Seasonal Dynamics of Shoot Growth in Forsythia ovata Nakai Plants: Rhythmicity of Apical and Radial Growth

• Published in: Biology bulletin reviews Vol. 14; no. 1; pp. 85 - 95
• Main Authors: Shavnin, S. A., Montile, A. A., Semkina, L. A., Montile, A. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2024; Springer Nature B.V
• Subjects: Air temperature; Biochemistry; Biomedical and Life Sciences; Cell Biology; Cell division; Ecology; Environmental conditions; Flowering; Forsythia ovata; Genotypes; Growth rate; Introduced species; Life Sciences; Meristems; Ornamental plants; Oscillations; Seasonal variations; Shoots; Woody plants; Zoology
• DOI: 10.1134/S2079086424010092
• ISSN: 2079-0864

The aim of the study was to establish the nature (linear or nonlinear) and shape (presence of extremes and trends) of time dependences of apical and radial growth rates for shoots of two types (branching and formation) in woody plants using the example of an ornamental early-flowering shrub species introduced in the Middle Urals Forsythia ovata Nakai. The seasonal dynamics of morphometric parameters of shoots differing in growth intensity and origin (growing from the apical and dormant buds of the skeletal branch) were studied, and their relationship to air temperature and precipitation values was assessed. Both types of growth are accompanied by oscillations of increments, the duration of individual phases of which is about 7 days or more, which allows us to attribute this phenomenon to infradian growth rhythms. The weak relationship between the characteristics of the observed oscillations and weather conditions indicates the predominantly endogenous nature of the morphogenetic processes that determine them. The growth of formation shoots begins 4 weeks later than branching shoots, which is apparently associated with the time necessary for the activation of dormant bud growth. Seasonal dynamics curves of the rates and accelerations of apical and radial growth of shoots have the form of oscillations with phases decaying in amplitude and varying in duration that have not been observed before, which ends 1–2 months before the onset of unfavorable environmental conditions for growth. The processes that cause changes in the rate of shoot growth are apparently associated with the action of two or more differently directed factors that determine the characteristics and temporal stipulation for the increase in the volume of different shoot segments (including the different contribution of cell division and elongation to changes in the geometric dimensions of the apical meristem domains). In both types of shoots, there are differences in the seasonal dynamics of the apical and radial increments in terms of the growth duration (6–8 and 4 weeks, respectively), the number of extremes, and the amplitude and duration of individual phases of oscillations. The curves of the dynamics of the apical growth rates have two maxima, and those of the radial growth have only one. Each type of growth, despite the delay in its onset in the formation shoots, has the same total duration in different types of shoots, and the shapes of the curves of seasonal changes in rates and accelerations in different types of shoots are similar. The similarity of the curve shapes of the seasonal dynamics of individual growth types in different types of shoots indicates the presence of identical growth regulation programs in the shoots, ultimately determined by the genotype, which are manifested in the observed oscillations. The growth rhythmicity of both types of shoots during the season allows us to assume the existence of a temporal relationship between the rates of division and growth of individual cells located in functionally different groups of cells in the apex zone. The differences of dynamics in different types of shoots are that the amplitude of oscillations is higher in formation shoots than in branching shoots. This feature explains the well-known fact of higher values of their total increments.