I. Leaf Anatomy as an aid in the Classification of Living Gymnosperms

117 Pages·2001·5.88 MB·English

I. Leaf Anatomy as an aid in the Classification
of Living Gymnosperms
Introduction
The gymnosperms are of scientific Importance to Indian Fores­
try, since they are well represented in the Flora of India, parti­
cularly in the Himalaya where there are extensive regions of coni­
ferous forests from the stand-point of resin, yield and timber
production which together constitute a potential source of revenue
(Raizada and Sahni, 1958). The first time we have a glimpse of
them in the fossil records, the remains can be conveniently divi­
ded into two broad groups, namely, the Cycadophyta and Conifero-
phyta. The compound leaf is an outstanding feature of the Cycado­
phyta. The former group included relatively small plants with un­
branched stems and pinnate leaves, thick cortex, thin wood and
large pith whereas the latter group had large trees with profusely
branched stems and simple leaves, thin cortex, thick wood and
small pith.
From the phylogenetic view-point, the gymnosperms are much
more ancient than the anglosperms. The gymnosperms represent the
most primitive type of seedplants (Datta, 1973). They were abun­
dant In thelj^te Paleozoic and apparently had evolved from psilop-
sldan stock in the Late Devonian, perhaps independently of the
ferns and fern-allies. The Cycadofilicales and Cordaitales made
their greatest display before the Triassic. The Paleozoic plants
gave rise to the wealth of forms Including the Bennettitaies and
Cycadales which literally covered the landscape during the Meso-
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zoic. The time of maximum development of the ancient gymnosperms
coincided almost exactly with the age of giant dinosaurs. It is
believed that young leaves and seeds of the extinct Cycads were
consumed by certain hervivorous dinosaurs (Chamberlain, 1934),
The extant gymnosperms, numbering about 70 genera with 725
species and belonging to the Coniferales, Cycadales and Gnetales,
are considered to be remnants of an once-large and diversified
group (Datta, 1973). Despite the loss of much splendour, they
now comprise a major forest type of primarily temperate regions
of both southern and northern hemispheres. A case in point is the
taiga (coniferous-spruce, fir forest) of North America and
Eurasia which has surpassed the geographical extent of any vege­
tation in the world. The recent cycads symbolise veritable living
fossils and are confined to limited areas of the tropics or sub­
tropics. Ginkgo biloba is one of the wonders of ,the plant world,"
It is, in the words of Seward (1938), "cne of a small company of
living plants which Illustrates continuity and exceptional power
of endurance in a changing environment'*. It exists in the wild
state in south-eastern China and as an ornamental plant in many
parts of the temperate zone now-a-days. The,living members of the
Gnetales contain many puzzling.features of anatomy, organography
and reproduction. As their evolutionary status is a speculative
topic, they form a somewhat isolated group.
Though the anatomical characters of vegetative parts have
long been extensively used in the study of cycads, conifers and
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the other vascular groups (Durrell, 1915; Lamb, 1923$ Poole, 1923$
Harlow, 1931$ Marco, 1931 & 1939$ Sutherland, 1933$ Bannan, 1934$
Fulling, 1934$ Peirce, 1935$ Abbe and Crafts, 1939$ Florin, 1940,
1951, 1958 & 1963$ Cross, 1941$ Johnson, 1943$ Orr, 1944$ Buchholz
and Gray, 1948$ Johnson and Thomas, 1963$ Konar, 1963$ Griffith,
1971$ Rao, 1972$ Ziepski, 1972; Alfieri and Evert, 1973$ Behnke and
Paliwal, 1973$ Ghouse, 1973 & 1974$ Grill, 1973$ denOuter and
Toes, 1974$ Litvintseva, 1974$ Miller, 1974$ Paliwal et al., 1974$
Eremin, 1975$ Gaussen and Waltz, 1975$ Kausik, 1975 & 1976$ Kausik
and Bhattacharya, 1977$ Lotova, 1975$ Baig and Tranqullini, 1976),
there is no elaborate effort to classify living gymnosperms on
the basis of their leaf anatomy. Keeping this object in view, the
present work was designed to evolve a simple
the easy identification of the Indian specimens based on the micros­
copic study of the readily-available leaf material. Moreover, an
attempt has been to present a concise account of the anatomical
features of foliage leaves of the different families, genera and
■ species, as information is hard to get from the relevant literature
regarding most of the Indian forms. This, it is hoped, will provide
an easy means to identify gymnospermous plants by leaf specimens
alone, since very often complete material is not forthcoming and
makes identification a difficult task. An explanatory note on
anatomical features selected has been provided$ this is indica­
tive of the uses to which such features can be put.
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Materials and Methods
In the present study, leaf material of the following species
were collected from Forest Besearch Institute (Dehra Dun), Lloyd
Botanic Garden (Darjeeling) and Indian Botanic Garden (Howrah)s
Cycadaceae s 1) Cyca3 rumphii Miq.
2) £• revoluta Thunb.
3) Encephalartos villosus__Lem.
4) Zamia, angustifolia Facq.
Ginkgoaceae : 5) Ginkgo biloba Linn.
Araucariaceae 8 6) Agathis loranthifolia Salisb.
7) Araucaria bldwillii Hook.
8) A. columnaris Hook.
9) A. cunnlnghamii Sweet.
Cupressaeeae 8 10) Gallitris robusta B. Br,
11) Chamaecyparls pisifera Sieb. & Zucc.
12) Cupressus cashmeriana Boyle ex Carriers
13) C, torulosa D. Don
14) Juniperus recurva Buch.-Ham.
15) J. wallichiana Hook.
16) Thu.ia occidentalis Linn.
17) T. orientalis Linn.
. 18) Tfau.1opsi3 dolabrata Sieb. & Zucc.
Cephalotaxaeeae % 19) Cephalotaxus drupacea Sieb. & Zucc.
20) C. griffithii Hook.
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Pinaceae s 21) Abies spectabilis Spach.
22) Cedrus libani Laudon
23) Picea smithlana Boiss
24) . Pinus densiflora Sieb. & Zucc.
25) P. gerardlana Wall, ex Lamb
26) P, kesiva, Royle
27) P. roxburghii Sarg.
28) £,' sylvestris Linn.
29) P. wallichiana A. B. Jacks
30) Tsuga dumosa Eiehl.
Podoearpaceae s‘ 31) Podocarpus macrophyllus D. Don
32) P. neriifolius D. Don
33) P, sinensis Teijsm. & Binn.
Taxaceae 8 34) Taxus baccata Linn.
Taxodiaceae : 35) CrvPtomeria .laponica D. Don
36) Cunninghamia sinensis R, Br.
37) Metasequoia glyptostroboides Hu et Cheng
38) Taxodlum distichua Rich.
A number of leaves from each source of collection were used
to avoid any discrepancy, in the. observations originating from
natural variation. Unless otherwise stated, only fully matured
leaves were selected for sectioning. In each case, the sections
were chosen from various regions of the same leaf to depict an
overall picture of its anatomical characters. Free-hand sections
were made and stained with Bismarck Brown and Safranin and Fast-
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green. Finally, the sections were mounted in Canada balsam.
Herbarium specimens were revived by boiling in water until
they came to their natural form and size. Some of the dry speci­
mens were preserved in 10% glycerine at room temperature for 2
days, while most of the fresh specimens were fixed in FAA before
sectioning.
In studying the stomata! type and stomatal frequency, a.
somewhat different procedure was adopted. Those leaf materials,
fixed in FAA overnight, were washed in tap water. Then cut pieces
from the middle and from two ends of a leaf were boiled in 95%
alcohol for 15-30 min. Again, the same material was boiled in a
mixture of 1:1 5% NaOH and 95% ethyl alcohol for additional 15-20
min. Next, the material was washed in tap water and finally rinsed
with distilled water. Later on, the washed material was kept in
4% sodium hypochlorite solution for a single night or two nights.
Those materials, provided with thick cuticle, took at least two
nights to be completely cleaned. Finally, these materials were
mounted and observed under the compound microscope (Olympus^__
brand). _ ]
vCl.
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Fig. I. Key to tissues of living gymnosperms.
Fig. II. Diagrams of the transverse sections of the leaves
of Cycads j (1) Cycas rumphii: (2) C, revoluta:
(3) Bncenhalartos villosus: (4) Zamla floridana.
Fig. Ill, Diagrams of the transverse sections of the leaves
of ginkgos and conifers i (5) Ginkgo bllobat (6)
Asathis loranthifolias (7) Araucaria bidwillii;
(8) A. columnaris: (9) A. cunningha.mil.
Fig. IV. Diagrams of the transverse sections of the leaves
of conifers j (10) Callltris robustat (11) Chamae-
cyparis pisiferas (12) Cupressus cashmeriana;
(13) C. torulosa: (14) Juniperus recurva.
Fig. V. Diagrams of the transverse sections of the leaves
of conifers s (15) Juniperus wallichiana: (16)
Thuja occidentaliss (17) T. orientalis: (18)
Thu.lopsis dolabrata
Fig. VI. Diagrams of the transverse sections of the leaves
of conifers i (19) Cephalotaaius drupacea:
(20) C. griffithil;
Fig. VII. Diagramms of the transverse sections of the leaves
of conifers s (21) Abies spectabilist (22) Cedrus
libani; (23) Picea smithiana: (24) Pinus densi.
flora? (25) P. gerardiana.
Fig. VIII, Diagrams of the transverse sections of the leaves
of conifers s (26) P. kesiyat (27) P. roxburghii:
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(28) P. sylvestrls: (29) P. wallichianas (30) Tsuga
dumosa.
Fig. IX. Diagrams of the transverse sections of the leaves
of conifers s (31) Podocarpus macrophvllus : (32)
P- neriifolius: (33) P. sinensis: (34) Tax us baccata.
Fig. X. Diagrams of the transverse sections of the leaves
of conifers : (35) Cryptomeria iaponicat (36)
Cunnlnghamia sinensis: (37) Metasequoia glypto-
stroboides: (38) Taxodium distichum.
Fig. XI, Camera lucida drawings of stomatal apparatus s
(1) Cycas rumphli - Paracytic; (2) C. revoluta -
Actinocytic; (3) Encephalartos vlllosus - Hypocytic;
(4) Zamla angustlfolia - Paracytic.
Fig. XII. Camera lucida drawings of stomata! apparatus j
(5) Ginkgo biloba - Anomocytic; (6) Agathis loran-
thlfolia - Staurocytic; (7) Araucaria bidwillii -
Anisocytie; (8) J\,. columnaris - Anisocytie; (9) JL.
cunnlnghamil - Anomocytlc.
Fig. XIII. Camera lucida drawings of stomatal apparatus j
Callltris robusta - Paracytic5 (11) Chamaecyparis
pisifera - Anomocytlc; (12) Cupressus cashmeriana -
Anomocytic; (13) C. torulosa - Anomocytlc; (14)
Juniperus recurva - Anomocytlc.
Fig. XIV. Camera lucida drawings of stomatal apparatus s
(15) J. wallichiana - Anomocytic; (16) Thu.la
occldentalis - Anomocytlc and Paracytic; (17)
Thu.la orientails - Actinocytic; (18) Thu.1opsl3
dolabrata - Anomocytic.
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Fig. XV. Camera lucida drawings of stomatal apparatus s
(19) Cenhalotaxus drupacea - Hexacytic; (20) C.
griffithii - Paracytic.
Fig. XVI, Camera lucida drawings of stomatal apparatus 5
(21) Abies spectabilis - Pericytic; (22) Cedrus
libani - Tetracytic; (23) Picea smith!ana •
Tetracytic; (24) Pinus densiflora - Graminaceous;
(25) P. gerardiana - Semiactinocytic.
Fig. XVII, Camera lucida drawings of stomatal apparatus 5
(26) Pinus kesiva - Paracytic; (27) P. roxburghii
Graminaceous; (28) P. recurva - Staurocytic and
Paracytic (complex type); (29) P. wallichiana -
Paracytic; (30) Tsuea dumosa- Paracytic.
Fig.XVIII. Camera lucida drawings of stomatal apparatus 5
(31) Podocarpus macrophvllus - Staurocytic;
(32) P. neriifoliU3 - Paracytic; (33) P. sinensis
Paracytic; (34) Taxus baccata - Paracytic and
Hexacytic.
n
Fig, X3X. Camera lucida drawings of stomatal apparatus s"
(35) Cryptomeria .laponica - Actinocytic or Cyclo-
cytic; (36) Cunninghamia sinensis - Anomocytic;
(37) Metaseauoia glyptostroboides • Anomocytic;
(38) Taxodlum distichum - Anomocytic.
S = subsidiary cell; g = guard cell; a = epidermal cell;
us = undifferentiated subsidiary cell; st = storm.