Anatomy in relation to taxonomy

1. M.Venkatesh.
I M.Sc Botany

2. INTRODUCTION
 Anatomical features have played an increasingly
important role in elucidation of phylogenetic
relationships .
 Anatomical characteristics are investigated with the
help of a light microscope where as ultra structure and
micromorphology are brought out using an electron
microscope.
 Anatomical work of taxonomic significance was largely
under taken by Bailey and his students.

3. WOOD ANATOMY
Wood represents secondary xylem constituting the
bulk of trees and shrubs formed through the activity
of vascular cambium .
It primarily consists of tracheids and vessels .
Tracheids are long narrow elements with tapering
ends, it transfer of water and minerals occuring
through pit-pairs.
Vessel elements are joined end to end to form long
tubes the vessels
Vessels are absent in gymnosperms but present in
angiosperms.

5. The separation of Paeonia into a distinct family
Paeoniaceae and Austrobaileya into a separate family
Austrobaileyaceae has been supported by studies of
wood anatomy.
Nodal anatomy has considerable significance in
angiosperm systematics.
The node may have single gap from single leaf trace is
called as unilacunar.
The node is three leaf traces or three gaps is called as
trilacunar.

7. TRICHOMES
Trichomes constitute appentages of epidermis which
may be non-glandular or glandular.
Non glandular trichomes may be in the form of simple
unicellular or multicellular hairs common in
Brassicaceae, Lauraceae.
Glandular trichomes may be sessile or stalked and
present a variety of forms.

9. EPIDERMAL FEATURES
o Epidermal features are also of considerable taxonomic
interest.
o Prat (1960) demonstrated that one can distinguish a
festucoid type (simple silica cells, no bicellular hairs)
and panicoid type (complicated silica cells, bicellular
hairs ) of epidermis in grasses.
o Stomatal types are distinctive of certain families such
as Ranunculaceae (anomocytic) Brassicaceae
(anisocytic) Caryophyllaceae (diacytic) Rubiaceae
(paracytic) and poaceae (graminaceous).

11. o Stace (1989) lists 35 types of stomata in vascular plants.
o Closely related families Acanthaceae and
Scorpulariaceae are distinguished by the presence of
diacytic stomata in the former as against anomycytic
in the latter.

12. LEAF ANATOMY
 Leaf anatomy has been of special taxonomic help in
Poaceae family.
 The occurance of c-4 path way and its association with
Kranz anatomy
 Melville(1962,1983) developed his gonophyll theory
largely on the basis of the study of venation pattern of
leaves and floral parts.
 The rejection of Sanmiguelia and Furcuta as
angiosperm fossil from the triassic has largely been on
the basis of detailed study of the venation pattern of
leaves.

13. FLORAL ANATOMY
 Floral anatomy has been one of thoroughly explored
areas , with singnificant contributions to the
understanding of the phylogeny of angiosperms.
 Melvile (1962, 1983) developed his gonophyll theory
after studing the vasculature of carpel and other floral parts
through the clearing technique.
 The inferior ovary in angiosperms has been formed in two
ways : appendicular origin or by axial invagination.

14.  Floral anatomy also supports the seperation of
Menyanthes from Gentianaceae into distinct family
Menyanthaceae.
 Developmental studies have indicated that some
flowers, such as Apiaceae and Ericaceae that appear to
have free petals, are gamopetalous early in
development.
 They are therefore considered to have evolved from
gamopetalous ancestors.

15. EXAMPLE:1
Aizoaceae
 Mollugo
 Trianthema
 Sesuvium
 Gisekia
Aizoaceae
Aizoaceae Molluginaceae
 Trianthema Mollugo
 Sesuvium
 Gisekia

16. Anatomy plays in a major role of ‘P’and ‘S’ plastids
o It is proposed by Hutchinson.
o Phloem consists of the following elements
a)Sieve tubes
b)Companion cells
c)Phloem fibre
d)Phloem parenchyma

17. Companion cells contain two types of plastids
‘P’ Plastids
‘S’ Plastids
P means of Protein bodies.
S means of Starch granules.
Aizoaceae is the presence of ‘P’ Plastids.
Molluginaceae is the presence of ‘S’ Plastids.

18. o Phloem consists of the following elements
a)Sieve elements
b)Companion cells
c)Phloem fiber
d)Phloem parenchyma

19. Floral anatomy also supports the separation of Menyanthes from
Gentianaceae into distinct family Menyanthaceae.
EXAMPLE: 2
Gentianaceae
Centella
Hydrocotyle
Gentianaceae
Gentianaceae Menyanthaceae
Centella Hydrocotyle


20. EXAMPLE: 3
Ranunculaceae:
Ranunculus
Thalictrum
Delphinium
Aquilegia
Ranunculaceae
Ranunculaceae Helleboraceae
Ranunculus Delphinium
Thalictrum Aquilegia


21. Reference book:
 Plant Taxonomy by O. P. Sharma
 Systematic Botany by Guru Sharan Singh
 Plant Anatomy by M.S.Tayal
 12th Standard Botany Book