Cytokinins and Abscisic Acid Act Antagonistically in the Regulation of the Bud Outgrowth Pattern by Light Intensity

Abstract

Bud outgrowth is a key process in the elaboration of yield and visual quality in rose crops. Although light intensity is well known to affect bud outgrowth, little is known on the mechanisms involved in this regulation. The objective of this work was to test if the control of bud outgrowth pattern along the stem by photosynthetic photon flux density (PPFD) is mediated by sugars, cytokinins and/or abscisic acid in intact rose plants. Rooted cuttings of Rosa hybrida ‘Radrazz’ were grown in growth chambers under high PPFD (530 μmol m-2 s-1) until the floral bud visible stage. Plants were then either placed under low PPFD (90 μmol m-2 s-1) or maintained under high PPFD. Bud outgrowth inhibition by low PPFD was associated with lower cytokinin and sugar contents and a higher abscisic acid content in the stem. Interestingly, cytokinin supply to the stem restored bud outgrowth under low PPFD. On the other hand, abscisic acid supply inhibited outgrowth under high PPFD and antagonized bud outgrowth stimulation by cytokinins under low PPFD. In contrast, application of sugars did not restore bud outgrowth under low PPFD. These results suggest that PPFD regulation of bud outgrowth in rose involves a signaling pathway in which cytokinins and abscisic acid play antagonistic roles. Sugars can act as nutritional and signaling compounds and may be involved too, but do not appear as the main regulator of the response to PPFD.

Sugar availability suppresses the auxin-induced strigolactone pathway to promote bud outgrowth

“…Surprisingly, we found little evidence that cytokinin levels mediate the antagonistic effect of sugar to auxin. Cytokinins are positive endogenous signals responsible for the stimulation of tissue sink strength (Roitsch & Ehness, 2000; Werner et al , 2008; Roman et al , 2016a) and of bud outgrowth by light or nitrogen nutrition (Takei et al , 2002; Kamada-Nobusada et al , 2013; Roman et al , 2016b; Corot et al , 2017). Sugars stimulate cytokinin biosynthesis and/or level in different physiological processes (Barbier et al , 2015b for review).…”

Sugar availability suppresses the auxin‐induced strigolactone pathway to promote bud outgrowth

“…As shown in Fig. 4c, plants were partially defoliated and vascularly supplied with GR24 (5 µM) 1 cm below the second downmost node, as described in Corot et al (2017). Partial defoliation consisted of removing four out of the five leaflets at each node.…”

“…Surprisingly, we found little evidence that cytokinin levels mediate the antagonistic effect of sugar to auxin. Cytokinins are positive endogenous signals responsible for the stimulation of tissue sink strength (Roitsch & Ehness, 2000;Werner et al, 2008;Roman et al, 2016) and of bud outgrowth by light or nitrogen nutrition (Takei et al, 2002;Kamada-Nobusada et al, 2013;Roman et al, 2016;Corot et al, 2017). Sugars stimulate cytokinin biosynthesis and/or levels under different physiological processes (Barbier et al, 2015b for review).…”

Non-structural Carbohydrates in Dormant Woody Perennials; The Tale of Winter Survival and Spring Arrival

“…Other research suggests that phloem sieve tubes can remain active at temperatures below −10 • C (Fisher, 1983). Because analyzing functional phloem is technically challenging, our current knowledge relies upon only a few classical studies, which are now being challenged and complemented by advances in molecular biology and with the popular use of isotopes (Knoblauch and van Bel, 1998;Tarkowski and Van den Ende, 2015;Corot et al, 2017).…”