Light and fluctuating temperatures are two important factors triggering seed germination. The aim of this work was to: (1) elucidate the effect of temperature, light regime and storage time on seed germination in nine taxa of Verbascum spp., collected from different habitats in the Mediterranean area; and (2) estimate threshold temperatures for seed germination. For all taxa, germination assays were performed at constant and fluctuating temperatures, both in continuous darkness (D) and in alternating light/dark (L/D; 12h photoperiod). Final germinated proportions (FGPs), base (T-b), optimal (T-o) and cut-off (T-c) temperatures were derived. At constant temperatures, seed germination was strongly suppressed under the D regime. In L/D, the effect of storage time was very small and the highest FGPs were observed from 15 to 30 degrees C (40-100%), depending on the species. T-b ranged from below 7 to above 10 degrees C and it appeared to be constant within each seed lot. T-o and T-c showed some within-lot variability and were higher for fast-germinating seeds in each lot. Considering fluctuating temperatures, germination appeared to be quicker and more complete than at constant temperatures. The germination of Verbascum spp. is favoured in L/D and fluctuating temperatures, which explains their pioneer character when positioned near the soil surface and under a low vegetation canopy. V. arcturus and V. pinnatifidum were shown to be less favoured by L and fluctuating temperatures, which might explain their ability to germinate in rocky areas or sandy dunes, even when they are not directly exposed to the light.

Threshold temperatures for seed germination in nine species of Verbascum (Scrophulariaceae)

ONOFRI, Andrea
2016

Abstract

Light and fluctuating temperatures are two important factors triggering seed germination. The aim of this work was to: (1) elucidate the effect of temperature, light regime and storage time on seed germination in nine taxa of Verbascum spp., collected from different habitats in the Mediterranean area; and (2) estimate threshold temperatures for seed germination. For all taxa, germination assays were performed at constant and fluctuating temperatures, both in continuous darkness (D) and in alternating light/dark (L/D; 12h photoperiod). Final germinated proportions (FGPs), base (T-b), optimal (T-o) and cut-off (T-c) temperatures were derived. At constant temperatures, seed germination was strongly suppressed under the D regime. In L/D, the effect of storage time was very small and the highest FGPs were observed from 15 to 30 degrees C (40-100%), depending on the species. T-b ranged from below 7 to above 10 degrees C and it appeared to be constant within each seed lot. T-o and T-c showed some within-lot variability and were higher for fast-germinating seeds in each lot. Considering fluctuating temperatures, germination appeared to be quicker and more complete than at constant temperatures. The germination of Verbascum spp. is favoured in L/D and fluctuating temperatures, which explains their pioneer character when positioned near the soil surface and under a low vegetation canopy. V. arcturus and V. pinnatifidum were shown to be less favoured by L and fluctuating temperatures, which might explain their ability to germinate in rocky areas or sandy dunes, even when they are not directly exposed to the light.
2016
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/1384995
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