Presentation on theme: "Division: Pinophyta / Coniferophyta II. Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. –Cupressaceae – Cypress / Redwood."— Presentation transcript:
Division: Pinophyta / Coniferophyta II
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. –Cupressaceae – Cypress / Redwood family –Podocarpaceae – Podocarp family –Araucariaceae – Norfolk Isl. Pine family –Taxaceae – Yew family –Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Phylogeny of the Pinophyta based on cladistic analysis of molecular data. (Derived from papers by A. Farjon and C. J. Quinn & R. A. Price in the Proceedings of the Fourth International Conifer Conference, Acta Horticulturae 615 (2003))
Family: Cupressaceae It is the most widely distributed of all gymnosperm families, occurring in diverse habitats on all continents except Antarctica Wetlands dry soils; sea level high mountain elevations Consists of 32 genera and 148 species ¾ of species occur in N. Hemisphere
Cupressaceae This family was formerly divided (on the basis of leaf morphology) into: –Cupressaceae (sensu stricto) Leaves opposite & scale-like or whorled and linear –Taxodiaceae leaves mostly alternate Recent study of plastid (rbcL – ribulose biphosphate carboxylase) molecular sequences has further confirmed the close relationship between the Cupressaceae “sensu stricto” and the genera formerly assigned to the Taxodiaceae
Cupressaceae Similarities between Cupressaceae & Taxodiaceae include: –Fusion of cone scale & bract –Lateral wings on seeds (derived from the seed coat) –≥ 2 microsporangia per microsporophyll –≥ 2 seeds per cone scale –Shedding of dwarf shoots –Non-saccate pollen with no prothallial cell development –Clustered archegonia –Peltate cone scales –DNA sequences
Cupressaceae Trees or shrubs Resinous & pycnoxylic: fragrant, insecticidal, fungicidal wood Bark fibrous and furrowed (smooth or exfoliating in plates in some Cupressus and Juniperus species) Twigs terete, angled, or flattened. Dorsiventrally clothed by scale-like leaves or by decurrent leaf bases Buds undifferentiated and inconspicuous (except in Sequoia, Juniperus) Leaves simple; spirally arranged, or basally twisted to appear 2-ranked
leaves with twisted basal portion so they appear 2-ranked
Cupressaceae Roots fibrous to woody (bearing aboveground “cypress knees" in Taxodium). Leaves –simple, usually persisting 3-5 (≤12) years –Scale-like leaves deltate; otherwise linear, decurrent, sessile or petiolate –mature leaves appressed or spreading, often differing between lateral and leading shoots (twigs heterophyllous), sometimes strongly dimorphic on each twig –alternate and spirally arranged but sometimes twisted so as to appear 2-ranked, or opposite in 4 ranks –shed with lateral shoots Monoecious (but dioecious in Juniperus)
Cupressaceae Male/pollen cones –mature and shed annually, –Solitary & terminal (rarely in clusters) –simple, spherical to oblong –sporophylls overlap, bearing 2-10 abaxial microsporangia (pollen sacs) –pollen spheric & non- saccate –No prothallial cells during development
Cupressaceae In the female cones –maturing in 1-2 seasons –shed with short shoots or persisting indefinitely on long- lived axes (shattering at maturity in Taxodium ) –compound, solitary, terminal (rarely in clusters ) –scales overlapping or abutting, fused to subtending bracts with only bract apex sometimes free
Cupressaceae Female cones: –The ovuliferous scale and associated bract are fused for most of their common length. –Each scale-bract complex are peltate or basally attached; flattened and woody (juicy in Juniperus) at maturity –Ovules are erect (micropyle faces away from cone axis) and they vary in number from 1 – 20 adaxially; however, may invert during maturity (e.g. Sequoia and Sequoiadendron) –Archegonia clustered and variable in number/ovule Seeds 1 – 20 per scale –May or may not have 2-3 symmetric or asymmetric wings –Embryo with 2-15 cotyledons During embryogenesis the zygote shows some variations.
Cupressaceae The zygote divides into eight free nuclei Two tiers are formed: a lower tier of 4 embryonal cells and an upper tier of 4 cells that open towards the archegonial neck The cells of the upper tier divide again into a middle / pro- suspensor tier and an upper tier giving three tiers (fig C).
Cupressaceae The number of cells may vary in each tier. The prosuspensor cells elongate and push the embryonal cells out of the archegonium. Later the primary embryonal cells divide transversely to cut off: –an upper tier of suspensor cells and –a lower tier of embryonal cells. Later the suspensor cells start elongating (after the prosuspensor cells stop elongation) and cleavage takes place. So cleavage polyembryony takes place.
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. Cupressaceae – Cypress / Redwood family –Podocarpaceae – Podocarp family –Araucariaceae – Norfolk Isl. Pine family –Taxaceae – Yew family –Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Podocarpaceae Second-largest conifer family, of the Pinophyta Mainly Southern Hemisphere conifers Consist of genera and about species of evergreen trees and shrubs. Trunk usually straight and with more or less horizontal branches Leaves are –lanceolate to oblong, falcate (sickle-shaped) in some species, –a distinct midrib –spirally phyllotaxy
Podocarpus aristulatus - branch with ovulate cones
Podocarpaceae - reproduction Dioecious (rarely monoecious) Pollen cones usually catkin-like –stamens numerous, close together, –2 sporangia / microsporophyll –pollen grains with 2 (0-3) saccae The male/pollen cones are 5-20 mm long, often clustered several together
Podocarpaceae - reproduction Female cones maturing in one year, much reduced to a few fleshy bracts or scales –pendant, usually borne on a thin peduncle, containing a single inverted ovule In the female cone the ovuliferous scale is folded around the ovule to form an extra envelope called the epimatium which is either partially or completely fused with the integument.
Podocarpaceae - embryogeny During embryogenesis 4 – 5 free nuclear divisions occur and gives 16 – 32 nuclei and then cell walls develop and results in the formation of two tiers. These organize themselves into upper (15-22 celled) and embryonal (9-12 celled) tiers. No rosette tier is present.
Podocarpaceae - reproduction Cells of upper tier divide open upper tier and suspensor tiers Embryonic cells undergo nuclear division binucleate cells Suspensor tier pushes embryonal tier into gametophyte Later bi-nucleate embryonal cells divide tetrads of cells Cleavage polyembryony is rare; mostly simple polyembryony The embryo has 2 cotyledons
Podocarpus lawrencei – female cone
Seeds with red epimatium
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. Cupressaceae – Cypress / Redwood family Podocarpaceae – Podocarp family –Araucariaceae – Norfolk Isl. Pine family –Taxaceae – Yew family –Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Family: Araucariaceae Three genera with 40 species Mostly restricted to S. Hemisphere Evergreen trees, typically with a single stout trunk and very regular whorls of branches, giving them a formal appearance Several have edible seeds similar to Pinus sp., and others produce valuable resin and amber Dioecious or monoecious Male cones relatively large, cylindrical –numerous microsporophylls –±12 inverted pollen sacs –pollen grains non-saccate and exine pitted –a number of prothallial cells are produced.
Monkey-puzzle, ( Araucaria araucana )
Araucariaceae The female cones are –almost spherical, subglobose to ovoid –usually borne erect –maturing in two years –relatively large and milky –falling upon maturity or disintegrating on tree –scales one-seeded, without distinct bracts. The ovuliferous scale is intimately fused with the bract scale except in Araucaria. –Cotyledons 4, often fused into 2 double cotyledons The embryogenesis in Araucariaceae differs from the other conifers. Free nuclei divisions of the zygote takes place until there are about 32 nuclei in Araucaria and 64 nuclei in Agathis.
Araucariaceae Initially all the nuclei are grouped in the center of the egg cell. Cell walls are then laid down and the cells are arranged in a central group with 2 tiers of cells surrounded by an outer jacket on all sides. The upper cells of the jacket (those facing the archegonial neck) elongate to form the suspensor, whereas the cells towards the chalazal end act as cap cells (see fig).
Araucariaceae The upper tier of the central two tiers divides periclinally to form an upper tier of secondary suspensor cells and the lower tier of embryonal cells. The latter divide and develop into the embryo proper that has two cotyledons. There is no cleavage polyembryony.
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. Cupressaceae – Cypress / Redwood family Podocarpaceae – Podocarp family Araucariaceae – Norfolk Isl. Pine family –Taxaceae – Yew family –Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Taxaceae 5 Genera, 17 species Small to moderately sized highly branched evergreen trees or shrubs Usually neither resinous nor aromatic –no (or very few) resinous canals Linear, flattened leaves with acute apex The wood is pycnoxylic Dioecious (rarely monoecious) –The male cones are 2-5 mm long –The female cones are highly reduced, with just one ovuliferous scale and one seed
Taxaceae The Taxaceae and Cephalotaxaceae may be associated with the Podocarpaceae because of the solitary ovules associated with fleshy coverings Taxus is the type genus of this family Plants are mostly unisexual and rarely monecious. Taxus is represented by 9 species. They are found in North America, Malaysia and Europe. The wood of Taxus is very elastic and is used in making bows in archery. Taxus brevifolia and T. canadensis are the sources of paclitaxel (taxol®), a chemo-therapeutic drug used in breast and lung cancer
Taxaceae - reproduction The microsporangia are arranged in small male / pollen cones. –Pollen cones solitary or clustered –Axillary –globose to ovoid –sporophylls bearing microsporangia (pollen sacs) –pollen ± spherical no saccae
Taxaceae - reproduction
Prothallial cells are not formed, the androspore cell acts directly as an antheridal initial –The microspore nucleus divides periclinally to produce: The antheridal initial which divides to form a tube cell and a generative cell. The generative cell may divide periclinally to form a spermatogenous cell The spermatagenous cell divides ultimately into two male gametes / male cells.
Taxaceae - reproduction The ovule has an aril which incompletely surrounds it The mature aril is brightly red coloured, soft, juicy and sweet, and is eaten by birds which then disperse the hard seed undamaged in their droppings. Taxaceae members are unique as their solitary seeds are not associated with cone scales Why a conifer? –embryology– chemistry –wood anatomy– leaf & pollen morphology Cone thought to be lost
Taxaceae - reproduction After fertilization up to 32 free nuclei are formed by the zygote. Then they organize themselves into 9 – 13 open upper cells and 9 – 13 suspensor cells and 6 – 14 embryonal cells (no rosette cells are present). Polyembryony rarely occurs in this group Seeds 1 per "cone," erect, not winged, hard seed coat
Torreya californica Young cones developing
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. Cupressaceae – Cypress / Redwood family Podocarpaceae – Podocarp family Araucariaceae – Norfolk Isl. Pine family Taxaceae – Yew family –Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Cephalotaxaceae a small group of conifers 3 genera containing ~ 20 species closely allied to the Taxaceae –included in that family by some botanists – highly branched small trees/shrubs Family Taxaceae Cephalotaxaceae Cone aril Cone aril partly encloses seed partly encloses seed fully encloses seed fully encloses seed Cone maturation Cone maturation 6-8 months 6-8 months months months Mature seed length Mature seed length 5-8 mm 5-8 mm mm mm
Phylogeny of the Taxaceae and Cephalotaxaceae - note that both groups have evolved from within the other conifers
Cephalotaxaceae Shrubs or small trees Leaves simple and usually spirally arranged Plants are dioecious Male cones arise in clusters of 6-8 cones in axils of short-shoot scale leaves 3-4 microsporangia borne abaxially Pollen grain spherical; bear no saccae No prothallial cells formed during pollen grain development
Globose pollen cones of Cephalotaxus harringtonia
Cephalotaxaceae Megasporangiate cones occur singly in the axils of lowermost leaves of young branches Appear green when young but redden at maturity “Cones” consist of a central axis bearing 5-7 pairs of bracts Each bract bears 2 ovules within its axil separated by reduced cone scale Usually one or two ovules ripen in one cone
Cephalotaxaceae - reproduction Zygote divides into 16 free nuclei which evenly associates upper and embryonal tiers Upper tier divides into open tier and prosuspensor tier The open tier cells disorganise eventually and prosuspensor cells elongate and push the embryonal tier out of the archegonium at the expense of female gametophyte Prosuspensors degenerate after secondary suspensor formation and embryonal cells divide large embryonal tissue No cleavage polyembryony
Pinophyta / Coniferophyta Pinophyta Families Pinaceae – pines & spruces etc. Cupressaceae – Cypress / Redwood family Podocarpaceae – Podocarp family Araucariaceae – Norfolk Isl. Pine family Taxaceae – Yew family Cephalotaxaceae –Sciadopityaceae – Umbrella-pine family
Sciadopityaceae The family was formerly included as a genus within Cupressaceae (Taxodiaceae), but recent genetic studies (Brunsfeld et al. 1994) have shown that it is clearly not allied with that group.