Seedling establishment, bud movement, and subterranean diversity of geophilous systems in Apiaceae

Abstract

Summary Geophilous systems of plants are not only regarded as organs of underground storage. Such systems also undergo a large range of modifications in order to fulfill other ‘cryptical’ functions, e.g. positioning of innovation buds, vegetative cloning, and vegetative dispersal. Seedlings should always be the point of departure for any investigation into the structure of geophilous systems. This is because in the ability to survive of geophilous plants it is of primary importance that innovation buds can reach a safe position in the soil by the time the first period hostile to vegetation commences. Our analysis of such systems thus focused on examining the development of 34 species of the Apiaceae, beginning with their germination. Independent of life-form and life-span, all species exhibit noticeable terminal bud movement with the aid of contractile organs. Movement was found to be at least 5 mm, reaching a maximum of 45 mm. All species exhibit a noticeable contraction of the primary root. In most cases the contraction phenomenon also occurs in the hypocotyl, and some species show contraction of their lateral and / or adventitious roots. Analysis of movement shows the functional importance of pulling the innovation buds down into the soil. Furthermore, in many species it becomes obvious that, even in the first year of development, modifications of the geophilous system take place in order to fulfill other cryptical functions. Finally, our functional viewpoint highlights the redundancy of differentiating between Raunkiaer’s cryptophytes and hemicryptophytes, and proposes that plants surviving at least one unfavorable season in the soil should all be subsumed in one category, the geophilous plants.