Germination syndromes in response to salinity of Chenopodiaceae halophytes along the intertidal gradient

Abstract

Germination is a crucial stage in the life cycle of plants and salinity is one of the most important factors conditioning it in salt marshes. This work analyses the effects of salinity on the germination of eight dominant Chenopodiaceae species inhabiting the intertidal gradient in the Gulf of Cádiz. Seeds were collected from Sarcocornia perennis, Atriplex portulacoides, Sarcocornia fruticosa, Salicornia ramosissima, Arthrocnemum macrostachyum, Suaeda vera, Salsola vermiculata and Sarcocornia alpini. They were placed in Petri dishes at 0.0, 0.1, 0.2, 0.3, 0.6 and 0.9M NaCl and germination was recorded during 30days. Ungerminated seeds were transferred to distilled water and germination recovery was recorded. High salinities inhibited germination, although tended to accelerate it in the recovery assays. Beyond these common responses, the studied halophytes showed four germination syndromes: 1) high germination at low-medium salinities and reduced germination after high salinity exposure; 2) no germination at hypersalinity and high recovery germination in fresh water; 3) increased and rapid germination after salinity exposure; and 4) germinating along a wide salinity range. The two species colonising the ecotone between marshes and dunes, Suaeda vera and Salsola vermiculata, shared Syndrome 2. Syndromes 3 and 4 were shared by species colonising different habitats and Syndrome 1 by A. macrostachyum, and fruits of A. portulacoides without bracteoles and S. vermiculata without calyx. The germination of species from high marshes was characterized by marked responses to salinity changes, whereas the germination of low marsh species was based on low sensitivity to salinity fluctuations.