Salsola Kali, Russian Thistle
Total Page：16
File Type：pdf, Size：1020Kb
Of interest this week at Beal... Russian thistle Salsola kali Family: the Goosefoot family, Chenopodiaceae Also called tumbleweed, prickly saltwort, and windwitch W. J. Beal Botanical Garden The genus name Salsola means ‘salted’ in Latin. This alludes to the fact that many spe- cies of Salsola are salt-loving or halophytic in their preferences. Our species, Salsola kali is one such salt tolerating species. In many parts of the Midwest, Russian thistle is best established along roads that are salted during the winter. This creates a belt of territory along the roadside that is a somewhat halophytic environment. Tumbleweed is a cultural and botanical icon of the American West. Until late in the nineteenth century, the term ‘tumbleweed’ usually meant a native plant, Amaranthus alba. This species of amaranth grows into a rounded bushy configuration connected to the ground only where its taproot enters the soil. When this annual weed dies, the weak attachment to the taproot breaks off allowing it to roll, tumbling across the ground distributing its seeds along the way. However, the tumbling habit is in no way unique to the Amaranthus tumbleweed. In 1874, (the year of Winston Churchill’s birth) Russian thistle arrived in South Da- kota, from Russia, as a contaminant of flax seed. Its habit of becoming a tumbleweed allowed it to spread quickly across the arid, alkaline, and often salty soils of the West. Salsola has been the majority stockholder in the U. S. tumbleweed category for many decades. Today it can be seen forming gigantic drifts along fence rows and actually fill- ing small ravines throughout the plains in the late summer and fall. The indigenous tribes of the West found its roasted seeds could be human food and the tender young shoots were acceptable horse fodder. However, in today’s world we know that under certain conditions it can accumulate toxic amounts of nitrates that are dangerous to livestock. The flowers of Russian thistle are perfect although they prevent self fertilization within the same flower by maturing the male and female aspects of the flower in succession, Russian thistle flowers mature in two phases. First the female aspect of the flower (upper flower below) presents its two-part stigma to catch wind-blown pollen from the air; then in the second phase the anthers of the male open (lower flower) releasing pollen. instead of simultaneously. After the ovary has been fertilized, Salsola kali does some- thing unusual. From the surrounding sepals fast-growing wings are produced that have the effect of simulating the appearance of a flower (see first page, middle center photo). It is superficially much more floral appearing that the actual flowers themselves. The resulting seed, in a fruit called a utricle, has a spirally coiled embryo that is ready to grow, but contains no endosperm. Most angiosperm seeds are furnished with endo- sperm, the 3n tissue that originates as a consequence of double fertilization and is the first nutrition source for seeds that are so endowed..