Diurnal Photosynthesis and Pigment Analysis

The net photosynthetic rate (Pn), stomatal conductivity (Gs), transpiration rate (Tr), and intercellular CO₂ concentration (Ci) of the OY saplings were measured using the LI-6400 Portable Photosynthesis System (Li-Cor, Lincoln NE, USA) on August 10. Five healthy and mature leaves were selected for each treatment. The diurnal changes were measured once every 2 h from 6:00 to 18:00. According to a modified version of an established method (Lichtenhaler and Wellburn, 1983 (link)), apple leaves were placed in 10 ml tubes. After adding 5 ml 80% acetone, the tubes were incubated at 4 °C in a black box. The samples were mixed several times every 4 h. As the color intensity of the solutions decreased, the chlorophyll content per unit area was determined by measuring the absorbance at 663 and 645 nm.