Topic 12 - Photosynthesis responses and adaptation to light and temperature
Essential elements from Topic 12:
In this lecture, we discuss how photosynthesis at the leaf level responds to changes in light and temperature and how plants have adapted to contrasting light environments and thermal growth conditions. We will see that
Essential elements from Topic 12:
In this lecture, we discuss how photosynthesis at the leaf level responds to changes in light and temperature and how plants have adapted to contrasting light environments and thermal growth conditions. We will see that
- Leaf-level photosynthesis responds to changes in light and temperature conditions over the course of a day. These responses represent a biochemical regulation.
- Over the course of leaf development, there can be level-level acclimation responses that allow plants to develop leaves with capacities to photosynthesize under contrasting light environments or thermal conditions.
- Responses to high versus low light levels can be manifested in changes in leaf morphology and through adjustments in biochemical and morphological characteristics. As plants respond to different light growth environments (e.g., sun versus shade), we see differences in the thickness of the palisade layer, changes in dark respiration rates, and changes in the photosynthetic light saturation levels. The photosynthetic efficiency (quantum yield of CO2 uptake) is not influenced by changes in light levels at moderate light levels.
- The photosynthetic responses to changes in leaf temperature reflect the influence of enzyme concentrations at low temperatures, CO2 diffusion at moderate temperatures, and thermal instability at high temperatures.
- Leaves of many plants species can acclimate to changes in the thermal growth conditions by increasing photosynthetic rate at low temperatures when grown at low temperatures or increasing photosynthetic rate at high temperatures when grown at high temperatures (an acclimation response). Other plant species seem incapable of photosynthetic temperature acclimation when exposed to contrasting thermal growth conditions.
- Photosynthetic thermal instability at high temperatures can be lethal to leaves. This photosynthetic thermal instability is associated with increased membrane fluidity and a progressive loss of Photosystem II function following brief exposures to high temperatures.