Influence of microgravity on root-cap regeneration and the structure of columella cells in Zea mays

• Published in: American journal of botany Vol. 74; no. 2; p. 218
• Main Authors: Moore, R, McClelen, C.E, Fondren, W.M, Wang, C.L
• Format: Journal Article
• Language: English
• Published: United States 01.02.1987
• Subjects: CAPA PILIFERA; CELL STRUCTURE; COIFFE; ENDOPLASMIC RETICULUM; Endoplasmic Reticulum - physiology; ESTRUCTURA CELULAR; GRAVIDEZ; GRAVIPERCEPTION; GRAVITE; GRAVITY; Gravity Sensing - physiology; Plant Root Cap - cytology; Plant Root Cap - growth & development; Plastids - physiology; REGENERACION; REGENERATION; RETICULO ENDOPLASMATICO; RETICULUM ENDOPLASMIQUE; ROOT CAP; Space Flight; STRUCTURE CELLULAIRE; TROPISME; TROPISMO; TROPISMS; Weightlessness; ZEA MAYS; Zea mays - cytology; Zea mays - growth & development; NASA Discipline Number 00-00; NASA Program Space Biology; NASA Discipline Number 40-10; NASA Program Flight; NASA Discipline Plant Biology; Non-NASA Center
• ISSN: 0002-9122; 1537-2197
• DOI: 10.1002/j.1537-2197.1987.tb08599.x

We launched imbibed seeds and seedlings of Zea mays into outer space aboard the space shuttle Columbia to determine the influence of microgravity on 1) root-cap regeneration, and 2) the distribution of amyloplasts and endoplasmic reticulum (ER) in the putative statocytes (i.e., columella cells) of roots. Decapped roots grown on Earth completely regenerated their caps within 4.8 days after decapping, while those grown in microgravity did not regenerate caps. In Earth-grown seedlings, the ER was localized primarily along the periphery of columella cells, and amyloplasts sedimented in response to gravity to the lower sides of the cells. Seeds germinated on Earth and subsequently launched into outer space had a distribution of ER in columella cells similar to that of Earth-grown controls, but amyloplasts were distributed throughout the cells. Seeds germinated in outer space were characterized by the presence of spherical and ellipsoidal masses of ER and randomly distributed amyloplasts in their columella cells. These results indicate that 1) gravity is necessary for regeneration of the root cap, 2) columella cells can maintain their characteristic distribution of ER in microgravity only if they are exposed previously to gravity, and 3) gravity is necessary to distribute the ER in columella cells of this cultivar of Z. mays.