Abstract
Production of heteromorphic seeds is common in halophytes growing in arid environments with strong spatial and temporal heterogeneity. However, evidence for geographic variation (reflecting local adaptation) is almost nonexistent. Our primary aims were to compare the life history traits of two desert populations of this halophytic summer annual Suaeda corniculata subsp. mongolica and to investigate the phenotypic response of its plant and heteromorphic seeds to different levels of salt stress. Dimorphic seeds (F1) of the halophyte S. corniculata collected from two distant populations (F0) that differ in soil salinity were grown in a common environment under different levels of salinity to minimize the carryover effects from the field environment and tested for variation in plant (F1) and seed (F2) traits. Compared to F1 plants grown in low soil salinity, those grown in high salinity (>0.2 mol⋅L-1) were smaller and produced fewer seeds but had a higher reproductive allocation and a higher non-dormant brown seed: dormant black seed ratio. High salinity during plant growth decreased germination percentage of F2 black seeds but had no effect on F2 brown seeds. Between population differences in life history traits in the common environment corresponded with those in the natural populations. Phenotypic differences between the two populations were retained in F1 plants and in F2 seeds in the common environment, which suggests that the traits are genetically based. Our results indicate that soil salinity plays an ecologically important role in population regeneration of S. corniculata by influencing heteromorphic seed production in the natural habitat.
Highlights
In arid and semi-arid regions of the world, soil salinity is an environmental stress factor to plants, partly because soil conditions are strongly heterogeneous in space and time (Bernstein, 1975)
We previously reported that maternal soil salinity can affect heteromorphic seed germination and seedling growth (Yang et al, 2015b), but our knowledge of seed morph production is much lower than that of other life history traits influenced by soil salinity
Key Life History States of Plants (F1) Grown in Common Environment Experiment. Population, salinity and their interactions all had a significant effect on the length of three key life history stages, but seed morph had an effect only on length of the vegetative period (Table 2)
Summary
In arid and semi-arid regions of the world, soil salinity is an environmental stress factor to plants, partly because soil conditions are strongly heterogeneous in space and time (Bernstein, 1975). As a link between two generations, seeds traits have a direct impact on population regeneration and dynamics (Harper, 1977; Donohue, 2009). Seed dormancy and germination responses enable seedling populations to emerge at the right time under relatively favorable environmental conditions that ensure establishment and completion of the life cycle (Hoyle et al, 2015; Huang et al, 2016). Seed traits and subsequent growth strategy are important for seedling survival and reproductive success in arid and saline habitats (Ungar, 1987; Gutterman, 2002; Yang et al, 2012)
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