The P&PDL Picture of the Week
for 16 June 2003

Purpling in Corn

Bob Nielsen, Department of Agronomy, Purdue University

Purpling of corn plant tissue results from the formation of a reddish-purple anthocyanin pigment that occurs in the form of a water-soluble cyanidin glucoside. A hybrid's genetic makeup greatly determines whether corn plants are able to produce anthocyanin. A hybrid may have none, one, or many genes that can trigger production of anthocyanin. Purpling can also appear in the silks, anthers and even coleoptile tip of a corn plant.

Well, you may say, that's fine but what triggers the production of the anthocyanin in young corn at this time of year? The answer is not clearly understood, but most agree that these pigments develop in young plants in direct response to a number of stresses. These stresses include cool temperatures, high solar radiation levels, and water stress (both waterlogged and droughty conditions).

Does the leaf purpling lead to yield losses later on? The cause of leaf purpling, not the purpling itself, will determine whether yield loss will occur by harvest time. If the cause of the stress is temporary (e.g., cool soils), then yield loss will be negligible. If the cause of the stress lingers for some time (e.g., effects of soil compaction), then yield loss is possible.

Click on the small image to view a larger image.

What’s Growing In My Mulch????

Gail Ruhl, Interim P&PDL Director, Senior Diagnostician, Dept. of Botany and Plant Pathology, Purdue University

Thanks to the excessive wet weather, moisture-loving slime molds are appearing abundantly in mulch. Initially some may appear as a bubbling yellow mass, however, as the days progress, and the fungus matures, the slime mold will usually become more powdery in appearance, drying to a white, yellow, tan or dark brown ‘blob’.

Slime molds get their nutrients from bacteria and small bits of organic matter which is why it is common to see them growing on mulch. Although slime molds may grow up onto nearby plants, they do not harm plants. After several days slime molds will usually be less noticeable. If you want to speed this process, you may rake the mulch to promote air drying.

Slime mold growing on mulch	Slime mold on mulch one day later
Slime mold growing on mulch	Slime mold growing on mulch

Photos courtesy of Peggy Sellers, Master Gardener State Coordinator

Slime mold growing on dead organic matter in lawn

Photo courtesy of George Knaphus at Iowa State University

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