Photosynthesis in Developing Asparagus Plants

Abstract

The gas exchange characteristics of asparagus shoots at various stages of development are described. Reassimilation in spears conserved 50-100% of the carbon dioxide produced in respiration. Refixation was influenced by light intensity and CO₂ concentration in the surrounding air, but not by oxygen concentration. The absence of an inhibitory effect of oxygen on refixation is attributed to suppression by high levels of CO₂ inside the spear. Assimilation of radioactive CO₂ in both the spear and fern forms of asparagus was by the C₃ pathway. Fern forms displayed more usual C₃ properties, with photosynthesis and CO₂ compensation points showing sensitivity to oxygen concentration.