ginkoales.pptx

It is called as “living fossil”
The whole order is extincted except one species Ginkgo biloba
This order was occurred in Triassic periods of Mesozoic age (200,000,000 years ago)
This order consists of 16 genera and many species (all in fossil forms except one)

1. SEMINAR ON GINKGOALES

2. GINKGOALES CLASSIFICATION : GROUP : Gymnospems DIVISION : Coniferophyta CLASS : Coniferopsida ORDER : Gingoales

3. INTRODUCTION It is called as “living fossil” The whole order is extincted except one species Ginkgo biloba This order was occurred in Triassic periods of Mesozoic age (200,000,000 years ago) This order consists of 16 genera and many species (all in fossil forms except one)

4. GENERAL FEATURES The trees are tall and have an excurrent habit. The root penetrates deep into the substratum and forms tap root system. The leaves are decidious and fan shaped . The venation is open to dichotomous The plant is dioecious and slow growing. The wood is Pycnoxylic Inflorescence – catkin, which bears 2 to 12 microsporangia in it.

5. GENERAL FEATURES Characteristic feature of endosperm is “Tent pole” The mature seed are large, fleshy, and about in the size of small apricot. Outer layer- fleshy orange coloured Inner layer- hard and stony The fleshy coat gives unpleasent odour The seeds are produced in large in numbers The spermatozoids are usually motile and bear spiral band of cilia.

6. FAMILIES IN GINKGOALES Sporne in 1965 classifies Ginkgoales into two families: Trichopityaceae including Trichopitys . It is an extinct family. Ginkgoaceae includes both extinct and one living member. The living member is Ginkgo biloba .

7. DISTRIBUTION It grows wild in a small, restricted and almost inaccessible region in south-eastern china and in province of chekiang in eastern china Later it is successfully cultivated in US, as the most valuable shade tree. The tree has also been cultivated in India and grow well under mild climate (-30°F),but the reproductive cycle is rarely complete at such a lower temperature range.

8. HABIT AND HABITAT Ginkgo biloba is tall tree that may grows up to 100 feet tall with excurrent habit but may achieve irregular form in older trees. These are slow growing trees considered to be best shade trees. It can grow along the hill slopes or even in the plains They are dioecious .

9. GINKGOALES- HABIT

10. HOW TO IDENTIFY THE Ginkgo biloba ? EXTERNAL CHARACTERS : STEM : The stem is erect, woody, tall and branched The stem has two types of branches: Long shoot - arise from main axis, may bear long and dwarf shoots. T hey arise from a singly node. B uds and foliage leaves present.

11. PARTS OF THE PLANT

12. 2. Dwarf shoot - They arise from axils of foliage leaves. They differ from long shoots in their short length. They bear reproductive organs.

13. ROOT The tap roots are extensively branched and grow quite deep into the soil. The root caps and root hair are present

14. LEAVES They are simple, large fan shaped ,expands at apex and narrowed base. They are petiolate and are highly variable. When the leaves emerges it is folded towards each other but later it becomes flattened.

15. In the early stages, the leaves are pale yellow in color but it becomes typical dark green during half development.

16. ANATOMICAL STRUCTURES STEM : EPIDERMIS – Single layered, brick shaped. Distinct in young plants. CORTEX – Extensive in short shoots and narrow in long shoots. Outer cortical layers are filled with calcium oxlate crystals and tannin filled cells There is no distinct endodermis and pericycle . Bundles are conjoint, collateral, open and endarch . Pith – present, larger in dwarf plants and narrow in long shoots

17. ROOT : Young root have extensive cortex contains mucilage cavities and calcium oxlate crystals. Endodermis distinct in young roots. Next is pericycle . Young roots are diarch or triarch . (2 or 3 xylem strand alternating same no. of phloem). Secondary growth is not distinct, shows indistinct annual rings. The P hellogen develops in the outer cortical layer and forms the outer corky layers of root.

18. LEAF : Has upper and lower epidermis Upper epidermis has thick outer cuticle membrane . T hey are polygonal between the veins and rectangular over the veins. Stomata is surrounded by a guard cells and 4-6 layers of accessory cell. Mesophyll tissue- between both epidermis consists of spongy and palisade parenchyma. They are loosely arranged and contain mucilage ducts. Lower epidermis is wavy in nature. Stomata are arranged broad but indistinct between the veins.

19. REPRODUCTION They are Dioecious . They are separate as male and female trees. It is very difficult to differentiate between male and female trees. It is possible only after they bear male and female fruitifications .

20. THE MALE AND FEMALE PLANTS

21. MICROSPORANGIUM Male reproductive organ The development is eusporangiate . The microsporangium arises fron single initial cell and divides into primary wall cell and primary sporogenous cell. The tapetum arises from outer most sporogenous cell. Several layer arises from the periclinal and anticlinal division of primary wall cell.

22. MEGASPORANGIUM STROBILUS The female reproductive organ has a little to remind one of a strobilus. The megasporangiate strobilus borne on dwarf shoots. They have long stalk. Initially 2-3 ovules formed but only one develops The young ovule is cream coloured .

23. DEVELOPMENT OF MEGASPORANGIUM During initial stages of development, ovule has mound of tissue called the nucellus . The development starts from megaspore mother cell. The nucellar apex expands. The pollen chamber is formed by the break bown of the nucellar apex. The contents of breakdown nucellar apex forms the pollination drop. The integument around the nucellus forms a small pore.

24. This pore is called micropyle . The pollen exudes through the pollen chamber and catches the pollen grains into it. The pollen drop dries and seals the micropyle . During all these stages the mother cells under go meiotic division and forms tetrad. As the ovules mature and integument becomes thick, the outer layer is green and fleshy, the middle layer is stony and the inner layer is fleshy and supplied with watery substances. The megaspore develops into female gametophyte. They contains two or three archegonia.

25. MATURE OVULE POLLINATION- Anemophilous (by wind)

26. GAMETOPHYTIC GENERATION

27. ECONOMIC IMPORTANCE Ginkgo is commoly a “ Ornamental tree ”. In US, it is also grown as the “ shade tree ” In china and Japan it is worshipped The endosperm of roasted seed is edible, if taken more it is proven as FATAL It is proven that trees of Ginkgo biloba is resistant of bacterial attacks.

28. MEDICINAL USES : Ginkga biloba is used in medicine for the memory illness. It helps to maintain mental alertness It is also prevent acidity and digestion problems.

29. In china, it is used in tea making

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