Morphological and physiological responses of Scaevola sericea (Goodeniaceae) seedlings to salt spray and substrate salinity

Abstract

The effects of substrate salinity and salt spray upon seedlings of Scaevola sericea were examined in this study. Three levels of substrate salinity: 0.0 ppt, 3.0 ppt, and 10.0 ppt were examined in conjunction with three levels of salt spray: zero, medium (200 mg m‐2mdd‐1), and high (1200–1500 mg‐m‐2mdd‐1). Leaf surface area, root to shoot ratio, as well as leaf, stem, and root mass decreased significantly (P 0.05) with increasing substrate salinity. Biomass accumulation was very low at 10.0 ppt substrate salinity, suggesting that higher levels of substrate salinity cannot be tolerated by the seedlings. Salt spray had a substantial effect on several of these variables, however its effects were less pronounced than those of substrate salinity. Cell sap osmolarity, leaf thickness, and leaf specific mass increased significantly (P 0.05) with both increasing substrate salinity and salt spray levels. Leaf carbon isotope ratios (δl3C) became more positive with increasing salinity, indicating an enhancement of the intrinsic water use efficiency of the seedlings at higher salinities. Scaevola sericea is one of the dominant plants found at the leading edge of strand communities in the Hawaiian archipelago and throughout much of the tropical Pacific. Since substrate salinity and salt spray increase with proximity to the ocean, the two factors may act together to limit the seaward expansion of S. sericea in coastal habitats.

Trait convergence and diversification arising from a complex evolutionary history in Hawaiian species of Scaevola

“…Reich et al 2003). S. taccada is widely distributed and a major component of Hawaiian coastal communities, but has remained a single species lineage (Carlquist 1980;Alpha et al 1996). As the floating fruits of S. taccada are highly adapted to widespread oceanic distribution (cf.…”

“…Both S. taccada (lineage B) and S. coriacea (lineage C) existed within a narrow coastal band typified by higher MAT (up to 30 °C) and relatively low precipitation (Table 3); these species can be found coexisting (Online Resource 2, Table S1). Hydraulic stress from saltwater spray and sandy soils with high drainage is substantial in these coastal environments (Alpha et al 1996), and S. taccada and S. coriacea shared particular traits, such as low habit, orbicular and succulent leaves, and relatively few stomata, that would limit effects of salt received on the surface area of their leaves relative to narrower leaves (cf. Alpha et al 1996).…”

“…Hydraulic stress from saltwater spray and sandy soils with high drainage is substantial in these coastal environments (Alpha et al 1996), and S. taccada and S. coriacea shared particular traits, such as low habit, orbicular and succulent leaves, and relatively few stomata, that would limit effects of salt received on the surface area of their leaves relative to narrower leaves (cf. Alpha et al 1996). However, S. taccada differed strongly from S. coriacea in other traits (Fig.…”

Reproductive phenology of Scaevola plumieri; a key coloniser of the coastal foredunes of South Africa

“…The foredune habitat is very unstable and plant survival and performance can be affected by many factors ͑e.g., sand movement, salt spray, inundation͒ that vary significantly with dune position ͑Van der Valk 1974; Moreno-Casasola 1986;Hesp 1991;Alpha et al 1996;Houle 1997͒. Sand movement, especially, is of importance and can affect plant distribution, morphology, biomass, and flowering and fruiting phenology ͑Wallen 1980; Moreno-Casasola 1986;Primack 1987;Alpha et al 1996;Brown 1997͒.…”

“…Sand movement, especially, is of importance and can affect plant distribution, morphology, biomass, and flowering and fruiting phenology ͑Wallen 1980; Moreno-Casasola 1986;Primack 1987;Alpha et al 1996;Brown 1997͒. Some coastal foredune species exhibit high vigour following partial burial ͑Wallen 1980; Eldred and Maun 1982;Zhang and Maun 1990; Van der Putten et al 1993͒.…”