Embedded Files
Sago palms; cycads
Sago palms; cycads
Cycads, sometimes called sago palms, are an ancient gymnosperm lineage with 11 living genera and almost 300 species. All cycads have compound leaves appearing palm-like, which are frequently tough and filled with sclerenchyma. Some cycads form stout trunks (caudex) with small amounts of wood, while others are ground-dwelling. They tend to be slow-growing plants that produce enormous cones during reproduction.
This group inhabited a wide range of habitats during the dinosaur age (Mesozoic), including arid environments. This was before the advent of angiosperms and plants such as cacti, and they may have been some of the earliest arid-adapted plants. In fact, the "Age of Dinosaurs" is also known as the "Age of Cycads" to plant-loving folks. The abundance of "cycad" fossils during this time is due to the success of this group, and a convergent look-alike called the Bennetittales or cycadeoids.
Ecology & Form
Ecology & Form
Palm-like gymnosperms, inhabiting tropical (moist and arid) environments
Stems
Usually possess a single trunk
Eustele w/ cambium to produce small amounts of wood
Wood production is polyxylic; forming successive cambia
Largest pith in the plant kingdom
Leaf traces that wrap around the cortex (girdling)
Charmorgia dijolii †
Ash, 1985
Late Triassic in the Petrified Forest National Park, USA
Lyssoxylon †
Daugherty, 1941
Late Triassic of New Mexico and Arizona
Michelilloa waltonii †
Archangelsky & Brett, 1963
Triassic of northern Argentina
Vladiloxylon †
Lutz et al., 2003
Triassic of Chile
Geologic Range
Geologic Range
Pennsylvanian (?) - present
Pennsylvanian origin (Norstog & Nicholls, 1997; Pant, 2002)
Early Permian: Cycadodendron (Luthardt et al., 2023)
Cycadodendron galtieri †
Cycadodendron galtieri †
Early Permian of eastern Germany
Slender stem with wide parenchymatous pith
Primary vascular system consisting of densely arranged interconnected medullary bundles scattered throughout the pith and circularly arranged bundles in the pith periphery
Metaxylem tracheids of vascular bundles with multiseriate-bordered pits
Successive vascular segments with centripetal xylem and centrifugal phloem
Innermost vascular segment with distinctly wider primary rays compared to the outer segments
Wide-lumen secondary xylem tracheids with araucarioid-type pitting
Medullary bundles obliquely traversing the vascular segment(s) through primary rays
Right: Sketch of cross-section of stem (Luthardt et al. 2023; Figure 4)
Leaves
Fronds; large pinnately compound leaves
Many are rigid and tough
Possess hypodermis to prevent water loss
Mesodescolea †
Artabe and Archangelsky, 1992
Nilssonia †
Harris, 1964
Kurtziana †
Artabe et al., 1991
Yixianophyllum †
Zheng et al., 2005
Cycadinorachis †
Lower Cretaceous of India
Sharma, 1973a
Cretocycas †
Upper Cretaceous of Japan
Nishida et al., 1996
Pterostoma †
Morphogenus for large fronds with simple pinnae contracted near the base and with simple or dichotomizing veins (Hill, 1980).
Roots
Above-ground roots that look like coral (=coralloid)
These roots contain cyanobacteria
Reproductive Structures
Dioecious (separate male and female plants)
Large ♂ and ♀ cones
simple cones (=born on modified leaves)
Pollen sacs on male modified leaves (=microsporophylls)
Seeds on female modified leaves (=megasporophylls)
Beetle pollination
Cone-like in many families
Largest sperm cells in the plant world; zoidogamous (sperm swim to egg)
Additional Resources
Additional Resources
Stem carbohydrate richness in two cycad species (Phys.org 17Oct2024)
└Marler (2018) Stem Carbohydrates and Adventitious Root Formation of Cycas micronesica following Aulacaspis yasumatsui Infestation
Invasive insect herbivore alters ecosystem services delivered by cycads (Phys.org 31Jul2024)
└Marler (2024) Aulacaspis yasumatsui infestations accelerate Cycas leaf litter decomposition and nutrient release
Searching for a female partner for the world's 'loneliest' cycad - Encephalartos woodii (Phys.org 16June2024)
The oldest potted plant in the world (Royal Botanic Gardens Kew, July 2019)
Cycads as house plants (YouTube 2020)
North American Cycad & its Butterfly (In Defense of Plants, Jan 2015)
Nitrogen fixation of cycads (In Defense of Plants, 2017)
Cycads: The Most Endangered Plants on Earth (In Defense of Plants 2017)
Page updated
Google Sites
Report abuse