Energy dynamics in corn

We can study the one dead plant to understand the phenomenon resulting in stalk rot.  Roots starved because of insufficient carbs reaching them. This was due to some combination of insufficient photosynthesis to meet the demands of the grain fill and root metabolism.  But that one plant does not concern the growers. It is the percentage of plants in a field that lodges and become difficult to harvest that bothers the grower and the seed provider.  Physiologically, the concentration should be on energy captured by corn in the field (photosynthesis per acre) and harvestable carbohydrates captured.
A comparison of 44 commercial hybrid parents for the carbon exchange ratio (CER) for a small section of leaf tissue was done about 35 years ago. This was done by putting a known area of fresh live leaf tissue in a chamber with appropriate light wave frequencies, with known amounts of CO2 added and uptake in the leaf tissue measured.  The result showed very large range in CER among the inbreds.  It was interesting, and probably meaningful, that highest CER occurred in those that were visibly darker in color.  But they were all commercial hybrid parents!  Inbreds with highest CER also tended to have the more narrow leaves.  Of course, the hybrids were selected based upon good grain yields and stalk quality (among other things) in field trials.  They must have attained this not only through CER per area of leaf tissue but whole plant photosynthesis at the plant densities and other environments in the field. Those with more leaf area or canopies that allowed light penetration to lower leaves, or better uptake of minerals to support photosynthesis, or more plants per acre were the successful ones.  My take home from the CER experiment is that we still have lots of room for selection of more photosynthesis per acre but it is too complicated to concentrate on only one factor.
 
Just as with selection of best commercial grain yields, selection of stable stalk quality is dependent upon performance in the real world of dynamics of growers’ fields.  Selecting single traits might be useful but the final proof is in testing the whole plants and not only single components of performance. Ultimately, it is the combination of hybrid genetics, the season’s environment and the culture of the crop that determines the occurrence of stalk rot, just as it does the yield.
 
For more details about stalk rot, consider the stalk rot booklet in the tab above.