Ontogeny of Photosynthetic Performance in Fragaria virginiana under Changing Light Regimes

Apparent photosynthesis and dark respiration were followed during development in four light environments of leaves of Fragaria virginiana Duchesne. Leaf expansion was completed more rapidly the higher the growth photon flux density and leaves senesced more quickly in high light. Maximum photosynthetic capacity coincided with the completion of blade expansion and declined quickly thereafter. Leaves were transferred from high to low and low to high photon flux densities at several stages during expansion. Leaf photosynthetic performance and anatomy were subsequently analyzed. Leaf anatomy and apparent photosynthesis per unit dry weight can be modified during expansion to reflect the predominant light conditions. Adaptive potential is greatest early in blade expansion and decreases as expansion is completed.