LAUSR

The relationships between alternate bearing and variations in mineral nutrient composition of the shoots and leaves of pistachio trees (Pistacia vera L. ‘Uzun’) and the effects of these relationships on flower abscission were investigated over 2 years (2015 and 2016). The mineral contents of leaves and shoots of “On” and “Off” year trees were measured at different periods of pistachio growth. Determination of total nitrogen (N) content was performed using a Kjeldahl instrument and other minerals were analyzed using the age-burning method via microwave digestion and by atomic absorption spectrometry. The concentrations of some minerals (P, K, Ca, Mg, Fe, Zn, Mn, and B) were higher in the leaves of “On” trees than in “Off” trees, while some others (N, K, Mg, Ca, Zn, and Cu) were higher in the shoots. The concentrations of N, P, K, Mg, Zn, and Mn in the leaves and shoots reached minimum levels during the flower abscission and nut kernel development period. Fruiting state had a significant effect on the contents of P, K, Zn, and Mg in both leaves and shoots, but did not affect the amount of N in these two organs. Levels of B, a sufficient supply of which is essential for successful flowering, in “On” trees decreased to deficient levels during flower blooming. Our results indicate that N, P, K, Ca, B, and Fe may play key roles in annual fruit production in pistachio and the changes in nutrient content during different development periods are associated with flower abscission.