Relationships Among CO2‐exchange Rate and Plant Traits in Iowa Stiff Stalk S1ynthetic Maize Population1

We measured CO2‐exchange rates (CER), morphological traits, and yield traits of 64 maize (Zea mays L.) inbred lines randomly derived from Iowa Stiff Stalk Synthetic (BSSS). Our experiments were grown for 2 years at one location. Genotypic correlations among these traits were calculated to determine if selection for high CER would cause correlated responses in other traits. We also studied possible physiological limitations to grain and dry matter yield of these inbreds. Genotypic correlations between CER and plant traits were low, suggesting that one could develop high CER genotypes displaying various morphological traits. Nonsignificant correlations between CER and yield traits indicated CER was not the primary factor limiting yield of these inbreds. Correlations showed that dry matter yield was limited by amount of leaf area and by traits associated with efficient use of light energy. We concluded grain yield of these inbred lines was limited by sink size and by lack of a receptive sink because: 1) grain yield was highly correlated with ear length, ear diameter, 300‐kernel weight, and number of ears per plant and 2) potential dry‐matter production during grain filling was 208 g plant ‐1 compared with 49.6 g plant‐1 actually stored in the grain.