Occurrence and proposed cause of hollow husk in maize
In 2007, a maize (Zea mays L.) ear abnormality that we term here as 'hollow husk' occurred in research trials designed to alter the level or the sensing of plant ethylene. The unique experimental conditions of 2007 enabled us to document the occurrence of hollow husk and propose a physiological mechanism for its cause. Ears exhibiting hollow husk have normal appearing husks that feel hollow due to an abrupt cessation in ear development and a concomitant lack of silk emergence. Hollow husk occurred when the foliage of actively growing plants was sprayed before the VT growth stage with a chemical treatment that should either lower the level of plant ethylene (a strobilurin fungicide), or one that should decrease the plant's sensitivity to ethylene (1-MCP). An attempt to increase ethylene status (via ethephon) led to virtually no hollow husk symptoms. The percentage of plants exhibiting hollow husk symptoms depended on the hybrid, the stage of plant growth when sprayed, and the combination of management conditions that promoted plant growth. Plants sprayed at V15 generally exhibited greater symptoms than those sprayed at V11, and hollow husk successively increased with increases in N supply and decreased with increases in plant population. Based on our data, we speculate that hollow husk is a physiological ear abnormality related to a perturbation in the level or the sensitivity of the plant to ethylene.