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ARS Home » Research » Publications at this Location » Publication #108722
Title: VARIABILITY IN PHOTOSYNTHESIS AND GROWTH OF COMMON COCKLEBUR ACCESSIONS

Author
item KNEPP, ANDREW - UNIV OF ILLINOIS
item TRANEL, PATRICK - UNIV OF ILLINOIS
item WAX, LOYD
item WASSOM, JAMES - UNIV OF ILLINOIS

Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/9/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Common cocklebur is a widespread and troublesome weed in many crop production systems. Many geographic ecotypes of common cocklebur exist which vary in physiological and morphological characteristics. Greenhouse studies were conducted to analyze the variability of traits relevant to weediness among common cocklebur accessions. Parameters used to access variability among the six selected accessions were photosynthetic rate, leaf area, above and below-ground biomass, and stomatal density. Cocklebur accessions from Arkansas, Iowa, Missouri, New Mexico, Ohio, and South Carolina were selected based on previous sudties. Photosynthetic rates varied significantly among the cocklebur accessions at four different light regimes. The Ohio cocklebur accession had the highest photosynthetic rate of 21 umol CO2 m-2s-1 folowed by the New Mexico, South Carolina, Missouri, Iowa, and Arkansas accessions under a light intensity of 1310 umol m-2s-1. Relative rankings among accessions were observed at all four light regimes. Leaf area and biomass of each cocklebur accession were highly correlated (R2=0.98). A strong negative correlation (R2=-0.80) was observed between photosynthetic rate and leaf area. This negative correlation suggests that accessions with smaller leaf areas were more photosynthetically active per unit of leaf area. Accessions with high photosynthetic rate per unit leaf area may be less competitive with crops because of their smaller leaf area. Stomatal density varied among cocklebur accessions on both the abaxial and adaxial leaf surfaces. No trends relating these differences with photosynthetic rate, biomass accumulation, or leaf area were apparent.