Study of Ca absorption and movement in cherry trees using ⁴⁵Ca as a tracer

Calcium is correlated with postharvest fruit condition and quality, and as a consequence commercial orchards carry out many foliar applications of this element. With the aim of identifying the absorption and movement of foliar applied Ca, we carried out an experiment using ⁴⁵Ca tracer (5 µL) applied 15 days after full bloom in a 15-year-old cherry orchard in central Chile, ‘Royal Dawn’ on Gisela 6. Treatments were: 1) control (baseline levels), and applications on the 2) upper and 3) lowers surfaces of leaves at the base of fruiting spurs and 4) directly on the surface of young fruit (<5 mm diameter). At harvest, leaves, spurs and fruit were collected and ⁴⁵Ca was measured with a Liquid Scintillation Counter. Additionally, to determine the morphology of tissues at the time of application, leaves and fruit were collected and then observed with electron microscopy (SEM). Results indicated that ⁴⁵Ca applied on the upper surface of leaves showed neither absorption nor presence in neighboring organs. ⁴⁵Ca applied on the lower surface of leaves was absorbed and mostly stayed within this tissue, with a small proportion moving to neighboring fruit, but not to spurs. ⁴⁵Ca applied directly to fruit was absorbed and mostly stayed within this tissue, with no movement to the spur. SEM observations showed that stomata were present in the lower surface of the leaves and, in a lower amount, in fruits. Therefore, the presence of stomata in organs is important for Ca absorption, but this element had very little movement between organs.