ASSESSMENTS OF OAK LEAF MORPHOLOGY

 

  1. SAMPLING

Five fully expanded leaves should be sampled on each tree in the upper part of the crown. The leaf morphological assessments should be made separately on each of the five leaves. Select disease and insect free leaves. Make sure that the petiole is not hurt during the harvest. Avoid leaves on proleptic or lammas shoots.

  1. LEAF MORPHOLOGY MEASUREMENTS

Except pubescence all other measurements can be made on fresh or dry leaves. For pubescence it is recommended to make the assessments shortly after the harvest, although hairiness is still present on dry leaves but more difficult to observe.

2.1. Morphological descriptors (primary variables to be measured on the leaves).

There are 9 morphological descriptors that are used as primary variables. For comparisons among sites and countries these raw variables are combined into secondary variables (paragraph 2.2.) in order to be size independent.

Lamina length (LL)

Total length of the lamina starting from the insertion point of the lamina on the main vein to the end of the lamina (Figure 1), in millimeters.

Petiole length (PL)

Length of the petiole from the insertion point to the stem to the insertion point of the lamina (Figure 1), in millimeters.

Lobe width (LW)

This is measured from the mid rib to the tip of the lobe at, or immediately below, the widest part of the lamina (Figure 1). If the leaf is asymmetric (between the right or the left half of the lamina relative to the mid rib vein) make the measurements on the half exhibiting the largest LW

Sinus width (SW)

Lamina width measured from the midrib to the base of the sinus at, or immediately below, the widest part of the lamina (Figure 1). If the leaf is asymmetric (between the right or the left half of the lamina relative to the mid rib vein) measure SW on the half exhibiting the largest LW.

 

Length of lamina from the lamina base to the widest part (WP)

As indicated on Figure 1

Number of lobes (NL)

This is the total number of lobes including those on the right and the left part of the leaf, except the terminal lobe (irrigated by the midrib). A lobe is considered to be a lobe when it is clearly irrigated by an axillary vein. There is no size limit to a lobe, because of two main reasons:

- There is a great variability of the leaf size, which induces a variability in the number of lobes. A size limit of the lobes would therefore biased downwards NL for small leaves.

- Q. petraea usually exhibits at the end of the leaves several lobes that decrease in size when reaching the extremety of the leaves. These numbers contribute to the shape of the leaf, they should therefore be counted.

The only criteria for the number of lobes is to be irrigated by an axillary vein.

Number of intercalary veins (NV)

An intercalary vein is a secondary vein irrigating the basis of a sinus. An intercalary vein is deemed to be present if it runs more than half way to the base of the sinus. On Figure 1, an intercalary vein is identified (I) whilst another more minor vein (arrowed) would not be counted.

Basal shape of the lamina (BS)

This is scored as an index varying from 1 to 9 as indicated on Figure 1.

On some leacves, petiole maybe much shorter than shown on Figure 2. discard any observation of petiole in scoring from BS.

Abaxial lamina pubescence (HR)

A scoring of the density of pubescence is made using Kissling’s grading system (Figure 3), from 1 to 6. Make observations on a section of the lamina separated by two axillary veins (see Figure 1 for location of observation)). Pubescence takes into account both stellate and simple hairs. A stereomicroscope should be used at magnification 30 X. An oblique illumination enhances the presence of hairs. The grading system is recorded on a square of 2mm* 2mm. It is recommended therefore to carve a square (2mm*2mm) in a translucent plastic that could be used as a window to score for pubescence.

 

2.2. Secondary characters used for comparisons among contries and sites

 

The raw variables can be combined in several ways so that comparisons can be made accross experimental stands in the different contries. They can also be used for comparisons between trees within a given site. Proposed secondary characters are as follows, others may be added.

Lamina shape or obversity (OB)

OB = LL / WP

Petiole ratio (PR)

PR = PL / (LL+PL)

Lobe depth ratio (LDR)

LDR = LW / (LW - SW)

Percentage venation (PV)

PV = NV * 100 / NL

Basal shape of lamina (BS)

Abaxial pubescence (HR)

 

3. RECORDING OF DATA

It is recommended to store the data in standard format, so that future comparison across institutes could be made. An EXCEL or QUATRO PRO spreadsheet is indicated for the measurements in Table 1/

 

4. INDICATION ON SPECIES DIFFERENCES

 

Here are some values for different characters as available in the literature or from studies conducted on large sample sizes. These should only be considered as indicative, since their variation accross countries are not known.

 

 

Characters

Q. robur

 

Q.petraea

Référence

PL (mm)

7 a

6.5 a

(3.5 to 10) b

(2 to 7) c

7.6 a

16 a

15.8 a

(6 to 25) b

(12 to 30) c

16.8 a

1

2

 

3

4

PR (percentage)

(0 to 10) c

7.7 a

(10 to 25) c

15.4 a

1

4

NV (number)

4.9 a

(3 to 9) c

2.4 a

0.5 a

(0 to 1) c

0.5 a

1

 

4

NL (number)

9.2 a

(6 to 10) c

12.2 a

(11 to 15) c

1

HR (score)

(1 to 1.1) c

1..3 a

(3.5 to 4.5) c

3.1 a

1

4

a : mean value

b : extreme values

c : most frequent values

References:

1 : Oaks from North East of France

J.L. Dupouey, V. Badeau 1993. Morphological variability of oaks (Quercus robur,L. Quercus petraea (Matt) Liebl, Quercus pubescens Willd) in northeastern France: preliminary results.

Ann. Sci. Forest. 50, Suppl 1: 35s-40s

V. Badeau 1990. Etude de la variabilité morphologique des chênes en Lorraine. Rapport de DEA de l’Université de Nancy, 35 pages

2 : Oaks from Germany and Poland

G.Aas Taxonomical impact of morphological variation in Quercus robur and Quercus petraea: a contribution to the hybrid controversy. Ann. Sci. For. 50, Suppl. 1: 107s-113s

3 : Oaks from central European populations.

J.H. Ietswaart A.E. Feij, 1989. A multivariate analysis of introgression between Quercus robur and Q. petraea in The Netherlands. Acta Bot. Neerl. 38(3) : 313-325

4 : Oaks from Alsace

N. Breda, J.L. Dupouey, M. Peiffer 1997. Etude taxonomique des chênes de la forêt Domaniale de la Hardt (Haut Rhin). Rapport final, Convention ONF/INRA 48 pages

 

 

 

Table 1 Format of the speadsheet for the oak leaf morphlogical data

 

 

 

# Tree

#leaf

LL

PL

LW

SW

WP

NL

NV

BS

HR

1

1

105

15

35

25

54

8

3

8

0

1

2

etc..

                

1

3

                  

1

4

                  

1

5

                  

2

1

                  

2

2

                  

2

3

                  

2

4

                  

2

5

                  

etc...