Table 1.

Differences in aerial (A) and subterranean (S) seeds of amphicarpic plants and of the plants derived from them. CH, chasmogamous; CL, cleistogamous

Seed morphology/structure/physiology
Desiccation sensitivity	A < S (Schnee & Waller, 1986; Zhang et al., 2015)
Fruits dehiscent versus indehiscent	A fruits dehiscent, S fruits indehiscent (Maheshwari & Maheshwari, 1955; Speroni & Izaguirre, 2001; Kumar et al., 2012; Zhang et al., 2015)
Moisture content	A < S (Schnee & Waller, 1986; Zhang et al., 2015)
Seed coat and pericarp anatomy	A seedcoat well developed, S seedcoat not well developed (Zhang et al., 2015)
Seed morphology/structures associated with diaspores	Differs among morphs and species (Alinoglu & Durlu, 1970; Durlu & Cornelius, 1970; Evenari et al., 1971; Weiss, 1980; Gopinathan & Babu, 1986; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998; Conterato, Schifino‐Wittmann, & Dall'Agnol, 2010; Zhang et al., 2015)
Seed size/mass	A < S (Maheshwari & Maheshwari, 1955; Koller & Roth, 1964; Alinoglu & Durlu, 1970; Durlu & Cornelius, 1970; Evenari et al., 1971; Cheplick, 1983, 1987, 1994; Cheplick & Quinn, 1983; Gopinathan & Babu, 1986; Schnee & Waller, 1986; Trapp & Hendrix, 1988; Kawano et al., 1990; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998; Conterato et al., 2010; Talavera et al., 2010; Kumar et al., 2012; Choo et al., 2014, 2015; Zhang et al., 2015)
Seed dispersal
Dispersal ability	A > S (Koller & Roth, 1964; Evenari et al., 1971; Mattatia, 1977a,b; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998; Talavera et al., 2010; Zhang et al., 2015)
Seedlings from A and S seeds
Growth	A < S (Koller & Roth, 1964; Cheplick, 1988)
Size	A < S (Koller & Roth, 1964; Loria & Noy‐Meir, 1979/80; Weiss, 1980; Schnee & Waller, 1986; Cheplick, 1987; Trapp & Hendrix, 1988; Talavera et al., 2010; Choo et al., 2015)
Stress tolerance and competitive ability	A < S (Koller & Roth, 1964; Evenari et al., 1971; Loria & Noy‐Meir, 1979/80; Cheplick, 1987) A = S (Kim et al., 2016)
Survival	A < S (Loria & Noy‐Meir, 1979/80; Cheplick & Quinn, 1982; Cheplick, 1987, 1988; Talavera et al., 2010)
Vegetative growth of plants derived from A and S seeds
Allocation of biomass to reproductive parts	Plants from S seeds allocate more biomass to A seed production than plants from A seeds (Cheplick, 1983, 1987; Cheplick & Quinn, 1983; Ruiz de Clavijo & Jimenez, 1998; Kaul et al., 2002; Choo et al., 2015) A = S (Kim et al., 2016)
Competitive ability	A < S (Weiss, 1980; Cheplick & Quinn, 1982, 1983; Ruiz de Clavijo & Jimenez, 1998; Sadeh et al., 2009; Zhang et al., 2017)
Leaf number/area	A < S (Weiss, 1980; Trapp & Hendrix, 1988; Choo et al., 2015; Zhang et al., 2017)
Plant size/dry matter production	A < S (Ruiz de Clavijo & Jimenez, 1998; Choo et al., 2015; Zhang et al., 2017) A = S (Kim et al., 2016)
Relative growth rate	A < S (Cheplick, 1983; Cheplick & Quinn, 1987, 1988b ) A = S (Kim et al., 2016)
Root/shoot mass ratio	Root/shoot ratio of plants derived from A and S seeds were negatively affected by nutrient availability and positively affected by intraspecific density (Sadeh et al., 2009)

Reproduction
Flower development	A and S flowers diverged at mid‐ to late development stage (Zhang et al., 2006) A and S flowers have normal ovule and embryo sac development (Speroni et al., 2010)
Flower size and number	A > S (Durlu & Cornelius, 1970; Fukui & Takahashi, 1975; Trapp & Hendrix, 1988; Jiang & Kadono, 2001; Zhang et al., 2006)
Flower structure/colour/anatomy	A CH flowers are large and brightly coloured and S flowers are small and white (Alinoglu & Durlu, 1970; Durlu & Cornelius, 1970; Gopinathan & Babu, 1986; Schnee & Waller, 1986; Trapp & Hendrix, 1988; Speroni & Izaguirre, 2001; Zhang et al., 2006; Conterato et al., 2010; Kumar et al., 2012) A and S flower size not influenced by position on the plant (Ortiz et al., 2009)
Flower types	A CH and CL and S CL (Schnee & Waller, 1986; Gopinathan & Babu, 1987; Trapp, 1988; Trapp & Hendrix, 1988; Zhang et al., 2005; Kawano, 2008) (amphicarpic sensu stricto) A CH and S CL (Maheshwari & Maheshwari, 1955; Raynal, 1967; Cheplick, 1983; Cheplick & Quinn, 1988b ; Speroni & Izaguirre, 2001, 2003) (amphicarpic sensu stricto) CL are submerged and CH emerged in two aquatic macrophyte taxa of Blyxa (Jiang & Kadono, 2001) (amphicarpic sensu stricto) A CH and basal (but not subterranean) CH (Koller & Roth, 1964; Evenari et al., 1977; Weiss, 1980; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998) (amphicarpic sensu lato)
Number of inflorescences	Plants derived from A < S (Alinoglu & Durlu, 1970; Ruiz de Clavijo & Jimenez, 1998; Kumar et al., 2012)
Phenotypic plasticity	Plants derived from A > S (Cheplick, 1983, 1994; Cheplick & Quinn, 1983; Kawano et al., 1990; Ruiz de Clavijo & Jimenez, 1998; Sadeh et al., 2009)
Pollen viability (%)	Plants derived from A = S (Conterato et al., 2013)
Pollen/ovule ratio	Plants derived from A > S (Gopinathan & Babu, 1986; Kaul et al., 2002; Kawano, 2008; Kumar et al., 2012)
Ratio of seed and fruit number to seed and fruit mass	Plants derived from A > S (Cheplick, 1987; Kawano et al., 1990; Sadeh et al., 2009; Conterato et al., 2010)
Reproductive output of plants derived from A and S seeds	Plants derived from A < S (McNamara & Quinn, 1977; Loria & Noy‐Meir, 1979/80; Cheplick & Quinn, 1982, 1988b ; Cheplick, 1987, 1994; Trapp & Hendrix, 1988; Kawano et al., 1990; Jiang & Kadono, 2001; Conterato et al., 2010) Plants derived from A = S (Kim et al., 2016)
Seed number/plant	Plants derived from A > S (Maheshwari & Maheshwari, 1955; Fukui & Takahashi,1975; Cheplick, 1983, 1987, 1988; Gopinathan & Babu, 1986; Cheplick & Quinn, 1987; Ruiz de Clavijo, 1995; Choo et al., 2014; Nam et al., 2017)
Seed set (%)	S CL flowers > A CH flowers (McNamara & Quinn, 1977; Cheplick & Quinn, 1986; Jiang & Kadono, 2001; Speroni et al., 2010)
Time to flowering	Plants derived from A < S (Zeide, 1978; Cheplick & Quinn, 1982; Cheplick, 1983) S flowers open earlier than A flowers (Schnee & Waller, 1986; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998; Berjano et al., 2014; Choo et al., 2014) A flowers open earlier than S flowers (Kim et al., 2016)
Life history
Life history trade‐offs	A flower and seed production are correlated with vegetative mass (Zeide, 1978; Weiss, 1980; Schnee & Waller, 1986 ; Trapp & Hendrix, 1988), while S flower and fruit production are (Schnee & Waller, 1986; Trapp & Hendrix, 1988) or are not correlated (Zeide, 1978; Weiss, 1980)
Quantitative genetics of life‐history traits	Seed set and seed mass of both seed types had low quantitative genetic variation relative to other traits (Cheplick & Quinn, 1988a ; Cheplick, 1994)

Dormancy and germination
Degree (depth) of dormancy	A > S (Koller & Roth, 1964; Alinoglu & Durlu, 1970; McNamara & Quinn, 1977; Walker & Evenson, 1985b ; Schnee & Waller, 1986; Trapp & Hendrix, 1988; Ruiz de Clavijo, 1995; Ruiz de Clavijo & Jimenez, 1998; Choo et al., 2014, 2015; Zhang et al., 2015) A < S (Evenari et al., 1977)
Germination and viability response to storage	Germination of A and S decreased with dry storage in Amphicarpum amphicarpon (McNamara & Quinn, 1977) Germination of A increased with dry storage, whereas S lost viability (Zhang et al., 2015)
Germination of water‐permeable seeds	Scarification of seed coat increased germination of A more than it did in S (Walker & Evenson, 1985b )
Germination percentage	A > S (Koller & Roth, 1964; Alinoglu & Durlu, 1970; Durlu & Cornelius, 1970; Weiss, 1980; Ruiz de Clavijo, 1995) A < S (McNamara & Quinn, 1977; Gamm, 1983; Walker & Evenson, 1985b ; Schnee & Waller, 1986; Trapp & Hendrix, 1988; Choo et al., 2015; Zhang et al., 2015)
Germination response to cold stratification	Cold stratification increased germination of intact A and S seeds (McNamara & Quinn, 1977) Cold stratification increased germination percentage of scarified A seeds and of intact S seeds (Zhang et al., 2015)
Germination response to dry heat	Dry heat increased germination of A seeds more than it did for S (Walker & Evenson, 1985b )
Germination response to light	Light increased germination of A seeds more than it did for S seeds (Weiss, 1980) Light increased germination of S seeds more than it did for A seeds (Walker & Evenson, 1985b ) Light increased germination of both A and S seeds (Koller & Roth, 1964) Light decreased germination of both A and S seeds (Ruiz de Clavijo, 1995) Light had no effect on germination of either A or S seeds (Zhang et al., 2015)
Germination response to temperature	Subterranean seeds usually germinate to a higher percentage than those of A at a given temperature (Koller & Roth, 1964; McNamara & Quinn, 1977; Weiss, 1980; Walker & Evenson, 1985b ; Choo et al., 2015; Zhang et al., 2015; Baskin & Baskin, 2017)
Permeability to water and storage behaviour	Aerial seeds are water impermeable and orthodox and S water permeable and recalcitrant (Schnee & Waller, 1986; Zhang et al., 2015)
Germination ecology
Ability to form a persistent seed bank	A > S (Cheplick, 1987; Zhang et al., 2015)
Soil burial depth of seedling emergence	Greater seed burial depth decreased emergence percentages of A and S. With increase of seed burial depth, plants reared from both A and S seeds allocated more biomass to S seeds (Walker & Evenson, 1985a ; Cheplick & Quinn, 1987)
Seed germination phenology	Usually no difference in timing of seed germination (Cheplick, 1987) Earlier germination of S seeds (Choo et al., 2015)
Effect of abiotic and biotic environment on proportion of the two morphs
Competition (density)	Plants from A seeds had significantly less total growth and seed production than those from S seeds in both high and low competition, and S seed production was less affected than A seed production by density in both A and S plants (Weiss, 1980; Cheplick & Quinn, 1982, 1983; Ruiz de Clavijo & Jimenez, 1998; Cheplick, 2007; Sadeh et al., 2009; Nam et al., 2017)
Fire	S seeds (protected from fire) germinated after the fire, whereas A seeds were killed by fire (Cheplick & Quinn, 1987, 1988b )
Flooding	Flooding damage during late vegetative growth tended to decrease production of S seeds and total plant mass, while allocation to A seeds did not differ among treatments (Choo et al., 2014)
Pathogens	Infection by fungi increased pre‐reproductive mortality and decreased seed production of small and large plants of Amphicarpaea bracteata, whereas smaller plants were more affected. With an increase in intensity of fungal infection, the proportion of CL seeds (presumably) increased (Parker, 1986)
Irradiance	Plants from A seeds had significantly less total growth and seed production than those from S seeds under the same irradiance. However, with an increase in irradiance the number of A seeds increased more than that of S seeds for plants from both A and S seeds (Trapp & Hendrix, 1988; Berjano et al., 2014; Nam et al., 2017; Zhang et al., 2017)
Litter	S seeds on bare soil surface in clay pots were more likely to lose viability and less likely to germinate than seeds protected by litter or by burial in soil (Cheplick & Quinn, 1987)
Reciprocal transplanting between populations	S seeds placed in the same habitat as the parents produced seedlings of greater vigour and adults of higher reproductive capacity than plants from seeds transplanted to a different habitat far removed from the parents (Cheplick, 1988)
Soil moisture	Plants from A seeds had significantly less total growth and seed production than those from S seeds at both dry and wet sites (Cheplick & Quinn, 1982)
Substrate fertility (nutrients)	Plants from A seeds had significantly less total growth and seed production than those from S seeds under the same nutrient availability (Weiss, 1980; Cheplick, 1987, 1989; Jiang & Kadono, 2001; Sadeh et al., 2009; Kim et al., 2016) With an increase of nutrient availability, total A/S seed mass of plants derived from both A and S plants increased (Weiss, 1980; Cheplick, 1987, 1989; Sadeh et al., 2009; Kim et al., 2016)

[Correction added on 26 June 2020, after online publication: Table headings for Table 1 have been amended in this current version.]