Bases

The base of a leaf is the lower part of the lamina, where it is attached to the petiole or stem. Cuneate bases are sharp-pointed, with an angle less than 45 degrees between opposite sides which form a wedge or triangular shape that tapers to a narrow region at the point of attachment of lamina with petiole. Acute bases have a sharp-pointed base, with opposite sides forming an angle between 45 and 90 degrees at the position where the lamina joins the petiole. Obtuse bases have a blunt or narrowly rounded base with opposite sides forming an angle greater than 90 degrees at the position where the lamina joins the petiole. Rounded bases are curved to form a full, sweeping arc. Truncate bases look as though they were cut off at nearly a right angle to the midrib, forming a flat-topped or squared-off shape. Cordate bases are valentine-shaped, with both right and left margins forming broad arcs that meet in the middle of the junction between lamina and petiole. Inequilateral bases have asymmetrical left and right sides of different sizes or shapes. Auriculate bases have earlike lobes where the lamina joins the petiole.

Roger D. Meicenheimer

See also: Leaf anatomy; Leaf arrangements; Leaf lobing and division; Leaf shapes; Shoots.

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