Deciphering the developmental plasticity of walnut saplings in relation to climatic factors and light environment

Abstract

Developmental plasticity, the acclimation of plants to their local environment, is known to be crucial for the fitness of perennial organisms such as trees. However, deciphering the many possible developmental and environmental influences involved in such plasticity in natural conditions requires dedicated statistical models integrating developmental phases, environmental factors, and interindividual heterogeneity. These models should be able to analyse retrospective data (number of leaves or length of annual shoots along the main stem in the present case). In this study Markov switching linear mixed models were applied to the analysis of the developmental plasticity of walnut saplings during the establishment phase in a mixed Mediterranean forest. In the Markov switching linear mixed models estimated from walnut data sets, the underlying Markov chain represents both the succession and lengths of growth phases, while the linear mixed models represent both the influence of climatic factors and interindividual heterogeneity within each growth phase. On the basis of these integrative statistical models, it is shown that walnut saplings have an opportunistic mode of development that is primarily driven by the changing light environment. In particular, light availability explains the ability of a tree to reach a phase of strong growth where the first branches can appear. It is also shown that growth fluctuation amplitudes in response to climatic factors increased while interindividual heterogeneity decreased during tree development.

Morphoanatomy and ecophysiology of tree seedlings in semideciduous forest during high-light acclimation in nursery

“…The higher RGR of C. pachystachya seedlings under shade compared to the acclimated seedlings resulted from the maximisation of vertical growth, a behaviour exhibited by several light-demanding species in the understory (Henry and Aarssen 2001, Taugourdeau et al 2011, Valladares et al 2012. However, the increases in height and stem diameter were not proportional (Table 3), thus the acclimated seedlings of C. pachystachya had a lower H/D ratio, as also verified in C. speciosa in this study, and in other species by Gratzer et al (2004).…”

Identifying developmental phases in the Arabidopsis thaliana rosette using integrative segmentation models

“…Semi-Markov switching models for identifying developmental or growth phases in various plants species described at different scales Semi-Markov switching models are flexible models that were previously applied to identify and characterize developmental or growth phases in plants described at various scales. They were first used to identify growth phases in different forest tree species (Corsican pine, Scots pine, silver fir, Persian walnut, sessile oak) where the main stems were described retrospectively by annual shoots (Gu edon et al, 2007;Chaubert-Pereira et al, 2009;Taugourdeau et al, 2011Taugourdeau et al, , 2015. The observation models within Semi-Markov switching models were typically various distributions for modeling dimensions (annual shoot length) or counts (number of branches per tier for pines and silver fir, number of growth units for sessile oak).…”

“…The observation models within Semi-Markov switching models were typically various distributions for modeling dimensions (annual shoot length) or counts (number of branches per tier for pines and silver fir, number of growth units for sessile oak). More sophisticated observation models and in particular linear mixed models were also incorporated in semi-Markov switching models to model the influence of climatic factors on annual shoot characteristics and interindividual heterogeneity within growth phases (Chaubert-Pereira et al, 2009;Taugourdeau et al, 2011). Growth phases were also identified in mango vegetative growth units and inflorescences using semi-Markov switching models (Dambreville et al, 2015).…”

Retrospective analysis of tree architecture in silver fir (Abies alba Mill.): ontogenetic trends and responses to environmental variability

“…A retrospective analysis of growth can identify three main kinds of variation around this trajectory: (1) breaks due to the establishment of relay axes replacing dead axes; (2) inter-annual growth fluctuations linked with climate: see following section; (3) speed of the move along the trajectory (i.e. developmental plasticity) which may change and may be related to resource limitations (Yagi 2009;Barthélémy et al 2010;Taugourdeau et al 2011).…”

“…Alternatively, the effects of climatic events such as drought can be analysed by comparing growth variables for structures that developed at the same time (Chaubert-Pereira et al 2009). Also, the vigour of individual trees can be compared in order to assess the impact of different growing conditions (Taugourdeau et al 2011).…”