1) Pore 2) Stoma 3) Stomate 4) Water pore 5) Water stoma 
A specialized leaf structure with one or more openings through which water is discharged from the interior of the leaf to its surface. 
An epidermal structure specialised for secretion, or for exudation, of water. ... (09 Oct 1997) ... 
hydathode 1. An epidermal structure specialized for secretion, or for exudation (discharge) of water. 2. A pore in the outer layer of a leaf that secretes water when the rate of transpiration is low; for example, in humid conditions.
a specialized leaf structure through which water is exuded.