Cell wall development of chambered crystalliferous cells in the secondary phloem of Populus euramericana is described. These cells were differentiated from parenchyma strands which contacted with phloem fiber groups. A crystal was formed in a vacuole surrounded by tonoplast in each chamber. Then, the secondary wall deposition of chambered crystalliferous cells began only at the part adjacent to phloem fibers forming a protruding fringe which encircled the crystal. When the vacuole disappeared, the crystal had been surrounded by the wall substance on all sides except that away from the fiber. The wall on the crystal surface was not formed by the growth of any protrusion of the secondary wall, but formed independently by the deposition of wall substance on the crystal surface. The secondary wall development was completed after filling up the space between the crystal-surface wall and the thickened side wall adjacent to phloem fiber with newly deposited wall. The crystal-surface wall must be deposited after the tonoplast surrounding the crystal is converted into the plasma membrane多室結晶細胞は分化中の師部繊維に接する柔細胞ストランドから分化した。結晶は最初液胞中に認められた。師部繊維が二次壁の堆積を始める頃, 結晶細胞壁の師部繊維側の部分で二次壁形成が始まり, 結晶を取巻くように壁の突出部が形成された。結晶を取囲む液胞が見えなくなると, 師部繊維と反対側の面を除きすべての結晶表面に壁の堆積が起こった。しかし, この壁は結晶細胞の壁の突出部が張出してきて結晶表面を被ったものではなかった。最後に結晶表面の壁と結晶細胞の師部繊維側に堆積した二次壁との間が, 新たに堆積してきた壁物質によって埋められ, 結晶は厚い細胞壁中に取込まれた状態となる。結晶表面の壁は, 結晶を取囲んでいた液胞膜が原形質膜に置換えられた後に形成されたものと考えられる

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