foliar

Foliar is an adjective relating to leaves. In botany, it describes structures, processes, or phenomena pertaining to the leaves of a plant. The term distinguishes leaf-related aspects from those of stems or roots.

Leaves are the primary photosynthetic organs. Foliar tissues include the epidermis with a protective cuticle, the mesophyll (palisade and spongy), and stomata that regulate gas exchange and water loss. Foliar functions include photosynthesis, transpiration, and respiration, and leaf surfaces may bear trichomes and waxes.

Foliar fertilization is a horticultural practice in which nutrients are sprayed onto foliage for uptake through leaf surfaces. It can rapidly correct micronutrient deficiencies and supplement soil fertilization, but effectiveness depends on nutrient properties, leaf area, weather, and adjuvants. Common applications include micronutrients such as iron, zinc, manganese, copper, and boron; macro-nutrients are used less frequently. Risks include leaf burn and phytotoxicity; optimal timing is during mild, dry conditions with appropriate adjuvants and guidelines from manufacturers. Uptake occurs mainly through stomata and the cuticle, and some nutrients may require chelates or compatible formulations to enhance absorption.

Other uses: In herbal medicine and pharmacognosy, foliar can refer to preparations derived from leaves. In plant pathology, foliar describes symptoms or diseases that affect the leaves, such as leaf spots or powdery mildew.