Corn trichomes

Corn leaf blades, like leaves of most plant species, have small ‘hairs’ extending from some epidermal cells. These are called trichomes.  The functions of trichomes are not fully understood although in some species they are associated with insect resistance.  Nearly all corn varieties have these structures, at least after the 6th leaf stage, an indication of some significant importance to the corn plant.
 
Trichomes originate from the epidermal cells and vary with in shape within and among maize varieties.  There are mutants that extend the smooth epidermis of the younger plants to the older leaves. Although single gene mutants can nearly eliminate all macrohair trichomes, the actual production would still be under the control of several genes and apparently influenced by a plant hormone such as gibberellic acid.
 
Although corn trichomes probably lead to less insect injury to leaves, they have been associated with infection by a few pathogens. Three species of the fungal genus Fusarium (F. graminearum, F. proliferatum and F. verticilloides) have been shown to infect the epidermal cells via the trichomes (http://www.sciencedirect.com/science/article/pii/S1878614616300654 ).
 
The bacterium causing Goss Wilt (Clavibacter michiganensis subsp. nebraskense) has been shown to occasionally enter the leaf tissue through the trichome at the point where it attaches to the epidermal cell.  This does not occur with the frequency of leaf injury being associated with entrance of this pathogen. It does explain the occasional Goss-diseased plant that has no visible physical injury similar to what we have seen a few rows away from inoculated plants in our disease nursery.
 
A review of corn trichome genetics can be found at http://www.genetics.org/content/166/3/1451
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