Cycad

Cycads /ˈsaɪkædz/ are <a href="/facts/Seed_plant/MQBG4KEw">seed plants</a> that typically have a stout and woody (<a href="/facts/Ligneous/xXCI9yys">ligneous</a>) <a href="/facts/Trunk_(botany)/13Nq8CEC">trunk</a> with a <a href="/facts/Crown_(botany)/GMJJX23v">crown</a> of large, hard, stiff, <a href="/facts/Evergreen/bcLptUdV">evergreen</a> and (usually) <a href="/facts/Pinnate/1tm6hMyo">pinnate</a> leaves. The species are <a href="/facts/Dioecious/jwMHLkuM">dioecious</a>, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow slowly and have long lifespans. Because of their superficial resemblance to <a href="/facts/Arecaceae/5bN6Wwcr">palms</a> or <a href="/facts/Fern/e6Cngdyo">ferns</a>, they are sometimes mistaken for them, but they are not closely related to either group.
Cycads are <a href="/facts/Gymnosperms/lzcpfbUK">gymnosperms</a> (naked-seeded), meaning their <a href="/facts/Fertilization/g8u3UKzF">unfertilized</a> seeds are open to the air to be directly fertilized by <a href="/facts/Pollination/u383g7XJ">pollination</a>, as contrasted with <a href="/facts/Angiosperms/E5eGYIvY">angiosperms</a>, which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized <a href="/facts/Pollinator/DBJNeDtv">pollinators</a>, usually a specific <a href="/facts/Beetle/hv33fxsL">beetle</a>, and more rarely a <a href="/facts/Thrips/FEW4Njc0">thrip</a> or a <a href="/facts/Moth/bPrkvkGh">moth</a>. 
Both male and female cycads bear cones (<a href="/facts/Strobilus/WEVJDExF">strobili</a>), somewhat similar to <a href="/facts/Conifer_cone/rqHh3fVu">conifer cones</a>.
Cycads have been reported to <a href="/facts/Nitrogen_fixation/TeLoBpWS">fix nitrogen</a> in association with various <a href="/facts/Cyanobacteria/S8bKxIU9">cyanobacteria</a> living in the roots (the "coralloid" roots). These photosynthetic bacteria produce a <a href="/facts/Neurotoxin/I7nLuFE7">neurotoxin</a> called <a href="/facts/BMAA/nGtyYbPz">BMAA</a> that is found in the <a href="/facts/Seed/a4xGSLxJ">seeds</a> of cycads. This neurotoxin may enter a human food chain as the cycad seeds may be eaten directly as a source of flour by humans or by wild or feral animals such as bats, and humans may eat these animals. It is hypothesized that this is a source of some <a href="/facts/Neurological_disease/eQKKs7jX">neurological diseases</a> in humans. Another defence mechanism against herbivores is the accumulation of toxins in seeds and vegetative tissues; through <a href="/facts/Horizontal_gene_transfer/FPyUIsf2">horizontal gene transfer</a>, cycads have acquired a family of genes (<a href="/facts/Pseudomonas_protegens/XrGsXLp1">fitD</a>) from a microbial organism, most likely a fungus, which gives them the ability to produce an insecticidal toxin.
Cycads all over the world are in decline, with four species on the brink of extinction and seven species having fewer than 100 plants left in the wild.

Cycad open-in-new

Cycad