Net photosynthesis of Fe‐efficient and Fe‐inefficient soybean cultivars grown under varying iron levels

Abstract

Net photosynthesis (P_n), chlorophyll, and foliar Fe content of two Pe‐efficient (A7 and Hawkeye) and two Fe‐inefficient (T203 and Anoka) soybean cultivars (Glycine max (L.) Merr.) were measured at seven different Fe levels in modified Hoagland solution culture. Net photosynthesis of A7 remained relatively high with or without Pe even after 10 days, while that of T203 was low without Pe, increased with increasing Pe up to about 0.3 mg Pe/liter, and leveled off thereafter. Hawkeye P was low at 0 mg Fe/liter increased dramatically with as little as 0.1 mg Fe /liter, and was unchanged thereafter. Anoka P_n rose gradually between 0 and 0.6 mg Pe/liter after which it leveled off. Thus, rates of P for Pe‐efficient and ‐inefficient cultivars were similar at the nigher Pe levels, but were very different under Fe‐stressed conditions. Changes in P in all cultivars were generally paralleled by similar changes in chlorophyll and foliar Fe content. Stomatal diffusive resistance was unaffected by the Pe treatments.

Key words:

• Chlorophyll
• CO₂ fixation
• Glycine max (L.) Merr
• Iron stress