Comparative analysis of osmotic and ionic stress effects on seed germination in Tagetes (Asteraceae) cultivars

Abstract

[EN] Drought and salinity are the most adverse environmental factors affecting crop productivity worldwide. The increasing scarcity of fresh, high-quality irrigation water is forcing the use of alternative water sources-such as sewage, waste water or brackish water in agriculture, in general, and also in floriculture. Seed germination is the first and the most important stage in a plant s life cycle, but it is also the most sensitive to environmental conditions, representing a bottleneck in plant development. Checking for stress tolerance at the germination stage is a reliable approach for the rapid screening of a large number of plant cultivars. The aim of the present study was to analyze the responses to osmotic and ionic stress, induced by isotonic solutions of polyethylene glycol (PEG) and NaCl, in 13 cultivars of Tagetes patula, T. tenuifolia, and T. erecta at the germination stage. Germination percentages and rates, and radicle, hypocotyls, and cotyledon lengths were determined after seven days of treatment. Responses to osmotic stress induced by PEG were similar in all selected cultivars, but significant differences were detected upon the salt treatments. In general, T. erecta responded better to salt stress than the other two species, but a large variability among cultivars within each species was observed. The most stress-tolerant cultivars of T. patula were Orion and Robuszta , and those of T. tenuifolia were Luna Gold , Luna Rot and Luna Orange .