Bennettitalean Theory

The Bennettitalean theory was first proposed by Saporta and Marion (1885), later on elaborated by Arber and Parkin (1907). Bennettitales is the extinct group of gymnosperms which existed long back in the Mesozoic era. These investigators worked out the similarities between the stromboli of the Bennettitalean plant Cycadeoidea dacotensis and flowers of the primitive angiosperm Magnolia. Both these structures are bisexual, and have an elongated axis having protective bracts, microsporophyll’s and megasporophylls, arranged successively from below upwards.

However, in spite of these superficial resemblances, further studies have shown several differences, which are as follows:

1.In Magnolia, the microsporophyll’s (stamens) are free and are spirally arranged on the axis, whereas in Bennettitales they are whorled and mostly connate.
2. In Bennettitales, the megasporophylls are greatly reduced, simplified stalk-like structures, each bearing a solitary terminal erect ovule. Between megasporophylls, there are sterile scales (inter-seminal scales), which are protective in function. No such structures are present in the flowers of Magnolia.
3. The micropylar tube formed in the ovules of Bennettitales are absent in the angiosperms and the pollen grains are shed on the stigma of the carpel (megasporophyll).

4. The seeds of Magnolia and other primitive angiosperms are with copious endosperm and small embryo while those of Bennettitales are non-endospermic with a large embryo.

5.In the bennettitalean stem there is a large pith, a thin vascular cylinder and a thick cortex, while the angiosperm stem has a small pith, a thick vascular cylinder and a thin cortex.

These differences indicate that Bennettitales cannot be considered as the ancestors of angiosperms. The similarities with angiosperms, most probably, might have resulted due to a common ancestry and parallel evolution. Arber and Parkin have postulated that the two groups did have a common origin from seed ferns and they might have diverged very early.

Botanical Gardens

What are botanical gardens ?

•Botanical gardens are the institutions that maintain the living plant collections of different varieties of plants.

•They include ornamental, cultivated, wild, medicinal, economically important, plants of various geographical regions, of special interests.

•A big botanical garden contains plant species from several corners of the globe.

•It also includes greenhouses, a library, a herbarium, research labs, photographs, paintings, illustrations, reprints, notebooks and specimens of several types.

•So botanical garden is not only a garden but a botanical institution.

•Modern botanical gardens act as centres for documentation, research, reference, data storage, education, conservation etc.

•At present there are more than 600 botanical gardens in the world.

Major Botanical Gardens of the world:

1. The New York Botanical Garden:

        This garden contains 50 different gardens and plant collections. Garden highlights include an 1890s-vintage, wrought-iron framed, “crystal-palace style” greenhouse; the Peggy Rockefeller Rose Garden; a rock garden; a 37-acre conifer collection; extensive research facilities including a propagation centre, 550,000-volume library, and an herbarium of over seven million botanical specimens dating back more than three centuries.

2. Royal Bot garden, Sydney, Australia:

•The Royal Botanic Gardens is a major botanical garden located in the heart of Sydney, Australia. Opened in 1816, the garden is the oldest scientific institution in Australia and one of the most important historic botanical institutions in the world. Its stunning position on Sydney Harbour and immediately adjacent to the Sydney Opera House ensure it is one of the most stunning gardens in the world.

•Covering 74 acres, the Garden forms a large natural amphitheatre, wrapped around the ‘stage’ of Farm Cove. It’s divided into four major areas called the Lower Gardens, the Middle Gardens, the Palace Gardens and the Bennelong precinct. Within the four major zones are many smaller gardens and features as well as large amounts of lightly wooded lawn areas.

3. Singapore Bot Garden, Singapore:

•Founded in 1859, the Singapore Botanic Gardens is a 183-acre botanical garden in Singapore.

•The National Orchid Garden is the main attraction, with the hilly three-hectare site holding a collection of more than 1,000 species and 2,000 hybrids of orchids. The Singapore Botanic Gardens has a small tropical rainforest of around six hectares in size, which is older than the gardens themselves and is in fact one of only 2 tropical rainforests found within a major city, the other being in Rio de Janeiro.

•Other attractions include an evolution garden, a ginger garden, wild monkeys, terrapins and much more.

4. Kirstenbosch Bot Garden, South Africa:

•Located at the foot of Table Mountain, this 89 acres garden was founded in 1913 to preserve the country’s unique flora. It’s one of the few botanical gardens in the world that only cultivate indigenous plants with the botanical garden established for the express purpose of local flora conservation, and even now, almost all the species therein are indigenous. Perhaps most famous is the garden’s trademark Crane Flower, a yellow version of which is named Mandela’s Gold.

•The garden includes a large conservatory exhibiting plants from a number of different regions, including savanna, fynbos, karoo and others. Outdoors, the focus is on plants native to the Cape region, highlighted by the spectacular collections of proteas.

5. Botanischer Garten Munchen, Munich , Germany:

•Munich’s first botanical garden, now called the “old botanical garden”, was established in 1809 to designs by Friedrich Ludwig von Sckell near Karlsplatz, where its remains are still visible.

•The garden cultivates around 14,000 species on 18 hectares, and serves to educate the public and train students, as well as preserve rare plants and European bee species. Major areas include an alpine garden, arboretum, collection of moor and steppe plants, rhododendrons, rose garden, and systematic garden.

•The garden also contains an extensive greenhouse complex, including rooms for bromeliads and arecaceae, cactus and succulents, cycads, ferns, orchids, and Mexican plants. The orchid collection includes over 2700 species from 270 genera, as well as hybrids. Featuring the Great Pavilion, which is the largest glasshouse in the world and contains an exhibit of giant bamboo.

6. Royal Botanical Gardens, Kew, England:

•The number one botanical gardens had to be the biggest, Kew Royal Gardens in London, England.

•Kew Gardens is the world’s largest collection of living plants. Founded in 1840 from the exotic garden at Kew Park in the London Borough of Richmond upon Thames, UK, its collections include more than 30,000 different species of plants, while the herbarium has over seven million preserved plant specimens.

•With over 320 acres of landscapes and gardens, including a soaring treetop walkway, 18 metres high and 200 metres long, tropical glasshouses, art galleries, a serene lake and waterlily pools.

•Kew’s glasshouses provide hours of undercover discoveries. With amazing giant lily pads in the Waterlily House, exotic rainforests in the Palm House, and 10 climatic zones in the Princess of Wales Conservatory. While Kew Palace and the Royal Kitchens allows you to discover Kew’s history and explore a beautiful Georgian royal retreat.

•One of the most interesting features of the garden is the Davies Alpine House, an eco-friendly building that houses cool weather plants without the use of refrigeration, instead relying on a series of underground pipes to maintain the appropriate climate.

Major Botanical Gardens of India:

1. Indian Botanical Garden, Kolkata:

•This famous botanical garden which is the largest and oldest of its kind in India, and considered to be the oldest botanical garden in South East Asia, is located at Shibpur near Kolkata, on the west bank of the river Hooghly.

 

•It was founded by Lt. Col. Robert Kyd in 1787, with an aim to establish a stock of plants which may be disseminated and prove beneficial to the inhabitants, rather than with a purpose of collecting rare plants as things of mere curiosity or furnishing articles for the gratification of luxury.

2. National Botanical Garden, Lucknow:

•This garden situated on the banks of river Gomti, was established in 1789, by the emperor Nawab Sadat Ali Khan. It was named as Sikander Bagh by Nawab Wajid Ali Shah, in remembrance of his beloved wife Begum Sikander Mahal.

•It was later converted into a Botanical Garden in 1946 with Professor K.N. Kaul as its first director and is now known as the National Botanical Research Institute, Lucknow, which is one of the numerous national laboratories under the Council of Scientific and Industrial Research. It also has a sub-centre at Banthra, about 20 kms. from Lucknow, covering an area of 120 hectares, where economic plants are grown on large scale.

•The main garden covers an area of 30 hectares and is famous for its Palm house, Fern house, Rosarium, Cactus house, Orchid house, orchards of mango, guava and Citrus and medicinal plants section. Attached with this garden are a herbarium, library and laboratories carrying on extensive research in various fields of Botany.

3. Lalbagh or The Mysore State Botanical Garden, Bengaluru: 

•This is the best botanical garden in South India, which was named ‘Lalbagh’ by Hyder Ali in 1760 because of its beautiful rose garden and red flowers. Its first director was Major Waugh (1799- 1819), who introduced a number of exotic plants from various countries into this garden. Later, this garden was converted into a proper botanical garden in 1856 and Rao Bahadur H.C. Jayaraja was its first Indian director.

•This garden is now famous for its beautiful layout and as a big centre of horticultural activities. It has a grape orchard, economic garden, a herbal garden, a tropical nursery and well-equipped laboratories for seed testing and soil testing.

4. Government botanical garden, Ooty:

•Government botanical garden located in Udamangalam in Tamil Nadu which is famous for huge collection of roses. This garden is considered as the largest garden for roses in India. About three hundred varieties of roses are grown in this garden.  Colorful Nilgiri birds are seen in this garden. There are many lawns consisting thousands of species of exotic plants, shrubs, trees and bonsai plants.

•The total area covered is about 22 hectares. Visit the garden in the frosty months  from November to February. You can see cork tree, paper bark tree, monkey puzzle tree in this garden. The garden is divided in to 6 parts and each section have variety of things to view. There is a fossil tree trunk which is 20 million years old. The famous flower show occurs once in an year and usually in may month.

Role of Botanical Gardens:

•1. Taxonomic Studies:

•Botanical gardens provide valuable information on various plants Local flora, bonsai, rare plants etc. They act as “outdoor laboratories” for students and researchers.

•2. Botanical Research:

•Botanical gardens supply wide range of plant species, seeds, flowers, fruits for botanical research.

•3. Conservation:

•Botanical gardens conserve and propagate rare species and genetic diversity.

•4. Education:

•They supply facilities for courses in local flora, horticulture, hybridization, plant propagation, etc. There educational programmes include workshops, training sessions for teachers, students, naturalists etc.

•5. Public Services.

•They help the public in identifying the local and exotic plant species; provide instructions for home gardening’s, propagation of plants; supply plant resource;, through sale or exchange.

•6. Aesthetics and Recreation:

•They attract people who have made gardening their hobby.

•7. Employment:

•They create job opportunities for a large number of young botanists.

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Permanent Tissues

What is Permanent Tissue ?

          The tissues that have lost the capacity of growth and division temporarily or permanently are known as permanent tissue. It is formed as a result of division and differentiation of meristematic tissue.

Types of Permanent Tissue:

1. Simple tissue

2. Complex tissue

3. Special tissue or Secretory tissue

1. Simple tissue:

•Simple tissues called homogenous tissues. A simple tissue may be defined as a group of similar cells that perform a common function.

•These are classified into three groups:

•(a) Parenchyma

•(b) Collenchyma

•(c) Sclerenchyma.

(a) Parenchyma:

•Parenchyma: (Para= Soft, Enchyma = Tissue)

i. These are composed of isodiametric living cells which may be oval or rounded.

ii. Cells have intercellular spaces.

iii. Cell wall is thin and made up of hemicellulose and cellulose.

iv. Vacuole is present and nucleus size is small

v. Cells have dense and living protoplasm.

vi. Cells may show meristematic activity. So these are also called as potential meristematic tissue.

vii. It is found in cortex, pith, mesophyll tissue, and endosperm and also associated with xylem and phloem.

•According to specific function, parenchyma is classified into four groups:

1. Aerenchyma:

Parenchyma having large air spaces is known as aerenchyma. It is found in hydro­phytes and it gives buoyancy to plant.

2. Chlorenchyma:

Parenchyma with large amount of chloroplast is known as chlorenchyma. It is found in mesophyll of leaf and helps in photosynthesis.

3. Prosenchyma:

Parenchymatous cell becoming long and tapper at both ends, without intercellular space is known as prosenchyma. It helps in mechanical support.

4. Idioblast:

Parenchyma that stores unwanted or ergastic substances is known as Idioblast.

Functions of Parenchyma:

1. Parenchyma mainly serves as storage tissue.

2. Being meristematic in nature, parenchyma is associated with regeneration, formation of adventitious root, graft union, wound healing.

3. Aerenchyma renders buoyancy, prosenchyma gives mechanical support, chlorenchyma helps in photosynthesis and idioblast stores ergastic substances.

What is Taxon ?

Taxon (plural : taxa) is defined as "a named taxonomic group of any rank". In this way at Family level, taxa are Malvaceae, Asclepiadace, Papaveraceae etc. The examples of taxa of a genus (or generic taxa) are Hibiscus, Calotropis, Argentine etc.
The term 'taxon' was actually coined to replace awkward phrases like ' taxonomic entity' and 'taxonomic unit'.
Moreover, the organisms contained within a rank e.g. species, genus, or order can also be called as taxa.

Plant Identification

Plant identification is the determination of a taxon on the basis of overall similarities and differences with other taxa.
For any study based on a taxon, its proper determination is a prerequisite.
There are two methods of identification:
i) Direct Method: Done by comparing an unknown specimen with that of another which has been authoritatively predetermined.
ii) Indirect Method: Done with the help of keys, descriptions, illustrations etc.