Hydraulic architecture correlates with bud organogenesis and primary shoot growth in beech (Fagus sylvatica)

Abstract

In beech (Fagus sylvatica L.), the number of leaf primordia preformed in the buds determines the length and the type (long versus short) of annual growth units, and thus, branch growth and architecture. We analyzed the correlation between the number of leaf primordia and the hydraulic conductance of the vascular system connected to the buds. Terminal buds of short growth units and axillary buds of long growth units on lower branches of mature trees were examined. Buds with less than four and more than five leaf primordia formed short and long growth units, respectively. Irrespective of the type of growth unit the bud was formed on, the occurrence of a large number of leaf primordia was associated with high xylem hydraulic conductance. Xylem conductance was correlated to the area of the outermost annual ring. These results suggest that organogenesis and primary growth in buds correlates with secondary growth of the growth units and thus with their hydraulic architecture. Possible causal relationships between the variables are discussed.

Are marginal beech (Fagus sylvatica L.) provenances a source for drought tolerant ecotypes?

“…Due to its great economic importance in European forestry, much research has recently focused on the drought response of juvenile and adult beech plants and the mechanisms of drought tolerance of this species (e.g., Grossoni et al 1998;Peuke and Rennenberg 2004;Löf et al 2005;Meier and Leuschner 2008a, b). In comparison to other Central European broadleaved tree species, a sensitivity of beech upon drought was found particularly with respect to embolism in its conducting system (Cochard et al 2005), stem increment reduction in dry summers, pre-senescent leaf shedding in drought periods (Granier et al 2007), and a reduced Wne root biomass in dry soil (Meier and Leuschner 2008c). In addition, beech seedlings were also found to be sensitive to dry air (Lendzion and Leuschner 2008).…”

Bud development and hydraulics: An innovative way to forecast shoot architecture

“…5,6 Cochard et al 7 in Fagus confirmed that paralleling this acrotonic gradient there is an increase in the hydraulic conductance of the xylem sap pathway to the bud (K LAT ) prior to bud burst. Two recent works in a range of apple (Malus domestica) cultivars with contrasted shoot architectures suggest that this relationship is localized, i.e., at the level of each individual bud.…”

Simulation of morphogenetical gradients using a minimal functional-structural plant model (FSPM)

“…We assume that assimilated carbon is allocated according to common pool hypothesis and sink/source balance [18]. At this step the carbon is split between a global primary growth compartment and a global secondary growth compartment.…”

“…These assumptions exclude any preferential allocation, neither due to proximity [18] nor due to growth strategy [20]. No references were found about the biomass partitioning between primary and secondary growth at whole-tree scale.…”

“…It is arbitrarily set to 1 for all Gus of the trunk and, for other axes, is computed according to bearer Gu base demand (Fig. 1), apical dominance (parameter DA) and bearer Gu's ring crosssectional area to take conduction features into account [18]. The corresponding simulated tree mock-ups are provided on the right.…”