What is Torus in Botany?

In botany, a torus refers to a few different, but related, structures:

Primarily, a torus, also known as a receptacle or (older term) thalamus, is the thickened part of a stem from which the flower organs (sepals, petals, stamens, and carpels) arise. It's essentially the base of the flower where all the floral parts are attached. See Wikipedia's article on Receptacle (botany)

Torus in Bordered Pits

Secondly, in the context of plant cell walls, the torus is a thickened, central part of a pit membrane found within bordered pits of certain plant cells, particularly in the tracheids of conifers. This torus is surrounded by a thinner, more porous area called the margo. The torus plays a crucial role in regulating water flow within the plant's vascular system. The torus's structure and function have been extensively studied for their importance in cavitation resistance and hydraulic efficiency in conifers. See this research article on torus-margo pit membranes and another on solid mechanics of torus-margo. It is made up of lignin and regulates water flow. See Toppr.com

In summary: The term "torus" in botany has two primary meanings: the receptacle of a flower, and a structural component within bordered pits of plant cell walls, especially in conifers.