Insights into Bud Development and Dormancy in Poplar

Abstract

Dormancy is a survival strategy that enables plants or plant parts to grow synchronized with seasons and to endure periods that are unfavorable for growth. In addition, dormancy can be imposed upon plant organs to control the architecture of the whole plant in ways that are advantageous for growth and survival. Because bud dormancy is utilized for both adaptive and morphogenetic reasons, trees can adapt to a wide range of growth conditions while developing their characteristic form. Here, we will refer to dormancy as the temporary absence of visible growth of any plant structure containing a meristem (Lang, 1987).Depending on species, organ, and ontogeny, bud dormancy may include cessation of shoot extension, formation of the bud, formation of embryonic leaves inside the bud, arrest of meristematic activity, entry into dormancy, increase in drought resistance, leaf fall, and acquisition of frost resistance. Once dormancy has been imposed, no apparent changes in bud morphology can be observed. Nonetheless, metabolic changes are continuous, because when chilling temperature is perceived dormancy is released gradually. Finally, growth resumes when the environmental conditions are favorable.Dormancy is best described and regarded as a developmental process (as much as active growth is). The type, intensity, and duration of dormancy in a given organ is determined by its previous ontogeny and the dormancy-triggering process. The notion of dormancy as a developmental process (and not a state) implies that it consists of many interrelated subprocesses. The systematic dissection of the dormancy process into subprocesses may, in the end, give us a basis to distinguish mechanisms that are active during the different periods of this developmental process.Here, we will focus on the morphological events that occur at the onset of dormancy in photoperiodically-determined species. We will give a short survey on organogenesis during active growth and introduce the molecular network that controls meristem function 33 S.

A Molecular Timetable for Apical Bud Formation and Dormancy Induction in Poplar

“…To generate a bud, primordium differentiation is directed, immediately after SD perception, to bud scales and embryonic leaves instead of foliage leaves (Rohde and Boerjan, 2001). This process is initiated from the first primordium originating in SDs onward and, therefore, must be initiated downstream of the photoperiodic signal.…”

“…SDs trigger the cessation of internode elongation and the transition from a growing apex to a bud. The morphology of the apex is transformed to a bud through sequential changes in the differentiation of young primordia: first, toward enveloping bud scales, and then to embryonic leaves (Rohde and Boerjan, 2001).…”

Environment and position of first bud to break on apple shoots affects lateral outgrowth

“…is defined according to the location, type (vegetative or reproductive), and length of lateral shoots, and is derived from the activity of apical meristems. Apical meristems in the terminal position (terminal buds) provide the 'parent shoot' or main axis as well as give rise to leaves and axillary meristems which may (syllepsis, or immediate growth) or may not (prolepsis, or delayed growth) grow out in the year that they are formed (Barthélémy and Caraglio 2007;Bell 1991;Hallé et al 1978;Rohde and Boerjan 2001). As lateral proleptic buds, apical buds provide the lateral shoots that define branch architecture.…”

“…As lateral proleptic buds, apical buds provide the lateral shoots that define branch architecture. In this article, we understand meristems, buds and shoot types as defined in Bell (1991) and Rohde and Boerjan (2001). Branch architecture depends on the positional and temporal competitions (dominance) among meristems, buds and lateral shoots along the main axis (Bell 1991).…”