Hydrotropism and its interaction with gravitropism in maize roots

• Published in: Plant physiology (Bethesda) Vol. 96; no. 2; pp. 558 - 564
• Main Authors: Takahashi, Hideyuki, Scott, Tom K.
• Format: Journal Article
• Language: English
• Published: Headquarters American Society of Plant Physiologists 1991
• Subjects: Bending; Biological and medical sciences; Corn; Curvature; Darkness; Fundamental and applied biological sciences. Psychology; genetic variation; Gravitropism; Gravitropism - physiology; Humidity; Hydrotropism; Life Sciences (General); Light; Physical agents; Plant physiology and development; Plant Root Cap - physiology; Plant roots; Plant Roots - growth & development; Plants; racine; raices; Root tips; roots; Space life sciences; Tropism - physiology; tropisme; tropismo; Tropisms; variacion genetica; variation genetique; variedades; variete; varieties; Vegetative apparatus, growth and morphogenesis. Senescence; Water; zea mays; Zea mays - growth & development; Nasa Program Space Biology; Nasa Discipline Plant Biology; Non-Nasa Center; Nasa Discipline Number 40-50; Tropism; Monocotyledones; Zea mays; Root; Gramineae; Growth; Angiospermae; Humidity; Instrumentation; Spermatophyta; Cereal crop; Gravity; NASA Program Space Biology; NASA Discipline Number 40-50; NASA Discipline Plant Biology; Non-NASA Center
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.96.2.558

We have partially characterized root hydrotropism and its interaction with gravitropism in maize (Zea mays L.). Roots of Golden Cross Bantam 70, which require light for orthogravitropism, showed positive hydrotropism; bending upward when placed horizontally below a hydrostimulant (moist cheesecloth) in 85% relative humidity (RH) and in total darkness. However, the light-exposed roots of Golden Cross Bantam 70 or roots of a normal maize cultivar, Burpee Snow Cross, showed positive gravitropism under the same conditions; bending downward when placed horizontally below the hydrostimulant in 85% RH. Light-exposed roots of Golden Cross Bantam 70 placed at 70 degrees below the horizontal plane responded positively hydrotropically, but gravitropism overcame the hydrotropism when the roots were placed at 45 degrees below the horizontal. Roots placed vertically with the tip down in 85% RH bent to the side toward the hydrostimulant in both cultivars, and light conditions did not affect the response. Such vertical roots did not respond when the humidity was maintained near saturation. These results suggest that hydrotropic and gravitropic responses interact with one another depending on the intensity of one or both factors. Removal of the approximately 1.5 millimeter root tip blocked both hydrotropic and gravitropic responses in the two cultivars. However, removal of visible root tip mucilage did not affect hydrotropism or gravitropism in either cultivar.