Vibrational response of the male ‘peter’ pistachio branch organs to facilitate artificial pollination

Abstract

Artificial pollination may be a promising practice to both improve pistachio fruit production by mitigating the losses caused by phenological gaps or by adverse meteorological events and establish new production areas. Artificial pollination requires large quantities of pollen and manual collection is not economically viable. Mechanical capture of pollen, for subsequent storage and application, could achieved in two ways: by releasing mature pollen from the inflorescences and capturing it in the air, or detaching mature male inflorescences for taking pollen in laboratory. In this work, the dynamic behaviour of branches of the male ‘Peter’ variety was analysed under controlled laboratory conditions. A wide range of vibration frequencies was used for branch excitation, and the responses of the stem and its inflorescences were analysed. The stem and inflorescences had clearly differentiated dynamic responses according to the vibration frequency. The stem attained maximum acceleration transmissibility values at specified frequency values (8, 13.5, 20.5–22 Hz). At these values, the vibration applied amplified the stem movement and could clearly contribute to pollen release to the atmosphere. At the highest frequency values (45 Hz), the stem damped the vibration, but the inflorescences amplified the response. In the 54–59 Hz range, the inflorescences amplified the acceleration received by an average 5-fold. In this range, detachment of the inflorescences is facilitated without exciting the stems. Thus, current commercial trunk shakers must be adapted if they are used to collect pollen from pistachio trees owing to the higher transmission values of trees without leaves. • Stem and male inflorescences of the Peter variety have a different dynamic response. • Precise vibration frequency applied to branch enables a selective organ excitation. • Trunk shakers can be adapted for mass pollen detachment. • Absence of leaves during the pollination period may increase damage to shaken trees .