Pendulum walnut leaves exhibited various adaptive responses related to the regulation of photon interception such as specific downward orientation, greater leaf area, and larger pigment pool. Changes in the regulation of PS2 such as higher thermal dissipation (NPQ) and lower quantum efficiency (ΦPS2) that protect the photosynthetic apparatus against damages were also found. The growth and photosynthetic features of pendulum walnut leaf are interpreted as adaptations that allow the pendulum walnut tree to compensate the impaired ability by appropriate growth to ensure the energy needs for photosynthesis, respectively for biomass formation. and L. Atanasova ... [et al.].