The apple wasn’t trying to co-operate with Isaac Newton

Plants are in various ways able to adapt the geometry and material properties of their organs, tissues and cells to changing conditions during development. Apple (Malus) fruit peduncles are highly modified stems with limited secondary growth because fruit ripening lasts only one season. They must reliably connect heavy fruits to the branch and cope with increasing fruit weight, which induces dynamic stresses under oscillating wind loads.

A recent study in Annals of Botany focuses on tissue modification of these small, exposed structures during fruit development. A combination of microscopic and mechanical test methods, as well as Raman spectroscopy was applied to study structure–function relationships in apple peduncles. Anatomical investigations were accompanied by biomechanical tests under static and dynamic loads to trace tissue differentiation and ontogenetic changes in properties of Malus peduncles throughout the growing season. Mechanical investigation of peduncles after successive removal of tissues revealed insights into the specific mechanical properties and function of different tissues.

The findings confirm previous assumptions that sclereids generally strengthen the plant structure. However, this work shows that brachysclereids contribute to the stiffness mostly under bending (flexural rigidity) rather than to the strength during tensile loads, and verifies their effect on viscous damping.

Horbens, M., Feldner, A., Höfer, M., & Neinhuis, C. (2014) Ontogenetic tissue modification in Malus fruit peduncles: the role of sclereids. Annals of Botany, 113(1), 105-118.