Analysing branching pattern in plantations of young red oak trees (Quercus rubra L., Fagaceae) - PubMed (original) (raw)

Analysing branching pattern in plantations of young red oak trees (Quercus rubra L., Fagaceae)

Patrick Heuret et al. Ann Bot. 2003 Mar.

Abstract

Branching patterns of the growth units of monocyclic or bicyclic annual shoots on the main axis of 5-year-old red oaks were studied in a plantation in south-western France. For each growth unit, the production of axillary structures associated with each node was described in the form of a sequence. For a given category of growth units, homogeneous zones (i.e. zones in which composition in terms of type of axillary production does not change substantially) were identified on such sequences using a dedicated statistical model called a hidden semi-Markov chain. For instance, on the first growth unit of bicyclic annual shoots, a zone with 1-year-delayed branches was found systematically below a zone with buds and one-cycle-delayed branches. Branching patterns shown by the growth unit of monocyclic annual shoots and on the second growth unit of bicyclic annual shoots were very similar. Branches with a 1-year delay in development tended to be polycyclic at the top of the growth unit and monocyclic lower down. The number of nodes shown by the branched zone of the growth unit of monocyclic annual shoots was stable, irrespective of the total number of nodes of the growth unit. In contrast, the second growth unit of bicyclic annual shoots exhibited a correlation between the number of nodes in the branching zone and the total number of nodes. The contribution made by this method to understanding plant functioning is discussed.

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Figures

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Fig. 1. Structure of a red oak growth unit and description of the different scars. a.c, Apical cataphylls; i.c, intermediate cataphylls; l, leaves; b.c, basal cataphylls; c.r, cataphylls in ring; t.b, terminal bud; l.b, lateral bud; l.s, leaf (or leaf scar); s.s, stipule (or stipule scar).

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Fig. 2. Different types of branches were considered in the construction of branching sequences for growth units of monocyclic annual shoots (GU.mono; A), and first (GU.bi1) and second (GU.bi2) growth units of bicyclic annual shoots (B). One‐cycle‐delayed branches (1) were found solely on GU.bi1, while 1‐year‐delayed mono‐ (2) or polycyclic (3) branches were found on all types of GU. Short line represents intra‐annual interruption of growth; two short lines represent interannual interruption of growth.

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Fig. 3. A, Descriptions of axillary production distributions on three growth units (measured on GU.bi1 in this example) in the form of sequences of events. Coded elements include: bud (0); one‐cycle‐delayed branch (1); 1‐year‐delayed monocyclic (2) and 1‐year‐delayed polycyclic branch (3). Values are indexed according to the rank of the node bearing the branch, taken from the tip to the base of the growth unit. B, ‘Intensity’: the frequency of different events (i.e. bud, one‐cycle‐delayed branches or 1‐year‐delayed monocyclic and polycylic branches) is extracted for the different positions (node rank) along the growth unit from the apex. C, ‘Interval’ (time until the first occurrence, recurrence time, sojourn time) and ‘Counts’ (number of occurrences or number of runs per sequence) can be extracted for specific events.

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Fig. 4. A, Example of three sequences (measured on GU.bi1 in this example) divided into zones on the basis of a hidden semi‐Markov chain. The different model parameters are shown (initial probabilities, transition probabilities, sojourn time distribution, observation probabilities). B, Hidden semi‐Markov chain estimated from GU.bi1.

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Fig. 5. Correlation between the total number of nodes and the length (in cm) of the growth unit, the total number of branches borne by the growth unit and its length (in cm), and the total number of branches borne by the growth unit and its total number of nodes for GU.mono (A and B), GU.bi1 (C and D) and GU.bi2 (E and F).

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Fig. 6. Hidden semi‐Markov chain estimated from GU.mono branching sequences.

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Fig. 7. Hidden semi‐Markov chain estimated from GU.bi2 branching sequences.

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Fig. 8. Probability of the different types of axillary production in relation to node rank (‘intensity’) for GU.mono (A), GU.bi1 (B) and GU.bi2 (C). The cumulative distribution function of sequence length (directly deduced by summation of the frequency distribution) is shown as a dotted curve. obs., Observed; theor., theoretical.

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Fig. 9. Sojourn time distributions for 1‐year‐delayed monocyclic (A) and polycyclic (B) branches on GU.bi2; time until first occurrence for one‐cycle‐delayed (C) and 1‐year‐delayed (D) monocyclic branches on GU.bi1; number of occurrences per sequence distribution for one‐cycle‐delayed (E) and one‐year‐delayed (F) monocyclic branches on GU.bi1.

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Fig. 10. Hidden semi‐Markov chain estimated from the branching sequences of GU.mono (A), GU.bi1 (B) and GU.bi2 (C). The different types of branch are not differentiated, and only the branched/unbranched pattern is taken into account.

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Fig. 11. Correlation between the number of nodes in segmented zones corresponding to states A (apical unbranched zone), B (median branched zone) and C (basal unbranched zone) of the models in Fig. 10, with the total number of nodes in the growth unit considered for GU.mono (A), GU.bi1 (B) and GU.bi2 (C).

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