(11) Why does light saturation occur in plants? Explain why shade adapted plants have a higher Specific Leaf Area than shade intolerant plants. Plant A is a shade intolerant species and Plant B is a shade tolerant species. On the graph, label the light compensation point and light saturation point for each species. Explain why the light compensation point is lower for plant B than plant A.


A. When light saturation occurs, the dark reactions limit the rate of photosynthesis due to the limited products of the light reactions which are ATP and NADPH. The plant cannot exceed its working capacity.
Shade adapted plants have a higher specific leaf area than share intolerant plants because they want to maximize the uptake of sunlight by enlarging as much as they can their leaf surface areas.
The light compensation point is the point at which photosynthesis = 0. The photosynthesis rate of a shade intolerant plant is higher than a shade tolerant plant due to its ability to get more sunlight. Less photosynthesis means lower light compensation point.

B.Because plants have a limit on how much photosynthesis they can perform. Shade plants have higher SLA because it maximizes the light use for photosynthesis. Shade intolerant has lower SLA because they are in direct sunlight therefore do not need bigger leaves.

C.In some plants adapted to extremely shaded environments, photosynthetic rates decline as light levels exceed saturation. Plants growing in shaded environments ted tot have lower light compensation point, a lower light saturation point and a lower maximum rate of photosynthesis than plants growing in high-light environments. The shade-tolerant species showed little difference survival and growth rates under sunlight and shade conditions. In contrast, the survival and growth rates of shade-intolerant species were dramatically reduced under shade condition or dramatically increase in light condition this is where we see in the graph. The higher the rate of light saturated photosynthesis results in a high growth rate for the shade-intolerant species in the high-light environment.

D.Light saturation occurs because plants can only photosynthesize with so much light till they hit a maximum light saturation point (point where there is no limit to photosynthesis to the plant). Shade plants have a higher specific leaf area because they are limited to the amount of light they can receive being a shade plant. The larger the leaf area, the more SA it has to capture light. The light compensation point is lower for plant B because it requires a LOWER? amount of light in order to match up to the rate of photosynthesis to the rate of respiration. Plant B is shade adapted so it doesn’t require as high of a light compensation point than Plant A, which is a shade intolerant species.