Recovery of photosynthesis after environmental stress …
Leaves deep in canopies can suddenly be exposed to increased irradiances following e.g. gap formation in forests or pruning in crops. Studies on the acclimation of photosynthesis to increased irradiance have mainly focused on the changes in photosynthetic capacity (Amax), although actual irradiance often remains below saturating level. We investigated the effect of changes in irradiance on the photosynthesis irradiance response and on nitrogen allocation in fully grown leaves of Cucumis sativus. Leaves that fully developed under low (50 µmol m-2 s-1) or moderate (200 µmol m-2 s-1) irradiance were subsequently exposed to, respectively, moderate (LM-leaves) or low (ML-leaves) irradiance or kept at constant irradiance level (LL- and MM-leaves). Acclimation of photosynthesis occurred within 7 days with final Amax highest in MM-leaves, lowest in LL-leaves and intermediate in ML- and LM-leaves, whereas full acclimation of thylakoid processes underlying photosystem II (PSII) efficiency and non-photochemical quenching occurred in ML- and LM-leaves. Dark respiration correlated with irradiance level, but not with Amax. Light-limited quantum efficiency was similar in all leaves. The increase in photosynthesis at moderate irradiance in LM-leaves was primarily driven by nitrogen import, and nitrogen remained allocated in a similar ratio to Rubisco and bioenergetics, while allocation to light harvesting relatively decreased. A contrary response of nitrogen was associated with the decrease in photosynthesis in ML-leaves. Net assimilation of LM-leaves under moderate irradiance remained lower than in MM-leaves, revealing the importance of photosynthetic acclimation during the leaf developmental phase for crop productivity in scenarios with realistic, moderate fluctuations in irradiance that leaves can be exposed to
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Users of Amax-N relationships in modeling photosynthesis in different ecosystems should appreciate the strengths and limitations of regression equations based on different species groupings.",
This review summarizes current knowledge of potentials and limitations of acclimation of foliage photosynthetic capacity (Amax) and lightâharvesting efficiency to complex environmental gradients within the canopies.
Postrelease acclimation of translocated ..
Acclimation of photosynthesis occurred within 7 days with final Amax highest in MM-leaves, lowest in LL-leaves and intermediate in ML- and LM-leaves, whereas full acclimation of thylakoid processes underlying photosystem II (PSII) efficiency and non-photochemical quenching occurred in ML- and LM-leaves.
LI-6400XT CO2 Response Curves | LI-COR Environmental
Studies on the acclimation of photosynthesis to increased irradiance have mainly focused on the changes in photosynthetic capacity (Amax), although actual irradiance often remains below saturating level.
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Two-year-old seedlings of Picea rubens, growing in open-top chambers in Scotland were treated twice weekly from July 1987 to December 1987, with mist containing ammonium sulphate and nitric acid at a pH of either 2.5 or 5.0. The response of photosynthesis and stomatal conductance to light flux density and carbon dioxide concentration were measured in March 1989. Leaf chlorophyll a and b contents were also measured. Acid mist (pH 2.5) resulted in several significant changes. First, both the rate of light saturated photosynthesis (Amax) and CO2- saturated rate of photosynthesis (J) were substantially increased, when expressed per unit leaf area. Second, the apparent quantum yield and chlorophylls a and b content increased. Third, as a consequence of the greater chlorophyll content of the leaves treated with acid mist, the rate of Amax, and J, expressed per unit chlorophyll, was substantially reduced in pH 2.5 treated branches. Stomatal conductance was enhanced at all but the highest light flux densities, and was independent of the CO2 concentration, remaining high for all values of CO2 concentration used. These results show that acid mist caused a number of responses in the gas exchange and photosynthetic properties of red spruce.
ectoping expresing | Photosynthesis | Plants
Set-up of ACi curves, N, P and LMA values for dominant species. Establish the extent to which rates of light saturated photosynthesis, Vcmax and Jmax change in response to associated traits and to climatic moisture in the Great Western Woodlands. Experimental design and methods: In April and October 2013, we surveyed ACi curves and related leaf traits (area:mass ratios, and concentrations of nitrogen and phosphorus) in 37 species growing at the Great Western Woodlands TERN - SuperSite. Leaves were sampled from different trees ranging from 1 to 4 replicates per specie. Asat(light saturated photosynthesis), Amax (CO2 saturated photosynthesis), Ci (intercellular partial pressure of CO2) and Rlight(CO2 evolution from mitochondria in the light, other than that associated with the PCO cycle) were used to calculate rates of Vcmax (maximum velocity of the carboxylase) and Jmax (maximum rate of carboxylation allowed by the electron transport). Vcmax and Jmax were corrected for temperature.