Classification gymnosperms.............pdf
- 3. • Class 1: Cycadopsida – It includes fossil and living forms – Stem is large and stumpy – Large and pinnately compound leaves – Male cones are large and compact with simple microsporophyll – Female cones are loose or pinnate (leaf-like) – Megasporophyll is simple and the ovules are large – Anatomically the stem is with wide cortex – The wood manoxylic type with large amount of parenchyma
- 10. • It consists of four orders – Pteridospermales – Bennettitales – Pentoxylales – Cycadales
- 11. • Pteridospermales – Are also called cycadofilicales – They are cycad ferns – All are extinct ferns – They appeared in the Devonian period (The Devonian, part of the Paleozoic era, is otherwise known as the Age of Fishes, as it spawned a remarkable variety of fish) and abundant in the carboniferous period – The morphology and anatomy were similar to that of ferns and gymnosperms – Cones not produced – Ovules are directly borne on the leaf margin – Eg: Lyginopteris
- 13. • Bennettitales – Are also calledas Cycadeoidales – It is an extinct group – Appeared in the triassic period (The Mesozoic Era begins with the Triassic Period. This era is popularly known as the “Age of Reptiles” and for good reason: reptiles, and particularly dinosaurs, were the dominant land-dwelling vertebrate animalsat the time) – Completely extinct in the cretaceous period (The Cretaceous is defined as the period between 145.5 and 65.5 million years ago,* the last period of the Mesozoic Era, following the Jurassic and ending with the extinction of the dinosaurs (except birds). – Plant body resembles that of living cycads – Have stout or slender stem – Reproductiveparts were flower-like – Cones bisporangiateor monosporangiate – Eg: Cycadeoidea, Williamsonia
- 15. • Pentoxylales – A completely extinct group – Plants were shubby – Stems with five vascular strands – Each vascular strand with own cambial ring and undergo secondary thickening – This group was originally described by Prof. Birbal Sahni – Female inflorescence with many cones – Male structure are developed directly on dwarf shoots – Eg: Pentoxylon, Sahania
- 17. • Cycadales – They are the living cycadophyta – Most of them are xerophytic in nature – The plant body is palm like and very slow growing – Stem short, un branched covered with persistent leaf scars – Leaves pinnately compound, arranged as a terminal crown – Leaves show circinate vernation – All cycads are dioecious – Ovules are straight (anatropus) – Eg: Cycas, Zamia, Dioon
- 18. • Class II-Coniferopsida – Members are large, profusely branched tree forms – Plants with cone like appearance – Leaves are simple – Anatomically the pith is small – Xylem is dense and massive – The wood is pycnoxylic type – Male and female strobili compact and contain complex sporophylls – It consist of four orders • Cordaitales • Confierales • Taxales • Ginkgoales
- 19. • Cordaitales – They are the early conifers – Appeared during the carboniferous period – All are extinct, no living representatives – The plants were small tress with star shaped leaves – The reproductive structures were catkin-like clusters – Eg: Cordaites, Mesoxylon
- 21. • Coniferales – Mostly evergreen trees – Coniferales present the largest Gymnosperm order (living form) – Plants possess xerophyte adaptations – Leaves usually needle-like and spirally arranged – Wood with a large number of resin canals – Plants monoecious or dioecious – Pollination by wind – Eg: Pinus
- 25. • Ginkgoales – Consist of only one extinct genus with one species- Gingko biloba (maindenhair tree) – Living fossil – The plant is native to China – Leaves are broad, bi-lobed with dichotomous viening
- 27. • Taxales – Members of Taxales are evergreen small tress or shrubs – An extensively branched plant – Leaves simple, solitary, flat and distichous – Leaf arrangement is spiral – Secondary wood is picnoxylic – Ovules are surrounded by arils – Eg: Taxus
- 29. • Gnetopsida – Shrubs or woody climbers – Morphologically similar to angiosperm – Leaves are opposite – Gnetales are only gymnosperm having wood with vessels – Embryo dicotyledonous – Resin canals are absent – A connecting link between Gymnosperm and angiosperm – Contain only one order: Gnetales – Eg: Gnetum, Ephedra, Welwitschia