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Interaction of gibberellins and phytochrome in the control of cowpea epicotyl elongation
Author(s) -
MartínezGarcía Jaime F,
GarcíaMartínez José L.
Publication year - 1992
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1992.860208.x
Subject(s) - epicotyl , elongation , gibberellin , phytochrome , vigna , etiolation , biophysics , biology , botany , explant culture , horticulture , chemistry , hypocotyl , biochemistry , in vitro , enzyme , materials science , red light , metallurgy , ultimate tensile strength
The physiological response of cowpea ( Vigna sinensis L.) epicotyl explants to far‐red light (FR) and its interaction with gibberellins (GAs) have been investigated. The effect of FR and GA 1 varied with the age of the seedlings from which the explants were made: for FR, it decreased progressively with age (though the sensitivity of the epicotyls to FR did not change significantly until at least day 11), whereas it remained essentially constant for applied GA 1 between days 5 and 9 after sowing. This indicates that the loss of response to FR may be due to a decrease in endogenous GA levels in the epicotyl. For a range of GA 1 and GA 20 (0.01–1 µg explant −1 ), both hormones were more active in FR than in R irradiated epicotyls, suggesting that phytochrome may affect GA sensitivity besides GA metabolism. The location of the epicotyl region most sensitive to FR (between 5 and 20 mm below the apex) was different from that to GAs (the upper 10 mm). Nevertheless, FR extended the region responsive to applied GAs, even in paclobutrazol‐treated epicotyls where elongation was due entirely to exogenous GAs. This means that modulation of epicotyl elongation by phytochrome, that occurs in a zone different from though overlapping with the GA‐sensitive subapical zone, is also mediated by GAs. Growth in the most FR‐sensitive region of the epicotyl stimulated by FR or GA 1 was due to cell elongation, and in the most GA‐sensitive region to both cell division and elongation. The effect of FR and GA 1 was negated by colchicine, indicating that microtubules may be involved in the response to both factors.