A new experimental device for germinating seeds under controlled soil water potentials, a step beyond PEG.

Abstract

Abstract Background and Aims. Seed germination as a function of soil water potential (h) is modelled by polyethylene glycol (PEG) experiments. However, this methodology does not consider the soil properties. In this paper, we demonstrate the limitation of PEG experiments to model seed germination, while demonstrating the interaction between soil type, h and seed characteristics on seed imbibition. Methods. We present a new experimental device, the tension germinator (TG), which allows the monitoring of seed imbibition under controlled h. TG was tested on barley and vetch seeds placed on loam (TG-loam) and sand (TG-sand) with h values of 0, -0.002, -0.006 MPa. PEG experiments (0 to -2.5 MPa) were performed to detect the h critical, hPEG, from which the seed imbibition curve is affected. PEG curves for 0 > h > -0.01 MPa were compared with TG. Results. No differences between PEG and TG curves were observed at 0 MPa. hPEG for barley and vetch was within [0, -0.01] MPa. Comparison between TG and PEG within [0, -0.01] MPa showed that while similar curves were observed with PEG and TG-loam, TG-sand curves at -0.002 and − 0.006 MPa behaved differently to the equivalent PEG curves. Unlike with PEG, no imbibition was observed in barley and vetch in TG-sand at -0.006 MPa. The h in TG-loam had negligible influence on the imbibition curves. Conclusions. PEG is not adequate to describe seed germination in soil. We propose a new device that can improve seed germination modeling in relation to h.