Browsing by Subject "gas exchange"

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  • Wang, Fang; Robson, T Matthew; Casal, Jorge J; Aphalo, Pedro J. (2020)
    The UV-A/blue photoreceptors phototropins and cryptochromes are both known to contribute to stomatal opening (∆gs) in blue light. However, their relative contributions to maintenance of gs in blue light through the whole photoperiod remains unknown. To elucidate this question, Arabidopsis phot1 phot2 and cry1 cry2 mutants (MTs) and their respective wild types (WTs) were irradiated with 200 μmol m-2 s-1 of blue-, green- or red-light (BL, GL or RL) throughout a 11-hour photoperiod. Stomatal conductance (gs) was higher under BL, than under RL or GL. Under RL, gs was not affected by either of the photoreceptor mutations, but under GL gs was slightly lower in cry1 cry2 than its WT. Under BL, the presence of phototropins was essential for rapid stomatal opening at the beginning of the photoperiod, while maximal stomatal opening beyond 3 h of irradiation required both phototropins and cryptochromes. Time courses of whole-plant net carbon assimilation rate (Anet) and the effective quantum yield of photosystem II photochemistry (ΦPSII) were consistent with an Anet-independent contribution of BL on gs both in phot1 phot2 and cry1 cry2 mutants. The changing roles of phototropins and cryptochromes through the day may allow more flexible coordination between gs and Anet.
  • Kolari, Pasi; Chan, Tommy; Porcar-Castell, Albert; Back, Jaana; Nikinmaa, Eero; Juurola, Eija (2014)
  • Khazaei, Hamid; Wach, Damian; Pecio, Alicja; Vandenberg, Albert; Stoddard, Frederick L. (2019)
    Increasing productivity through improvement of photosynthesis in faba bean breeding programmes requires understanding of the genetic control of photosynthesis-related traits. Hence, we investigated the gene action of leaf area, gas exchange traits, canopy temperature, chlorophyll content, chlorophyll fluorescence parameters and biomass. We chose inbred lines derived from cultivars 'Aurora' (Sweden) and 'Melodie' (France) along with an Andean accession, ILB 938, crossed them (Aurora/2 x Melodie/2, ILB 938/2 x Aurora/2 and Melodie/2 x ILB 938/2), and prepared the six standard generations for quantitative analysis (P-1, P-2, F-1, F-2, B-1, and B-2). Gene action was complex for each trait, involving additive and dominance gene actions and interactions. Additive gene action was important for SPAD, photosynthetic rate, stomatal conductance and F-v/F-m. Dominance effect was important for biomass production. It is suggested that breeders selecting for productivity can maximize genetic gain by selecting early generations for canopy temperature, SPAD and F-v/F-m, then later generations for biomass. The information on genetics of various contributing traits of photosynthesis will assist plant breeders in choosing an appropriate breeding strategy for enhancing productivity in faba bean.
  • Robson, T. Matthew; Hartikainen, Saara M.; Aphalo, Pedro J. (2015)
    We hypothesized that solar ultraviolet (UV) radiation would protect silver birch seedlings from the detrimental effects of water stress through a coordinated suite of trait responses, including morphological acclimation, improved control of water loss through gas exchange and hydraulic sufficiency. To better understand how this synergetic interaction works, plants were grown in an experiment under nine treatment combinations attenuating ultraviolet-A and ultraviolet-B (UVB) from solar radiation together with differential watering to create water-deficit conditions. In seedlings under water deficit, UV attenuation reduced height growth, leaf production and leaf length compared with seedlings receiving the full spectrum of solar radiation, whereas the growth and morphology of well-watered seedlings was largely unaffected by UV attenuation. There was an interactive effect of the treatment combination on water relations, which was more apparent as a change in the water potential at which leaves wilted or plants died than through differences in gas exchange. This suggests that changes occur in the cell wall elastic modulus or accumulation of osmolites in cells under UVB. Overall, the strong negative effects of water deficit are partially ameliorated by solar UV radiation, whereas well-watered silver birch seedlings are slightly disadvantaged by the solar UV radiation they receive. We hypothesized that solar ultraviolet (UV) radiation would protect silver birch seedlings from the detrimental effects of water stress. Plants were grown under nine combinations of solar UV treatments and water deficit conditions. In seedlings under water deficit, UV attenuation reduced growth compared with seedlings receiving the full spectrum of solar radiation; whereas the growth and morphology of well-watered seedlings was largely unaffected by UV attenuation. There was an interactive effect of the treatment combination on water relations, which was more apparent as a change in the water potential at which leaves wilted or plants died than through differences in gas exchange.
  • Guseva, Sofya; Aurela, Mika; Cortés, A; Kivi, Rigel; Lotsari, Eliisa; MacIntyre, Sally; Mammarella, Ivan; Ojala, Anne; Stepanenko, Victor; Uotila, Petteri; Vähä, Aki; Vesala, Timo; Wallin, M.B.; Lorke, Andreas (2021)
    Inland waters, such as lakes, reservoirs and rivers, are important sources of climate forcing trace gases. A key parameter that regulates the gas exchange between water and the atmosphere is the gas transfer velocity, which itself is controlled by near-surface turbulence in the water. While in lakes and reservoirs, near-surface turbulence is mainly driven by atmospheric forcing, in shallow rivers and streams it is generated by bottom friction of gravity-forced flow. Large rivers represent a transition between these two cases. Near-surface turbulence has rarely been measured in rivers and the drivers of turbulence have not been quantified. We analyzed continuous measurements of flow velocity and quantified turbulence as the rate of dissipation of turbulent kinetic energy over the ice-free season in a large regulated river in Northern Finland. Measured dissipation rates agreed with predictions from bulk parameters, including mean flow velocity, wind speed, surface heat flux, and with a one-dimensional numerical turbulence model. Values ranged from similar to 10-10m2s-3 to 10-5m2s-3. Atmospheric forcing or gravity was the dominant driver of near-surface turbulence for similar fraction of the time. Large variability in near-surface dissipation rate occurred at diel time scales, when the flow velocity was strongly affected by downstream dam operation. By combining scaling relations for boundary-layer turbulence at the river bed and at the air-water interface, we derived a simple model for estimating the relative contributions of wind speed and bottom friction of river flow as a function of depth.