Ephemerals

(in Russian, ingredienty), species of plants that temporarily become part of plant communities in arid regions (dry steppes, semideserts). Ephemerals develop episodically: they may be represented in large numbers in wet years. Some ephemerals use excess moisture in early spring, others in late autumn, when components or species that constitute the permanent base of the plant cover (prevailers) are just beginning to grow or finishing growing. In dry years ephemerals may not develop altogether, surviving through unfavorable times in the form of seeds that retain their germinating power for a long time. Biennials develop leaf rosettes in late autumn and blossom and bear fruit in early spring. Typical ephemerals include bristly brome, hop clover, common whitlow grass, and perfoliate pepperwort. The term ingredienty was proposed by J. K. Paczoski in 1910 for the southern Russian steppes.

a group of annual herbs that complete a full cycle of development in a very short period of time. Ephemerals have fall-winter-spring vegetative cycles that last from six weeks (Gamanthus gamocarpus, orache) to eight months (desert bos-tryx, desert madwort, Ceratocephala falcata). They constitute a large part of the vegetative cover of deserts, semideserts (57–63 percent of the species composition), and some steppe regions. Ephemerals are noted for their exceptional adaptability to changes in the environment.

Early ephemerals retain a mesomorphic leaf structure; later ones have a xeromorphic structure that is expressed in various degrees. The seeds of vernal ephemerals germinate in the spring; those of winter forms, in the fall. The dormant period of the seeds and fruits coincides approximately with the summer season. The seeds of grasses and legumes remain viable for as many as seven years; those of other ephemerals, for no more than three years.