INFLUENCE OF PERIODIC SHADING ON THE LENGTH AND SOLIDNESS OF THE INTERNODES OF RESCUE WHEAT

Shading at the initiation of elongation shortened the internodes of Rescue wheat whereas shading later in the elongation period caused the internodes to elongate as much as or more than if they had not been shaded.The solidness of the bottom Internode, 1, was reduced mainly by shading from the 2-leaf to the boot stage, while that of Internodes 2 and 3 was reduced mainly by shading from the 4-leaf to the boot stage. The solidness of Internode 4 was reduced mainly by shading from the boot to the heading stage. The solidness in the lower 3 internodes was affected by reduction in light intensity even after the boot stage. Severe lodging occurred only in stems shaded from the boot to the heading stage.Two methods were used for rating stem solidness, namely, measurement in the split stem of proportion of the internode filled with pith, and classification of solidness of cross-sections at designated points in each internode. They were strongly correlated and appeared to give equally accurate estimates of solidness, although their degrees of sensitivity varied with the amount of stem solidness present.