Plant signals trigger remarkable bacterial transformation

The cycad Cycas revoluta is a palm-like plant that grows on rocky coastal cliffs in the sub-tropics and tropics. It has a symbiotic relationship with the Nostoc species of bacteria that can convert nitrogen from the atmosphere ...

Cycad leaf physiology research needed

The living cycad species are among the world's most threatened plant groups, but are also among the world's least studied plant groups. The need for a greater understanding of basic physiology of cycads has been discussed ...

Literature on cycads continues to accumulate

As traditional print journals merge with contemporary web-based journals, publishing scientists find themselves in a rapidly evolving transition. In order to understand how these changes in publishing culture have influenced ...

Parsing conservation information on cycad species

Human activity continues to threaten the world's terrestrial flora. Extensive formal compilations of information and data have become useful for understanding these global threats. The International Union for Conservation ...

Mexico's ancient native plants and a new invasive insect threat

Benjamin Normark, professor of biology at the University of Massachusetts Amherst, was recently selected as a Fulbright scholar and will spend the fall 2016 semester in Mexico documenting the spread of the insect, cycad aulacaspis ...

Native Guam plant on cover of international journal

Research from the University of Guam (UOG) has been published in this month's issue of the International Journal of Plant Sciences. The research was conducted within the Western Pacific Tropical Research Center (WPTRC) at ...

Cycads in central Australia are not ancient relics

(Phys.org) -- An ancient plant isolated in the heart of Australia, more than 1200km from its coastal cousins, is now believed to have arrived inland far more recently than initially thought.

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Cycad

Cycadaceae cycas family Stangeriaceae stangeria family Zamiaceae zamia family

Cycads /ˈsaɪkædz/ are seed plants typically characterized by a stout and woody (ligneous) trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female (dioecious). Cycads vary in size from having a trunk that is only a few centimeters tall to trunks up to several meters tall. They typically grow very slowly and live very long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes confused with and mistaken for palms or ferns, but are only distantly related to either.

Cycads are found across much of the subtropical and tropical parts of the world. They are found in South and Central America (where the greatest diversity occurs), Mexico, the Antilles, southeastern United States, Australia, Melanesia, Micronesia, Japan, China, Southeast Asia, India, Sri Lanka, Madagascar, and southern and tropical Africa, where at least 65 species occur. Some can survive in harsh semidesert climates (xerophytic), others in wet rain forest conditions, and some in both.[citation needed] Some can grow in sand or even on rock, some in oxygen-poor swampy bog-like soils rich in organic material, and some in both.[citation needed] Some are able to grow in full sun, some in full shade, and some in both.[citation needed] Some are salt tolerant (halophytes).

Cycads belong to the biological division Cycadophyta. There are three extant families of cycads, Cycadaceae, Stangeriaceae, and Zamiaceae. Though they are a minor component of the plant kingdom today, during the Jurassic period they were extremely common. They have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions.

Cycads are gymnosperms (naked seeded), meaning that their unfertilized seeds (ovules) are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, who have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized pollinators, usually a specific kind of beetle. They have been reported to fix nitrogen in association with a cyanobacterium living in the roots. These blue-green algae produce a neurotoxin called BMAA that is found in the seeds of cycads. A neurotoxin cycling through the food chain from the cyanobacterium through cycads to its seeds, to bats eating the seeds, to humans consuming the bats, is hypothesized to be a source for some neurological diseases in humans.

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