Cupressus morphology anatomy and reproduction

1. CUPRESSUS

2. SYSTEMATIC POSITION
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressasceae
Genus: Cupressus

3. ■ Occurrence
■ They are evergreen trees or large shrubs growing to 5- 4 m tall.
■ These are native to scattered localities in mainly warm temperate regions in the
Northern Hemisphere.
■ All have decorative merit, particularly in a young state.
■ Common species planted in the plains and hills of India include: C. funebris ,
C.cashmeriana, C.sempervirens.

4. ■ Morphology
■ Tree is evergreen, large (5-40m ) tall, with pyramidal appearance.
■ The bark is thin, fibrous and greyish brown and peel off in long strips.
■ Branching is of 2 types: horizontal or erect main branches, which are
spirally arranged on the main stem and drooping side branches.
■ Main branches are devoid of leaves, whereas the drooping branches bear
small, greyish-green opposite and decussate leaves adpressed to the axis.
■ The leaves of the lateral pair are folded face to face and those of the facial
pair are flattened and grooved in the middle .
■ 2 types of leaves are seen : The leaves of the apical zone are small, closely
placed with acute apex and serrated margin. Mature leaves are longer,
brownish and distantly placed due to elongation of the internode.
■ The leaves are characterized by a prominent midrib and scattered stomata
on both the surfaces.

5. ■ The male cones (6-7mm long) , borne terminally on pendulous branch,
are brownish when mature.
■ 6 to 8 pairs of microsporophylls, each bearing 2 to 6 sporangia
abaxially, are arranged in a opposite and decussate manner on the
cone axis.
■ The female cones (10-12 mm long) are axillary on the pendulous
branches and each consist of four pairs of seed scale complexes
arranged in a opposite and decussate manner.
■ The lower most pair is generally sterile.
■ The fertile scales are peltate bearing 3-7 ovules/seeds per scale.
■ The fertile seed scales complexes are thick, four to six sided and have
a central pointed process called the boss.
■ The mature cone is brown and woody and persists on the tree long
after the seed shed.
■ The seed are dark brown , orbicular, compressed and narrowly winged.
The wings of successive seeds overlap.

6. ANATOMY
STEM
■ Both cortex and pith are narrow and consist of parenchymatous cells in young
stem.
■ After Secondary growth, distinct annual rings are formed.
■ Xylem Cylinder is thicker than the periderm, cortex and secondary phloem.
■ Secondary phloem is composed of sieve elements, phloem parenchyma, phloem
fibres and resin ducts.
■ Sieve areas are confined to the radial walls. The resin canals are large, bounded by
2 or 3 layers of secertory cells.
■ Phloem fibres occur at regular intervals in single tangential layers. These
alternative with rings of parenchyma and resin cells.
■ The phloem rays are uniseriate and 4 or 5 cell high . These are thin walled with
simple pits .
■ The tracheids of Secondary xylem are long and narrow with circular to elliptical
bordered pits on their radial walls.

7. ■ In the tracheids of summer wood , tangential pitting is also seen.
■ Parenchymatous cells are resinous.
■ Xylem rays are uniseriate, 1-5 cells high, comprising parenchymatous cells and
showing simple pits.
■ The wood is devoid of resin canals.
■ Thd pith get obliterated and is seen as a dense region in the centre.

8. ■ LEAF
■ Epidermis is covered with a thin cuticle.
■ Single-layer of thick walled cells constituting the hypodermis which may be
discontinous at places.
■ Mesophyll is differentiated into a layer of elongated palisade cells and spongy
parenchyma.
■ The palisade cells are towards the abaxial side or lower surface and contain
abdundant chloroplast.
■ The spongy tissue is composed of large irregular cells with numerous intercellular
spaces.
■ This is single vascular bundle with a resin canal below it.

9. REPRODUCTION
Microsporangium &Microsporogensis
■ Microsporangia arise on the abaxial side of the microsporophyll.
■ Below the epidermis few hypodermal archesporial cell differentiate which divide
periclinally to give rise to primary perietal layer and primary sporogenous cells.
■ The former after division forms the middle layer towards outside and tapetum
towards inside.
■ Primary sporogenous cells divide in all planes to form sporogenous tissue, the last
cell generation of which eventually give rise to MMC.
■ MMC undergo reduction division followed by cytokinesis which is simultaneous.

10. ■ The microspore tetrads are isobilateral and tetrahedral.
■ A young microspore has a large nucleus, dense cytoplasm and numerous dtrach
grains.
■ The pollen grains are shed at the uninucleate stage.
■ No prothallial cells ate formed.
■ Pollen wall consist of a fine granular, thin exine and a thick uniform intine.
■ Pollen are non-winged
■ Prior to meiosis , the strach grains which were present at the periphery get
distrubuted throughout the cytoplasm of the microspore mother cell.
■ After meiosis 1 the strach grains get divided in 2 groups and after meiosis 2 four
ssuch groups are seen.
■ There is thus a equal distribution of strach in the 4 microspore.

11. ■ MALE GAMETOPHYTE
■ The wind dispersed pollen grains are caught in the pollination drop and sucked in
reaching nucellus.
■ The micropylar canal which is very wide during pollination is closed after
pollination by the repeated division of the cells of the inner layer.
■ Also the edges of the seed scales complex give out teeth-like appendages which
closely interlock with each other.
■ The pollen grains are aporate and germinate on the nucellar tip .
■ At the time of pollen germination , the exine is thrown off after it gets ruptured
irregularly.
■ The microspore divides to form a small lenticular antheridial cell and a large tube
cell.

12. ■ The tube nucleus moves into the pollen tube followed by the antheridial cell which
divides to give rise to a large spermatogenous cell and a stalk cell.
■ The stalk cell soon loses its wall and comes to lie near the tip of the pollen tube
along with the tube nucleus.
■ Just before the pollen tube reaches the archegonium the tube and the stalk nuclei
degenerate and spermatagenous cell divides into 2 equal male cells.
■ Multiple male gamates have been reported.
■ The multiple male cells are produced by the super numerary division of the
spermatogenous cells.

13. ■ MEGASPORANGIUM & MEGASPOROGENESIS
■ The ovules are unitegmic and crassinucellate.
■ Several deep-seated sporogenous cells have been reported.
■ The megaspore mother cell after meiosis gives rise to linear tetrad of megaspores.
■ Some times 2or more megaspore may start enlarging , but these become arrested
soon.

14. ■ FEMALE GAMETOPHYTE
■ Nuclear divisions in the early stages are Simultaneous.
■ The gametophyte become cellular through alveoli formation.
■ A very conspicuous spongy tissue comprising 2or 3 layer surrounds the free nuclear
gametophyte. It is derived from the non-functional sporogenous cells.
■ Few cells at the micropylar end of the female gametophyte become prominent and
differentiate into archegonial initials.
■ They divide transversely to give rise to a small neck initials and a large central cell.
■ The neck is made up of 8 cells arranged in 2 tiers of four cells each.
■ The central cell divides to form an ephemeral ventral canal nucleus and a egg nucleus.
■ The latter enlarges and comes to lie in the centre of the devolping archegonium.

15. ■ A mature archegonium is oblong othe elongated a large egg nucleus , a ventral
canal nucleus and eight neck cells.
■ The archegonia occur in archegonial complexes. A group of archegonia is
surrounded by a common jacket.
■ With the development of the archegonial complex, the adjacent gametophytic
tissue grows upward, resulting in the formation of an archegonial chamber.
■ The total number of archegonia is 10-13.
■ The archegonia differentiate in that region where the pollen tubes make contact
with gametophyte.
■ The archegonial complexes are terminal at the micropylar end.

16. ■ FERTILIZATION
■ After traversing the nucellus, the pollen tube arrives in the archegonial chamber
and releases the male cells.
■ Subsequent to the degeneration of neck cells, a passage is formed through which
the male cells enter the archegonium.
■ Generally only one male cell finds its way into an archegonium.
■ The male nucleus is thus surrounded by its middle and inner cytoplasmic zones
while moving through the egg or maternal cytoplasm.
■ As it reaches the egg nucleus, the male nucleus moves in advance of the
cytoplasmic sheath.
■ The two fusing nuclei make contact with each other and take a turn of 180° so
that the male nucleus comes to lie below the egg nucleus.

17. ■ The two inner zones of the male cytoplasm envelope the zygote and later become
incorporated into the neocytoplasm.
■ After the fusion of the nuclear membrane , the zygote is formed surrounded by the
neocytoplasm, the egg cytoplasm having degenerated.

18. ■ EMBRYOGENY
■ The zygote nucleus divides thrice to give rise to 8 free proembryonal nuclei at the
archegonial base.
■ Wall formation take place resulting in primary proembryo comprising 2 tiers of 4
cells each.( Primary upper tier and Primary embryonal cells)
■ The primary upper tier again divides transversely to form an upper open tier and a
middle suspensor tier.
■ The primary embryonal cells also divide to form embryonal cells resulting in a 16-
celled secondary proembryo.
■ The cells of suspensor tier elongate to push the embryonal tier deep into the
gametophytic tissue.
■ Each cell between the terminal embryonal cell and suspensor elongates forming
embryonal suspensor.

19. ■ Both simple and cleavage polyembryonal are common.
■ The apical embryonal cells divides in all planes to form a meristamatic tissue.
■ The shoot apex and the root apex are differentiated by the activity of cells at
proximal end and distal end , respectively.
■ The cells between the root and shoot apices elongate along the long axis of the
embryo.
■ In peripheral region of the shoot apex , a group of cells become active and divides
more rapidly than the rest resulting in 2- well developed cotyledons.