Abstract
AbstractThe environmental conditions under which parental plants are reared can affect the seed characteristics of the progeny. The variation originating from such maternal effects has rarely been incorporated into models of seed germination. Here, using Palmer amaranth (Amaranthus palmeriS. Watson), we examined the effects of water stress during the growth of parental plants on the progeny seed characteristics, including weight, size, final germination, and parameters of a hydrotime germination model. We grew two populations (from California and Kansas) under continuous water-deficit or well-watered conditions. In bothA. palmeripopulations, progeny seeds originating from water-stressed plants were heavier and larger than those from well-watered plants. Plants exposed to water stress also produced seeds that were ~30% less dormant than seeds from control plants. To test whether the maternal environment affects the parameters of a hydrotime model, progeny seeds were subject to five water potentials (0, −0.2, −0.4, −0.6, and −0.8 MPa) and incubated at 20 and 30 C; germination was monitored daily. The estimated median base water potential (Ψb(50)), that is, the water potential at which 50% of seeds cannot germinate, was consistently lower for seeds from water-stressed plants than for seeds from well-watered plants. Our results showed thatA. palmeriplants experiencing drought during their growth produce seeds that are less dormant and can germinate from drier conditions—a maternal response that seems to be adaptive. These findings also call for development of germination models that incorporate the environmental conditions of both the current and past seasons to better describe the variability in germination of weed seeds.
Highlights
Seed germination is highly regulated through environmental cueing (Donohue et al 2010), and weeds often exhibit high levels of variation in timing and extent of germination (Baskin and Baskin 1985; Egley and Williams 1991; Forcella et al 2000)
Analysis of progeny 1,000-seed weight showed significant differences between the two maternal water treatments both in the California (P-value = 0.0003) and the Kansas (P-value = 0.0003) populations. In both populations of A. palmeri, seeds produced under water stress were 18% heavier than those produced by plants under normal irrigation (Figure 2)
Similar to our findings, a greenhouse study with redroot pigweed (Amaranthus retroflexus L.) showed that plants subjected to water stress produced heavier seeds than those grown without drought (Chadoeuf-Hannel and Barralis 1982)
Summary
Seed germination is highly regulated through environmental cueing (Donohue et al 2010), and weeds often exhibit high levels of variation in timing and extent of germination (Baskin and Baskin 1985; Egley and Williams 1991; Forcella et al 2000). Variation in seed germination is determined, by the immediate microenvironment of the seed and by the conditions experienced by parental plants (mainly maternal; Baskin and Baskin 2019) during the preceding growing season (Fenner 1991; Roach and Wulff 1987). Maternal environment effects on seed germination have been reported for a wide range of plant species in response to temperature (Donohue et al 2008), soil moisture (Wright et al 1999), CO2 (Farnsworth and Bazzaz 1995), daylength (Nurse et al 2004), solar irradiance (Adkins and Armstrong 2007), light quality (Van Hinsberg 1998), nutrients (Allison 2002), herbicides (Andersson 1996), competition (Nurse and DiTommaso 2005), viral infection (Kathiria et al 2010), and even presence (or absence) of earthworms in the soil (Laossi et al 2010). Understanding what regulates the observed variation in germination patterns is a fundamental question in weed seed ecology and has implications for management of weeds
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