Character of morphoses caused in the Barley (Hordeum distichum L.) spike by 2-Methyl-4-Chlorophenoxycetil acid (MCPA)

The preparation of MCPA had no formative effect on the shoot apex although it affected the development of lateral buds formed at the sides. As soon as the compound ceased to act the development of the spike continued normally. The formative effect of MCPA is displayed in the structure of the ear by a partial or complete reduction of its internodes. The inhibitory action of the preparation is sometimes reflected in a blockade of the formation of lateral shoots in a part of one or both orthostichs, or else the lateral bud is initiated but does not continue to develop and thus a branchless node is produced. Occasionally, on the contrary, the preparation has a stimulating effect; segments of the lateral stem of the first order are elongated and develop similarly to the main stem which brings about the so-called “branching” of the spike frequently imitating dichotomy. Rich branching occurs on stimulating several lateral stems. A frequently met morphosis is a locally disturbed distichy, and a decussation of orthostichs or their rotating by an angle of less than 90° and a disturbance in the normal course of mesotonic branching. The formation of apparent or true flower whorls formed in consequence to a reduction of the ear internodes or a disturbance of distichy is usually connected with the reduction of individual inflorescence parts, with an increase in the number of inflorescence parts, with their partial or complete cohesion and with a change of their position.