Abstract
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 °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 °C, yet it declined within the range of 24 to 28 °C and generally decreased as water potential became more negative within each temperature setting. Maximum FGP was observed at 20 °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 (Tb) and optimum temperatures (To) for seed germination were 7.0 and 20.5 °C, respectively. In addition, base water potential for the fraction of germination within the seed lot (Ψb(g)) shifted to 0 MPa as temperature increased from Tb to ceiling temperature (Tc). For obtaining 50 % seed germination, Ψb(50) and Tc(50) were estimated to be −0.67 MPa and 27.2 °C, respectively. These values for Tb and Ψb(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 °C and soil water potential less negative than −0.67 MPa offers information to forecast suitable settings to enhance crop production.
Highlights
Seed germination is an essential process in establishing stable plant populations and is regulated by many environmental factors (Atashi et al, 2015; Juan-Vicedo et al, 2016)
We aimed to focus on the response of seed germination to various temperatures and water potential conditions in A. tenuissimum: (i) characterizing seed germination dynamics of A. tenuissimum using HT and hydrothermal time (HTT) models, and (ii) defining cardinal temperatures and base water potentials for A. tenuissimum seeds based on model parameters
Different water potential levels were produced by mixing aqueous solutions of polyethylene glycol (PEG) 6000 with distilled water according to Michel & Kaufmann (1973)
Summary
Seed germination is an essential process in establishing stable plant populations and is regulated by many environmental factors (Atashi et al, 2015; Juan-Vicedo et al, 2016). Among these factors, temperature and moisture conditions strongly regulate germination dynamics (Bakhshandeh & Gholamhossieni, 2019), and characterizing the base, optimum, and ceiling temperatures is one way of describing how temperature influences seed germination dynamics (Bakhshandeh et al, 2013; Bewley et al, 2013). TT models may inaccurately predict seed germination responses under supra-optimal temperature ranges (Bakhshandeh et al, 2015; Bradford, 2002)
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