Day-neutral flowering in some Desert Blepharis spp.

Abstract

In the desert areas of Israel, Sinai and the neighbouring countries, there are three species of Blepharis. In addition at least six different populations of types not yet classified were also found in various locations and habitats. Differences such as rates of root elongation in response to temperature, structure of inflorescences and spiny bracts, and mechanisms of seed dispersal were found in these species and types. In all of them, irrespective of the growing conditions, three pairs of leaves and one terminal inflorescence develop above the cotyledons. A lateral branch from the axil of each of the pairs of upper leaves bears two pairs of leaves and a terminal inflorescence. From these branches, additional lateral branches sometimes appear in the axil of two upper leaves, again bearing two pairs of leaves, and a terminal inflorescence, and so on. Flowering in these plants was found to be day-neutral. The quantity and distribution of rain, soil humidity and temperature seem to regulate the age of the plant at flower-bud appearance and flowering. The ecological importance of this behaviour is discussed.