Cycadophyta & Gingkophyta

• There are 3 mostly fossil groups of cydadophytes: Pteridospermales, Bennettitales, and Cycadophyta
• Pteridospermales (seed ferns): diverse group (365-210 MY BP) and is extinct, foliage looks just like ferns, had slender branches, dichotomous branching or venation, large seeds, microsporangia in synangia, can see gradual fusion of integument lobes over time
• primitive reproductive features of pteriodpspermales: often no pollen tube, integument not completely fused to nucellus, pollen captured by a drop secreted by a nucellar beak within pollen chamber
• Cycadophyta: 250 MY BP to present, 11 genera, approximately 140 species, tropical to subtropical, looks palm like
• cycadophyta have usually one stem, upright, unbranched, big apical meristem, eustele with slow secondary growth, large pith and cortex
• cycadophyta leaves are long, pinnate, perennial (2-4 years before they die), circinate (curl like ferns)venation of leaf or pinnae, have thick cuticles, stomatal crypts, dichotomous venation with anastomoses
• anastomoses = veins join up together
• cycadophyta roots: thick long tap roots, apogeotropic roots (coralloid roots - look like coral) - grows upwards and branch dichotomously
• reproduction in cycadophyta: dioecious (2 houses - separate male and female plant), female and male strobili on separate plants,
• megaspornagiate strobili (seed cones) are large with large ovules, and sporophylls are leafy and scaly
• microsporangiate strobili (pollen cones) - sporophylls are thick & scaly, and beetles are important in pollination
• cycadophyta post pollination: pollen germinates on nucellus, 2 large flagellated sperm released in archegonia chamber, sperm swim between neck cells and fertilize egg to develop into zygote (undergoes extensive free nuclear division before cells walls form)
• in cycdophyta, seed requires after ripening, and seed coat has an inner stony layer and may have outer fleshy layer (sarcotesta)
• Bennettitales : extinct fossil group (220-60 MY BP), pinnately compound leaves, short conical stems with eustele (like cycads), lateral strobili, monoecious (1 house - male and female together on 1 plant), monosporangiate or bisporangiate strobili
• ginkgophyta: 1 order (ginkgoales), 1 genus and 1 species (ginkgo biloba), fossils from 270 MY BP
• ginkgophyta stem: big diameter trunk, spreading branches, slow growing, eustele, dense wood with tracheas (like conifers)
• there are two branch types in ginkgophyta: short shoots (spur shoots) and long shoots (main axes)
• ginkgophyta leaves: deciduous, dichotomous venation with anastomoses (like cycads), notched or lobed (fan shaped)
• ginkgophyta reproduction: dioecious, ovules and pollen cones on short shoots, male (simple strobilus), female -no strobilus, stalk with 2 or 3 ovules at tip (only 1 matures), large ovules
• ginkgophyta is wind pollinated, have pollination drop, haustoria pollen tube (soaks up nutrients from female nucellus), multi flagellated sperm, archegonia chamber
• in ginkgophyta, the integument matures in 3 layers (cycad has 2 layers): inner thin fleshy layer(prothalle), middle hard stony layer(sclerotesta), and outer thick fleshy layer (sarcotesta)