Step 1: Understanding the Question:
This question tests knowledge of ecological terminology.
Step 2: Detailed Explanation:
Ecotypes are plants of a particular region growing in a specific climatic zone and adapted to that zone.
They are genetically adapted to local conditions.
Genotypes (A): Genetic constitution.
Sub-species (C): Taxonomic rank.
Species (D): Basic taxonomic unit.
Thus, the correct answer is ecotypes.
Step 3: Final Answer:
Thus, plants adapted to a climatic zone are called ecotypes, which corresponds to option (B).
[0.5cm]