2017 Solved Old Paper (BOT - 202) New

Ans.
Classification of Gymnosperms:- Sporne (1965) classified gymnosperms into 3 classes, 9 orders and 31 families. 
The classes include:
i. Cycadospsida 
ii. Coniferopsida 
iii. Gnetopsida 
General Characters of Main classes:-
Class I – Cycadopsida:-
> Plants are palm-like or fern-like.
> Compound, frond-like pinnate leaves.
> Manoxylic wood.
> Sperms are motile.
> Flower like structures are absent. Strobili are simple.
> Example:- Cycas, Zamia.
Class II – Coniferopsida:-
> Tall trees with simple leaves of varied shape.
> Wood is pycnoxylic.
> Cone like strobili are present.
> Motile sperms are absent (except Ginkgo biloba). 
> Example:- Pinus.
Class III – Gnetopsida:-
> Shrubs, trees and lianas.
> Leaves are elliptical or strap-shaped, simple, opposite or whorled.
> Motile sperms are absent.
> Wood contains vessels.
> Strobili is called as inflorescence.
> Flower like structure with perianth is present. 
> Example:- Gnetum, Ephedra.

Ans.
Ginkgo biloba:-
Classification:-
Division - Coniferophyta
Class - Coniferopsida
Order - Ginkgoales
Family - Ginkgoaceae
Genus - Ginkgo 
Species - biloba
Distribution of Ginkgo:-
> Ginkgo biloba is a tall, slender and beautiful tree. 
> It is commonly called Maiden-hair Tree because its new leaves resemble very much like those of Adiantum (called maiden hair fern) both in form and venation.
>  It is the oldest living seed plant. 
> It is cultivated for its edible seeds in some parts of China and Japan. 
> Ginkgo still exists in the wild state in South-eastern China, along “the north western border of Chekiang and south eastern Anhwei”. 
> In China and Japan it is grown as a sacred tree in temple gardens. 
> It is cultivated in the United States as a shade tree. 
> t is also successfully cultivated in some gardens of Europe, America and India.
Ginkgo: A Living Fossil:-
> Ginkgo is known to have occurred in rocks as old as Triassic or even much earlier. 
> Fossils of its leaves have been identified in the Permian and probably also in the Carboniferous. Ginkgo biloba occurs even today. It is, therefore, referred as living fossil by the botanists. Or, it may also be referred as the oldest living seed plant.
> The plant body of Ginkgo biloba is sporophytic, and the sporophyte resembles several conifers in
general habit. 
Ans.
Pentoxylales:-
Characters of Pentoxylales:-
1. Extinct Mesozoic plants found in Jurassic period.
2. Although the exact habit of these plants is not clearly established, these were probably shrubs or very small trees.
3. Long and short shoots were present on these plants.
4. Short shoots had spirally arranged leaves and terminally located reproductive organs.
5. Leaves were thick, simple, lanceolate, and had diploxylic leaf trace.
6. Stomata were formerly thought to be syndetocheilic, but now they are considered to be haplocheilic.
7. Leaves possessed open venation.
8. Stems were polystelic. Basinger et al. (1974) opined that “it may be more appropriate to call each stele as vascular segment or sympodium”.
9. Wood of Pentoxylon was pycnoxylic and resembled Araucaria.
10. Ovules were sessile.
11. Female reproductive organs were like stalked mulberry, consisting of about 20 sessile seeds attached to central receptacle and surrounded by stony layer and then fleshy outer layer of integument uniting them.
12. Male reproductive organs or microsporophyll’s form whorl of branched micro-sporangiophores.
13. The micro-sporangiophores were fused basally into a disc-like structure.
Stem Genera of Pentoxylales:-
1. Pentoxylon Sahnii:-
> Pentoxylon sahnii and Nipanioxylon guptai are the stem genera of “Pentoxyleae”. The stems of Pentoxylon sahnii attained a diameter from 3mm to 2 cm. The stem has always been reported in association with the leaves called Nipaniophyllum.
2. Nipanioxylon:-
> This stem genus of Pentoxyleae was discovered from the village Nipania and hence named Nipanioxylon. Village Nipania is in Rajmahal Hills, near Dumarchir in the Amrapara district (Santhal Parganas) in Bihar (India). 
Ans.
Fossil Gymnosperm in India:-
1. Cycadales:-
> Indian Cycadales are represented by only 5 species of Cycas and occur mainly in South India. These are Cycas beddomei (Madras and dry hills of Cudapah in Andhra Pradesh), C. circinalis (Andaman and Nicobar Islands and some dry deciduous forests of South India), C. rumphii (Andaman and Nicobar Islands), C griffithi (Manipur and Nega Hills) and C. pectinata (Assam, Bihar, Sikkim and several parts or Eastern India).
> C. revoluta, a Japanese species, is cultivated commonly in Indian gardens. It does not occur in wild state.
2. Gnetales:-
> Indian Gnetales include species of Gnetum and Ephedra. Welwitschia, the third genus of the order, has not been reported from India. Five species of Gnetum (viz. G. ula, G. contractum, G. gnemon, G. montanum and G. latifolium) occur in various parts of the country.
> According to Bhardwaj (1957) various Indian species of Gnetum along with their places of distribution in parenthesis include G. ula (Western Ghats near Khandala, forests of Kerala, Nilgiris, Andhra Pradesh and Orissa), G. contractum (Nilgiri Hills, Conoor and hills of Kerala), G. gnemon (eastern parts of the country, particularly Assam), G. montanum (Assam, Sikkim and parts of Orissa) and G. latifolium (Andaman and Nicobar Islands).
> Ephedra, in India, is represented by only 6 species. These are Ephedra foliata, E. gerardiana, E. intermedia, E. nebrodensis, E. regeliana and E. saxatilis. These are distributed widely in dry parts of Haryana, Punjab, Rajasthan, and parts of Sikkim, Kashmir, and also at high altitudes in Himalayas.
3. Coniferales:-
> Coniferales are the dominant forest-makers of the world. Out of 54 living genera of Coniferales in the world, ten have been reported from different parts of India. These are Abies, Cedrus, Cephalotaxus, Cupressus, Juniperus, Larix, Picea, Pinus, Podocarpus and Tsuga. The distribution of the majority of these members is restricted mainly in the Himalayas, and governed chiefly by altitudes.
Brief description of their distribution:-
- Abies is represented in the country by only 4 species, of which A. delavayi and A. densa grow in eastern Himalayas, whereas A. pindrow and A. spectabilis are restricted to western Himalayas. A. pindrow grows luxuriantly at about 2500 metres above sea level, whereas A. delavayi occurs commonly at an altitude of about 2750-3350 metres above sea level. A. densa grows luxuriantly in Darjeeling and adjacent hills.
- Cedrus, in India, is represented by only one species i.e. Cedrus deodara (vern. Deodar). This beautiful tree is famous for its wood, and grows in western Himalayas between 1200-3300 metres. Cephalotaxus grows in eastern Himalayas, and is represented by only two species (C. griffithi and C. mannii).
- Cupressus tortulosa grows throughout in the outer and middle ranges of Himalayas from Chamba hills in Himachal Pradesh to Aka Hills in Assam at an altitudes from 1800 to 2800 metres C. funiberus and C. sempervirens are cultivated as ornamental plants in Indian gardens.
- Six species of Juniperus have been reported from higher altitudes of eastern as well as western Himalayan regions of India and Bhutan. J. communis occurs between 2900-4250 metres in Garhwal Himalayas, whereas J. coxii grows both in eastern as well as Western Himalayas.
- J. macropoda grows between 2500-4300 metres in Laddakh, Kanawar and Alaknanda valley, whereas J. recurva and J. squamalata grow between 3000-5000 metres in the eastern Himalayas. J. wallichiana grows at an altitude between 3000 to 4200 metres in the Himalayan ranges.
- Larix griffithiana occurs generally mixed with Abies, Pinus and Tsuga in Sikkim, Chumbi valley of Tibet, Bhutan and Mishmi Hills in Assam. Picea smithiana grows in western Himalayas and attains a height of about 60 metres. It grows from Afghanistan to Kumaon.
- Pinus is represented by 6 species in India. These are P. roxburghii, P. wallichiana, P. insular is, P. gerardiana, P.armandi and P.merkusii. They are distributed throughout in Himalayas. Pinus roxburghii (vern. Chir) grows at lower altitudes between 2000-5000 feet, whereas P. wallichiana grows in north-west Himalayas ranging from an elevation of 5000-12000 feet.
- Pinus gerardiana (vern. Chilgoza) occurs on the Himalayan flanks extending from Punjab to Afghanistan and Baluchistan ranging within the altitudes of 5000 to 12000 feet. Pinus insularis grows in Khasia and Chittagong hills.
- Two species of Podocarpus (P.neerifolia and P. wallichianus) occur in India. The former grows in Andaman Islands and eastern Himalayas, whereas latter grows in Nilgiri hills and Assam. Tsuga dumosa grows luxuriently in Darjeeling and adjacent regions, along with Abies densa, above an altitude of 2700 metres.
- Besides the above-mentioned 10 genera, which grow naturally in different parts of India, some Coniferales are cultivated as ornamentals in Indian gardens.
- There include Araucaria cooki and A. cunninghamii of Araucariaceae, Thuja occidentalis and Cupressus cashmeriana of Cupressaceae. Callitris cupressi of Cupressaceae is grown as a hedge plant in Nilgiris, whereas Cryptomeria japonica of Taxodiaceae is grown in Darjeeling and other areas.

Ans.
Geological time scale:-
> Earth’s history is approximately 350 million years old.
> Geologists have used two major units for subdividing the geological history of the earth these are- time and strata.
> On the basis of time the geological history of earth has been divided into five Eras namely Archaeozoic, Proterozoic, Palaeozoic, Mesozoic and Coenozoic.
> Eras have been divided into periods and periods into epochs.
> Similarly on the basis of strata, the geological history of the Earth is divided into system,series, stage and zone.
> The various eras and their age along with plant groups evolved during that period have been described in the given figure.
1. Precambrian Era:- Aarchaeozoic and Proterozoic eras are together known as Precambrian. It is said that life originated on the earth in Precambrian. The Rocks of this era have only a few fossils because either the environment was not suitable for fossilization or the organisms present during that time had so soft tissues that it was not fit for fossilization. Therefore, the absence of any fossil records makes it very difficult to tell something about the environment of Precambrian era.
2. Palaeozoic Era:- 
> This era had vegetation including both aquatic and land plants. The aquatic plants included species such as Nematothallus and Prototaxites. These two species show similarities with thallophytes. The first fossils of land plants were found in the Silurian and Devonian periods of this era (225-350 million years ago). Manograptus, Sporogonites, Zosterophyllum, Cooksonia, Rhynia, Horneophyton and Psilophyton were important fossil genera discovered.
> In the Carboniferous and Permian periods, Lycopsids, Sphenopsids and Pteropsids formed dense forests. Seed ferns (Pteridospermatophytes) were also abundant in this period (age of seed ferns). Presence of annual rings in certain fossil plants of this period indicates seasonal changes.
> Significant changes in environment occurred in late carboniferous resulting in the development of swampy regions. This type of habitat was unstable for woody vegetation and in the late Devonian period the vegetation present on the earth was converted into coal due to geological events. The coal beds of Pennsylvania and West Virginia we are formed due to coalification of Lycopsids, Sphenopsids, seed ferns and gymnosperms of that period. Fortunately few Psilopsids, Lycopsids and Sphenopsids escaped destruction and eventually gave rise to the present forms.
3. Mesozoic Era:- 
> The environment for the Triassic period of this era was very arid (dry) and thus unsuitable for the growth of plants requiring in humid climate. Fossil records however indicate the presence of many ferns, Cycadophytes and conifers in the Triassic period. This period is also known as the age of Cycads. Although flowering plants also originated in the period, their number was negligible.
> Significant changes occurred in the vegetation of the Cretaceous. Of the 300 cretaceous species collected from North America 200 species belong to angiosperms. It shows that angiosperm formed a significant part of the cretaceous vegetation.
4. Coenozoic Era:- 
> This era is known as the “age of angiosperms”. High mountain ranges such as Himalayas in Asia and Alps in Europe were formed during this era. As a result, the effect of hot winds got reduced and ICE AGE started. Gradually the ice shifted towards the poles.
> Simultaneously the development of tropical and temperate regions occured. These changes had major effect on vegetation. The seed plants gradually migrated towards tropical regions and those which could not migrate became extinct. As most plants of the late coenozoic era were deciduous, it shows that there was seasonal variations too.
> The vegetation of the temperate and the Polar Regions mostly consisted of annual and biennial herbs which could withstand low temperature.
Ans.
General accounts of Taxales:-
> Family Taxaceae, along with 5 of its living genera and 200 species, was usually treated as belonging to Coniferales until the beginning of the twentieth century. Besides the present members of Taxales, certain members of Podocarpaceae and Cephalotaxaceae, such as Podocarpus and Cephalotaxus, were also included under Taxaceae.
> It was Professor Birbal Sahni (1920), a well-known Indian botanist, who suggested that Cephalotaxus, Taxus and Torreya should be treated under Taxales. Florin (1948, 1951) has, however, opined that Cephalotaxus should not be included under Taxales but under Coniferales because it is a true Conifer.
> According to Florin (1948) Taxales include six genera, namely Taxus, Austrotaxus, Pseudotaxus (=Nothotaxus), Torreya, Amentotaxus and Palaeotaxus. Palaeotaxus is the only fossil genus of the family. Sporne (1965) has also followed the same classification.
> According to Turrill (1959), out of the total 19 species of Taxales, 7 species belong to Taxus, 1 each to Austrotaxus and Nothotaxus, 6 species to Torreya and 4 to Amentotaxus. Ramanujam (1976) mentioned that the order Taxales is poorly represented in the fossil flora of India.
General Characters of Taxales:-
i. The sporophytic plant body consists of evergreen, slow-growing, profusely branched shrubs or small trees.
ii. The leaves are simple, linear with acute apex. They are spirally arranged on the branches.
iii. The secondary wood is compact and pycnoxylic.
iv. The wood is elastic because tertiary spirals are present on the walls of the tracheids.
v. The resin canals are absent in wood or leaves.
vi. Plants are unisexual with only a few exceptions.
vii. Micro-sporangiophores are arranged in the form of small cones.
viii. On each micro-sporangiophore 2-8 pollen sacs are present on a scale-like or peltate disc.
ix. Prothallial cells are absent in the male gametophyte.
x. The ovule is solitary and borne terminally on a dwarf shoot.
xi. An aril is present at the base of each ovule.
xii. Pollination takes place by pollination drop mechanism.
xiii. The embryo is dicotyledonous.
xiv. The seeds are endospermic.
Types of Taxales:-
1. Palaeotaxus:-
> It is the only known fossil representative of Taxales. Its fertile specimens have been discovered from the rocks of the Triassic period of Mesozoic era. Plants had solitary terminal ovules, a characteristic feature only of Taxales.
> The ovule and later on the seed was borne at the tip of a short shoot. Its lower parts were enclosed by spirally arranged bracts. Aril was also present. Except at the top of the micropylar end, the ovule was enclosed by the aril.
2. Austrotaxus:-
> It is a living Taxad, represented by only one species. Plants are found growing in New Caledonia. Its male cones are quite peculiar and made up of micro-sporangiophores.
> Each micro-sporangiophore remains subtended by a bract, and only because of this peculiarity Nakai (1938) suggested that Austrotaxus should be placed in a separate family Austrotaxaceae. Each micro-sporangiophore terminates into a synangium formed by the fusion of 3 or 4 microsporangia.
3. Pseudotaxus (= Nothotaxus):-
> It is found growing these days in a small region of the forests of east China. It is also represented by only one species. Its male cones are also made of micro-sporangiophores similar to Austrotaxus, but here the bracts are irregularly distributed.
> Each micro-sporangiophore of Pseudotaxus is actually a highly reduced male cone, and, therefore, the entire structure, formed by a group of micro-sporangiophores, is a compound structure.
4. Torreya:-
> It is represented by 5 species and occurs in some east-Asian countries and some parts of USA, including Florida and California. Plants are mostly large trees attaining a height of 25 to 30 metres but some are only shrubs. The leaves of some of the species (e.g. Torreya californica) attain a length of 6 to 9 cm. or even more.
> Only a single vascular bundle is present in each leaf. Wood parenchyma is present in the secondary wood of the stem. The tertiary spirals are well-developed in the tracheids. In the ovule (Fig. 12.22B) the aril remains fused with the integument for most of its length except near the micropyle.
> There is no vascular bundle in the integument of its own. Two vascular bundles, however, run inside the aril and reach up to the apex of the mature ovule.
> From each of these vascular bundles develops a branch which passes through a foramen and supplies the stony layer of the ovule. Each of these branches then divides and forms a loop which surrounds the mature ovule or seed. The female gametophyte in the mature seed develops very fast and without any definite division pattern.
> The ultimate result is the formation of an irregular- shaped surrounding tissue. The micro-sporangiophores are not peltate. They are dorsiventral, scale-like structures. Each micro-sporangiophore contains four pendulous microsporangia or pollen sacs.
> Male prothallial cells are absent. The size of the male gamete cells is quite unequal. Each female gametophyte contains only one archegonium. The ventral canal nucleus is absent in the archegonium of Torreya.
5. Amentotaxus:-
This occurs in several parts of some east-Asian countries and represented by only four species. Its chief characteristic feature is shown by its seed which remains surrounded by its aril and several bracts, and all these structures develop at the terminal part of a peduncle. The peduncle attains a length of 1 – 2 cm. The aril remains fused with the integument, and there is no vascular supply at all to the integument.