At each leaf growth stage, six randomly chosen plants were used for measurements.
In addition, the two set of plants (2- and 5-year-old plants) were exposed to summer drought and mature leaves were collected prior (18 May, control) and during summer drought (29 July, stress) to compare the physiology of leaves in terms of water contents, pho- tosynthetic pigment and anthocyanin levels and the Fv/Fm ratio.