The Use of the Awns.

King Country Chronicle, Volume III, Issue 143, 29 March 1909, Page 4

The Use of the Awns.

Many a botanist, on looking at a cornfield and examining the long awns of barley, must have asked himself — What may be the use of these long appendages? There are no useless structures in plants—each separate structure having been developed in the course of time to answer some useful purpose—and the long awns of rye and barley are no exception to the rule. Two Austrian naturalists, Zoebl and Mikosch, have discovered that they play a most important part in the transpiration of the plant, and transpiration is known to be one of the mo<t important acts for promoting the formation of all sorts of nourishing elements within the tissues and the seeds. When the upper parts of the plant discharge into the air considerable quantities of the water which they contain, the sap rises through the vessels of the stem to the transpiring parts and carries upwards the nourishing substances which are drawn by the roots from the soil. The awns aid in this process. They are usually of a triangular shape, and have, along two of their sidss, rows of very small apertures which permit the plant to discharge water through them. The amount thus thrown off has been measured, and it appears that through its awns the spike discharges, in the twenty-four hours, three times*its own weight in water; while as soon as the awns are removed, the transpiration is reduced to one-third of its prevkus amount. The awns alone discharge as much water as the totality of the leave?. It is now easy to understand how important they are in the life of our corn-producing plants. The grain of barley or rye must be matured within a relatively short period of time; so the awns provoke a rapid exchange of sap, exactly at the spot where the grain lies. Several species even lose their awns when the corn TTas reached maturity, and they are no longer required.