The maidenhair tree, scientifically known as Ginkgo biloba, is one of the oldest living tree species, recognized as a 'living fossil'. It is cultivated globally for its medicinal properties despite being endangered in the wild and features distinct fan-shaped leaves that turn golden in autumn. The tree's reproductive structures are dioecious, with male and female trees being indistinguishable until they produce cones, and the seeds are characterized by their unpleasant odor and hypogeal germination.

1. GINKGO
MERIN ALICE GEORGE

2. • CLASS: CONIFEROPSIDA
• ORDER: CONIFERALES
• FAMILY: GINKOACEAE

5. • The maidenhair tree is one of the oldest living tree species in the
world.
• Known as a ‘living fossil’, it is the sole survivor of an ancient group
of trees that outlived the dinosaurs.
• Though endangered in the wild because of deforestation, the
maidenhair tree is cultivated throughout the world and prized for the
medicinal properties of its leaves.

6. • It has fan-shaped, greenish-yellow leaves that have two or more distinct lobes.
• In autumn, the leaves of the maidenhair tree turn golden and fall to the ground.
• Whilst male trees have pollen-producing floral spikes, fertilized female trees bear
round, fleshy, yellowish fruits that contain a large seed and have an unpleasant
scent.
• It takes 20—35 years for maidenhair trees to reach maturity and start bearing
fruits.

7. • MORPHOLOGY
• An attractive tree – pyramidal shape. Trees 30 m tall, fan-shaped
deciduous leaves. Fruits – orange in colour – resemble apricot in size &
colour. Female tree – fruits emit offensive odour – due to lactic acid – hence
only male trees are preferred in gardens.
• Male & female trees identical – takes 20 years to flower – seed propagation
not common – since female plants are not preferred.
• Propagation mainly by layering, grafting and cuttings.
• Stem – 2 types of branches – shoot dimorphism – long shoots & dwarf
shoots.

8. • Long shoots – 1 meter long – unlimited growth – elongate rapidly –
grow fast – bear scattered leaves.
• Dwarf shoots – spur shoots – limited growth – slow growth – cluster of
leaves at apex – arise from axils of leaves on the long shoot – produce
crown of leaves and reproductive structures.
• Leaves - bilobed, fan – shaped – deciduous – golden yellow when they
are shed – resemble Adiantum – so called “Maiden hair tree”.
• Root - tap root.

9. ANATOMY
• Root Anatomy – diarch. Endodermis with conspicuous thickening on
radial walls (casparian thickening). Pericycle broad. Sec. growth – as
usual – but annual rings not so conspicuous. Xylem parenchyma – some
cells with crystals.
• Phloem – with thick walled fibres.
• VAM found in the roots. Fontana 1985, reported Glomus epigaeum
fungus from roots. Growth of seedlings increased when inoculated with
G. epigaeum.

10. • Stem Anatomy – Epidermis highly cuticularised. Cortex & pith
prominent and large.
• Tannin cells, Ca-oxalate crystal cells, etc. found in outer cortex. Large
mucilage canals in inner cortex.
• Old stem – cortex with fibres & sclereids. Long shoots – cortex & pith
small. . Pri. structure like other gymnosperms. Sec. thickening as usual.
• Wood is brittle & of no commercial value. Xylem & phloem as in others.
Rays uniseriate. Trachieds narrow, X-parenchyma with Ca-oxalate
crystals. So Ginkgo wood differs from other Coniferales. Dwarf shoot with
manoxylic wood & phloem with crystals & so similar to Cycads. Cork
cambium also formed.

11. • Long Shoot – cortex & pith narrow, few mucilage ducts present, wood is
hard & pycnoxylic & leaf traces few as leaves are scattered.
• Dwarf Shoot – cortex & pith more, more mucilage ducts present, wood is
less, manoxylic & double leaf traces in dwarf shoot due to crown of leaves.
• Leaf Anatomy – wavy margins – Upper & lower epidermis – thick cuticle.
Stomata sunken – present on lower side - haplochelic.
• Mesophyll with palisade & spongy in leaves of long shoots. No palisade in
leaves of dwarf shoots.
• Mucilage canals seen in mesophyll between the veins. Vas.bundles many –
each with sclerenchymatous & crystal celled bundle sheath.

12. REPRODUCTION
• Most primitive among living seed plants. Heterosporous – dioecious. Male
& female trees indistinguishable till cones are produced.
• Male cone – axillary, not compact – a loose structure resembling a catkin
inflorescence - central axis 2.3 to 3 cm with 2 vas. traces.
Microsporophylls stalked & spirally arranged.
• Each sporophyll – has a slender stalk with knob-like hump or projection
& 2 pendant sporangia – longitudinal dehiscence – lines face each other.
• Hump has a mucilage cavity – which on shrinkage pulls the sporangia
apart – lines are exposed & pollen shed.

14. • Female cone – greatly reduced – axillary in origin of a leaf or scale leaf – with a long
peduncle – that bifurcates at apex & each branch bears a single ovule. Of the two
ovules 1 aborts. Sometimes both develop into seeds.
• At the base of ovule – a rim of swelling present – the collar – it sometimes grows into a
leafy structure – hence it represents a reduced megasporophyll. Collar originates after
integument – devoid of vas. supply.
• Ovules of Ginkgo are considered as cauline & terminal on lateral axes.
• MICROSPOROGENESIS- Same as in other gymnosperms

16. • POLLINATION – by wind – pollination drop.
• FERTILIZATION – Zygote formed.
• EMBRYOGENY
• Zygote nucleus
• 256 free nuclei
• Cells of micropylar region elongate rapidly to form massive suspensor
• Cells of chalazal region develop into proembryo / embryonal mass.
• Cotyledons 2 – rarely 3
• A weak coleorrhiza present.
SEED
• Bilaterally symmetrical. Of two ovules - one aborts – so each branch has one seed – germination is hypogeal.
• Fruit – orange red coloured – emits offensive smell.
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