Ben-Gurion University of the Negev

3. Results
3.1. Red color phenomenon in Pistacia
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During the lifecycle of Pistacia, leaves turn into bright red twice a year, in early spring
up to mid-summer in new leaf growth and in autumn before leaf fall (Figs. 2A and 3A).
During leaf formation in early spring, not only leaves but also newly formed
inflorescences are becoming bright red (Fig. 2B, circled), later on in summer leaves turn
green, male inflorescences reach anthesis within 2 to 3 weeks and senesce. Female
flowers set fruits, turn red and towards the end of summer, upon fruit maturation, in
fertile fruits, the pericarp turns turquoise-green (Fig. 3D). A similar reddening process
occurs in autumn, just before leaf senescence, however, the color change involves a
more complex variety of colors from light yellow to deep red, and the spectrum is quite
different in the various species (Fig. 3, A-F). Moreover, newly growing branches are
red (Fig. 3B) and later turn brown-gray. Leaves that had been shaded by neighboring
leaves, and by this had been protected against UV radiation, exhibit less redness and
were mostly yellowish (Fig. 3B, circled).
A
A B
B
Fig. 2. P. palaestina leaves in early spring (A); Newly developing male inflorescence (circled)
(B)