Algal Morphology I. Internal thallus morphologies II. External thallus morphologies III.Algal Growth Unicells- solitary cells can be motile or non motile ex. Chlamydomonas Colony- an assemblage of individual cells, variable or predictable number of cells, flagellated or non motile coenobium- predictable number and arrangement of cells ex. Volvox Filamentous- daughter cells remain attached to each other following cell division forming a chain of cells Uniseriate- cells occuring in a single row Coenocytic/ Siphononous one large multi-nucleate cell lacking crosswalls Utricles -swollen, terminal end of the siphon Multiseriate- consisting of several rows of cells in a longitudinal seriesin one or two planes Codium 1
Limited cell differentiation compared to terrestrial plants Coenocytic thallus construction - What does this allow? Chloroplast movement Terrestrial Leaf Algal blade What special issues does it raise? Herbivory healing Well developed cytoskeleton Repairs membrane in 1-2 seconds cuticle parenchyma (palisade, spongy) veins epidermal guard cells stomates Cortex-pigmented cortical cells Medulla unpigmented medullary cells Parenchyma undifferentiated, isodiometric cells generated by a meristem Cells division in any plane, not filamentous Pseudoparenchyma- form of thallus composed of interwoven continuous filaments, superficially resembles parenchyma Sarcodiotheca Filaments Hypnea 2
Parenchymatous vs. Pseudoparenchymat ous Polysiphonous composed of tiers of vertically elongated cells, transversely arranged, the lateral cells around a central axis (siphon) Reds only central cell surrounded by 4 or more pericentral cells Polysiphonia Petalonia Mazzaella Cortication elaboration of polysiphonous condition where pericentral cells continue to proliferate Filament (Central Tissue) Ceramium nitens Ceramium Cortical Cells (Outer Tissue) Cortical Cells (Banded Pattern) Complete Cortication Partial Cortication 3
II. External thallus morphologies Algal morphology: Can affect: - Photosynthesis - Nutrient uptake - Resistance to herbivory - Resistance to physical disturbance (e.g. wave stress) thallus sori blade stipe holdfast Filamentous Chaetomorpha non-branching forms branching forms Filamentous Chaetomorpha Cladophora Derbesia 4
Foliose = a sheet of cells, blade like, no stipe Monostromatic one cell thick Distromatic - two cells thick Polystromatic many cells thick Petrocelis stage Petrospongium Prostrate / Procumbent: trailing on the ground Ulva Hildenbrandia Ralfsia Bladed- flattened leaf like thallus, may have a stipe Stipitate = has a stipe 5
Saccate = sac-like Pneumatocysts- -a large float containing gas found in heterokontophyta -provide buoyancy to lift the blades toward the surface, allowing them to receive more sunlight for Ps - can hold O2, CO2, CO Botryocladia Halosaccion Cystoseria osmundacea -catenate series Sargassum muticum -singly Midrib-thickened longitudinal axis of flattened branch or blade Midvein-a delicate median line of cells, the blade is thicker through this region Alaria fistulosa Undaria sp. 6
Tubular- tube of cells, hollow in center Geniculate corallines Geniculum (flexible joint) Intergeniculum (hard part between genicula) upright articulated geniculate Calliarthron cheiliosporiodes Non-geniculate corallines Branched- axillary divisions crustose encrusting non - geniculate 7
Dichotomous/Bifurcate Pectinate/Secund Whorled/Verticillate Pinnate-feather-like, regular branching Distichous-branching on both side of the axis, irregular Opposite Alternate Monopodial-having a distinct main axis of continuous growth & giving off branchlets Sympodial- apparent main axis does not extend by continuous growth 8
Holdfast Characteristics III. Algal growth apical holdfast intercallary basal stoloniferous/rhizoidal hapterous discoid Where on the algal thallus does cell division occur? Meristem = area of cell division and growth Apical growth =Apical cell or apical meristem Multiaxial- several longitudinal medullary filaments, each derived from an apical cell 9
Uniaxial- one longitudinal central filament forming the axis Apical around margin Intercalary Intercalary growth Diffuse growth = No defined area of cell division or growth; occurs throughout the thallus transition zone Growth in both directions away from meristem Usually between stipe and blade (or blade and pneumatocyst) 10
Trichothallic Growth: Cells divide to form hair (filament) above and thallus below (in this case, psuedoparenchymatous polysiphonous ) Heterotrichous growth filamentous growth in 2 directions, results in thallus composed of both prostrate + erect components Filaments Polysiphonia Upright Form Thallus Prostrate Form (Crustose, spreading) Lithophyllum congestum 11