| Name | Structure/ Category | Description |
|---|---|---|
| Asymmetric | (2) [Seed cones] {symmetry} | Not divisible into essentially equal halves along any plane. |
| Attenuate | [Leaf bases, Leaflet bases] {shape} | Tapering gradually to a narrow base. |
| Auriculate | [Leaf bases, Leaflet bases] {shape} | With ear-shaped appendages at the base. |
| Autotrophic | [Plants] {nutrition} | Able to synthesize the nutritive substances an organism needs from the non-living environment; in plants, photosynthetic. |
| Awl-shaped | [Leaflets, Leaves] {shape} | Narrowly triangular and sharply pointed, like an awl. |
| Awn | A slender, more or less straight and stiff, fine-pointed appendage; may be located at the tip of a leaf or bract and a continuation of the midvein, or comprising the pappus in fruits of the sunflower family (Asteraceae). | |
| Axil | The point of the upper angle formed between the axis of a stem and any part (usually a leaf) arising from it. | |
| Axile | [Placentation] {type} | Attachment of ovules at or near the center of a compound ovary which has more than one inner compartment (multilocular), the ovules located on the inner angle formed by the interior partitions (septa). |
| Axillary | [Buds, Inflorescences, Seed cones] {position} | On the stem just above the point of attachment of a leaf (or leaf scar) or branch; borne in the axil of a leaf or branch. |
| Axis | Any relatively long, continuous, supporting structure that typically bears other organs laterally, and represents the main line of growth and/or symmetry; as a stem that bears leaves or branches, or the rachis of an inflorescence that bears flowers along its length. |
