Plant Diversity and Angiosperms in India

INTRODUCTION

Angiosperms or flowering plants (also called Angiospermae, Magnoliophyta, or Anthophyta) are the most diverse group of the plant kingdom, comprising of about 2,50,000 species in 350 families (Kenrick, 1999). Flowering plants are by far the most numerous, diverse, and “successful” extant plant group, containing well over 95% of all land plant species alive today (Simpson, 2006). Angiosperms are characterized by (i) seeds produced within a carpel with a stigmatic surface for pollen germination, (ii) a much reduced female gametophyte, consisting in most cases of just eight nuclei in seven cells; and (3) double fertilization, leading to the formation of a typically triploid nutritive tissue called endosperm (Judd et al., 2002). Several apomorphies distinguish the angiosperms from all other land plants: (1) the flower, usually with an associated perianth, (2) stamens with two lateral thecae, each composed of two microsporangia, (3) a reduced, 3-nucleate male gametophyte, (4) carpels and fruit formation, (5) ovules with two integuments, (6) a reduced, 8-nucleate female gametophyte, (7) endosperm formation and (8) sieve tube members (Simpson, 2006). Some of these apomorphic features, which represent the product of a unique evolutionary event, have become further modified in particular lineages of angiosperms. Almost all angiosperms produce vessels in the xylem tissue, though this feature probably evolved within the group. Angiosperm phloem differs from that of all other plants in having sieve tube elements accompanied by one or more “companion cells” that are derived from the same mother cell.

Flowering plants grow in virtually every habitable region and are dominant in some aquatic and most terrestrial ecosystems, the notable exception to the latter being coniferous forests. Angiosperms comprise the great bulk of our economically important plants, including our most valuable food crops.

India with a geographical area of about 32, 87,263 sq km is the seventh largest and tenth industrialized country of the world. It is situated between 804' N to 3706' N latitude and 6807' E to 97025' E longitude. The longitudinal variation divides Indian subcontinent into four climatological zones, viz., equatorial, tropical, subtropical and warm temperate. The forest cover of the country have been estimated to be 6, 37,293 km2 (19.39% of the geographic area of the country) and includes dense forest (3, 77,358 km2), open forest (2, 55,064 km2) and mangrove (4,871 km2).

India represents about 11% of world’s flora in just about 2.4% of total land mass. Out of the 25 biodiversity ‘Hotspots’ identified in the world (Myers, 1990), India has two, namely Eastern Himalaya and Western Ghats. These hotspots posses majority of plant diversity in India. In terms of species diversity, approximately 45,000 plant species are found in India (Khoshoo, 1994, 1995; Sharma et al., 1997). The angiosperms are represented by c. 17,500 species out of which 5725 species are endemic to India. About 28% of the total Indian flora and about 33% of angiosperms occurring in India are endemic (Nayar, 1996). It is roughly estimated that about 10% of flowering plant species in India are threatened and 34 plant species have been reported to be extinct (Nayar and Sastry, 1987-1990).

The studies on Indian plants were first initiated by the European visitors. Even before the publication of Species Plantarum by Linnaeus (1753), Hendrik Van Rheede (1678-1703) started publication of his monumental 12 volume work ‘Hortus Malabaricus’. However, actual work on Indian flora was initiated by Roxburgh (1814, 1820- 1824) and later by Hooker and Thompson (1855). The publication of Flora of British India by Sir J.D. Hooker (1872- 1897) gave a stimulus to taxonomic studies in our country and since then several regional and state floras have been published. In 1954, Botanical Survey of India was revived with a view to make intensive studies of local flora especially to gather precise information on the identity, floristic diversity, distribution, ecological association, phenology, medicinal and economic uses of plants.

India is immensely rich in biological diversity. Such richness is largely due to varied physical environment, latitude, altitude, geology and climate. The climate and altitudinal variations coupled with varied ecological habitats have contributed in the development of immensely rich vegetation wealth, and varied flora and fauna forming a very unique biodiversity. Seeing the rich plant diversity, Hooker (1904) commented that ‘The Indian flora is more varied than that of any other country of equal area in the eastern hemisphere, if not on the globe’. The Indian flora represents taxa occurring in different countries including Afghanistan, Bhutan, Bangladesh, China, Nepal, Pakistan, Myanmar, Malaysia, Indonesia, Thailand and Indo-China. There are even the representatives from African, American, Australian and European countries.

DISTRIBUTION AND HABITAT

Bio-geographical Territories in World

The Indian region is one of the most diverse bio-geographic regions of the world having wide ranging topography from permanently snow covered high Himalayan ranges to plains at sea level, low lying swamps and mangroves, island systems, tropical evergreen rain forests, fertile alluvial plains, hot deserts and high altitude cold deserts. The climate ranges from tropical and sub-tropical in Indo-Gangetic plains and in the peninsular regions to temperate and arctic in the Himalayan region.

Biogeographically India represents two of the major realms (Palaearctic and Indo-Malayan) and three biomes. Considering the vastness of the country and variation pattern in different areas, the country is divided into ten botanical regions with distinct bioclimatic conditions. These include: Coromandal coast, Malabar, Indus plain, Indian desert, Gangetic plain, Assam, Eastern Himalaya, Central Himalaya, Western Himalaya, Andaman and Nicobar Islands and Lakshdweep and minicoy group of islands (Mudgal and Hajra, 1997).

India harbors very diverse climatic conditions and thus fosters different types of habitats. The major mountain ranges in India are the Himalaya and the Western Ghats. The Indian Himalayan region is spread over the states of Jammu and Kashmir, Himachal Pradesh, Sikkim, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, and a part of Assam, along with eight districts of Uttarakhand and one district of West Bengal. Biogeographically, the Indian Himalayan region falls under Boreal Zone which has two sub-zones, viz., Sino-Siberian and Sino-Himalayan. The area can be divided into four distinct zones longitudinally: (i) the Siwalik (900 – 1500 m), (ii) the outer Himalaya (1500 – 3500 m), (iii) the middle or lesser Himalaya (3600 – 4600 m), and (iv) the Greater Himalaya (above 4,600 m). This complex mountain system consists of narrow and deep valleys, glaciers and fertile terrain.

Five climatic zones can be delineated in the Himalayan region based on geographic and physiographic factors. These are: (1) Warm tropical, (2) Warm sub-tropical, (3) Cool temperate, (4) Alpine and (5) Arctic. While these are only broad zonations, there are many local variations in the climate due to precipitation, temperature, wind patterns, humidity etc. The type and nature of soils also vary vastly in the Himalayan region from deep alluvial to the thin and bare soils of the high mountains. The nature of the soil depends upon the rocks, the prevailing climatic conditions, topography and vegetation.

According to Udvardy (1975), biodiversity exists on earth in 8 broad realms with 193 bio-geographical provinces. It has been estimated that world’s 12 countries Australia, Brazil, China, Columbia, Ecuador, India, Indonesia, Madagascar, Malaysia, Mexico, Peru and Zaire together hold 70% of its total flowering plant diversity. These countries have been termed as “Megadiversity” countries (Mc Neely et al., 1990)

Rodgers and Panwar (1990) have divided India into 10 phytogeographic zones and 24 biotic provinces. Gadgil and Meher-Homji (1990) have recognized 16 phytogeographical zones in India. On the other hand, Das (1996) has recognized 9 physiographic regions within the Indian Territory. Chowdhery and Murti (2000) have recognized 11 phytogeographic regions for India, each of which have its uniqueness in ecosystem, vegetation and floristic composition. These phytogeographic regions are: Western Himalaya, Eastern Himalaya, Gangetic plains, North East India, Semi arid and Arid regions, Deccan Plateau, Western Ghats, Eastern Ghats, Andaman and Nicobar Islands, Lakshdweep and Coastal regions.

Distribution of Angiosperms in India

In India, the vascular plants form the most dominant and conspicuous vegetation cover comprising of over 17,500 species of angiosperms which represents more than 7% of the world's known flowering plant species (Hooker, 1872-1897; Karthikeyan et al., 1989; Sharma and Balakrishnan, 1993; Sharma and Sanjappa, 1993; Sharma et al., 1993; Hajra et al., 1995; Mudgal and Hajra 1997- 1999; Singh et al., 2000; Karthikeyan, 2000). These species are distributed in more than 4000 genera occurring in diffenent ecosystems from the humid tropics of Western Ghats to the Alpine zones of the Himalayas and from Mangrooves of tidal Sunderbans to the dry desert of Rajasthan.

In India, dicots are represented by 2,282 genera and 12,750 species whereas monocots are represented by 702 genera and 4,250 species. Dicots account for c. 75% of flowering plants in terms of both genera and species. On the other hand, remaining 25% is contributed by monocots. Out of 511 recognized plant families (Brummit, 1992), 320 families with more than 4000 genera are represented in the Indian flora. Of which Poaceae is the largest family with about 263 genera and more than 1200 species. In India, over 60 families of flowering plants are monotypic, e.g., Illiciaceae, Ruppiaceae, Turneraceae, Tetracentraceae, etc. Asragaluts, Carex, Dendrobium, Ficus, Habenaria, Impatiens, Primula, Rhododendron, Saussurea, Taraxacum, etc. are some of the dominant genera of flowering plants in India. Out of the estimated 17,500 species of angiosperms, approximately 15% species are trees which include some of the highly valued timber species of the world and belong to the families like Annonaceae, Dipterocarpaceae, Euphorbiaceae, Fabaceae, Lauraceae, Moraceae, Meliaceae, Verbenaceae, etc. There are several botanical curiosities like Aeginetia indica, Balanophora dioica, Boschiniackia himalaica, Drosera, Epipogium, Galeola, Mitrastemon yamamotoi, Monotropa, Nepenthes khasiana, Pinguicula, Sapria himalayana, Utricularia spp., etc. Species in certain groups like Orchids, Bamboos, Rhododendrons, Citrus, Hedychiums, Impatiens, Pedicularis, Primulas, etc. exhibit remarkable diversity in India (Rao, 1994). Dominant angiospermic families in India are given in table1 (after Groombridge, 1992; Sharma et al., 1997).

Table 1. Dominant families of dicots and monocots

Families No. of Genera Species

Dicots Asteraceae 116 892 Fabaceae 133 975 Rubiaceae 113 616 Acanthaceae 92 510 Euphorbiaceae 84 527 Lamiaceae 72 435 Apiaceae 72 288 Brassicaceae 64 Scrophulariaceae 62 368 Asclepiadaceae 57 260 Monocots Poaceae 263 1291 Orchidaceae 184 1229 Liliaceae 45 214 Cyperaceae 38 545 Araceae 29 126 Arecaceae Zingiberaceae 24 191

Insectivorous and parasitic plants

The carnivorous plants (insectivorous plants) trap and digest insects to meet the requirement of nitrogen deficiency. Altogether over 450 species of carnivorous plants have been reported of which approximately 30 species occur in India. The insectivorous taxa belong to family Droseraceae (3 spp.), Nepenthaceae (1 spcies) and Lentibulariaceae (36 spp.). The parasitic plant species are prominent in Loranthaceae (46 spp.), Santalaceae (10 spp.), Balanophoraceae (6 spp.), Rafflesiaceae (1 spp.), Cuscutaceae (12 spp.) and Orobanchaceae (54 spp.).

Aquatic plants

About 2 percent of all flowering plants known in the world inhabit water bodies and more than 50 percent of these are represented in Indian subcontinent (Lavania et al., 1990). Some important aquatic plants families are: Alismataceae (8 spp.), Aponogetonaceae (6 spp.), Azollaceae (1 sp.), Barclayaceae (2 spp.), Butomaceae (1 sp.), Cabombaceae (2 spp.), Callitrichaceae (3 species), Isoetaceae (10 spp.), Lemnaceae (14 spp.), Najadaceae (7 spp.), Nelumbonaceae (1 sp.), Nymphaeaceae (7 spp.), Podostemaceae (24 spp.), Pontederiaceae (13 spp.), Ceratophyllaceae (3 spp.), Hydrocharitaceae (13 spp.), Potamogetonaceae (18 spp.), Ruppiaceae (1 sp.), Salviniaceae (3 spp.), Trapaceae (2 spp.), Typhaceae (4 spp.), Zannichelliaceae (1 sp.), etc. The members of families Podostemaceae and Tristichaceae grow on rocks under water in fast flowing streams.

The aquatic plants in India are highly diversified comprising free-floating forms (Eichhornia crassipes, Lemna perpusila, Nymphoides hydrophylla, Trapa natans var. bispinosa, Pistia stratiotes, Wolffia microscopia, W. globosa), rooted aquatics with their foliage floating (Nymphaea nouchali, N. stellata, Euryale ferox, Nelumbo nucifera), submerged aquatics (Vallisnaria natans, Hydrilla verticillata, Najas graminea, Potamogeton pectinatus) emergent aquatics (Scirpus maritimus, Cyperus articulates, Sagittaria trifolia, S. guayanensis subsp. leppula) and marsh plants (Ranunculus scleratus, Hydrolea zeylanica, Panicum paludosum, Polygonum barbatum, P. glabrum). The aquatic flora play an important role as water purifier by absorbing heavy metals, e.g. Ceratophyllum demersum (chromium), Bacopa monnieri (copper and cadmium). Limosella aquatica, Hippuris vulgaris occur in subalpine-alpine lakes.

Mangroves

Mangroves are the plants that inhabit coastal regions and estuaries. They are adapted to survive under marshy conditions. In India, mangroves cover an area of approximately 6700 Km² which constitutes c. 7 percent of the world’s mangroves. The largest stretch of mangroves in India occurs in Sunderbans (West Bengal) which covers an area of about 4200 km². It has been designated as World Heritage site of which 80% of them are restricted to Sunderbans (West Bengal) and Andaman & Nicobar islands (Chowdhery and Murti, 2000). The remaining taxa are scattered in the coastal areas of Andhra Pradesh, Tamil Nadu, Orissa, Maharashtra, Gujarat, Goa and Karnataka. Some of the dominant mangrove species include Avicennia marina, A. officinalis, Bruguiera gymnorrhiza, B. parviflora, Ceriops tagal, Heritiera fomes, Lumnitzera spp., Rhizophora mucronata, R. apiculata, R. stylosa, Sonneratia spp., Xylocarpus spp., etc. The shrubby Aegialitis rotundifolia and Acanthus ilicifolius are common on poor saline plains. The herbaceous succulent halophytes are represented by Aegiceras corniculatus, Suaeda brachiata, Sesuvium portulacastrum and Salicornia brachiata. The characteristic mangrove palms are: Nypa fruticans and Phoenix paludosa.

Indicator species

Some species of angiosperms growing on metalliferous soils accumulate large amounts of metals in their roots and reflect the levels of metal present in the soil (indicators). For example, presence of copper is indicated by Astragalus spp., Croton roxburghii, Hyptis suaveolens, Holarrhena pubescens, Impatiens balsamina, Vernonia cinerea, and indicates presence of Uranium (Aery, 1977; Venkatesh, 1964, 1966).

Diversification of Primitive and Advanced Families

The primitive families are confined to those regions which are very old in geological time scale in comparison to the newly developed areas. Assam, North-east Indian region and Deccan Peninsula are older in comparison to the other phytogeographical regions of India. These regions are more or less identical in age with Sri Lanka, South West Chinese region and Malay Peninsula. The Deccan Peninsula shows its floristic relationship with Sri Lanka and Malay provinces, while the North east India shows its floristic relationship with Myanmar, South West Chinese Provinces and Malay Peninsula. Thus the Malay region shows similarity with Deccan Peninsula on one hand and North east India on the other. By this way the North East India shows similarity with Deccan Peninsula to some extent (Mitra and Mukherjee, 2006).

India (Eastern Himalaya including North east India) is considered as a sanctuary of primitive flowering plants. The occurrence of such a large number of primitive angiosperms led Takhtajan (1969) to designate this region as the ‘Cradle of Flowering Plants’ where angiosperms have diversified (Table 2)

Table.2. Primitive flowering plants occurring in India (after Rao, 1994)

Species	Family	Distribution (in India/world)
Alnus nepalensis	Betulaceae	Himalaya (India), China
Altingia excels	Hamamelidaceae	E. Himalaya (India), China, Japan, Thailand, Taiwan
Aspidocarya uvifera	Menispermaceae	E.Himalaya (India), S.E.Asia
Betula alnoides	Betulaceae	Himalaya (India), E.Asia
Decaisnea insignis	Lardizabalaceae	E. Himalaya (India), W. China
Distylium indicum	Hamamelidaceae	Himalaya (India), China, Japan, Taiwan, Laos, Korea
Euptelea sp.	Magnoliaceae	E. Himalaya (India), China, Japan
Exbucklandia populnea	Hamamelidaceae	E. Himalaya (India), Sumatra
Haematocarpus thomsonii	Menispermaceae	E. Himalaya (India), W. Malaysia, New Guinea
Holboellia latifolia	Lardizabalaceae	W. & E. Himalaya (India), China
Houttuynia cordata	Saururaceae	Himalaya (India), China, Japan, Thailand, Taiwan
Magnolia griffithii	Magnoliaceae	E. Himalaya (India), Myanmar
M. gustavii	Magnoliaceae	E. Himalaya (India), Myanmar
M. griffithii	Magnoliaceae	E. Himalaya (India), Myanmar
Magnolia spp.	Magnoliaceae	E. Himalaya (India), S. China, Indo-China, Java
Myrica esculenta	Myricaceae	W. & E. Himalaya (India), China, Korea, Japan
Parvatia brunoniana	Lardizabalaceae	E. Himalaya (India), S. W. China
Pycnarrhena pleniflora	Menispermaceae	E. Himalaya (India), N. W. Australia
Stauntonia spp.	Lardizabalaceae	E. Himalaya (India), S. China, Taiwan,Vietnam, Korea, Japan
Tetracentron sinense	Tetracentraceae	E. Himalaya (India), Myanmar, S.W. China

The advanced families occur in those areas which are comparatively very young in the geological time scale. On the basis of this idea it can be stated that the Himalayan region of India is very young in its age as compared to Deccan Peninsula and North East Indian regions of India, as it harbours most of the advanced families with well diversified restricted genera and species. A comparative account of diversification of primitive and advanced families of India and its adjoining area is given in table 3.

Table 3. A comparative account of diversification of primitive and advanced families of India and its adjoining area (after Mitra and Mukherjee, 2006).
S.No.	Advanced Families	No. of genera	No. of species
1.	Apiaceae	10	42
2.	Asteraceae	12	92
3.	Fabaceae	11	17
4.	Lamiaceae	11	22
5.	Orchidaceae	27	83
6.	Poaceae	17	40
7.	Rubiaceae	19	58
Primitive Families
1.	Annonaceae	3	16
2.	Circaeasteraceae	1	1
3.	Hamamelidaceae	2	3
4.	Magnoliaceae	1	2
5.	Menispermaceae	4	5
6.	Ranunculaceae	4	6

The advanced families are young in their age and also they are confined to the areas which are also geologically young, they are unable to spread in the wider regions. On the other hand, primitive plant families are older in their age and also found to confined in those areas which are geologically very old. So they get sufficient time to spread over larger areas, as a result of which the primitive families show less number of restricted genera and species in their credit in comparison to the advanced families (Mitra and Mukherjee, 2006).

Habitats

Different ecological habitats occur in India ranging from tropical rainforest, subtropical savanna or shrublands, temperate forest, alpine mosses to xerophytic variation of desert.

The habitat types vary from the humid tropical Western Ghats to the hot deserts of Rajasthan, from cold deserts of Ladakh to the long, warm cost line stretches of peninsular India. While Cherrapunji and Mawphlong in the north-eastern state of Meghalaya are the two wettest places on earth, Dras in Ladakh is the coldest inhabited place of the world.

Phytogeographically, the eastern Himalaya forms a distinct floristic region. The area comprises Nepal, Bhutan, and neighboring states of northern India along a continuous sector of the Yunnan province in south-west China. In Nepal, there are around 7000 plant species, many of which overlap those of India, Bhutan and even Yunnan. Of these species, at least 500 (almost 8%) are believed to be endemic to Nepal. Bhutan possesses an estimated 5000 species, of which as many as 750 (15%) are considered to be endemic to the eastern Himalaya (Anonymous 1999). This region is the meeting ground of the Indo-Malayan, Afro-tropic and Indo-Chinese biogeographical realms as well as the Himalayan and Peninsular Indian elements, formed when the peninsular plate struck against the Asian landmass, after it broke off from Gondwana land. The region is recognized as refugium of flowering plants and center of active speciation (Rao, 1994). The numerous primitive angiosperm families found in this region include Degeneriaceae, Eupomatiaceae, Himantandraceae, Lardizalbalaceae, Magnoliaceae, Trochodendraceae, Tetracentraceae, Winteraceae. The primitive genera are Alnus, Aspidocarya, Betula, Decaisnea, Euptelea, Exbucklandia, Haematocarpus, Holboellia, Houttuynia, Magnolia, Mangelietia, Pycnarrhena, and Tetracentrol (Malhotra and Hajra 1977).

Regions of High Diversity

India is one of the 12 mega biodiversity countries of the world. It represents an example of conglomeration of diverse bioclimates influenced by neighbouring areas (particularly Mediterranean), the unique location, peninsular land mass, Gangetic plains and the crown of complex chain of mountain systems – the Himalaya. The Himalayan region with only 18% of India’s land area, houses 81.4% of the country’s stock of gymnosperms, 47% of angiosperms, 59.5% of lichens, 58.7% of pteridophytes, 43.9% of bryophytes and 53.07% of fungi found in India.

Orchidaceae with over 1331 taxa (S. Misra, 2007) is one of the dominant families and probably the second largest among all families of flowering plant known from India. Of these 407 taxa are endemic to India. Out of the 18 monotypic orchid genera of India, 13 are found in the Himalayan region. In the Eastern Himalaya, the Orchid family is the largest, with 60% species, whereas in the Western Himalaya, Asteraceae with 540 species is the largest family followed by Poaceae with 439 species and Fabaceae with 362 species. Carex with more than 100 species and infraspecific categories is the largest genus in the Himalaya. Rhododendron with 96 species and infra-specific categories, and Astragalus with 90 species, is the largest genera in the Eastern and Western Himalaya, respectively.

Some other plants with pronounced diversity in the Eastern Himalaya include the Hedychium (Zingiberaceae) with 18 species out of 35 Indian species, and numerous species of bamboos. The Eastern Himalaya is a cradle of numerous primitive angiosperms, such as Manglietia and Euptelea (Magnoliaceae) and Tetracentron (Tetracentraceae). Christollea himalayensis, recorded from Mt. Camet is the flowering plant occurring at the highest altitude (6300 msl). Arceuthobium minutissimum, (small angiosperm) grows on Himalayan conifers. Apart from these botanical curios, the Himalayan region has a rich diversity of medicinal and aromatic plants.

The floristic richness has also rendered the North-Eastern region and Western Ghats to be recognized as two hotspots among 25 hotspots identified throughout the world. The humid tropical conditions met within these regions not only support exceptionally diverse vegetation but have also resulted in speciation in several genera, thus adding to the high endemicity of the flora (Nayar, 1996). In addition to these two, there are about 40 other sites in different phytogeographical zones of India which have high degree of endemism and genetic diversity. Mc Neely et al. (1990) estimated that 70% of world's total flowering plants occur in 12 countries and these have been designated as Mega diversity centres or mega­biodiversity country. The earth’s 25 biodiversity hotspot regions collectively cover about 2% of the planet’s land surface, yet claim more than 50% of all terrestrial species diversity. They have within them a phenomenal 1, 25,635 plant species. The top 11 hotspots (out of 25) for plant endemism harbor 5000 or more species as endemics. It accounts for 93,214 plant species, or 37.3% of the total global plant endemics (Myers 1988).

Western Ghats

The Western Ghats, which covers an area of approximately 1, 60,000 Km², are among the 25 biodiversity hotspots globally identified. The wide variation of rainfall patterns in the Western Ghats, coupled with the region's complex geography, produces a great variety of vegetation types. These include scrub forests in the low-lying rain shadow areas and the plains, deciduous and tropical rainforests up to about 1,500 meters, and a unique mosaic of montane forests and rolling grasslands above 1,500 meters. Based on the ecological factors and floristic composition, four major forests and 23 floristic types have been identified.

Eastern Himalaya

Eastern Himalaya covering the states of Sikkim, Darjeeling district of West Bengal, Assam, Manipur, Tripura, Meghalaya, Arunachal Pradesh, Mizoram and Nagaland is the richest of the phytogeographic regions of India affording the highest plant/ animal diversity (Rao, 1994). This region is characterized by high rainfall and humidity. The abundant rains and high humidity contribute the occurrence of largest number of species in this region. North eastern region of India, blessed with wide range of physiography and ecoclimatic conditions, is the richest biodiversity centres of the Indian subcontinent (Hooker and Thompson, 1855; Hooker, 1905; Chatterjee, 1962; Rao, 1974). The north eastern India has a geographical area of about 2, 55,050 Km². The rich plant wealth of this region has been reported by Hooker (1854). Further, Hooker’s work on “Flora of British India” (1872-97) and “Sketches on Flora of British India” (1905), presents a very detailed account on vegetation and flora of this region. Kanjilal et al. (1934-1940), in their “Flora of Assam” have provided a detailed account with emphasis on woody flora of this region. There are works on “Forest flora of Meghalaya” by Haridasan and Rao (1985, 1987) and “Grasses of North eastern India” by Shukla (1996).

There are several genera endemic to Eastern Himalaya. Some important endemic genera are Aucuba, Bryocarpum, Pleurospermopsis, Gamblea, Lepidostemon, Parajaeschkaea, Paroxygraphis, Risleya, Sphaerosacme, Treutlera and Brachycaulos. Cyathopus is endemic to Sikkim. Some genera like Biswarea, Hymenandra, Jejosephia, Neoluffa, Pauia, etc. are endemic to North eastern India.

Some important Eastern Himalayan endemic species are Abies densa, Agapetes incurvata, A. sikkimensis, Dipsacus atratus, Eriobotrya hookeriana, Geum macrosepalum, Larix griffithiana, Lindera heterophylla, Liparis perpusilla, Lloydia flavonutans, Maddenia himalica, Meconopsis grandis, M. superba, M. villosa, Myricaria albiflora, Primula whitei, Rhododendron baileyi, R. camelliaeflorum, R. ciliatum, R. glaucophyllum, R. grande, R. lantanum, R. lindleyi, R. wallichii, R .wightii, Rubus fragarioides, Sassurea conica, Acanthus leucostachys, Aconitum assamicum, Anoectochilus sikkimensis, Aeschynanthus parasiticus, Baliospermum micranthum, Berberis dasyclada, Calamus leptospadix, Calanthe densiflora, Capparis acutifolia, Cotoneaster assamensis, etc. (Chowdhery and Murti, 2000)

Plant Diversity in Western Himalaya

The Western Himalayan region is one of the 12 biogeographic regions of India and includes Jammu and Kashmir, Himachal Pradesh, and Uttaranchal. This region constitutes the alpine zone, temperate, humid and warm climatic conditions. The main portion of Western Himalaya lies in J & K state comprising 67.5% of total western Himalaya whereas Himachal and Uttarakhand comprise only about 17% and 15.5% respectively (Kachroo, 1983; Dhar et al., 2002; Singh et al., 2002). The extreme variations in climate (subtropical to alpine cold desert), altitude and habitat have contributed significantly for the great diversity in its flora. Though the Western Himalaya is relatively less varied in floristic composition than eastern Himalaya, particularly in Rhododendrons, bamboos, orchids and gymnosperms, it has the distinction of having greater diversity of high altitude Gentians, Primulas, Saussureas, Saxifragas, etc. (Rau, 1975; Awasthi, 1997; Kumar and Chauhan, 2006).

There are more than 4500 species of flowering plants in Western Himalaya, the Asteraceae being the largest plant family represented by c. 540 species (Sharma and Singh, 2001). Other important plant families include Poaceae, Fabaceae, Cyperaceae, Roasaceae, Lamiaceae, etc. The ten largest plant families of flowering plants in different states are given in table 4.

Table 4. Dominant families of Western Himalaya (after Kumar and Chauhan, 2006)

S.No.	India	Jammu & Kashmir	Himachal Pradesh	Uttarakhand
1.	Poaceae	Asteraceae	Asteraceae	Poaceae
2.	Orchidaceae	Poaceae	Poaceae	Asteraceae
3.	Fabaceae	Fabaceae	Fabaceae	Fabaceae
4.	Asteraceae	Cyperaceae	Rosaceae	Cyperaceae
5.	Rubiaceae	Brassicaceae	Scrophulariaceae	Lamiaceae
6.	Cyperaceae	Lamiaceae	Lamiaceae	Ranunculaceae
7.	Euphorbiaceae	Scrophulariaceae	Cyperaceae	Brassicaceae
8.	Acanthaceae	Rosaceae	Ranunculaceae	Rosaceae
9.	Lamiaceae	Ranunculaceae	Apiaceae	Orchidaceae
10.	Rosaceae	Apiaceae	Brassicaceae	Scrophulariaceae

Endemic flora

The diverse climatic and habitat conditions in India provide favourable conditions for speciation and endemism. Although India is connected by land with a number of other countries, it has a large proportion of endemic flora. Infact India harbours more endemic species of plants than any other region of the world except Australia. About 36% of flowering plants are endemic to India. The reason for the presence of such a high percentage of endemic plants in India is the presence of lofty Himalayan mountain ranges on the north-east and north-west of the mainland, sea on the three sides in the peninsular region and the extreme hot and arid conditions in West, which have effectively prevented migration or the intermingling of floristic elements of other regions. The moist humid, tropical condition of Western Ghats and the North east India favour the evolution and speciation of endemic elements. It is interesting to note that though there is an admixture of various foreign floras, the Indian flora has as many as c. 6100 species belonging to over 140 genera and 47 families which are endemic to Indian region (Table 5) (Chatterjee, 1939; Nayar, 1980; Balakrishnan, 1996).

Table 5. Endemic species in India

Region	Approximate number of species
Eastern Himalaya and North-eastern region	2500
Western Ghats and Peninsular India	2600
North-Western Himalaya	800
Andaman & Nicobar Islands	200

In India areas rich in endemism are north-east India, the Western Ghats and North-western and eastern Himalaya. A small pocket of local endemism also occurs in eastern Ghats (Mackinnon and Mackinnon, 1986). The Gangetic plains are generally poor in endemics, while the Andaman and Nicobar Islands contributes at least 220 species to endemic flora of India. Of all the flowering plants the family Orchidaceae shows high degree of endemism and it is estimated that approximately 35% of species of Orchids are endemic to India. In the neighboring state of Sikkim (geographical area 7,298 km2), of the 4,250 plant species, 2,550 (60%) are endemic. Some of the endemic taxa are: Astragalus kashmirensis, Dalbergia coromandeliana, Frerea indica, Mangifera andamanica, Nepenthes khasiana, Nilgirianthus reticulates, Oryza nivara, Prunus himalaica, Pterocarpus santalinus, Syzygium andamanicum, Syzygium travancoricum.

Due to peculiar features of Western Himalaya, high degree of endemism has been reported from this region (Chatterjee, 1939; Ahmedulla and Nayar, 1986; Ahmedulla, 2000). Trans-Himalayan cold desert and Western Himalaya of Himachal Pradesh and Uttarakhand are designated amongst the 12 important centres of endemism in India which are also considered as centers of genetic diversity and speciation (Dhar and Kachroo, 1983a; b; Dhar et al., 1987; Kumar and Chauhan, 2006).

Invasive species

The climatic conditions and micro habitats in India have favoured the establishment of alien taxa migrated from different part of the world. Many alien plants such as Lantana camara, Ageratum conyzoides, Eupatorium adenophorum, Tithonia tagetifolia, Jatropha gossypifolia, Opuntia elatior, etc. which have become a part of Indian flora were introduced as ornamentals. Some plants such as Stellaria media, Spergula arvensis, Sagina apetala, Anagallis arvensis, Convolvulus arvensis, Trigonella corniculata, etc. came to India as impurities with seeds of cultivated plants.

The weeds of family Asteraceae such as Eupatorium adenophorum, Parthenium hysterophorus, Mikania micrantha, Erigeron karvinskiskianus, Conyza bonariensis, Xanthium strumarium and Tridax procumbens have naturalized in different parts of india and have become aggressive weeds. The aggressive weeds like Parthenium hysterophorus have spread throughout India and threatened the native vegetation. Mikania micrantha has invaded the forest of North eastern region wereas Eupatorium adenophorum and E. odoratum have spread from Himalayan region to Western Ghats. Croton bonplandianum, Euphorbia prostrata (Euphorbiaceae), Amaranthus spinosus (Amaranthaceae), Argemone Mexican (Papaveraceae), Lantana camara (Verbenaceae), have become established in India. Aquatic taxa like Eichhornia crassipes, Pistia stratiotes have spread to such an extent that they have threatened other aquatic angiosperms.

Angiospermic genera restricted to India

Mitra and Mukherjee (2006) recorded 267 genera and 782 species belonging to 80 families restricted to India and its adjoining areas. Of these restricted taxa of flowering plants, 72 families belong to dicots and 8 monocots. Dicot families comprise 213 genera and 622 species whereas monocots include 54 genera and 160 species. Based on their survey, Mitra and Mukherjee (2006) reported that the Orchidaceae is the most diversified family which shows highest number (27) of restricted genera followed by Rubiaceae (19), Poaceae (16), Asteraceae (12), Lamiaceae (11), Fabaceae (11) and Apiaceae (10). On the basis of the number of species, Asteraceae is the most diversified family (having 92 species) followed by Orchidaceae (83 species), Rubiaceae (58 species), Apiaceae (42 species), Poaceae (40 species), Lamiaceae (22 species) and Fabaceae (17 species).

ECONOMIC UTILITY

Since time immemorial man has been using plant resources to meet his daily requirements. Besides food, shelter and clothing, plants provide us many useful products including medicine for the cure of various ailments. The immense diversity which occur in flowering plant in India provides economic benefits as they are important sources of food, fodder, timber, medicine, fibers, spices, dyes and tannins, beverages, gums and resins, etc. (Singh et al., 2002). The members belonging to families Poaceae, Fabaceae, Rosaceae, Solanaceae, Asteraceae and Cucurbitaceae, etc. have been domesticated for food. Out of c. 17,500 species of flowering plants, nearly 3000 are utilized as food (cereals, pulses, fruits, vegetables, beverages, etc.). Wheat, rice and maize accounts for nearly 75% of India’s cereal supply whereas pseudocereals (Amaranthus, species of Chenopodium, and Fagopyrum esculentum) and others (Avena sativa, Elusine coracana, Echinochloa sp., Hordeum vulgare, Panicum miliaceum, Pennisetum sp., Secale cereal, Setaria italica, Sorghum bicolor) account only for the remaining 25% supply.

Legumes or pulses are obtained from more than 20 species, of family Fabaceae. These include Cajanus cajan, Cicer arietinum, Dolichos uniflorus, Lablab purpureous, Glycine max, Lathyrus sativus, Lens esculenta, Phaseolus spp., Pisum sativum, Vicia faba, and Vigna spp., Cyamopsis tetragonoloba. Fruits and nuts are obtained from members of different families such as Rosaceae (Malus pumila), Rutaceae (Citrus spp.), Anacardiaceae (Anacardium occidentale, Mangifera indica), Vitaceae (Vitis vinifera), Musaceae (Musa sapientum), Arecaceae (Cocos), Bromeliaceae (Annanas comosus), Myrtaceae (Psidium gujava), Punicaceae (Punica graniatum), Rhamnaceae (Zygiphus), Moraceae (Morus alba), Cucurbitaceae (Cucumis, Citrulus), Annonaceae (Annona squamosa), Caricaceae (Carica papaya) provide fruits. Some principal nut yielding species are: Anacardium occidentale, Aleurites moluccana, Buchanania angustifolia, Castanea sativa, Cola acuminate, Corylus avellana, Juglans regia, Pistacia vera, Prunus communis, Trapa bispinosa, Euryale ferox, etc.

More than 1200 species of both cultivated and wild herbaceous plants are consumed as vegetables. They chiefly belongs to families Brassicaceae (Brassica spp, Raphanus sativus), Solanaceae (Solanum tuberosum, S. melangena, Capsicum spp, Lycopersicon esculentum), Cucurbitaceae (Cucurbita spp., Citrullus spp., Cucumis spp., Momordica charantia) Convolvulaceae (Ipomoea batatas), Euphorbiaceae (Manihot esculenta), Dioscoreaceae (Dioscorea spp), Liliaceae (Alliums pp.), Chenopodiaceae (Chinopodium spp., Spinacia oleracea, Beta vulgaris), Amaranthaceae (Amaranthus), Asteraceae (Lactuca sativa), Araceae (Colocasia spp.), Malvaceae (Abelmoschus esculentus).

Essential oils and fatty acids are obtained from a variety of flowering plants including Arachis hypogea, Brassica spp., Carthamus tinctorius, Cocos nucifera, Elaeis guinneensis, Gossypium spp., Guizotia abyssinica, Glycine max, Helianthus annuus, Linum usitatissimum, Sesamum orientale and Ricinus communis. Seeds of some wild species like Pongamia pinnata, Actaea acuminate, Prinsepia utilis, Sorbus aucuparia, Derris indica, Madhuca longifolia var. latifolia, Shorea robusta, and Schleichera oleosa are used for extraction of fatty oils. More than 400 species of angiosperms have been exploited for extraction of essential oils. Some essential oil yielding plants are: Acorus calamus, Santalum album, Vetiveria zizanioides, Cinnamomum camphora, Cymbopogon spp., Boswellia, Citrus spp., Eucalyptus sp., Jasminum spp., Mentha spp., Lavandula, and Rosa spp.

India is one of the major spice producing countries in the world. Some of the important taxa used as spices, condiments and flavoring agents are: Anethum sowa, Apium graveolens, Brassica juncea, Cinnamomum verum, Carum carvi, Coriandrum sativum, Cuminum cyminum, Crocus sativus, Capsicum spp., Curcuma longa, Elettaria cardamomum, Eugenia caryophyllus, Myristica fragrans, Piper nigrum, Pimpinella anisum, Foeniculum vulgare, Trigonella foenum-graecum, Nigella sativa, Amomum spp., Murraya koenigii, and Zingiber officinale. Non-alcoholic beverages are obtained from Camelli sinensis (Tea), Coffea arabica (Coffee) and Theobroma cacao (Cocoa). Fresh sap from Phoenix sylvestris, Borassus flabellifer are also used as beverages.

The wood of many trees are used as timber, furniture making, for agricultural implements and household articles. Some of the important timber yielding plants are Albizia lebbec, Dalbergia sissoo, Gmelina arborea, Shorea robusta, Tectona grandis, Terminalia spp.

Fibers are obtained from members belonging to families like Arecaceae (Borassus flabellifer, Caryota urens, Calamus spp., Cocos nucifera), Bombacaceae (Bombax ceiba, B. insigne, B. malabaricum and Ceiba pentandra), Cannabinaceae (Cannabis sativa), Fabaceae (Crotalaria juncea), Linaceae (Linum usitassimum), Malvaceae (Hibiscus cannabinus, H. sabdariffa, Gossypium spp.), Tiliaceae (Corchorus capsularis, C. olitorius) Poaceae (Eulaliopsis binata, Dinochloa andamanica, Phragmites karka, Themeda spp., species of Dendrocalamus, Sehima, Saccharum, Sorghum, Arundinaria, Bambusa, Chimonobambusa); Cyperaceae (Cyperus corymbosus); Agavaceae (Agave sisalana, Yucca gloriosa); Musaceae (Musa textilis). These fibers are used for rough weaving, making mats, baskets, paper, ropes, cordages, brushes, etc.

Gums and resins are obtained from the members of families such as Fabaceae (Acacia spp., Astragalus spp.,); Sterculiaceae (Sterculia urens); Cochlospermaceae (Cochlospermum religiosum) and Combretaceae (Anogeissus pendula). Resin is obtained from Boswellia spp. and Bursera gummifera of the family Burseraceae. In India, chief rubber producing taxa are: Hevea brasiliensis, Manihot spp. (Euphorbiaceae); Ficus elastica (Moraceae) and Parthenium argentatum (Asteraceae). Tannins and dyes are obtained from members of families Fabaceae (Acacia nilotica, A. senegal); Anacardiaceae (Schinopsis lorentzii, Rhus spp.); Myrtaceae (Eucalyptus spp.); Polygonaceae (Rumex hymenosephalus); Rhizophoraceae (Rhizophora mucronata, R. apiculata, Ceriops tagal, Bruguiera spp.); Combretaceae (Terminalia spp., Anogeissus spp.). Bixa orellana, Acacia catechu and Pterocarpus santalinus are good sources of natural dyes. Besides, these Mallotus philippinensis, Butea monosperma, Erythrina spp., Carthamus tinctorius, Crocus sativus, Lawsonia inermis, Indigofera spp., are used as sources of dye.

Plants used for the manufacture of paper mainly belong to family Poaceae such as Bambusa arundinacea, Arundinaria sp., Dendrocalamus strictus and Eulaliopsis binata. The wood of trees like Boswellia serrata, Populus spp. is used for making paper pulp. Sugar is manufactured from Saccharum officinarum and Beta vulgaris.

Medicinal Plants:

More than 1300 species of flowering plants are used for preparation of herbal drugs. Some of the important medicinal plants are: Adhatoda zeylanica, Withania somnifera, Panax assamicus, Tinospora cordifolia, Plantago ovate, Holarrhena antidysentrica, Boerhavia diffusa, Terminalia chebula, T. bellarica, Phyllanthus emblica, Achyranthes aspera, Acorus calamus, Andrographis paniculata, Asparagus adscendens, A. racemosus

Bacopa monnieri, Gymnema sylvestre, Holarrhena pubescence, Rauvolfia serpentina, Catharanthus roseus, Gloriosa superba, Centella asiatica, Orozylum indicum, etc.

CONSERVATION OF BIODIVERSITY

India is rich in all aspects of biodiversity (ecosystem, species and genetic level) due to its varied climatic conditions and geographical/physical features. The loss of biodiversity is mostly pronounced in the tropical rain forests. The rainforests in the tropics have been alarmingly disturbed and cleared for expansion of agriculture, logging, mining and many other activities. Destruction of these forests has resulted in the degradation of environment and habitat of the species. The rich genetic diversity has been depleted and many plant species are facing threat in their natural habitats (Haridasan & Rao, 1985; 1987; Manilal and Pandey, 1995).

There are 85 National parks, 448 Sanctuaries and 12 Biosphere Reserves with a total area of over 10 million hectares. About 4.5% of the total geographical area is currently under in situ programme for habitat and ecosystem conservation. In addition, there are more than 300 zoological gardens; deer parks safaris, aquaria etc. for ex situ conservation, multiplication and dissemination of economically important, endemic, rare and threatened plant species. A chain of Botanic Gardens have been established in different climatic zones of the country. There are a number of Gene Banks, seed banks established for the conservation of germplasm of economically important species, e.g. National Bureau of Plant Genetic Resources. After the ratification of “Conservation of Biological Diversity” (CBD) by India in 1994, various schemes/ programmes have been launched by the Ministry of Environment and Forests- the nodal agency for implementing CBD in the country. “National Action Plan on Biodiversity Conservation”, “Capacity building in taxonomy”, “Assistance to Botanic Gardens”, etc. are some of the important programmes launched by the MoE & F.

Many effective conservation programmes like World Wide Fund (WWF), Man and Biosphere (MAB), Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), Convention on Biological Diversity (CBD) etc. have been launched. The India acceded to the CITES in 1976, and Ministry of Environment and Forests was opted as Management authority for CITES in 1976. Botanical Survey of India was designated as Scientific Authority for CITES on plants.

The area of conserving the rare and threatened plants through the use of biotechnological approaches is vital to the conservational needs of the country. It is necessary to have a well conceived production programme for the conservation of plants which usually do not produce prolific viable seeds and therefore are under constant threat of elimination. In vitro techniques are being increasingly applied to supplement conventional methods of propagation.

India with its rich diversity has a great responsibility for preserving its environment for future generations. In managing the genetic resources of the country two vital principles related to diversity should not be ignored. Firstly, the biomass/productivity ratio of an ecosystem is proportional to its diversity. Secondly, ecosystems rich in diversity are indeed rich (because the country has parts of two biogeographical realms-the Paleraitic and Indo-Malayan and its arid western parts harbour communities of distinct Afro-tropical affinities). Despite attempts at conservation through a protected area system of national parks, sanctuaries and biosphere reserves, the coverage is not comprehensive nor is the security of all protected areas assured in the long term. Wildlife conservation has proved to be the best means for securing biodiversity and preserving genetic resources and endangered species. The current problems being faced in forest and wildlife conservation arise directly from the resource dependencies of the people inhabiting forested regions. These dependencies are becoming more intense because the productivity of several ecosystems in these regions is going down due to overuse of land resources (Ramachandran, 1992, Pandey, 1995).

The wasteland/forest land should be utilized for in situ conservation of threatened, endangered and economically important species. Encouragement towards conservation of biodiversity may be achieved by developing awareness through various work agencies especially forest and agriculture departments as well as through NGOs. Comprehensive Ethnobotanical surveys of the plants, animals and microorganisms used by human populations throughout India are to be taken on priority basis. Documentation of the interactions between traditional human societies and their useful plants and animals, including the preservation of germplasm, need special attention of conservation biologists.

THRUST AREAS FOR FUTURE STUDIES

The efforts made by the taxonomists in India have resulted in the survey and exploration of many unexplored areas and a large number of voucher specimens have been deposited in different Herbaria throughout the country. The exploration of unexplored areas and accumulation of a large number of herbarium specimens have resulted in the publication of state floras, district floras and regional floras. In many institutes and organizations the taxonomy divisions are neglected. This trend needs to be reversed. Mo En &F had come forward with AICOPTAX projects to strengthen the skilled manpower. Important research needs for India are inventorization of diversity and distribution, phenology, reproductive biology, growth rates, nursery techniques, cultivation practices, harvesting and preservation techniques, tissue culture propagation and in situ conservation of gene pool and ex situ storage of germplasm (Pandey, 1995).

The Hooker’s flora of British India is more than a century old and has several drawbacks as for as nomenclatural changes and addition of new taxa are concerned. Botanical Survey of India has been assigned ‘The flora of India’ project. This goal of publishing the national flora can only be achieved if floristic studies are done at micro level and taxonomic revisions/ monographs are prepared on different families and genera. There is a need for preparing comprehensive inventories of the plant species at state, regional and national level. Long back, Santapau, (1958) suggested that for the revision of flora of India first we must have district and provincial floras because local floras will be the basis for compilation of regional floras and the regional floras will form the basis for the preparation of flora of India. It was further suggested that universities should be encouraged and help to produce flora of University campus, towns and neighboring regions.

Taxonomists have to identify reasons for changes in the existing species diversities which would help in formulating effective conservation strategies. The extensive surveys and explorations being undertaken by active taxonomic research centre in India need to be analyzed to prepare a comprehensive list of rare, threatened, endangered and endemic plant species. Also there is a need for revision of Red Data Book because a large number of new taxa have been described and status of several species has changed. Ministry of Environment and Forest, Government of India has initiated focused studies on the flora of protected areas and fragile ecosystems. The floristic studies of several biosphere reserves and national parks have been completed and published. However, a number of protected areas are yet to be fully explored. There is need for a holistic approach by creating awareness among people towards conservation and this can be achieved by peoples participation.

Herbaria, especially in the universities and smaller institutions need to be strengthened and biodiversity registers may be maintained at the district level. Besides making collections, on the spot critical observations are to be made during field trips. This is possible only when limited areas are explored intensively. Besides, floristic studies, new comparative data such as DNA sequences and DNA barcoding are to be incorporated in future systematic studies on Indian flora.

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i. Gene sequencing and genomics

ii. Molecular analysis

b. Diversity in Vegetative Propagation

Vegetative reproduction takes place by means of tuber, runner, sucker….

c. Diversity in Sexual Reproduction

Angiosperms reproduce both sexually and asexually.

2. CLASSIFICATION

3. SYSTEMATIC STUDIES

4. INFRASTRUCTURE AND MAJOR STUDIES

a. Institutes involved in the past and present studies

b. Centres of Excellence

c. Important contributors

d. Floristic studies

e. Books, Monographs and Dedicated Journals

f. Experimental studies

g. Molecular and biotechnological Advances

5. ECONOMIC UTILITY

a. Food: Out of ca 3000 plant species being exploited for food by man, nearly 200 are more or less domesticated but only about 20 of them constitute major food crops. Three major crops- wheat, rice and maize account for 54% of caloric consumption in developing countries.

b. Industrial:

c. Medicinal

d. Trade

e. Ethnobotanical aspects

f. Benefits to rural and forest communities

g. Negative aspects (pathogenecity, diseases, allegenicity)

6. ENVIRONMENTAL SIGNIFICANCE

a. Ecology

i. Ecological adaptations

ii. Relationship with other organsms

iii. Rare and endangered taxa

iv. Climatic, edaphic and water requirements

v. Ecosystem services

vi. Invasive species

vii. Impact of pollution

viii. Assessment of effect of climate change

b. Resistance and Tolerance to Abiotic Factors

Apomixis has been reported in more than 300 plant species but is especially prevalent within the Asteraceae, Poaceae and Rosaceae. Within the Poaceae, apomixis has been reported in more than 125 species, including members of the economically important genera Bothriochloa, Brachiaria, Dichanthium, Eragrostis, Paspalum, Pennisetum, Poa, Tripsacum (Poaceae). Diplospory (Generative apospory) is reported in several Compositae. Diplospory may be Antennaria type (Antennaria, Erigeron and Eupatorium), Taraxacum type (Taraxacum, Chondrilla) and Ixeris type (Ixeris). Paspalum (Poaceae) also show Taraxcum type of diplospory. Apospory (somatic apospory) is reported in Hieracium, Crepis (Asteraceea), Panicum, Paspalum (Poaceae). Apomixis has been transferred from Pennisetum squamulatum (2n=6x=54) to pearl millet (2n=4x=28) (Hanna, 1995). The presence of occasional apospory in diploid Panicum antidotale (2n=18) and its predominance in a tetraploid race (2n=36) of the species affords an example in support of the views expressed by Gustafsson (1947) that “the action of many of these apomixis influencing genes is stronger on the polyploidy level than it is on the diploid level”. The work of Leblanc et al. (1995) on maize-Tripsacum hybrids have confirmed the one dominant gene hypothesis for apomeiosis, but also suggested that apomixis might rather be determined by a complex of

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