Departmental Bulletin Paper オジギソウの振動傾性反応に伴う小葉枕細胞の微細構造変化と細胞内イオン動態
Ultrastructural Changes and Intracellular Ion Movements in Tertiary Pulvinus Cells duing the Seismonastic Response of Mimosa pudica L.

青木, 唯  ,  Aoki, Yui  ,  丸茂, 幸  ,  Marumo, Sachi  ,  西方, 秀之  ,  Nishikata, Hideyuki  ,  小塚, 麻衣子  ,  Kozuka, Maiko  ,  深田, 麻希  ,  Fukada, Maki  ,  小浦, 七美  ,  Koura, Nanami  ,  早津, 学  ,  Hayatsu, Manabu  ,  鈴木, 季直  ,  Suzuki, Suechika

26pp.53 - 69 , 2015-06-30 , 神奈川大学総合理学研究所
To examine the mechanism regulating tertiary pulvinar motor cells in the seismonasticresponse of Mimosa pudica L., light and electron microscope studies on the structuralchange of those tissues and cells and the movement of K, Ca, and other ions during leafletclosure were carried out. Light microscopic observation and the measurement of cell volumechanges using the montage method revealed that abaxial parenchymatous cells in the tertiarypulvini were markedly swollen during leaflet closure, in contrast to the inverse volume changeof adaxial parenchymatous cells, indicating that those are the motor cells. Concomitant withthe cell volume change, in the adaxial region, epidermal folding and the shrinkage of intercellularspaces were caused during leaflet closure. On the other hand, similar structural changeswere found in the abaxial region in the leaflet opening state. The epidermal and parenchymatouscells of tertiary pulvini contained large central vacuoles, in which electron-dense materials,probably including tannin as demonstrated by FeSO4 cytochemistry, were located alongthe inner surface of the tonoplast. The electron-dense material changed form from a largeglobule to a small grain or an amorphous shape in the adaxial cells during leaflet closure. Atthe same time, an inverse change of electron-dense materials occurred in the abaxial cells. Acytochemical study using potassium pyroantimonate (PA) indicated that, in the abaxial motor cells, PA precipitates containing Ca were located along the inner surface of tonoplast in the leaflet opening state, while they were diffusely distributed in the vacuolar lumen during leaflet closure. This result suggests that Ca ions play a significant role in initiating the volume change of motor cells. Quantitative X-ray microanalysis of cryosections showed that, during leaflet closure, the concentrations of Ca, K, and Cl increased significantly in the vacuolar electron-dense material, vacuolar lumen, and cell walls in the abaxial cells, while the concentrations of Ca and K decreased only in the vacuolar electron-dense material in the adaxial cells. In the tertiary pulvini, Ca and K ions released from the vacuolar electron-dense material in the adaxial cells may cause the Ca, K, and water movement to the abaxial region, and eventually turgor movement by the swelling of abaxial motor cells.

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