Effects of light quality on apical dominance in Xanthium strumarium and the associated changes in endogenous levels of abscisic acid and cytokinins

Abstract

Apical dominance in Xanthium strumarium was influenced by the quality of illumination received at the end of the photoperiod. The involvement of the red/far-red regions of the spectrum was apparent. The persistence of the effects was partially dependent on the age of the individual buds concerned. Plants receiving 30 minutes of illumination from tungsten lamps after a 16-hour photoperiod from fluorescent tubes failed to branch, whereas plants given an identical photoperiod, both in terms of day-length and photosynthetically available light energy, but lacking the far-red from tungsten lamps, branched profusely.The influence of the spectral distribution of illumination on the levels of cytokinins and abseisic acid in the plant, and the correlation with the degree of branching, is presented and discussed. The cytokinin content was much higher in inhibited than released buds. The cytokinins present were probably not able to particinate in bud growth because of an accumulation of inhibitors resembling abscisic acid. The concentration of the inhibitors in inhibited buds was 50 to 250 times that occurring in all other plant parts examined.

Effects of Red and Far Red Light on the Initiation of Cold Acclimation in Cornus stolonifera Michx.

“…R and FR irradiation at the end-of-day, can also influence apical dominance (19, 3 1). levels of auxins, cytokinins and ABA (10,13,31), alkaloids, soluble phenols (30), free sugars and organic acids (18). Furthermore, far red light at the end of a long day may stimulate floral initiation in some short day plants (3,5,8,16).…”

Abscisic Acid Regulates Axillary Bud Outgrowth Responses to the Ratio of Red to Far-Red Light

“…ABA levels in dormant axillary buds of a variety of species have been observed to decrease in response to decapitation of the main shoot (Knox and Wareing, 1984;Gocal et al, 1991;Mader et al, 2003) and in response to fruit removal, a treatment that also promoted bud outgrowth (Tamas et al, 1979). Additionally, early work investigating the regulation of branching by the R:FR in Xanthium strumarium and tomato (Solanum lycopersicum) suggested that low R:FR promoted ABA accumulation while high R:FR reduced ABA levels and also permitted bud outgrowth (Tucker and Mansfield, 1972;Tucker, 1977). Although elevated ABA levels have often been shown to be associated with bud dormancy, there is little evidence demonstrating a direct role of endogenous ABA in regulating bud outgrowth in intact plants.…”

Abscisic Acid Is a General Negative Regulator of Arabidopsis Axillary Bud Growth

“…Studies using a wide variety of species showed that ABA abundance in buds negatively correlated with bud activity (Tucker and Mansfield, 1971;Tucker, 1977;Tamas et al, 1979;Knox and Wareing, 1984;Gocal et al, 1991;Mader et al, 2003). Exogenous ABA inhibited bud growth in pea (Arney and Mitchell, 1969), Arabidopsis (Chatfield et al, 2000), Ipomoea nil (Cline and Oh, 2006), and tomato (Solanum lycopersicum; Cline and Oh, 2006), while the carotenoid (and ABA) biosynthesis inhibitor fluridone promoted bud growth in Rosa hybrida (Le Bris et al, 1999).…”