INVESTIGATING ECOTYPES OF WOOD
SAGE TEUCRIUM SCORODONIA
Abstract
Dissertation work is a feature
of most biological courses in higher education. The following paper describes
an easily executed investigation into the effect of soil type on the growth
performance of two clones from differing metapopulations
of wood sage Teucrium scorodonia L. Suggestions are made for using plants, other
than wood sage, for similar investigative projects.
Key words: Soils, Ecotypes,
Wood sage.
This paper describes an
easily-executed investigation into the effect of soil type on the growth
performance of two clones from differing metapopulations
of wood sage Teucrium scorodonia L.
Introduction
Wood sage is a member of the Labiate Family. The species, and its ecological
requirements, have been described by Hutchinson (1968) and Grime, Hodgson, and Hunt (1990). The plant is a herbaceous, downy perennial varying in height from 10 to
50 cm and arises from branching underground rhizomes (figure 1). The
heart-shaped, toothed leaves with dark green upper and lighter green lower
surfaces are usually in opposite pairs on the square stems. The flowers are
greenish-yellow. Seeds grown under laboratory conditions produce flowering
plants within six months.
The species is widespread within the British
Isles and continental Europe. It tends to
colonize woods, wood and wall margins, hedges, heaths, dunes, and screes. It is found in acidic and alkaline soils,
particularly those which are well-drained. Drought conditions with high summer
temperatures reduce occurrence. The plant grows in a variety of soil types from
pH 3.6 to 8.2. The species appears to be divided into physiologically distinct
populations with those from drier unshaded habitats
developing extensive root systems, and those from damp and shaded conditions
producing greater amounts of photosynthetic tissue. In addition, there appears
to be a division between ecotypes adapted to calcareous and non-calcareous
soils, with the latter showing a susceptibility to lime-induced chlorosis and phosphate deficiency. Data calculated from Hutchinson
(1968) from analysed soils in which wood sage was
naturally occurring reveal the tolerance of the species to a wide range of
mineral levels. Exchangeable cation concentrations
were calcium 520-15 600 mg kg[sup-1], potassium 40-240
mg kg[sup-1], sodium 30-130 mg kg[sup-1], and magnesium 20-690 mg kg[sup-1].
The aim of this study was to
investigate the educational project opportunities in comparing the growth
performance of ecotypes of a species, which are found in contrasting soils.
Method
Wood sage plants were
propagated by soft-wood stem cuttings from material obtained from woodland
habitats. The stems of actively growing plants were severed at a 45 Degrees
angle just below the fourth node down from the stem apex. Leaves were removed
from the third and fourth nodes and the cuttings were inserted up to the
remaining leaves into a medium containing controlled-release fertilizer of 1:1
v/v sphagnum peat:cornish
grit (figure 2). Cuttings were kept under polythene until rooted, which
occurred in 10-14 days. The rooting rate was 100 percent.
One sample of wood sage
originated from an acidic soil in the Sussex Weald and the other from
lightly-wooded carboniferous limestone scree from the
Mendips, Somerset. Associated vascular flora was recorded. The Sussex site included Bracken Pteridium aquilinum, Broom Cytisus scoparius, Bramble Rubus fruticosus egg., Sweet Chestnut Castanea saliva, Oak Quercus robur, Birch Betula spp., Holly Ilex aquifolium,
Sycamore Acer pseudoplatanus, Ling Calluna vulgaris, Heath Bedstraw Galium
saxatile, Honeysuckle Lonicera
periclymenum, Foxglove Digitalis purpurea,
Knapweed Centaurea nigra, Self-heal Prunella vulgaris, and Yorkshire Fog Holcus
lanatus. The Mendip sites
flora included Harts Tongue Phyllitis scolopendrium, Ash Fraxinus
excelsior, Ivy Hedera helix, Shining Cranesbill Geranium lucidum, Herb
Robert G. robertianum, Hairy Rockcress
Arabis hirsuta, Wood Avens Geum urbanum,
Figwort Scrophularia nodosa
, Wall Lettuce Mycelis muralis,
Ragwort Senecio jacobaea,
Wood False-brome Brachypodium sylvaticum,
and Wood Melick Melica uniflora. Hazel Corylus avellana was present at both sites.
Soil from Sussex was a silty loam and that from
the Mendips was an organic soil containing small
limestone fragments.
Organic matter was determined
by ashing at 500 Celsius for 3 h (based on O'Hare,
1992). Extractable nitrate-nitrogen, phosphate-phosphorus, sodium, potassium,
calcium, and magnesium concentrations in both soils were measured with methods
based on MAFF (1986). Four treatments were set up, namely Sussex plants in Sussex soil, Sussex plants in Mendip soil, Mendip plants in Mendip soil, and
Mendip plants in Sussex soil. Ten similarly-sized stem cuttings from a plant from
each locality were used in each treatment. Each plant was grown individually in
a 0.5 dm[sup-1] pot. Watering was with rainwater.
After four months, the 40
plants were scored for greenness on a scale of 1 (the most yellow) to 40 (the
most green). This was achieved by asking a team of five people to rank the
specimens in order of colour. In addition, heights,
dry weights and aerial portions, number of leaves showing necrosis or
deficiency were recorded and concentrations of plant dry matter calcium,
magnesium, sodium, and potassium were measured (based on MAFF, 1986).
Parametric determinations were compared by analysis of variance and Tukey multiple comparison analysis using the Minitab
statistics programme.
Results
The soil from the Sussex Weald
was more acidic (pH 3.4) than that of the Mendips (pH
6.8). The Sussex soil was also comparatively lower in organic matter (17.8
to 36.8 per cent) and There were no significant differences
between treatments with plant heights, which ranged from 13.1 to 14.7 cm.
However, there was a significant difference (p<0.05) in aerial dry weight
with Mendip plants in Sussex soil producing the heaviest specimens, and Mendip plants in Mendip soil the
lightest. There was a very significant difference in greenness score (p
<0.0001) with Sussex plants in their own soil being the most green, and Mendip plants in Mendip soil the
least. Table 2 shows recordings and significant differences between individual
treatments.
Table 3 gives the number of
plants showing signs of leaf necrosis, leaf yellowing or leaf red-purple
discoloration. No clear pattern emerged from this data. Concentrations of
magnesium, potassium, and calcium in aerial dry matter, together with
significant differences, are shown in table 4. Sussex plants in Mendip soil had the
highest calcium levels and Mendip plants in Sussex soil the lowest. Sussex plants in Mendip soil had
significantly lower magnesium content than the other three treatments. Sussex plants in their own soil had the highest potassium content
with Mendip plants in their own soil the lowest.
Discussion
Soil mineral concentrations as
described in table 1, with the exception of elevated calcium levels of the
limestone scree from Mendips,
were within the range calculated from Hutchinson (1968). The Mendip soil, with a
near neutral pH, had considerably higher concentrations of analysed
minerals and organic matter than that of the acidic Sussex Wealden
soil (table 1). It would be expected that the acidity of the Sussex soil would have reduced the availability of phosphate and
potassium and increased the availability of iron, manganese, and zinc (Brady,
1990). Calcium levels were particularly high in the Mendip
soil. It was interesting that the Sussex plants grown in the calcareous Mendip
soil had the highest plant calcium levels, and the Mendip
plants grown in the Sussex soil had the lowest. The Sussex plants, coming from a soil low in extractable calcium,
appeared to be adapted to maximize calcium uptake. Similarly, Sussex plants showed higher potassium dry matter levels than
those from the Mendips, suggesting some adaptation to
greater potassium absorption. However, notwithstanding the elevated magnesium
levels in the Mendip soil, Sussex plants growing in that soil had the lowest concentrations
of dry matter magnesium. Adaptations for maximizing calcium, and to a less
extent potassium absorption, appeared to have interfered with magnesium uptake.
The interference of potassium and calcium with magnesium uptake is well
documented (ADAS, 1986). Differences in the greenness score may be attributed
to iron availability and adaptation to iron absorption. Sussex plants growing in their own low-pH soil exhibited the
maximum greenness.
Linking signs of deficiency to
specific elements is often difficult due to similar symptoms being produced by
the deficiencies of different minerals. In this trial, no clear pattern emerged
with deficiency symptoms (table 3). One feature of growth performance was the
greater aerial dry matter production of the Mendip
plants in Sussex soil over other treatments (p<0.05). Although both
specimens originated from wooded habitats, it was not found possible to extract
roots from soil in order to examine aerial/root ratios. Therefore conclusions
could not be reached about evidence for ecotype based on partitioning of
photosynthetic effort in shoot or root growth as described by Hutchinson (1968).
It can be concluded from
aerial dry weight and greenness measurements, that despite the comparatively
elevated levels of measured minerals in the Mendip
soil, performance was superior in the acidic Sussex soil. In addition there was evidence of adaptation for
mineral absorption based upon extractable soil mineral levels. In retrospect,
it would have been useful to have measured dry matter iron concentrations.
In an educational situation,
this type of investigation is not difficult to undertake. Requirements are (a)
a species which is found in contrasting soil types and (b) sufficient soil in
which to grow the plants. From a practical point of view, obtaining sufficient
soils could be the most inconvenient aspect of the investigation. In this
exemplar, cuttings were produced but depending upon the species, it may be possible
to use gathered seed. Plants can be allowed to grow for a shorter period than
the four months used in this trial. Analysis can be at varying levels of
complexity depending upon equipment available.
Plants suggested for project
work on the basis of soil acidity are Common Bent Agrostis
capillaris, Creeping Bent Agrostis
stolonifera, Sheep's Fescue Festuca
ovina egg., White Clover Trifolium repens, Devilsbit Scabious Succisa pratensis, Self-heal Prunella vulgaris, Thyme Thymus polytrichus,
and Common Catsear Hypochaeris
radicata. Effects of soil salinity could be
investigated using Red Fescue Festuca rubra from dunes or saltmarshes
compared with specimens collected from inland sites. Ecotypes of species such
as Common Bent A. capillaris, Yorkshire Fog Holcus lanatus, and Ling Calluna vulgaris (Grime et al., 1990) colonizing mine waste
heaps could also be compared with those from uncontaminated land. Bradshaw, McNeilly and Putwain (1990)
described plant tolerance on heavy metal mine spoil heaps to be localized to a
few metres. Species which had been growing under
galvanized fences for 25 years were found to be tolerant to elevated zinc
concentrations. Therefore, with available contrasting edaphic
conditions, trials can be based upon local plants and soil. In conclusion, the
possibilities of this type of project are endless.
Acknowledgements
We would like to thank Pat
Mitchell and Jo Ringham for their assistance with
analysis and Chris and Anne Yarrow for providing soil and plants from the
Sussex Weald.
Sussex Weald Mendip
pH 3.4 6.8
organic matter % 17.8 36.8
nitrate-nitrogen 54.0 60.0
phosphate-phosphorus 6.5 10.5
sodium 100.0 217.0
potassium 112.0 225.0
calcium 950.0 43167.0
magnesium 55.0 135.0
Plant Sussex Sussex Mendip
Soil Sussex Mendip Mendip
Height (cm) 13.1 13.4 14.7
SE 0.8 1.0 1.2
Aerial dry(g) 1.5 1.4 1.3a
SE 0.1 0.2 0.1
Median green score 33.8cfh 13.5ae 6.5age
Plant Mendip Difference
Soil Sussex
Height (cm) 14.4 NS
SE 1.4
Aerial dry(g) 2.0b p = 0.05
SE 0.2
Median green score 22.5bdf p = 0.0001
Means with the following letters are significantly different:
ab or cd (p<0.05); ef (p<0.01); gh (p<0.001)
Plant Sussex Sussex Mendip Mendip
Soil Sussex Sussex Mendip Sussex
Leaf necrosis 7 8 5 9
Leaf yellow 5 6 4 4
Leaf red/purple 7 7 3 4
Plant Sussex Sussex Mendip
Soil Sussex Mendip Mendip
Calcium 14663bc 18378bd 14710bc
SE 580 758 1403
Magnesium 1378a 989b 1348
SE 125 44 127
Potassium 9905a 8998 6919b
SE 840 594 612
Plant Mendip Difference
Soil Sussex
Calcium 10867a p = 0.0001
SE 667
Magnesium 1266 p = 0.05
SE 75
Potassium 7930 p = 0.05
Means with the following letters are significantly different:
ab or cd (p<0.05).
PHOTO (BLACK & WHITE):
Figure 1; Wood sage Teucrium
scorodonia.
PHOTO (BLACK & WHITE):
Figure 2; Stem cutting of wood sage.
References
ADAS (1986) Hypomagnesuemia in cattle and sheep. Alnick, Northumberland: MAFF
Publications.
Bradshaw, A. D., McNeilly, T., and Putwain, P.D.
(1990) The essential qualities in heavy metal
tolerance in plants: evolutionary aspects (ea. Shaw, A. J.). Boca Raton, Florida, USA: CRC Press.
Brady, N. C. (1990) The nature and properties of soil. New York. USA: Maxwell Macmillan
Grime, J. P.
Hodgson J. G., and Hunt, R. (1990) Comparative plant ecology. London: Unwin Hyman.
Hutchinson T. C. (1968)
Biological flora of the British
Isles: Teucrium scorodonia.
Journal of Ecology. 56(4), 901-911.
MAFF (1986) The
analysis of agricultural materials: Reference Book 427. London: HMSO.
O'Hare, G. (1992)
Soils, vegetation, ecosystems. Harlow,
Essex: Oliver & Boyd.
~~~~~~~~
By Clem Maidment
and Darrel Watts
Dr D. C. J. Maidment
is Principal Lecturer in Environmental Biology, and Darrel Watts is Plant
Demonstrator at Bath College of Higher Education, Newton Park, Bath BA2 9BN
