Sphagnum L Classification Kingdom: Sub-kingdom: Division: Class: Sphagnopsida Ochyra Order: Sphagnales Limpr. Family: Sphagnaceae Dumort. Genus: Sphagnum.

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1 Sphagnum L Classification Kingdom: Sub-kingdom: Division: Class: Sphagnopsida Ochyra Order: Sphagnales Limpr. Family: Sphagnaceae Dumort. Genus: Sphagnum L. Species: S. cuspidatulum C. Müll Commonly known as Peat Moss/ Bog moss Single genus with 151 to 350 species 3 species are reported from Bhutan (Long, 1994) S. cuspidatulum, S. girgensohnii, S. palustre Only commercially important moss

2 Habitat Known from most temperate, sub-arctic and highland climate areas. Also found in tropic region. Found primarily in acidic bog habitats as semi-aquatic and also as submerged aquatics, and that too in poorly mineralized water – Grows closely mated together covering the surface of acidic pools, lakes and ponds making them bogs of peat land – The growth of Spahgnum increases the acidity of the surrounding aquatic environment. This is due to selective ion absorption. – Sphagnum cells selectively absorb mineral ions from and release hydrogen ions into the surrounding water – The bog water is antiseptic and lacks oxygen, thus it acts as preservative

3 Habit Plant is erect and perennial with green to deep red, yellow or brown colour. As the plant grows the basal parts die and get accumulated filling up their aquatic habitat along with other plants growing together The partially decomposed tissues (due to acidic water) are slowly compressed by weight of the fresh deposit above. The compacted, partially decomposed and hardened dead plant deposit is called peat - brown or dark-coloured spongy substances, rich in carbon and use as fuel after air dry

4 Gametophyte Protonema (juvinile stage) Filamentous when young but becomes plate-like of one cell thickness Attached to the substratum by multicellular rhizoids From the margin of the protonema develops gametophore Gametophore bears few rhizoids (oblique wall) at base when young and disappears at maturity. Mature gametophyte are devoid of rhizoid Plate like protonema with rhizoids and first formed leaves of gametophore

5 Gametophyte Leafy gametophyte Matured gametophyte consist of upright perennial shoots bearing leaves and leafy branches Matured gametophyte devoid of rhizoids Branches freely and branches arises in fascicles at every fourth leaf on the main stem S. monocladum with single branch and some like S. wulfianum with 8 branches in a fascicle Both stem and branches with small leaves At the top of each stem there is a cluster of crowded branches, called the capitulum or the head

6 Branches of two types Divergent branches Short and stout branches Grows laterally extending outward horizontally and arched at mid with distal end carving downward Pendent/drooping branches Long, slender and descending branches Hang down close to the main stem Acts as water conductor

7 Sphagnum leaf Leaves on branches overlap and little apart in main stem Leaves are small thin and scale like Sessile and arranged spirally on the stem Leaves on divergent branches are small at the base, large in the middle and narrow at the apex Leaves on pendent branches are long and narrow No midrib, margin entire, apex acute Leaf consist of single layer of cells in thickness Cells elongated

8 Cells of two types Chlorophyllous cells Small, narrow and living Contain chloroplast, green and are photosynthetic in function Hyaline cells Large and dead (no protoplasm) cells Colorless wide and filled with water Hyaline cell Chlorophulous cell Pore Spiral thickening Inner walls of the cells have annular wall thickening which provides mechanical support and prevents cells from collapsing Cells also have circular openings (pore) which functions to take up water like sponge-hence hyaline cells are also called capillary cells

9 Leaf in cross section Mature leaf appears bead-like It consist of large hyaline cells and small chlorophylous cells each alternating Chlorophylous cells differ in position in different species In S. acutifolium the base of the cell is towards the upper surface of the leaf and apices towards the lower surface, in S. tenellum is opposite while in others (S. squarrosum) chlorophylous cells are completely enclosed Chlorophylous cells Hyaline cells

10 Chlorophylous cells form network and forms meshes. Within each mesh are single hyaline cells

11 Spahgnum- stem anatomy Shows three distinct zone Outer Cortex Compactly arranged In young stem and branches is one cell thick but becomes 3-6 layers of cells in old stem Cortex of older stem becomes spongy and stores water The cortical cells of side branches remain one cell thick Cortical cells lose their protoplasm gradually, increases size and becomes large, empty, dead, colorless cells In some species cortical cell develops large oval pores and spiral thickening too

12 Some cortical cells in S. tenellum & S. molluscum, becomes perforated and appear like retort and are called retort cells (absent in S. palustre) Neck of each retort cells is turned outward Middle parenchymatous region: thick-walled with small narrow elongated prosenchymatous (elongated, tapering cells which occur in supporting and conducting tissues) Supportive in function Inner central axial cylinder Thin-walled, elongated, colorless parenchymatous cel ls Storage of food Retort flask

13 A.Stem segment showing branch fascicle and stem leaves C. stem leaf B. branch leaf D. abaxial suface of upper mid- laminal cells of divergent branch leaf E. abaxial (lower) and F. adaxial surface (S. tenellum) I. part of T.S of stem with 4-5 rows of cortical cells and dense outer part of the sclerderm H. T.S. of branch G. T.S of divergent branch leaf

14 Reproduction in Sphagnum Vegetative Innovation Any branch in the axilary bud grow rapidly upward and becomes similar to main axis called innovation Due to progressive dying of the lower part of the plant innovation separates and grows as individual plant – Multiplication of protonemal stage Any cells of the margin of the potonema becomes meristimatic and develops secondary protonema from which arises leafy gametophyte – Gammae formation seen in S. capillaceum

15 Sexual reproduction Plant monoecious or dioecious Sex organs borne on modified branches Antheridia and archegonia borne n the different branch of the same or different plants Monoecious plant protandrous Paraphyses always absent

16 Antheridia Antheridial branch shorter and stouter than vegetative branches Often densely covered by dense colored leaves Antheridia occurs singly on the axil of the leaves of the antheridial branch towards tip Matured antheridia oval shape and borne on long and slender stalk Single cell layer of antheridial jacket with thick cuticle encloses numerous sperms

17 A: antheridial branch; B: antheridial branch with antheridial bracts removed; C: antheridium with protective antheridial bract; D: nearly matured anthridium

18 Archegonia Borne on short branches and consist of aggregate of archegonia and bracts Comparatively larger bracts than antheridial bracts Archegonial branch in cluster at apex within the terminal cluster branch Usually three archegonia on each branch Middle archegonia (primary ) grow directly from apical cells of the archegonial branch and side archegonia (secondary) from segments of apical cells Matured archegonia with long stalk, with massive venter and long twisted neck Water necessary for fertilization

19 Sporophyte Only one archegonia develops in to sporophyte Sporophyte consist of foot, seta (suppressed) and massive capsule Function of seta taken over by pseudopodium Leafless stalk formed by post fertilization intercalary growth of upper part of the axis of archegonial branch Cup-like sheath remains at the base surrounding the foot which is known as vaginula cup-like, basal portion of the calyptra together with the dilated tip of pseudopodium into which the foot of sporophyte is embedded Sp-spores Col-columella Ft-foot Ps -pseudopodium

20 Capsule Consist of hemispherical central sterile columella Dome-shape spore sac overarch columella No elaters Outer spore sac wall is cuticularized epidermis Among the spore sac wall cells are rudimentary stomata At the top of the of capsule is operculum marked off by annulus Peristomal teeth absent L.S. of capsule

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22 Sporangium with operculum removed

23 Spore dispersal Spores gets dispersed by explosion ( explosive mechanism) during sunny days Cells of columella breaks when spores matures creating a large air cavity The wall of the capsule under the influence of sun dries and shrinks causing to build air pressure in the lower half of the capsule The air, due to difference in pressure in two chambers, suddenly gets released, rupturing the thin-walled annulus layer and throwing a cloud of spores with it Mechanism is also referred to as air gun mechanism

24 Life cycle

25 Unusual features of this group includes: Plate-like protonema Pseudopodium in place of seta Capsule has no peristome Explosive spore discharge from spherical capsule Leaves with chlorophyllose (living) and hyline (dead) cells Branches in fascicles which arise about every 4 th stem leaf No leaf costa

26 Importance of Sphagnum Economic importance The peat deposits are cut, dried and used as fuel Absorptive and antiseptic property makes it worthy using it as dressing wounds- used during WW I Dried Sphagnum is remoistened and used as packing material for live plants and cut flowers to be transported Used as substratum by gardener Used as potting mix to lengthen water retention in the pot Ecological importance They are helpful in land reclamation Is employed as indicator of both atmospheric and aquatic pollution Is added to soil to improve its water-holding capacity and has been employed as an absorbing material for oil spills Slow rate of decay due to acidic environment enables reconstruction of past environment