A field experiment was conducted at Marana, AZ (2,000 ft. elev.) to evaluate the relationships of apparent photosynthesis rates (APS), total chlorophyll (Chl(T)) content, plant height, and lint yield of two species of cotton planted at five dates. upland cotton (Gossypium hirsutum L. var DPL 90) and Pima cotton (G. barbadense L. var Pima S-6) were compared. Mean APS values ranged from 14-25 micro moles CO₂ cm^-2. Maximum values for APS were found in plants planted on 21 April for DPL 90 and for the 1 April planting date with Pima S-6. In general, APS means decreased with later planting dates for both varieties. This same general pattern was also true for lint yield and Chl(T) for both DPL 90 and Pima S-6. Plant height increased for both varieties with later planting dates. Similar trends for the APS, Chl(T), and lint yield in this experiment indicated that a relationship of basic physiological photosynthetic capabilities to crop management (planting date) exists beyond changes in photosynate partitioning between vegetative and reproductive plant structures in cotton.