Photosynthesis temperature effect

Because of the interaction of many factors, especially the numerous temperature effects on both transpiration and photosynthesis, the effects of elevation on WUE are complex. Diffusion coefficients depend inversely on ambient (barometric) pressure [Z) = D 0(F0/F)(T/273)1 8 Eq. 8.9]. Barometric pressure averages 0.101 MPa at sea level, 0.079 MPa at 2000 m, and about 0.054 MPa at 5000 m. Thus diffusion coefficients are nearly twice as large at 5000 m as at sea level owing to the pressure change, which correspondingly increases the gas-phase conductances based on Ac (e.g., Eq. 8.2), whereas those based on AN (Eq. 8.8) are unchanged. The rate of decrease of ambient air temperature with increasing elevation, termed the lapse rate, can be — 5°C per kilometer of... 

Water Stress Effects on Canopy Photosynthesis, Temperature, Transpiration and Shedding of Leaves and Fruit in Cotton 733... 

Non-calorimetric studies of effects of hydrostatic high pressure on plant sources are more common. In general, pressure effects on plant metabolic rates are small, but some distinct changes have been noted in growth, photosynthesis, temperature responses, and plant structure [48]. Interpretation of the role of pressure on plant metabolism remains uncertain. Hypotheses that have been framed to explain pressure effects are generally written in terms of volume changes and structural transitions in chloroplasts and in lipid membranes, but there are equally tenable alternative explanations such as pressure effects on equilibria. 

By reference to the appropriate sections of this book they can be used to demonstrate normally difficult to illustrate concepts such as quantisation, radical ion recombination, electron transfer, energy transfer, temperature effects on reactions and thermodynamics. Interesting discussions on their relationship to photosynthesis, vision and photochemistry can be provoked. 

The effect of temperature fluctuations on net carbon dioxide uptake is ikustrated by the curves in Figure 18. As the temperature increases, net photosynthesis increases for cotton and sorghum to a maximum value and then rapidly declines. Ideally, the biomass species grown in an area should have a maximum rate of net photosynthesis as close as possible to the average temperature during the growing season in that area. 

The possible effects of increased atmospheric CO2 on photosynthesis are reviewed by Goud-riaan and Ajtay (1979) and Rosenberg (1981). Increasing CO2 in a controlled environment (i.e., greenhouse) increases the assimilation rate of some plants, however, the anthropogenic fertilization of the atmosphere with CO2 is probably unable to induce much of this effect since most plants in natural ecosystems are growth limited by other environmental factors, notably light, temperature, water, and nutrients. 

Photosynthesis and gas exchange of leaves are affected by many stresses including drought, flooding, salinity, chilling, high temperature, soil compaction and inadequate nutrition. Many, but not all, of these stresses have symptoms in common. For example, stomatal conductance and the rate of assimilation of CO2 per unit leaf area often decrease when stress occurs. Further, it is possible that several of the stresses may exert their effects, in part, by increasing the levels of the hormone abscisic acid (ABA) in the leaf epidermis. This hormone is known to close stomata when applied to leaves. 

Long, S.P., East, T.M. Baker, N.R. (1983). Chilling damage to photosynthesis in young Zea mays. 1. Effects of light and temperature variation on photosynthetic CO2 assimilation. Journal of Experimental Botany, 34, 177-88. 

The effects of photosynthesis are clearly seen in the low TDIC and nutrient concentrations of the surface water. The O2 concentrations are high because of contact with the sea surfece and production by phytoplankton. The temperature and O2 concentration data have been used to compute the percent saturation with respect to O2. The high degree of supersaturation in the surfece water suggests that the rate of O2 supply via photosynthesis is exceeding its removal via the dual processes of aerobic respiration and degassing across the air-sea interface. 

In the surface waters, geographic variability in 2CO2 and TA. are caused by the effects of temperature on CO2 solubility and by variations in the local rates of photosynthesis and biogenic calcification. In general, surfece water 2CO2 concentrations are lowest in warm surface waters due to the low solubility of CO2 at higher temperatures. The lower influx of CO2 also causes warm surface waters to have a higher carbonate ion concentration as compared to cold surfece waters. Carbonate ion concentrations are... 

Effect of temperature, light intensity, and evaporative stress on photosynthesis and respiration... 

Ku, S. B., Edwards, G. E., Tanner, C. B. (1977). Effects of light, carbon dioxide, and temperature on photosynthesis, oxygen inhibition of photosynthesis, and transpiration in Solanum tuberosum. Plant Physiol, 59, 868-872. 

Fig. 18. Effect of temperature on net photosynthesis for sorghum and cotton leaves. To convert mg/(dm2h) to lb/(ft2h), multiply by 2.373 x 10...

C02 assimilation. The amount of C02 available for photosynthesis decreases with decreasing C02 partial pressure at higher elevations, but this effect is offset by the increase in diffusion speed at lower air pressure (Gale 1972, 1973). The lower temperature at higher altitudes, however, decreases diffusion speed, and therefore the temperature lapse rate of the particular mountain determines whether C02 availability decreases (dry-moist lapse rate) or stays relatively constant (very wet lapse rate) (Smith and Donahue 1991). The lower air pressure at altitude does not just decrease C02 partial pressure but also 02 partial pressure, which results in lower photorespiration rates and more efficient photosynthesis. When all these effects are modeled, photosynthetic rates generally decrease with altitude, unless the temperature lapse rate is very low (which could occur in extremely wet mountain ranges), but the photosynthetic limitation is much less than expected based on just the partial pressure decrease (Terashima et al. 1995 Smith and lohnson 2007). 

For example, in the carbon cycle consider the balance between terrestrial photosynthesis and respiration-decay. If the respiration and decay flux to the atmosphere were doubled (perhaps by a temperature increase) from about 5200 x 1012 to 10,400 x 1012 moles y-l, and photosynthesis remained constant, the CO2 content of the atmosphere would be doubled in about 12 years. If the reverse occurred, and photosynthesis were doubled, while respiration and decay remained constant, the CO2 content of the atmosphere would be halved in about the same time. An effective and rapid feedback mechanism is necessary to prevent such excursions, although they have occurred in the geologic past. On a short time scale (hundreds of years or less), the feedbacks involve the ocean and terrestrial biota. As was shown in Chapter 4, an increase in atmospheric CO2 leads to an increase in the uptake of CO2 in the ocean. Also, an initial increase in atmospheric CO2 could lead to fertilization of those terrestrial plants which are not nutrient limited, provided there is sufficient water, removal of CO2, and growth of the terrestrial biosphere. Thus, both of the aforementioned processes are feedback mechanisms that can operate in a positive or negative sense. An increased rate of photosynthesis would deplete atmospheric CO2, which would in turn decrease photosynthesis and increase the oceanic evasion rate of CO2, leading to a rise in atmospheric CO2 content. More will be said later about feedback mechanisms in the carbon system. 

The tops of Jerusalem artichoke can also be cut off at 1.5 m to reduce the likelihood of wind damage (Wood, 1979), which in this instance prevented the plants from flowering. Wind also affects leaf temperature and the rates of photosynthesis and transpiration, with resulting but minor effects on growth rate (Meyer et al., 1973). 

---