Abstract
Single-flower cut Chrysanthemum (Dendranthema grandiflorum ‘Jinba’) holds a unique status in global floriculture industry. However, the extensive axillary bud outgrowth presents a major drawback. Shade is an environment cue that inhibits shoot branching. Present study was aimed at investigating the effect of ratio of red to far-red light (R:FR) in regulating the lateral bud outgrowth of Chrysanthemum and the detailed mechanism. Results showed that the fate of axillary buds at specific positions in stem exhibited difference in response to R:FR. Decreasing R:FR resulted in elevation of abscisic acid (ABA) accumulation in axillary buds. Expression of ABA, indole-3-acetic acid (IAA) and strigolactones (SL) -related metabolism and signal transduction genes was significantly changed in response to low R:FR. In addition, low R:FR caused the re-distribution of sucrose across the whole plant, driving more sucrose towards bottom buds. Our results indicate that low R:FR not always inhibits bud outgrowth, rather its influence depends on the bud position in the stem. ABA, SL and auxin pathways were involved in the process. Interestingly, sucrose also appears to be involved in the process which is necessary to pay attention in the further studies. The present study also lays the foundation for developing methods to regulate axillary bud outgrowth in Chrysanthemum.
Highlights
Escalation and development of lateral branches are the major determinants of diverse shoot architectures, and this plastic trait is controlled by genetic and environmental regulators, and the interactive effect of both
Our results indicated that the fate of axillary buds at specific positions in stem exhibited different response to R:FR, low R:FR not always inhibit bud outgrowth but its influence depends on the bud position in the stem in Chrysanthemum
When the plants were grown in low R:FR and high R:FR throughout the development stage, separately, the upper bud length of plants that grown in low R:FR was much shorter than the plants grown in high R:FR
Summary
Escalation and development of lateral branches are the major determinants of diverse shoot architectures, and this plastic trait is controlled by genetic and environmental regulators, and the interactive effect of both. PhyB deficiency and low R:FR are considered to be the major inhibitors of branching in A. thaliana by influencing the genetic expressions and pathways relating to bud kinetics [6,7,11,17]. Through polar auxin transport, restricts bud outgrowth indirectly, not entering the lateral buds This inhibitory effect of upper shoots on lower branches is a type of correlative inhibition called apical dominance. The ABA has been considered the inhibitor of bottom buds under both low and high red to far-red light ratios and may suppress the cell cycle associated genes expression [45]. In this study the Chrysanthemum bud growth responses to ratio of red to far-red light were defined in association with hormonal and genetic pathways. The present study lays the foundation for using R:FR to regulate axillary bud outgrowth in Chrysanthemum
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