Root graviresponsiveness in normal and carotenoid-deficient mutant seedlings of Zea mays was not significantly different. Columella cells in roots of mutant seedlings were characterized by fewer, smaller, and a reduced relative volume of plastids as compared to columella cells of normal seedlings. Plastids in columella cells of mutant seedlings possessed reduced amounts of starch. Although approximately 10 per cent of the columella cells in mutant seedlings lacked starch, their plastids were located at the bottom of the cell. These results suggest that (i) carotenoids are not necessary for root gravitropism, (ii) graviresponsiveness is not necessarily proportional to the size, number, or relative volume of plastids in columella cells, and (iii) sedimentation of plastids in columella cells may not result directly from their increased density due to starch content. Plastids in columella cells of normal and mutant seedlings were associated with bands of microtubule-like structures, suggesting that these structures may be involved in 'positioning' plastids in the cell.
|Original language||English (US)|
|Number of pages||8|
|Journal||Annals of Botany|
|State||Published - Jul 1985|
Bibliographical noteFunding Information:
This research was supported by grants from NASA and the University Research Committee of Baylor University. I thank Professor James D. Smith for kindly providing the vp-9 mutants used in this study.
- Columella cell
- Vp-9 mutant
- Zea mays