Light controls shoot meristem organogenic activity and leaf primordia growth during bud burst in Rosa sp.

Abstract

Light controls bud burst in many plants, which subsequently affects their architecture. Nevertheless, very little is known about this photomorphogenic process. This study ascertains the effects of light on bud burst and on two of its components, i.e. growth of preformed leaves and meristem organogenesis in six cultivars from three Rosa species (R. hybrida L., R. chinensis L., R. wichurana L.). Defoliated plants were severed above the third basal bud and exposed, either to darkness or to different intensities of white light, to blue, red or to FR, at constant temperature. Bud bursting was inhibited in darkness in the six cultivars of Rosa, but not in Arabidopsis, tomato and poplar plants under the same condition. In all Rosa cultivars, bud burst, growth of preformed leaves and meristem organogenesis were triggered by blue and red lights, and extended by increasing light intensities. FR was inhibitory of bud burst. Partial shading experiments demonstrated that bud and not stem was the active site for light perception in bud burst.

Cytokinins Are Initial Targets of Light in the Control of Bud Outgrowth

“…Such a signaling role for light is well described in the shadeavoidance syndrome, where perception by plant phytochromes (mainly phyB) of a low R/FR leads to bud inhibition even under a promoting photosynthetic photon flux density (Kebrom et al, 2006;Reddy et al, 2013). A signaling role for light in the triggering of bud outgrowth also was suggested in rose (Girault et al, 2008). In this species, bud outgrowth is inhibited within a few hours of dark exposure in rose plants first grown under white light (WL) and, thus, rich in sugars.…”

“…In this species, bud outgrowth is inhibited within a few hours of dark exposure in rose plants first grown under white light (WL) and, thus, rich in sugars. Yet, as low an intensity of WL as 2 mmol m 22 s 21 , which is far below the light compensation point of rose plants (40-70 mmol m 22 s 21 , according to Zieslin and Tsujita, 1990;Ueda et al, 2000), is sufficient to trigger their outgrowth (Girault et al, 2008). This suggests that, in rose plants too, the triggering of bud outgrowth requires a light signal that is different from the energy supply involved in photosynthetic assimilation.…”

“…In rose (Rosa hybrida) plants, darkness or far-red light (used as a single source of light) represses bud outgrowth (Girault et al, 2008). Even when buds are freed from apical dominance after decapitation, rose buds never grow out under such light conditions, and bud meristem organogenesis is inhibited (Girault et al, 2008).…”

“…A low light intensity or a low ratio of red/far-red (R/FR) light inhibits bud outgrowth and modulates the correlative inhibitions between buds in some species (Kebrom et al, 2006;Finlayson et al, 2010;Su et al, 2011;Demotes-Mainard et al, 2013;Furet et al, 2014;Drummond et al, 2015). In rose (Rosa hybrida) plants, darkness or far-red light (used as a single source of light) represses bud outgrowth (Girault et al, 2008). Even when buds are freed from apical dominance after decapitation, rose buds never grow out under such light conditions, and bud meristem organogenesis is inhibited (Girault et al, 2008).…”

Evaluation of Flowering Pattern, Yield and Yield Determinants of Hybrid Tea Rose in Response to Seasonal Variations and Applied Organic Manure Rates

“…Baby" was more prolific with increasing margin in flowering behaviour in experiment I but the "Immaculate" was triggered to produce more flowers in experiment II thereby reducing the margin of differences between both cultivars to a level of no significant difference. Earlier reports have stated that light quality affects morphogenesis and overall appearance of rose plants, where an increased red/far red ratio in roses reduced plant height and increased leaf chlorophyll content [36] and the number of flowers [37] [38]. In addition several plant species including roses which have leaves with different visual appearance [39]- [41], have red leaves containing higher concentration of anthocyanins which showed slightly higher absorptance of green light compared to the green leaves, hence the differences in absorptance of green light were attributed to the contribution of varying levels of anthocyanins in such leaves [42] [43].…”