Figure 5.
Diurnal courses of incident photosynthetically active radiation (PAR) measured on June 16 (top), transpiration rate (T) measured on June 16 (middle), and the relative concentration of total N-amino acids in xylem sap measured on May 27 (▴) and June 16 (○; bottom). T values are means of sap flow measurements on four trees. Concentrations are means for four trees. Relative concentration refers to the ratio of actual to maximum diurnal values. Bars are ses and are presented only every 3 h for sake of legibility. The fitted polynomial is y = −0.009x2 + 0.29x − 1.49.