Gymnarrhena

Appearance

''Gymnarrhena'' is a small, flowering, winter annual with a rosette of simple, narrow leaves and flower heads cropped at its hart. It does not contain latex and does not carry spines. ''Gymnarrhena'' flowers in March and April. One of the common names in Arabic is كَف الكَلْب meaning "dog's footprint", while in Hebrew it is called מוצנית קטנת-פרחים meaning "small chaff flower".

''Gymnarrhena micrantha'' is a dwarf annual herb of ½–2½ cm high, with all its leaves in rosette of up to 10 cm in diameter, and its flowers tucked away in the hart of this rosette, that is lacking latex, and does not have thorns. Two sources report twenty chromosomes , but one other publication says eighteen .

Naming

The genus name ''Gymnarrhena'' may be a contraction of two Greek words, ''γυμνός'' meaning "naked" and ''ἄῤῥην'' , "male", while the species epithet ''micrantha'' is a contraction of the Greek words ''μικρός'' , "small" and ''ἄνθος'' , "flower".

Distribution

''Gymnarrhena'' is known from North Africa, such as Algeria and Egypt, the Middle-East, such as Sinai, Israel, Jordan, Siria, Kuwait, eastern Saudi-Arabia, Quatar, the United Arab Emirates, Iraq, Iran and Pakistan . It grows on gravel plains, stony or rocky areas, in thin sandy deposits, alluvial plains and wadis.

Habitat

''Gymnarrhena'' is known from North Africa, such as Algeria and Egypt, the Middle-East, such as Sinai, Israel, Jordan, Siria, Kuwait, eastern Saudi-Arabia, Quatar, the United Arab Emirates, Iraq, Iran and Pakistan . It grows on gravel plains, stony or rocky areas, in thin sandy deposits, alluvial plains and wadis.''Gymnarrhena'' is a dwarf herbaceous winter annual plant. It is said to be poisonous and animals appear to avoid it. It has aerial flowers in March, April and - when sufficient moisture is around - May. Already after four leaves have grown, underground flowerheads develop that produce few larger cypselas, followed later on by many small cypselas from the aerial flower heads for as long as moisture is available. When the plant dies down in summer, the cypselas remain encased between the hardened bracts, presumably safe from harvester ants. After the first rain, which usually occurs the next winter, the bracts and pappus on the aerial flowerheads unfold, and the cypselas are dispersed by the wind, while many are gathered by ants. The cypselas in the underground flowerheads however germinate through the dead parts of the flowerhead, and remain protected against the ants. These seeds increase the chance that the plant continues its presence in a location that was favorable in the previous year. Aerial cypselas on average only weigh 5–6% of a subterranean fruit. After six days, seedlings of subterranean fruits are six times larger than those of aerial fruits and their survival rate is much higher. In very dry years, only subterranean fruits may develop and aerial florets may be entirely absent.

''Gymnarrhena'' is one of few species that grows where the sand has blown out from under tar tracks in Kuwait after the Gulf war, a strong confirmation of its ability to colonize disturbed habitat quickly. At Khirbet Faynan, in the southern Jordanian desert, ''Gymnarrhena'' grows on slag piles containing copper and lead and accumulates these heavy metals.

Evolution

The early production of few large seeds followed by production of many small seeds may have been the result of the variable and unpredictable growing season, fitting to a pioneer species.