Any substance capable of generating an antibody response is known as what?

I think the answer for the above question is Antigen. Antigens are substances that are capable of exciting the immune system and provoking an immune response. For example; foreign particles, large carbohydrates, nucleic acids, some lipids, pollen grains. microorganisms. Antigens are capable of inducing an immune response to produce antibodies in a host organism. 

That is true tge cactus as a structural adaptation to its envirinment has it leaves reduced to spines. but this doesnt mean it cant produce food it produces food because of the presence of chlorophyll in its stem

Closing a ring restricts the rotation around individual car bon carbon bonds hope it will you !