Light orientation in Iris leaves
Bot Notiser 1: 45-68
In strongly lighted localities I. pseudacorus is generally orientated in the north-south meridian or adjacent directions. If the plants are reorientated in the east-west direction, a phototropic reaction ensues which tends to return the leaves to the original position. Within certain limits, kind and degree of torsion is dependent on size of the maximal angle between the attachment of the leaves and the rhizome. Probably the perception of the light difference occurs in the upper parts of the leaves, while the growth reaction causing torsion occurs in the basal parts. In the shadow forms 2 types were observed: one reacts like the sun forms and one (in large majority) does not.