The one-word substitute for the scientific study of plants and their structure is "Botany."

• Plantation: Plantation refers to a large agricultural estate or farm where specific crops are grown, such as tea, coffee, or sugar. It does not capture the scientific study of plants.
• Environment: Environment refers to the surroundings or conditions in which living organisms exist, and it is a broader term that encompasses various aspects of the natural world, including plants, animals, and their interactions.
• Biology: Biology is the study of living organisms, including plants, animals, and microorganisms. While it includes the study of plants, it is not specific to the structure and characteristics of plants.
• Botany: This is the correct option. Botany is the scientific study of plants, including their structure, growth, development, reproduction, and classification. It focuses specifically on plants and their characteristics.