The rotated-lamina syndrome. VI. The range from partial to near-complete rotation in Tiliaceae and Sterculiaceae

摘要

The rotated-lamina syndrome is a condition most commonly found in dorsiventral shoots with distichous phyllotaxis. Typically, young laminae in bud appear to be rotated to face towards the upper side of the shoot. The syndrome arises by asymmetrical growth from leaf primordia that initially face the shoot apex in approximately the normal way. It was previously described inTilia. Further genera of Tiliaceae and the closely related Sterculiaceae were examined for the presence of the syndrome. Altogether it was found in 9 genera of the 30 examined. The syndrome is well developed in representatives ofCommersonia,Corchorus, andPterospermum, and less well developed inLuehia seemannii. Expression of the syndrome is minimal inLuehia divaricata,Theobroma,Byttneria, andGrewia. In all cases with distichous phyllotaxis that were examined in these families, the leaf primordia show at least some asymmetry in development and consequently there appears to be a predisposition to lamina rotation within the group. The syndrome is probably becoming suppressed in cases with minimal expression. The situation in dorsiventral shoots ofCorchorusandByttneriais complicated by the presence of inflorescences that arise in a leaf-opposed position.Key words: Sterculiaceae, Tiliaceae, leaf, development, dorsiventrality, lamina rotation.