4 8.4 Impact of Environmental Change on Plant Physiology
Learning Objectives
By the end of this section, you will be able to do the following:
- Describe the FACE experiments
- Connect environmental factors to plant behavior and adaptations
- Characterize how the system of a plant will change in response to varied environmental factors
Environmental Responses & Adaptations
Plants are visually different depending on the environment they are in. This phenomena is due to the alteration of water regulation strategy based on differing ecosystem pressures. Desert plants, such as CAM plants, have adapted to only open their stomata at night. This prevents water loss during the day, where extreme heat would quickly dry out the leaf’s reserves. CAM plants take in CO₂ at night and store it in the form of an organic acid. During the day time, the plant can perform photosynthesis without having to open its stomata. Common examples of CAM plants include cacti and pineapples.
Figure X. Comparison of CAM, C3, and C4 plants
C4 plants have also adapted to perform photosynthesis while in hot and dry conditions. While most plants fixate CO₂ from the atmosphere and convert it to a three carbon molecule, the C4 plant converts it into a four carbon molecule using an enzyme in the mesophyll called PEP carboxylase. This small molecular tweak allows the C4 plant to concentrate its CO₂ store without having to open its stomata – exposing it to dehydrating conditions.
Both C4 and C3 are important crops, and changing CO₂ levels may impact their productivity differently. C3 plants, such as rice and wheat, tend to benefit more from rising atmospheric CO₂ concentrations. This increase in carbon can potentially increase photosynthetic efficiency. In contrast, C4 plants like maize and sugarcane may not show as significant a response. Concentrating CO₂ internally by its complex physiology would imply added CO₂ is of no benefit.
Visual Connection
FACE Experiments
For the last three decades across the globe, Free Air Carbon Enrichment (FACE) experiments have exposed plants to heightened levels of carbon dioxide to study how ecosystems will respond to future atmospheric levels. FACE experiments help scientists observe changes in plant growth, water use, behavior, and nutrient cycling under close-to-identical environmental conditions. Thus far, results have shown that while increased CO₂ can boost photosynthesis and growth, responses vary widely depending on species, soil nutrients, and water availability.
Visual Connection
Media Attributions
- 1A.C.C3C4CAMplants © Hannah Nelson
