How may a plant respond to severe heat stress?
a. By reorienting leaves to increase evaporative cooling
b. By creating air tubes for ventilation
c. By producing heat-shock proteins, which may protect the plant's proteins from denaturing
d. By increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

Verified step by step guidance

1. Understand that plants, like all organisms, have mechanisms to cope with environmental stress, including heat stress.
2. Recognize that heat stress can cause proteins to denature, which can disrupt cellular functions.
3. Learn that one common response to heat stress in plants is the production of heat-shock proteins. These proteins help stabilize and refold denatured proteins, protecting the plant's cellular machinery.
4. Consider the role of leaf orientation in temperature regulation. By reorienting leaves, plants can reduce direct sunlight exposure and increase evaporative cooling, which helps in temperature regulation.
5. Evaluate the role of cell membrane composition. Increasing the proportion of unsaturated fatty acids generally increases membrane fluidity, not reduces it, which helps maintain membrane function under stress conditions.

Key Concepts

Heat Stress in Plants

Heat stress in plants occurs when temperatures exceed a plant's optimal range, potentially leading to cellular damage and impaired physiological functions. Plants have evolved various mechanisms to cope with heat stress, such as altering leaf orientation, producing protective proteins, and adjusting membrane composition to maintain cellular integrity and function.

Heat-Shock Proteins

Heat-shock proteins (HSPs) are a group of proteins produced by plants in response to elevated temperatures. They function as molecular chaperones, stabilizing and refolding denatured proteins, thus preventing aggregation and maintaining cellular homeostasis. This protective mechanism is crucial for plant survival under heat stress conditions.

Membrane Fluidity and Fatty Acids

The fluidity of cell membranes is influenced by the composition of fatty acids in the lipid bilayer. Unsaturated fatty acids increase membrane fluidity, while saturated fatty acids decrease it. In response to heat stress, plants may adjust the proportion of unsaturated fatty acids to maintain optimal membrane fluidity, ensuring proper cellular function and stability.