Phytochrome control of short‐day‐induced bud set in black cottonwood

Abstract

G, R, 1996, Phytochrome control of short-day-induced bud set in black cottonwood, -Physiol. In trees and other woody perennial plants, short days (SDs) typically induce growth cessation, the initiation of cold acclimation, the formation of a terminal bud and bud dormancy, Phytochrome control of SD-induced bud set was investigated in two northem clones of black cottonwood (Populus trichocarpa Torr, & Gray) by using night breaks with red light (R) and far-red light (FR), Eor both clones (BC-1 and BC-2), SD-induced bud set was prevented when R night breaks as short as 2 min were given in the middle of the night. When night breaks with 2 min of R were immediately followed by 2 min of ER, substantial reversibility of bud set was observed for BC-1 but not for BC-2, By comparing the effects of the R night breaks on bud set and the length of specific internodes, we determined that the R night breaks influenced intemode elongation in two opposing ways, Eirst, the addition of a R night break to the SD treatment prevented the cessation of intemode elongation that is associated with bud set. Those intemodes that would not have elongated under SDs (and would have been found within the terminal bud) elongated in the R treatment. Second, the R night breaks decreased intemode length relative to the long-day (LD) control. In contrast to the clonal differences in reversibility that we observed for bud set, the decrease in intemode length (i,e. the second effect of R) was R/FR reversible in both clones. Based on these results, we conclude that intemode elongation is influenced by two distinct types of phytochrome-mediated response. The first response is a typical response to photoperiod, whereas the second response is a typical "end-of-day" resptmse to light quality. Our results demonstrate that SD-induced bud set in black cottonwood is controlled by phytochrome but that clonal differences have an important influence on the R/FR reversibility of this response. The availability of an experimental system in which SD-induced bud set is R/FR reversible will be valuable for studying the physiological genetics of photoperiodism in trees.

Photoperiod‐ and temperature‐mediated control of phenology in trees – a molecular perspective

“…Experiments in which exposure to short days induce growth cessation and bud set demonstrate the involvement of photoperiodic signals in these processes, and findings that interrupting long nights by short pulses of light reverse SD induction of growth in poplar (Howe et al ., ) clearly suggest the involvement of the circadian clock in the photoperiodic control of growth in trees. Such physiological indications of photoperiodic controls in tree growth (Nitsch, ) have recently been complemented with explorations of the molecular basis of the mechanisms involved, especially in the model organisms poplar (Olsen et al ., ; Bohlenius et al ., ; Hsu et al ., ; Takata et al ., , ; Ibanez et al ., ; Karlberg et al ., ; Azeez et al ., ; Tylewicz et al ., ), spruce (Gyllenstrand et al ., , ; Karlgren et al ., ) and peach (Li et al ., ).…”

“…The involvement of phytochrome photoreceptors in the control of SD‐mediated growth cessation and bud set in poplar has been demonstrated in several studies (Howe et al ., ; Olsen et al ., ; Kozarewa et al ., ). Olsen et al .…”

Exome resequencing reveals signatures of demographic and adaptive processes across the genome and range of black cottonwood (Populus trichocarpa)

“…, ), which is consistent with the role of phytochromes and circadian clock‐associated genes in regulating seasonal dormancy (Howe et al . ; Olsen et al . ; Bohlenius et al .…”

Low night temperature and inhibition of gibberellin biosynthesis override phytochrome action and induce bud set and cold acclimation, but not dormancy in PHYA overexpressors and wild‐type of hybrid aspen

“…1997b). Photoperiodic regulation of growth in trees is believed to be dependent on the function of the phytochrome system in detecting night‐length (Howe et al . 1996) and light quality (Håbjørg 1972a; Junttila & Kaurin 1985; Clapham et al .…”