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GROWTH PATTERNS IN NUTATING AND NONNUTATING SUNFLOWER (HELIANTHUS ANNUUS) HYPOCOTYLS
Author(s) -
Berg Arthur R.,
Peacock Kenneth
Publication year - 1992
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1992.tb12626.x
Subject(s) - hypocotyl , helianthus annuus , sunflower , seedling , biology , elongation , botany , relative growth rate , helianthus , gravitropism , growth rate , darkness , horticulture , materials science , geometry , biochemistry , mathematics , arabidopsis , gene , mutant , metallurgy , ultimate tensile strength
Dark‐grown sunflower ( Helianthus annuus L.) seedling hypocotyls (15–30 mm) were marked with two rows of lanolin‐coated resin beads, and the events of the following 24 hr, in physiological darkness, were recorded on time‐lapse video. Nutational movement of the hypocotyl, followed for 20–24 hr for each of 21 seedlings, was found to have a mean period of 153 ± 26 min (ca. 24 C). Displacement of each bead, with time, was measured with a microcomputer‐controlled video analyzer, and relative elemental elongation rate and relative growth rate analyses were carried out to determine the spatial and temporal distribution of growth. Relative elemental elongation rates were plotted against distance and time to produce “growth landscapes.” A strongly nutating seedling showed periodic fluctuations in local growth rates that alternated between values of 0.0 hr −‐1 and >0.12 hr −‐1 near the hypocotyl hook. Nearer the base, maximum growth rates were lower but local periodic changes still were evident. Seedlings, in which nutation appeared during the time period analyzed, showed non‐synchronous pulses of growth along the axis. With nutational development, these local growth fluctuations became synchronized along each side and phased (usually 180° out of phase) with the coordinated growth fluctuations along the opposite side. In some seedlings the changes from low to high local growth rates occur nearly simultaneously over two‐thirds of the active region. In others, basipetally traveling waves of growth are suggested by the growth landscapes.