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Corn Response to Competition: Growth Alteration vs. Yield Limiting Factors
Author(s) -
Clay S. A.,
Clay D. E.,
Horvath D. P.,
Pullis J.,
Carlson C. G.,
Hansen S.,
Reicks G.
Publication year - 2009
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2008.0213x
Subject(s) - chlorophyll , biology , agronomy , biomass (ecology) , photosynthesis , stover , competition (biology) , horticulture , chlorophyll a , population , botany , field experiment , ecology , demography , sociology
Competition mechanisms among adjacent plants are not well understood. This study compared corn growth and yield responses to water, N, and shade at 74,500 plants ha −1 (1×) with responses to water and N when planted at 149,000 plant ha −1 . Plant biomass, leaf area, chlorophyll content, reflectance, and enzyme expression (transcriptome analysis) were measured at V‐12. Grain and stover yields were measured with grain analyzed for 13 C isotopic discrimination (Δ) and N concentration. At V‐12, 60% shade plants had increased chlorophyll and reduced leaf area and height compared to full sun plants. In the 2× treatment, plants had 11% less chlorophyll than 1× plants with leaf area and height similar to 60% shade plants. At harvest, plants in the 2× treatment were smaller, had increased water and N use efficiency, and an 11% per hectare yield increase compared with the 1× unstressed treatment. Per‐plant yields from 60% shade and 2× treatments were 50% less than 1× unstressed treatment. Yield reduction in shaded plants was attributed to light stress. Lower yield in the 2× treatment was attributed to a population‐density induced 20% decrease in the red/near‐infrared (NIR) ratio, which resulted in downregulation of C 4 carbon metabolism enzymes (phosphoenolpyruvate carboxykinase, phosphoenolpyruvate carboxylase, and pyruvate orthophosphate dikinase). Although the net impact of high plant density and shade stress on per‐plant yield were similar, the stress compensation mechanisms differed.