Modeling the influence of temperature and water potential on seed germination of Allium tenuissimum L.

Allium tenuissimum L. is a widely distributed perennial herbaceous species in temperate and desert steppes. Relative to other wild Allium species, it produces unique sweet flavors, more biomass in arid and cold environments, and has generated greater interest for crop production. Successful crop establishment, however, will depend on rapid and uniform seed germination. Our study aimed to characterize seed germination of A. tenuissimum under various temperature regimes (11, 15, 20, 24 and 28 degrees C) and water potential levels (0, -0.2, -0.4 and -0.6 MPa), and model germination by hydrotime (HT) and hydrothermal time (HTT) analysis. Final germination percentage (FGP) increased within the range of 11 to 20 degrees C, yet it declined within the range of 24 to 28 degrees C and generally decreased as water potential became more negative within each temperature setting. Maximum FGP was observed at 20 degrees C at all water potential settings and ranged from 55.0 +/- 5.3 to 94.8 +/- 1.4%. According to HT and HTT models, the base (T-b) and optimum temperatures (T-o) for seed germination were 7.0 and 20.5 degrees C, respectively. In addition, base water potential for the fraction of germination within the seed lot (psi(b)(g)) shifted to 0 MPa as temperature increased from T-b to ceiling temperature (T-c). For obtaining 50 % seed germination, psi(b)(50) and T-c (50) were estimated to be -0.67 MPa and 27.2 degrees C, respectively. These values for Tb and psi(b)(50) suggest seed germination of A. tenuissimum is both cold and drought tolerant and suitable for production in semi-arid regions. Our characterization of the ideal sowing conditions for A. tenuissimum, i.e., 20.5 degrees C and soil water potential less negative than -0.67 MPa offers information to forecast suitable settings to enhance crop production.