Photosynthesis 117 



16 24 8 



Alaska Standard Time 



16 



24 



FIGURE 4-7. Seasonal progression of the daily 

 course of net photosynthesis in 1972. The upper 

 curve represents the period 25 June to 4 July and 

 lower curves are at successive 1 0-day intervals pre- 

 dicted by regression equations for Dupontia fish- 

 eri (D.f), C. aquatilis (C.a.J, E. angustifolium 

 (Em.) and S. pulchra (S.p.). (After Tieszen 1975.) 



TABLE 4-5 



Mean Daily Totals of Net COi Uptake by Leaves 

 (in mg COi dm'^ day'^) by Important Vascular 

 Species Through Summer 1972 (from regression 

 estimates of Tieszen 1975) and Efficiencies of Con- 

 version (in parentheses, in percent) 



Efficiency is the ratio of the energy fixed per unit leaf area to the intercepted irra- 

 diance per unit leaf area. 



