Arg

 

Arg (Argenteum)

Argenteum is one of the genes that causes a distinctive change in the appearance of the leaf because of a physical separation of the leaf epidermis from the underlying structure. This separation allows the epidermis to release itself from the subtending tissues, resulting in a thin air space. Because of this air space, the epidermis takes on a transluscent appearance, rather than the transparency it exhibits when attached to the layer below, making it appear a relatively dull grey as compared to an attached epidermis. What distinguishes the Argenteum gene from the other genes that share this effect is the degree and distribution of this disattachment. The fl gene (flecking - also called aeromaculata), by comparison, causes only small scattered grey spots on leaf surfaces, which is common to most peas. The Aero gene (aeromaculata) is similar to fl except that the area covered by these small patches is much greater because the number of patches is greater. Argenteum, in contrast, has air spaces under large areas of leaves - often the entire leaf surface - giving the whole plant a dull grey appearance.

This gene was first reported by Dr Marx in Pisum Newsletter Volume 10. The mutation was actually found as a spontaneous mutation in PI 343333 by L.G. Cruger, of the Del Monte Corp. Argenteum is dominantly inherited, although its expression is usually incomplete, with a majority but not an entirety of the leaf surface of a plant showing the Arg phenotype.

The Argenteum gene has been included in a number of studies on peas, because the loose epidermis allows fairly easy manipulation of the leaf for absorption studies, and the like. The Argenteum mutation maps toward one end of linkage group VI. Seven accessions in this collection are described at the Arg locus, and if you would like to query for the Arg gene, click here.