Modelling photosynthetic photon flux density and maximum potential gross photosynthesis

Abstract

Irradiance data software developed by the NREL Solar Radiation Laboratory (Simple Model of Atmospheric Radiative Transfer of Sunshine, SMARTS) has been used for modelling photosynthesis. Spectra and total irradiance were expressed in terms of quanta [mol m -2 s -1 , photosynthetic photon flux density, PPFD (400-700 nm)]. Using the SMARTS software it is possible to (1) calculate the solar spectrum for a planar surface for any given solar elevation angle, allowing for the attenuating effects of the atmosphere on extraterrestrial irradiance at each wavelength in the 400-700 nm range and for the thickness of atmosphere the light must pass through during the course of a day, (2) calculate PPFD vs. solar time for any latitude and date and (3) estimate total daily irradiance for any latitude and date and hence calculate the total photon irradiance for a whole year or for a growing season. Models of photosynthetic activity vs. PPFD are discussed. Gross photosynthesis (P g ) vs. photosynthetic photon flux density (PPFD) (P g vs. I) characteristics of single leaves compared to that of a canopy of leaves are different. It is shown that that the optimum irradiance for a leaf (I opt ) is the half-saturation irradiance for a battery of leaves in series. A C 3 plant, with leaves having an optimum photosynthetic rate at 700 μmol m -2 s -1 PPFD, was used as a realistic worked example. The model gives good estimates of gross photosynthesis (P g ) for a given date and latitude. Seasonal and annual estimates of P g can be made. Taking cloudiness into account, the model predicts maximum P g rates of about 10 g(C) m -2 d -1 , which is close to the maximum reported P g experimental measurements.

The Use of Solar Radiation by the Photosynthetic Bacterium, Rhodopseudomonas palustris: Model Simulation of Conditions Found in a Shallow Pond or a Flatbed Reactor

“…Figure shows solar radiation from 350 to 1000 nm modeled using the SMARTS software (see ) as described by Ritchie for Bangkok (13°45′N, 100°W) for the Spring Equinox (SE, 19 March 2012), Summer Solstice (SS, 20 June 2012), Autumn Equinox (AE, 22 September 2012) and Winter Solstice (WS, 21 December 2012). Irradiance is shown at 1‐nm intervals for each wavelength (μmol (hυ) m −2 s −1 nm −1 ).…”

“… to compare photosynthesis (oxygenic and anoxygenic) to silicon‐based photocells. The SMARTS system (see ) by Ritchie was used to calculate irradiances and diel total irradiances for Bangkok (Lat 13°45′, Long. 100°W) for oxygenic organisms (photosynthetic photon fluence density [PPFD]: 400–700 nm), violet near‐UV (VNUV: 350–400 nm) + PPFD (400–700 nm) suitable for photosynthetic calculations on rhodopseudomonads where comparisons are made to oxygenic organisms and the total useable spectrum of irradiance for rhodopseudomonads (350–1000 nm).…”

Limitations and prospects of natural photosynthesis for bioenergy production

“…A recent re-evaluation [3] has provided information by which insolation at any point on the Earth can be modelled to yield annual, seasonal, and daily values. Despite decadal variation [4], the annual value of total solar energy received at the Earth's surface is $2,500,000 exajoules (EJ).…”

“…The values for daily carbon are for the summer solstice, the equinox and the winter solstice, except for the Equator where there is only one solstice. Taken from [3].…”

Distinguishing downregulation from other non-photochemical quenching of an Antarctic benthic macroalga usingin situfluorometry

“…Sensors were calibrated against a LiCor 190SA sensor (Lincoln, Nebraska, USA). Where additional irradiance data were required, terrestrial irradiance in watts m À2 was obtained from fixed pyranometers located at Casey Station, and these data were converted to mmol quanta m À2 s À1 by multiplying by 4.6, a correction factor for sunlight (McCree, 1981; see also Ritchie, 2010). Irradiance at depth was then calculated using an attenuation coefficient (Kd) according to equations in Kirk (1994).…”