Certified Professional Horticulturist (CPH) Practice Exam

Which types of plants are more likely to be injured by intracellular ice formation?

1. Deciduous trees

2. Herbaceous plants

3. Hardy shrubs

4. Container grown plants

The correct answer is: Herbaceous plants

Herbaceous plants are more susceptible to injury from intracellular ice formation due to their structural characteristics. Unlike woody plants, herbaceous plants have softer, more succulent tissues that contain higher water content. When temperatures drop, the water within these tissues can freeze, leading to the formation of ice crystals inside the cells. This intracellular ice can puncture cell membranes and disrupt cellular functions, resulting in significant tissue damage or death. In contrast, deciduous trees and hardy shrubs have protective adaptations, including the production of antifreeze proteins and the ability to tolerate some freezing, which allows them to withstand lower temperatures without severe damage. Container-grown plants may also experience different conditions due to their roots being above ground and more exposed to temperature fluctuations, but they can also benefit from insulation provided by the container itself. Thus, the unique physiology and structure of herbaceous plants make them particularly vulnerable to the harmful effects of freezing temperatures and ice formation in their cells.