GENERAL PLANT ORGANIZATION
LEAF STRUCTURE AND FUNCTION
In botany, a leaf is an above-ground plant organ specialized for the process of
photosynthesis. Leaves are typically flat (laminar) and thin, which evolved as a means to
maximise the surface area directly exposed to light. Likewise, the internal organisation of
leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts,
to light and to increase the absorption of carbon dioxide, in a process called photosynthesis.
Most leaves have stomata, which regulate carbon dioxide, oxygen, and water vapour
exchange with the atmosphere. The shape and structure of leaves vary considerably
depending on climate, primarily due to the availability of light and potential for water loss
due to temperature and humidity. Leaves are also the primary site, in most plants, where
transpiration and guttation take place. Leaves can also store food and water, and are
modified in some plants for these purposes. The concentration of photosynthesis in leaves
makes them rich in protein, minerals, and sugars. Because of their nutritional value, leaves
are prominent in the diet of many animals, including humans as leaf vegetables. In addition
to photosynthesis leaves are involved in other vital plant functions. Respiration is a metabolic
process which produces waste products. These products are deposited outside the plant when
the leaves are shed. Leaves are also important to the movement of water absorbed by the
roots and transported throughout the plant. Foliage is a mass noun that refers to leaves.
Functions
1. Photosynthesis
2. Transpiration
3. Gaseous exchange
Adaptation for function
1. Thin
2. Flat
