Absorption and translocation to fruit for cesium applied on apple tree leaf surface.

Area of Science:

• Agricultural Science
• Environmental Science
• Plant Physiology

Background:

• Understanding cesium (Cs) ion behavior in fruit trees is crucial for food safety and environmental management.
• Cesium uptake and translocation in plants can be influenced by various factors, including plant species, growth stage, and application method.

Purpose of the Study:

• To investigate the transfer of stable Cesium-137 (Cs+) ions from leaf surfaces to fruit in plumleaf crab apple trees (Malus domestica 'Alps Otome') at different fruit development stages.
• To determine the proportion of Cs transferred to fruit by harvest and analyze the influence of fruit growing stages on Cs absorption and translocation.

Main Methods:

• Stable Cs+ ions were applied in droplets to the leaf surfaces of 2-3-year-old apple trees at three distinct fruit growing stages: pre-bearing, early development, and late development.
• Cesium concentration in leaves, branches, and fruit was measured over time until harvest.
• A compartment model was constructed to describe Cs transfer dynamics.

Main Results:

• Most applied Cs rapidly transferred from leaf surfaces into the leaves and subsequently translocated to the fruit via branches.
• The mean proportion of Cs transferred to fruit by harvest ranged from 11% to 30%, showing no direct dependence on the fruit growing stage.
• Cs absorption from leaf surfaces was faster during early and late fruit development stages compared to the pre-bearing stage.

Conclusions:

• Cesium translocation to apple fruit occurs through leaf absorption and subsequent movement via branches.
• While Cs transfer rates vary with fruit development, the overall proportion reaching the fruit by harvest is significant.
• Current compartment models require refinement, indicating a need for further research to fully elucidate Cs transfer mechanisms in fruit trees.