Discussion in relation to previous studies

The only comprehensive wood anatomical study to date was performed by Carlquist (2003) on the basis of 30 woody species. Datta and Deb (1968) characterize the xylem of six Rumex species occuring in India. Pfeiffer (1926) describes two herbaceous species with interxylary phloem (Rumex) and successive cambia (Antigonum leptopus). Metcalfe and Chalk (1957) mention 10 genera, but the text is very condensed. Many authors have characterized just a few woody species (Gregory 1994). Comparable with the present study are Calligonum comosum (Neumann et al. 2001, Carlquist 2003 and Ma et al. 1994), Rumex lunaria (Carlquist 2003), Rumex vesicarius (Datta and Deb 1968) and Polygonum equisetiforme (Schweingruber 1990).

Most previous authors concentrated on the xylem of shrubs and dwarf shrubs. This study includes several growth forms of annual and perennial herbaceous species of different vegetation zones. Carlquist (2003) and the present analysis demonstrate the wide anatomical spectrum. All species have simple perforations but the distribution, diameter and frequency of vessels, the presence and absence of thin- and thick-walled fibers indicate the heterogeneity within the family. The material is not sufficient for a classification within the family.

Present features in relation to the number of analyzed species

IAWA code frequency

Present features in relation to the number of analyzed species

IAWA code frequency

Total number of species

41

1

growth rings distinct and recognizable

31

2

growth rings absent

3

2.1

only one ring

7

3

ring-porous

2

4

semi-ring-porous

17

5

diffuse-porous

14

6

vessels in intra-annual tangential rows

5

9

vessels predominantly solitary

25

9.1

vessels in radial multiples of 2-4 common

24

10

vessels in radial multiples of 4 or more common

3

11

vessels predominantly in clusters

11

13

vessels with simple perforation plates

41

20

intervessel pits scalariform

6

Left Fig. 31. Radially oriented groups of sclereids on both sides of a ray dilatation. Root collar of a 10 cm-high hemicrypto-phyte, dry ruderal site, hill zone, French Alps. Rumex acetosella ssp. angiocarpus, transverse section.

Right Fig. 32. Thick-walled strands of sclereids outside the living phloem. Stem of a 1.5 m-high shrub on dunes, arid zone, Oman. Calligonum comosum, transverse section.

29 vestured pits 2

39.1 vessel cell-wall thickness >2 pm 1

40.1 earlywood vessels: tangential diameter <20 pm 1

40.2 earlywood vessels: tangential diameter 20-50 pm 33

41 earlywood vessels: tangential diameter 50-100 pm 6

42 earlywood vessels: tangential diameter 100-200 pm 5

50.1 100-200 vessels per mm2 in earlywood 17

50.2 200-1000 vessels per mm2 in earlywood 24 56 tylosis with thin walls 1 58 dark-staining substances in vessels and/or fibers 13 60.1 fibers absent 1 61 fiber-pits small (<3 pm = libriform fibers) 39 65 septate fibers present 1

68 fibers thin-walled 14

69 fibers thick-walled 2

70 fibers thin- to thick-walled 25

75 parenchyma absent or unrecognizable 2

76 parenchyma apotracheal, diffuse and in aggregates 5 79 parenchyma paratracheal 28 79.1 parenchyma pervasive 14 89 parenchyma marginal 4

96 rays uniseriate 4

97 ray width predominantly 1-3 cells 11

98 rays commonly 4-10-seriate 10

99 rays commonly >10-seriate 13

99.1 vascular-bundle form remaining 19

99.2 stem lobed 1

104 ray: all cells procumbent (radial section) 4

105 ray: all cells upright or square 28

107 ray: heterocellular with 2-4 upright cell rows (radial section) 4

108 ray: heterocellular with >4 upright cell rows (radial section) 1 110 rays with sheet cells (tangential section) 1 117 rayless 5 120 storied axial tissue (parenchyma, fibers, vessels, tang. section) 2 135 interxylary phloem present 1 R1 groups of sieve tubes present 19 R3 distinct ray dilatations 23 R4 sclereids in phloem and cortex 24 R6 sclereids in radial rows 2 R7.1 with acicular crystals 2 R8 with crystal druses 29 R9 with crystal sand 1 R10 phloem not well structured 7 R13 tannins in parenchyma cells 2 R14 cortex with aerenchyma 6 P1 with medullary phloem or vascular bundles 1

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