title: Up and down asymmetrical world for flower blooming.
abstract: Form of plant body shows vertical polarity. Photosynthetic organs deploy upwards to seek light. Root system extends downward for water. In addition to this major polarity, flowers has similar features, because they bloom in the world where up and down asymmetry dominates. Many flowering plants co-evolved with pollinator animals. Success of their reproduction is linked to the shape of flower organs in many ways. Orientation of inflorescence and each individual flowers, arrangement and shape of flower organs exhibit various up and down asymmetry. Some flowers mimic female of its pollinator animal. In such case, posture of the target animal is copied to the flower. Since animal posture and shape have vertical polarity, flower happens to equip same kind of polarity. Tropic response of pistils is another up and down feature that improves fitness of flowering plants. Certain lily flowers show phototropism to bend pistil upward. Azalea flower depends on gravity as the major environmental cue, and light as the secondary signal for up. Molecular machinery for those tropic responses seems to be shared with other tropism expressed in shoot and root. However, certain differences are found in distribution of sediment amyloplast, or spatial allocation of photo-sensing and bending site. Tropic responses result in adaptation of those flowers against behavior of pollinator animals and terrestrial environment, where gravity affects living organisms and interaction among them.
authors.affiliation: Institute of Space and Astronautical Science/JAXA.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Yamashita
authors.forename: Kaori
authors.initials: K
authors.lastname: Tomita-Yokotani
authors.forename: Teruko
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D005075:Biological Evolution; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D006112:Gravitation; D018522:Gravitropism / Q000502:physiology*; D027762:Lilium / Q000235:genetics / Q000254:growth & development; D018524:Phototropism; D018521:Plant Physiological Phenomena; D011058:Pollen; D012641:Selection, Genetic; D013045:Species Specificity