To solve this problem, we need to identify the term that describes the ability of plants to form different structures in response to environmental conditions or life phases.$\newline \bullet$Elasticity: This term generally refers to the ability of a material to return to its original shape after deformation. It is not related to the formation of different structures in plants.$\newline \bullet$Flexibility: This term refers to the ability to bend without breaking. While it can describe physical properties, it does not pertain to the formation of different structures in plants.$\newline \bullet$Plasticity: This term refers to the ability of an organism to change its morphology or physiology in response to environmental conditions. In plants, plasticity allows them to form different structures based on environmental cues or life stages.$\newline \bullet$Maturity: This term refers to the state of being fully developed. It does not describe the ability to form different structures.$\newline$Based on the definitions, the correct term that describes the ability of plants to form different structures in response to environmental conditions or life phases is Plasticity.$\newline$Therefore, the correct option is Option 3: Plasticity.