Growth phenology in Pinus halepensis Mill.: apical shoot bud content and shoot elongation
The chronology of periods of organogenesis and elongation is highlighted in Pinus halepensis.The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year.
Analysis of annual shoot length growth phenology is crucial to assess the impact of climate change on tree production. Little is known about the basic growth characteristics and the phenology of pines.
The present study disentangles the roles of shoot organogenesis vs elongation in the annual growth cycle of the polycyclic Aleppo pine.
Growth of young Pinus halepensis trees was monitored monthly for 1 year. At each monitoring date, the bud content and meristem dimensions of the main stem shoots apices were analyzed.
The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year. The gap between a shoot organogenesis and its elongation may vary from 1 month, for the last growth unit, to half a year, for the first growth units.
Our results underline the importance of taking seasonal environmental conditions from both the previous and the current year into account, in order to study the plasticity of annual shoot growth and its response to climate change and variability.
KeywordsPolycyclic pine Shoot apical meristem Annual shoot Plant architecture
We thank JL Verdeil and F Montes for help with histological work, and M Lartaud for computer plugins in ImageJ software (PHIV, CIRAD, Montpellier).
This work was supported by funds from the “Adaptation of agriculture and forests to climate change, Assessing of the potential of forest adaptation to climate change project” (INRA-ACCAF FORADAPT Project), from the Botany and Computational Plant Architecture joint research unit (UMR AMAP), from the National Research Institute of Science and Technology for Environment and Agriculture (Irstea) and the Provence–Alpes–Côte d’Azur region (F Buissart's PHD grant).
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