Research data supporting "Cell wall compositions determine handedness reversal in helicoidal cellulose architectures of Pollia condensata fruits"
Chiral asymmetry in nature encompasses a wide range of disciplines and length-scales. While several natural biomolecules exist only with single-handedness, they can produce complex hierarchical structures with opposite chiralities. Understanding how the handedness is transferred from molecular to the mesoscopic scales is far from trivial. An intriguing example is the transfer of the handedness of helicoidal organisations of cellulose microfibrils in plant cell walls. These cellulose helicoids produce structural colours if their dimension is comparable to the wavelength of visible light. All previously reported examples of a helicoidal structure in plant are left-handed. Remarkably, in the Pollia condensata fruit both left- and right-handed helicoidal cell walls are found in neighbouring cells of the same tissue, which gives rise to an enhanced reflectance. By simultaneously studying optical and mechanical responses of cells with different handednesses, we conclude that the chirality of helicoids results from differences in cell-wall compositions. In detail, we observed that (i) light reflected from right-handed cells is red-shifted compared to light reflected from left-handed cells, (ii) right-handed cells occur more rarely than left-handed ones and (iii) right-handed cells are located mainly in regions corresponding to interlocular divisions. Finally, (iv) right-handed cells have an average lower elastic modulus compared to left-handed cells of the same colour. Our findings, combined with mechanical simulation, suggest that the different chiralities of helicoids in the cell wall may result from different amounts or compositions of hemicelluloses, in accordance with previous hypotheses on their importance in mediating chirality in helicoidal cell-wall architectures.