CDFA Pest Prevention Plant Regulation Practice Exam

To determine if a plant belongs to the citrus species, what method is most effective?

1. Hold a leaf to the light to see if "pin point" oil cells are present

2. Crush it to check for a typical citrus odor

3. Count the separations of the leaves

4. Compare the color to a color chart

The correct answer is: Hold a leaf to the light to see if "pin point" oil cells are present

The most effective method to determine if a plant belongs to the citrus species is by holding a leaf to the light to observe the presence of "pin point" oil cells. Citrus species are characterized by specific oil cells that contain aromatic oils, which are typically produced as a defense mechanism by the plant. When light passes through the leaf, these small, translucent oil cells become visible, allowing for a clear differentiation from non-citrus species that may not exhibit this feature. While crushing the leaf to check for a typical citrus odor can be helpful, it is not as definitive as the visual identification of oil cells, which provide a more direct morphological characteristic of citrus plants. Counting the separations of the leaves is not a reliable method, as the leaf structure can vary significantly among different species, and comparing color to a color chart lacks the specificity needed to accurately identify citrus plants. Thus, observing the oil cells in the leaf is the most effective and distinctive method for identifying whether a plant belongs to the citrus family.