EC initially increased the RuBPCO:Chl and Chl a/b ratios, but later decreased them in flag leaves. In the flag leaves but not in the penultimate leaves, ET initially decreased initial and specific RuBPCO activities at ambient CO2 (AC) and increased them at EC. Late in leaf growth, ET decreased Chl contents under AC in both kinds of leaves, and had no effect or a positive one under EC. Thus the differences between the two kinds of leaves were due to resource availability, and to EC-increased allocation of resources to photon harvesting in the penultimate leaves, but to increased allocation to carboxylation early on in growth, and to light harvesting subsequently, in the flag leaves. and P. Pérez ... [et al.].
Net photosynthetic rate (PN) of ear and flag leaf during grain filling stage and grain yield of plants with non-darkened or darkened flag leaf or darkened ear were examined in two different CO2 concentrations: ambient (AC) and AC+200 µmol mol-1 (EC). Ear showed much higher enhancement (56 %) of PN than flag leaf (23 %) under EC. Moreover, CO2 enrichment shortened the photosynthetic duration of flag leaf relative to ear. In this way the ratio of ear to flag leaf contribution to grain yield increased from 1.18 (AC) to 1.39 (EC). and C.-W. Zhu ... [et al.].
Broomcorn millet (Panicum miliaceum L.) is one of the important C4 crops in the semiarid regions of northern China. It is a close relative of biofuel crop switchgrass. Yet, there is no information on how these crops might respond to a climate change in China. In order to gain insight into such a response, we studied the effect of elevated CO2 concentration (EC) on broomcorn millet. The changes in leaf photosynthesis, chlorophyll fluorescence, morphological parameters, biomass and yield in response to EC [i.e., + 200 µmol(CO2) mol-1] over two years were determined at the open-top chamber (OTC) experimental facility in north China. EC increased net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, instantaneous transpiration efficiency, effective quantum yield of PSII photochemistry, and photochemical quenching coefficient of fully expanded flag leaves. Maximal quantum yield of PSII photochemistry declined under EC in 2013, but was not affected in 2014. EC significantly decreased intrinsic efficiency of PSII in 2013, but increased in 2014. Leaf nonphotochemical quenching decreased under EC both in 2013 and 2014. EC significantly enhanced the aboveground biomass and yield by average of 31.4 and 25.5% in both years, respectively. The increased yield of broomcorn millet under EC occurred due to the enhanced number of grains per plant. We concluded that photosynthesis of broomcorn millets was improved through increased stomatal conductance in leaves under EC, which led to an increase in height, stem diameter, aboveground biomass, and yield. This study extends our understanding of the response of this ancient C4 crop to elevated CO2 concentration., X. Y. Hao, P. Li, H. Y. Li, Y. Z. Zong, B. Zhang, J. Z. Zhao, Y. H. Han., and Obsahuje bibliografii
Drought is a normal, recurrent feature of climate. In order to understand the potential effect of increasing atmospheric CO2 concentration (Ca) on ecosystems, it is essential to determine the combined effects of drought and elevated Ca (EC) under field conditions. A severe drought occurred in Central Florida in 1998 when precipitation was 88 % less than the average between 1984 and 2002. We determined daytime net ecosystem CO2 exchange (NEE) before, during, and after the drought in the Florida scrub-oak ecosystem exposed to doubled Ca in open-top chamber since May 1996. We measured diurnal leaf net photosynthetic rate (PN) of Quercus myrtifolia Willd, the dominant species, during and after the drought. Drought caused a midday depression in NEE and PN at ambient CO2 concentration (AC) and EC. EC mitigated the midday depression in NEE by about 60 % compared to AC and the effect of EC on leaf PN was similar to its effect on NEE. Growth in EC lowered the sensitivity of NEE to air vapor pressure deficit under drought. Thus EC would help the scrub-oak ecosystem to survive the consequences of the effects of rising atmospheric CO2 on climate change, including increased frequency of drought, while simultaneously sequestering more anthropogenic carbon. and J. H. Li ... [et al.].