Occasionally, a field of seedling wheat may appear to have an off-color, and when examined more closely, color banding is evident on newly emerged seedlings. This banding can range from light yellow to reddish-purple in color (Figure 1).
Figure 1. Color banding on newly emerged wheat seedlings from temperature fluctuations, with a close-up view in the bottom photo. Photox by Jeanne Falk Jones, K-State Research and Extension.
What causes color banding?
The bands of color on an otherwise green plant are the result of temperature extremes, likely warm daytime highs and freezing (or near-freezing) temperatures at night. These wide swings in temperature result in significant fluctuations in photosynthate production and utilization within the plant, affecting plant growth. This typically occurs on the first leaf to emerge from the soil, on tender leaf tissue. You may see only one band or two to three bands, with each band representing a temperature swing. These plants are typically found throughout the field, not just on a field edge.
Color banding can occasionally be seen in the spring, after a cold event. This typically appears as a purple band on the stem, near the leaf collar of the most recently emerged leaf. The purple is typically a result of sugar accumulation in the tissue when crop growth is temporarily paused due to the cold temperatures. This area is the most tender plant tissue due to recent stem elongation. It is most often seen on the plants near the edge of a field, as these plants were the most exposed to the cold temperature.
What does this mean for the wheat?
The wheat will recover from this discoloration, and it will not affect plant growth and development. In the seedling wheat, if you revisit the field after a week of good growing conditions, additional leaves will have developed, and the banding will likely not be found.
Jeanne Falk Jones, Northwest Area Agronomist, Colby
jfalkjones@ksu.edu
Lucas Haag, Agronomist-in-Charge, Tribune
lhaag@ksu.edu
Romulo Lollato, Wheat and Forages Extension Specialist
lollato@ksu.edu
Tags: wheat weather color banding