The Mysterious Polarity That Reveals Plant Intelligence - Rupert Sheldrake

TL;DR

Plants exhibit a deep root-shoot polarity controlled by the hormone auxin, whose ultimate origin Sheldrake believes may be electrical gradients.

Key Points

• 1.Plant polarity is fundamentally expressed as the root-shoot axis. Shoots grow toward light against gravity while roots grow into darkness downward, and this polarity is established from the earliest embryonic stage, as seen in shepherd's purse embryos.
• 2.Auxin is the key hormone maintaining polar flow in plants. Chemically indole acetic acid (a tryptophan breakdown product), auxin moves from shoot tips toward roots at ~1 cm/hour and was first identified using radioactive carbon-14 tracer experiments in the early 20th century.
• 3.Sheldrake disproved the 'cell age' theory of polarity using monocot leaves. In grasses and daffodils, the youngest cells are at the leaf base — opposite to normal stems — yet auxin still transported toward the root end, proving cell wall age is irrelevant to polarity.
• 4.Radioactive auxin experiments confirmed extreme directional transport. In daffodil leaves, basipetal (root-ward) transport measured 4,616 counts per minute versus zero acropetal, demonstrating near-absolute polarity across grass, crocus, lily, orchid, and palm leaves.
• 5.Inverted cuttings retain their original auxin polarity despite reversed physiology. Tomato plants grown upside-down with roots at the apical end still transported auxin in the original direction, showing polarity is deeply embedded in cell identity and cannot be reversed by external conditions.
• 6.Fern protonemata revealed visible polar plasmolysis at the cellular level. In bird's nest fern (Asplenium nidus) single-cell threads, treating cells with mannitol caused the cell membrane to detach from the basal wall but remain attached to the apical wall, showing physically different membrane attachment at each cell end.
• 7.Different salts produce markedly different degrees of polar plasmolysis. Mannitol and magnesium sulfate showed near-total apical plasmolysis; calcium nitrate was weaker; potassium nitrate weaker still — suggesting ionic composition influences cell-wall membrane adhesion asymmetry.
• 8.Sheldrake proposes electrical gradients as the unresolved origin of plant polarity. The Earth carries ~100 volts per meter negative charge gradient; electrostatic spray experiments on flower petals confirm electrical gradients exist in plant tissue, and Sheldrake suggests this field may establish the initial auxin-transport polarity — still an open question after 50 years.