Sectioning Materials

Ulva Thallus
The given material is identified as thallus of Ulva
Reason: The given material is green in colour, flat and resembles garden lettuce. In cross section
shows two layers of cell with cup shaped chloroplast.
Description: Ulva is a green alga, common inhabitant marine environment and it prefers nutrient
rich environment. Some species of Ulva are also found in brackish water and polluted estuaries.
Ulva is commonly known as ‘sea lettuce’. Thallus is macroscopic and it appear sheath like
structures with two cells thick (distromatic). Thallus is lithophytic, epiphytic and some of them
are free floating. Holdfast is formed by the cells of the thallus, sending down long slender
filaments (like Rhizoids) that join together to form the holdfast. Growth of the thallus is diffuse
(Cell division may occur anywhere in the thallus).
In cross section of the thallus shows distromatic structure, each cell is isodiametric in shape,
uninucleate with one parietal laminate to cup shaped chloroplast and a single pyrenoid.

Reproduction in Ulva occurs by all three means: vegetative, asexual as well as sexual. Ulva has
an isomorphic alternation of generations, with the gametophyte forming biflagellate gametes and
the sporophyte producing quadriflagellate zoospores.

Sargassum – Stem
The given material is identified as the ‘Stem” of Sargassum.
Reason: The given material is brown in colour, firm, in cross section shows three regions, viz.,
meristoderm, cortex and medulla composed of thick walled cells.
Description:
Division: Chromopycota Class: Phaeophyceae
Order: Fucales Family: Sargassaceae
Cross section of the given material shows three regions. The outer most layer is a
meristoderm formed of small isodiametric, columnar or angular cells, compactly arranged
without any intercellular spaces. These cells are packed with plastids indicating their
photosynthetic function. Next to the meristoderm occur several layers of cortex formed of this
walled spherical cells, loosely arranged with intercellular space. Cells of the cortex are provided
with fucosan vesicles which function as storage structures that store the reserve food materials
such as laminarin and mannitol. Medulla occurs in center. Medullary cells are thick walled cells,
comparatively smaller than cortical cells. It shows pores in the end plate similar to sieve element.
It helps in the transport of food materials and also provides mechanical support to the ‘stem’.
Cell of Sargassum is uninucleated, have a cell wall formed of cellulose and alginic acid.
Presences of alginic acid in the cell wall of this alga make it economically important. Sargassum
is a marine alga, growing extensively in subtidal regions of the rocky shores of our country.

Sargassum - Receptacle
The given material is identified as the receptacle of Sargassum.
Reason:
The given material is small, brown in colour, freely branched and triangular or oblong in cross
section. Conceptacles are seen in cross sections of the receptacle.
Description:
Division: Chromopycota Class: Phaeophyceae
Order: Fucales Family: Sargassaceae

Receptacles of Sargassum are the structures that bear oogonia and antheridia in separate
conceptacles. The conceptacles are always unisexual. These are flask shaped structures with an
opening called ostiole and are deeply embedded in the receptacle. Just below the ostiole occur
hairs characteristic of the class Phaeophyceae.
Male conceptacles bear antheridial branches. Antheridia are formed alternately in an an
theridial branch. These are similar to unilocular sporangia, bear 64 antherozoids. Each
antherozoids is a male gamete, pyriform, bear two flagella that are laterally attached. Of these the
anteriorily forwarding flagellum is long and tinsel type and the posteriorily forwarding flagellum
is of short and whip-lash type. Antherozoids at maturity are released from the antheridium and
dispersed through the ostiole.
Female conceptacles bear oogonia. Oogonia are large structure, at time filing the entire
cavity of the conceptacle. Oogonium consists of a single egg. Young oogonium consists of three
layered covering, viz., outer exochite, middle mesochite and inner endochite. At maturity the
exochite ruptures, mesochite radially elongates to form a mucilaginous stalk to which attached
egg surrounded only by endochite. The fertilized egg starts further development without any
resting stage and at the time while still attached to the base of the female conceptacle by
mesochite.

Gracilaria thallus
The material identified as Gracilaria
Reason:
The thallus flat thick, repeatedly dichotomously branched and found with hemispherical
cystocarp on its surface. In Cross section, it shows cortex and medulla. These characters indicate
that the given alga belongs to Gracilaria.
Description:
Division: Rhodophycota Class: Rhodophyceae
Order: Gigartinales Family: Gracilariaceae.

Gracilaria is a red alga, growing in brackish water and marine environment. It is a thick,
leathery alga with parenchymatous construction. In cross section the thallus shows cortex and
medulla. The cortex is made of one to two layers of isodiametric cells, compactly arranged
without any intercellular space. These cells are provided with plenty of plastids indicating their
photosynthetic function. Inner to the cortex medulla is present. It is formed of abruptly enlarged
cells arranged with intercellular space. The cells are polygonal with pit connections connecting
them to the neighboring cells. The medullary cells represent axial filaments. Since Gracilaria is
multiaxially constricted thallus there are many axial filaments, each grows by mean of its own
apical cell. The given material is identified as the female gametophytic thallus by the presence of
large hemispherical cystocarp found distributed all over its surface.

Gracilaria with Cystocarp:

The figure kept in at spotter/ the given material shows vertical section of cystocarp of Gracilaria.
Division: Rhodophycota Class: Rhodophyceae
Order: Gigartinales Family: Gracilariaceae.
Cystocarp: Cross section of thallus shows vertical section of cystocarp. The median longitudinal
section of the cystocarp is provided wth an outer covering. It is a multilayered structure called
pericarp, formed by a female gametoohytic tissue that over grow on developing carposporophyte.
The pericarp is incomplete towards the distal portion of the cystocarp to form an opening called
ostiole through which the carpospores are liberated at maturity. The central portion of the
cystocarp contains carposporophyte. The carposporophyte is characteristic of having a large
placental cell at the center, gonimoblast filaments developed from the placental cell and
gonemonemata filamentous structures connecting the carposporophyte with pericarp – that are
nutritive in function. Carposporangia are produced in series from the gonimoblast filaments.
This alga shows a triphasic lifecycle with gametophyte (male and female gametophytic thalli),
carposporophyte and tetrasporophyte. The life cycle is called as diplobiontic life cycle or sporic
life cycle.
Gracilaria is a marine alga growing in the lower places of intertidal regions of coast of Tamil
Nadu in general and at rocks of Kovalam in particular. This alga is economically useful as agar-
agar is extracted from it.
Caulerpa Rhizome/stolon
The spotter is identified as the rhizome of Caulerpa
Reason: It is cyclindrical, tubular structure with rhizoids. The cross section shows cell wall
trabeculae and cytoplasmic masses. These characters confirm that the given material as that of
Caulerpa rhizome.
Description:
Division: Chlorophycota Class: Chlorophyceae
Order: Bryopsidales Family: Caulerpaceae.

Caulerpa has assimilators, rhizome and rhizoids. Rhizome is a siphonous strucute, growing
parallel to the substratum. Towards the lower regions of the rhizome arises the rhizoids and
towards the upper region arise assimilators. Assimilators are of many kinds in different species
of Caulerpa. Assimilators and rhizome are provided with stratified, thick wall of two layers, viz.,
inner layer and outer layer. The inner layer produces a number of tubular, freely branched
structures that traverse the cytoplasm. These structures are named as trabeculae. The trabeculae
give mechanical support to siphonous thalli of Caulerpa. The cytoplasm in Caulerpa contains
numerous nuclei and lot of cytoplasmic masses. The latter include amyloplasts and amylogenic
leucoplasts that store reserved food material.
The lenticular cell division takes place in the assimilator at the time of reproduction to
differentiate a lens shaped cell towards the peripheral portion of assimilator. This uninucleated
cells act as a gametangium, whose nucleus undergoes meiotic division to form numerous haploid
gametes which are discharged forcibly through a beak like projection formed on the surface of
assimilators. It is a marine alga, found abundantly on the coast of Tamil Nadu.

Spotters
Volvox
The spotter identified as thallus of Volvox.
Division: Chlorophycota Class: Chlorophyceae
Order: Volvocales Family: Volvocaceae

Reason: Thallus of volvox is spherical up to millimeter in diameter. A definite number of cells

join together to form a defiantly shaped colony called a coenobium. Individual cells are
Chalamydomonas like in having spherical cells, cup shaped chloroplast, two flagella. Cells are
polygonal due to mutual compression. Neighboring cells are interconnected by cytoplasmic
connections through which exchange of substances take place. Flagella of all cells show
coordinated movement by which the coenobium is spin around in its longitudinal axis that moves
the coenobium either move forward or backward. Reproductive structures such as daughter
colonies, antheridia and oogonia and subsequently zygospores are all formed and found only
towards the posterior region of the coenobium.

Hydrodictyon
Division: Chlorophycota Class: Chlorophyceae
Order: Chlorococcales Family: Hydrodictyaceae

The spotter identified as thallus of Hydrodictyon. Hydrodictyon forms a colony of definite shape
with a fixed number of cells. Such a colony is called as a coenobium. Here the cells of
coenobium are non-motile. Hence the thallus is called as a non-motile coenobium. The mature
coenobia are composed of large cylindrical cells joined together in three to form polygonal
structures. The whole colonu is cylindrical when young. The young cells are uninucleated.
Mature cells enlarge several times; develop numerous nuclei and large central vacuoles which
force the cytoplasm towards the periphery of the cell, Chloroplast of Hydrodictyon is reticulate.
It reproduces by asexual and sexual methods involving the formation of zoospores that are
retained within the cell wall and arrange themselves to form a micronet before released out. It is
found in nutrient rich water bodies.

Volvox
The Spotter is identified as thallus of Volvox
Reasons: Thallus is spherical in shape and is considered as a coenobium. The thallus is seen with
number of daughter colonies.
Description: Thallus of Volvox is spherical up to a millimeter in diameter. A definite number of
cells join together to form a definitely shaped colony called coenobum. Individual cells are
Chlamydomonas like in having spherical cells, cup shaped chloroplase, two flagella. Cells are
polygonal due to mutual compression. Neighboring cells are interconnected by cytoplasmic
connections through which exchange of substances take place. Flagella of all cells shows
coordinated movement by which the coenobium is spin around in its longitudinal axis that
moves the coenobium either move forward or backward Reproductive structures such as
daughter colonies, antheridia and oogonia and subsequently zygospores are all formed and
found only towards and found only towards the posterior region of the coenobium. It is a green
alga belonging to the family Volvocaceae and the order Volvocales. It is found in freshwater
environments rich in nutrients.

Sphacelaria – Propagules
The spotter kept here is a propagule of filaments of Sphacelaria. Species of Sphacelaria
reproduce propagules as a means of vegetative reproduction. Propagules are formed from the
branches of main axis. These are bi-radiate, tri-radiate or wedge shaped in structure. Triradiate
propagules are produced in Sphacelaria furcigera and wedge shaped propagules are formed in
Sphacelaria tribuloides. When these are liberated at maturity the distal cells of the arms of
propagule functions as apical cell of future filaments of Sphacelaria. Similar propagules such as
stellate propagules and hook shaped propagules are formed in red algae such as Hypnea
valentiae and Hypnea musiformis respectively. Propagules are also formed in Hildenbrandia
rivularis and Polysiphonia sp.

Hincksia – Plurilocular sporangium / Unilocular sporangium

Plurilocular sporangium: Plurilocular sporangium in Hincksia is cylindrical contains number
of locules or compartments. Each of these locules is provided with nucleus and cytoplasm that
metamorphoses into a biflagellate zoospore. Zoospores at maturity are liberated by dissolution of
cross walls of locules and then by the formation of an opening at the distal region of the
sporangium. Zoospores are pyriform in shape, biflagellated with laterally attached flagella. The
anteriorily forwarding flagellum is long and tinsel and the posteriorily forwarded flagellum is
short and whiplash type. Plurilocular sporangia are produced in both haploid and diploid
sporophytic generations.

Unilocular sporangium: Unilocular sporangium in Hincksia is oblong in shape. It is produced

only on diploid sporophytic generations. Unilocular sporangia are always stalked. The diploid
nucleus of this sporangium first undergoes a reduction division (meiosis) followed by mitotic
divisions to form up to 256 haploid daughter nuclei. These with accumulated cytoplasm are
called as protoplasmic units. Protoplasmic units develop into swarmers. These are always
haploid. Swamers are pyriform in shape, biflagellated with laterally attached flagella. The
anteriorily forwarding flagellum is long and tinsel and the posteriorily forwarded flagellum is
short and whiplash type. Swamers on liberation always develop into gametophytic thalli.

Laminaria: Vertical section of lamina showing unilocular sporangia:

Vegetative structure: Thallus of Laminaria in vertical section of the lamina shows the following
structures:

1. Meristoderm: This is the outermost layer formed of one or two rows of angular cells
compactly arranged. Cells of this layer are stuffed with plastids indicating photosynthetic
function. At maturity, Unilocular sporangia are produced from this layer.
2. Cortex: This layer is present next to meristoderm. Cortex is divided into outer cortex and
inner cortex. Cells of the outer cortex are polygonal in shape and are compactly arranged.
 Cells of the inner cortex are also compactly arranged but are slightly elongated. Cells of
the cortex are storage in function.
3. Medulla: This is the middle layer of the lamina. Here the cells are elongated and
filaments like. These are called as hyphae. There are two types of hyphae. One is a
normal hypha formed of elongated cells. The other one is trumpet hypha having a porous
cross wall comparable to that of sieve elements of higher plants and there is also the
presence of swelling on either side of the cross wall. These hyphae are conducting in
function.

Chara – Nucule and Globule

Sexual reproduction in Chara is carried out by the formation of male and female reproductive
structures such as globules and nucules respectively. Globules are terminal and nucules are
laterals. These structures are produced at one of few basal nodes of primary lateral.

Antheridium:

Antheridium or globule is a spherical structure externally surrounded by four

or eight shield cells. The inner layers of shield cells are ruminate as they are provided with
infoldings. From the centre of each of the shield cell arises a radially elongated manubrium. On
the distal region of the manubrium occurs a primary capitular cell which underges successive
longitudinal divisions to form capitular cells. Each of these secondary capitular cells undergoes
transverse division to form antheridial filaments. Antheridial filaments contain discoids cells
called antheridia. Each of these antheridia metamorphoses into an antherozoid. The mature
antherozoid is spirally coiled with two sub-apically inserted flagella. The body of the
antherozoids and flagella are covered with scales.

Oogonium:

Oogonium or nucule is ovate in shape. Oogonia are produced from the peripheral cell of the
basal node of the antheridium. A mature oogonium is attached to the basal node of the
antheridium by a stalk cell. It contains a basal node and the five peripheral cells of the basal node
undergo two successive transverse divisions to form basal tube cells and coronary cells. The five
tube cells grow spirally over the egg which brings the coronary cells to the distal region of the
nucules. The mature egg produces lot of mucilage which exudates through the space created by
pushing apart of the coronary cells.

Batrachospermum –Carposporophyte

The photograph kept is the carposporophyte of Batrachospermum. It is formed by the fertilized

carpogonium. The diploid nucleus undergoes mitotic division to form numerous nuclei which are
incorporated into small protrusions formed all over the fertilized carpogonium. When a cross
wall formed at the base of each of these protrusions they become gonimoblast initials. These
develop into small filaments of few cells in height called gonimoblast filaments. The distal cell
of these filaments are enlarged with dense content and called as carposporangia. The content of
the carposporangia are liberated as carpospores. Hence the fertilized carposporangium,
gonimoblast filaments and carposporangia all together constitute carposporophyte of
Batrachospermum. This represents one of the three phases in the life cycle of Batrachospermum
and it is considered to be growing on the gametophytes as a parasite.

Spot at Site

S. No Class Order Family Genus

1. Cyanophyceae Chroococcales Chroococcaceae Aphanothece
2. Chroococcus
3. Merismopedia
4. Microcystis
5. Nostocales Oscillatoriaceae Arthrospira
6. Spirulina
7. Lyngbya
8. Scytonemataceae Scytonema
9. Stigonematales Stigonemataceae Westiellopsis
10. Chlorophyceae Chlorococcales Chlorella
11. Chlamydomonas
12. Chlorococcales Hydrodictyaceae Hydrodictyon
13. Pediastrum
14. Volvocales Volvocaceae Volvox
15. Ulotrichales Ulotrichaceae Ulothrix
16. Oedogoniales Oedogoniaceae Oedogonium
17. Cladophorales Cladophoraceae Pithophora
18. Bryopsidales Caulerpaceae Caulerpa
19. Zygnematales Peniaceae/ Closterium
Desmidiaceae
20. Desmidiaceae Cosmarium
21. Micrasterias
22. Zygnemataceae Spirogyra
23. Zygnemataceae Zygnema
24. Charophyceae Charales Characeae Chara
25. Phaeophyceae Ectocarpales Ectocarpaceae Hincksia
26. Sphacelariales Sphacelariaceae Sphacelaria
27. Laminariales Laminariaceae Laminaria
28. Fucales Sargassaceae Sargassum
29. Turbnaria
30. Rhodophyceae Gigartinales Gracilariaceae Gracilaria
Spirulina

Spirulina contains 60-70% of protein when compared to the total constituents of cells on
dry weight basis. It has B-complex vitamins besides having vitamin C and vitamin E. For a long
time Spirulina is consumed in the Lake Tehad region of North America. Two 500 mg tablets of
Spirulina consists of substances equivalent to 1 kg of assorted vegetables with reference to its
minerals and vitamins. Spirulina for life force, Slimolin and Miraculin are marketed in USA.
These are being prescribed for persons who would like to shed weight without any side effect.
Spirulina is an excellent source of fatty acids such as Levulenic acid, Palmitic acid, Linoleic acid
& Oleic acid. These are of commercial value and used as pharmaceutical agents. Spirulina has
high amount of β-carotene, when consumed it acts as provitamin-a and will meet the requirement
of vitamin a.

Agmenellum, Anacystis & Spirulina are capable of growing at high cell density. Hence
these are grown on substrates such as CO2 enriched with 13C & 14C. The resulting labelled
compounds upon purifications can be utilized as tracers in biology, medicine, medical diagnosis
and analytic chemistry. Eg. 2H, 3H, 13C, 14C and 15N – labelled sugars, lipids, l-aminoacids and
protein fractions.

Spirulina can be cultivated in large quantity even using waste water containing lot of
nutrients. This is helpful to us in two ways. i.e., the nutrients in the waste water like sewage is
removed and utilized for the growth of Spirulina and the nutrient depleted waste water can safely
discharged in to natural water bodies. The harvested biomass of Spirulina can be used as cattle,
poultry and fish feed.

PORPHYRA
Porphyra (Bangiophyceae) is popularly known as Nori in Japan, Kim in Korea, and Zicai in
China, (see Chapter 1, Figure 1.24). It is among the most nutritious macroalgae, with a protein
content of 25–50%, and about 75% of which is digestible. This alga is an excellent source of
iodine, other trace minerals, and dietary fibers. Sugars are low (0.1%), and the vitamin content
very high, with significant amounts of vitamins A, complex B, and C, but the shelf life of
vitamin C can be short in the dried product. During processing to produce the sheets of nori,
most salt is washed away, so the sodium content is low. The characteristic taste of nori is caused
by the large amounts of three amino acids: alanine, glutamic acid, and glycine. It also contains
taurine, which controls blood cholesterol levels. The alga is a preferred source of the red pigment
r-phycoerythrin, which is utilized as a fluorescent “tag” in the medical diagnostic
industry.Porphyra has been cultivated in Japan and the Republic of Korea since the 17th century,
because even at that time natural stocks were insufficient to meet demand. Today Porphyra is
one of the largest aquaculture industries in Japan, Korea, and China. Because of its economic
importance and other health benefits, Porphyra cultivation is now being expanded to other
countries.