Figure 5. Relationship of the difference between the newer (‘NK N25-J7’) and older (‘Pride 5’) maize (Zea mays L.) hybrid in carbon exchange rate per unit absorbed photosynthetic photon flux density (CER Abs^–1) vs. the difference between the newer and older hybrid in thylakoid electron transport rate (ETR) for plants grown at low and high N levels. Differences are expressed as a proportion of the value of the newer hybrid (i.e., 100% x [NK N25-J7 – Pride 5]/NK N25-J7), and the dashed line indicates the 1:1 ratio.