Branches of Botany

Why Botany Is Divided into Branches

Botany today covers an enormous range of topics — from fossils millions of years old to the internal chemistry of a living leaf — so no single approach can study all of it at once. Over time, botanists organised the subject into distinct branches, each concentrating on one particular aspect of plant life. Grouping the subject this way makes it possible to study plants in far greater depth than a single, undivided science ever could.

Branches Based on Structure and Function

Several branches of Botany focus on how a plant is built and how it works. Morphology is the study of the external form of a plant — the shape and arrangement of its roots, stems, leaves, flowers, and fruits, as visible to the naked eye. Anatomy goes one level deeper, examining the internal structural organisation of plant organs — how tissues such as xylem and phloem are arranged inside a stem or root. Histology narrows the focus further still, studying plant tissues and their component cells in detail, typically under the microscope. Plant Physiology, in contrast, is concerned not with structure but with function — how a plant carries out its life processes, such as photosynthesis, respiration, water transport, and growth.

Branches Based on Groups of Organisms

Other branches are defined not by what aspect of a plant they study, but by which group of plant-like organisms they focus on. Phycology is the branch of Botany devoted to algae — organisms that are chlorophyllous (contain chlorophyll) and autotrophic (make their own food through photosynthesis), and that are classified among the thallophytes (plants without true roots, stems, or leaves). Mycology, by contrast, studies fungi — organisms that are non-chlorophyllous (lack chlorophyll) and heterotrophic (cannot make their own food and instead depend on other organisms), even though fungi too are traditionally grouped with the thallophytes.

A related and especially interesting branch is Lichenology, the study of lichens. Lichens are not single organisms but a stable partnership — a symbiosis — between two very different partners: an alga (called the phycobiont) and a fungus (called the mycobiont). The phycobiont, being chlorophyllous, photosynthesises and supplies food to the partnership, while the mycobiont provides physical structure, protection, and helps in water and mineral absorption. This mutually beneficial arrangement allows lichens to survive in extremely harsh habitats, such as bare rock, where neither partner could easily survive alone. …