BIOL 331
Lecture 8
Marine Plants
The Seaweeds (Macro Algae)
General Characteristics
 Multicellular
 Thallus = body
 Blades, same top & bottom, no vascular system like true
plants
 Complex kelps are more differentiated
 Holdfast
 Stipe
 Pneumatocysts
Life Cycles
 Highly variable
 See Fig. 5.21, p. 99
Chlorophycophyta
General Characteristics
 Well represented in the plankton.
 Also epiphytic on other algae, on animals, shells, or
even endophytic.
 Usually grass-green during vegetative stages.
 Pyrenoids in chloroplasts of most (starch condensation
area).
 Most have cell walls.
 Many have large central vacuole and smaller contractile
vacuoles.
5 Types of Organization
1. Motile unicellular or colonial.
2. Nonmotile unicellular or colonial.
3. Filamentous.
4. Membranous.
5. Coenocytic and tubular.
Cladophora (Gr. klados, Branch + Gr. phoros, bearer)
 Filamentous, zoospore producing.
 Free floating or attached to rocks by rhizoidal
branches.
 Growth of branching filaments is localized near the
apices of the filaments.
 Frothy cytoplasm with numerous nuclei (mitosis and
cytokinesis are totally independent).
Life Cycle (like Fig. 5.21 a)
 Both sexual and asexual reproduction occurs.
 Both diploid and haploid filaments occur,
indistinguishable.
 Diploids undergo meiosis to produce haploid
zoospores with 4 flagella.
 Zoospores with 4 flagella develop into haploid
filaments.
 Haploid filaments only produce zoospores with 2
flagella.
 Biflagellate isogametes also produced by similar
method.
 Referred to as a diplobiontic life cycle (others with
only one free-living form are haplobiontic).
 Cladophora is also isomorphic because alternating
generations look the same (heteromorphic when
different).
Ulva (L. marsh plant)
 Membranous, 2 cells thick.
Held to substrate by multicellular holdfast with
rhizoidal protuberances (cells often multinucleate).
 Cells of main body uninucleate.
 Life-cycle similar to Cladophora but dioecious (male &
female gametophytes).
 Parthenogenesis (egg becomes zygote without
fertilization) also occurs.
Codium (Gr. a fleece), Dead Man’s Fingers
 Branched, rope-like plants, tubes bear vesicular
branches with gametangia at the bases.
 Rapidly colonizes new areas and is highly destructive of
oysters, clams, and scallops.
 Life Cycle (like Fig. 5.21 c)
 Appears to be haplobiontic with the diploid stage
visible.
 Dioecious and produce anisogametes.
 Zygotes develop into small plants, but a new generation
of sexually mature plants has not been grown in culture
so life cycle is incomplete.
Phaeophycophyta
General Characteristics
 Approx. 250 genera, 1500 species.
 Flourish in colder waters on rocky coasts, many
attached in shallow water.
 Brownish shades of the plants due to the abundance of
fucoxanthin in the plastids.
 No starch in cells, excess carbohydrates stored as
laminarin, mannitol, or fat droplets.
 Large nuclei.
 Motile cells are laterally or sublaterally biflagellate.
 Plant body can be highly differentiated.

Referred to variously as rockweeds, wracks or kelps.
Ectocarpus (Gr. ektos, outside + karpos, fruit)
 Branching, filamentous, growing on stones, shells, or
epiphytically on larger algae.
 Life cycle much like that of Cladophora.
 Female gametes settle to the bottom and attract males
with ectocarpene.
 Life cycle may vary from area to area and haploid
(from parthenogenesis), diploid, and tetraploid
sporophytes are known to occur.
Laminaria (L. blade)
 Attached to rocks that are submerged even at extreme
low tide.
 Plant consists of a branching holdfast, a stipe and
expanded blade.
 Growth occurs at junction with stipe (intercalary) and
thus oldest part of blade is at apex.
Anatomy is Complex
 Only superficial cells photosynthetic.
 Central part of blade composed of long, colorless,
filamentous cells making up the medulla.
 Some central cells (trumpet hyphae) have flaring
ends and function as sieve elements.
Life Cycle
 Similar to Ulva (Fig. 5.21 a).
 Superficial cells of blade elongate and develop as
unilocular sporangia which occur in extensive
groups called sori.
 Sex chromosomes control the sex of gametophytes.
Fucus (L. fucus from Gr. phycos, seaweed)

Attached to rocks in the intertidal zone where they are
exposed at low tide.
 Anatomy complex.
 Derivatives of apical cells differentiate into
epidermis, cortex, and a central region of
branching filaments.
 Production of reproductive cells is localized at the
tips of the branches in fertile areas called
receptacles.
 Receptacles become enlarged due to excretion of
large amounts of hydrophilic compounds
internally.
 The receptacles bear scattered, pustule-like cavities
called conceptacles.
 Tufts of colorless filaments protrude from osteoles
in conceptacles.
Life Cycle (like Fig 5.21 c)
 Conceptacles bear egg and sperm.
 Dioecious or monoecious depending on species.
 Eggs attract sperm with fucoserratene.
 Liberation of gametes is timed carefully with tides,
drying action of low tide causes extrusion of
oogonia and antheridia, tide rising causes release of
gametes.
Other Common Genera
 Nereocystis (Gr. nereus, god of the sea + kystis, bladder).
Single stipe terminates in pneumatocyst with numerous
blades attached.
 Postelsia (After A. Postels, a German naturalist).
 Macrocystis (Gr. macro, large + kystis, bladder)
 Egregia (L. egregius, remarkable)

Division Rhodophycophyta
General Characteristics
 Mostly marine.
 Phycoerythrin usually masks chl a & d.
 Stores carbohydrates as Floridean starch (~15 glucose
subunits).
 Vegetative cells either uninucleate or multinucleate.
 Most are filamentous, membranous, or foliate.
 Most are diplobiontic with meiosis occurring in the
sporangia of a special alternate called a
tetrasporophyte.
Porphyra (Gr., purple)
General Characteristics
 Ulva-like plant body, 1-2 cells thick with thick
colloidal walls.
 Uninucleate cells, 1-2 stellate chloroplasts.
 Growth is generalized.
Life cycle (like Fig. 5.21 d)
 The laminar form is haploid and produces
spermatia and carpospores.
 Carpospores are diploid and may represent zygotic
products.
 Carpospores develop into the Conchocelis phase.
 Conchospores produced by Conchocelis phase and
become Porphyra stage.
 Porphyra phase can develop directly from filaments
of the Conchocelis phase.
 Both the Porphyra phase and the Conchocelis phase
are known to perrenate.
Polysiphonia (Gr. polys, many + Gr. siphon, tube)
General Characteristics
Epiphytic on larger algae and other plants or
rocks.
 Branching, filamentous.
 Growth strictly apical.
Life Cycle (like Fig. 5.21 d)
 Diplobiontic with dioecious gametophytes.
 Gametophyte and tetrasporophyte very similar in
appearance.
 spermatium and egg fuse to form zygote while still on
the gametophyte.
 zygote develops into a carposporophyte which forms
carpospores.
 Carpospores develop into a free-living
tetrasporophyte.
 Tetrasporophyte releases tetraspores that develop
into gametophytes.
Other Common Genera
 Gigartina (Gr. gigarton, a grape stone)
 Corallina
 Iridea (L. iris, stem: irid-, rainbow)
 Halosaccion (Gr. hals, the sea + sakkos, sack)
Flowering Plants (Division Anthophyta)
The "seagrasses"
 True plants with roots, stems, leaves and flowers.
 Not really grasses.
 Pollinated and seed dispersal by water movements
 Zostera (eelgrass) is found in protected areas.
 Phyllospadix (surf grass) is found in exposed, rocky
areas.
Halophytes
 Salt tolerant plants often found in salt marshes.




Cannot survive total submergence.
Spartina (cord grass)
Salicornia (pickle weed)
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