Diversity in leaf anatomy, and stomatal distribution and conductance, between salt marsh and freshwater species in the C₄ genus Spartina (Poaceae)

Abstract

Summary Leaf anatomy, stomatal density, and leaf conductance were studied in 10 species of Spartina (Poaceae) from low versus high salt marsh, and freshwater habitats. Internal structure, external morphology, cuticle structure, and stomatal densities were studied with light and electron microscopy. Functional significance of leaf structure was examined by measures of CO2 uptake and stomatal distributions. All species have Kranz anatomy and C4δ13C values. Freshwater species have thin leaves with small ridges on adaxial sides and stomata on both adaxial and abaxial sides. By contrast, salt marsh species have thick leaves with very pronounced ridges on the adaxial side and stomata located almost exclusively on adaxial leaf surfaces. Salt marsh species also have a thicker cuticle on the abaxial than on the adaxial side of leaves, and CO2 uptake during photosynthesis is restricted to the adaxial leaf surface. Salt marsh species are adapted to controlling water loss by having stomata in leaf furrows on the adaxial side, which increases the boundary layer, and by having large leaf ridges that fit together as the leaf rolls during water stress. Differences in structural–functional features of photosynthesis in Spartina species are suggested to be related to adaptations to saline environments.

Transcriptome de novo assembly from next-generation sequencing and comparative analyses in the hexaploid salt marsh species Spartina maritima and Spartina alterniflora (Poaceae)

“…Salt marsh Spartina species have thick leaves with pronounced ridges on the adaxial side. They are adapted to controlling water loss by having stomata on the adaxial side and by having large leaf ridges that fit together as the leaf rolls during water stress (Maricle et al, 2009). To prevent salt toxicity, Spartina have large vacuoles for salt storage (Munns and Tester, 2008) and salt-secreting glands to excrete inorganic ions (Zhu, 2001).…”

The Developmental Basis of Stomatal Density and Flux

“…Third, there may be a substantial contribution of diffusion resistances in the intercellular airspaces, especially in the case of a partly cutinized substomatal chamber (Roth-Nebelsick, 2007;Feild et al, 2011). Fourth, leaf surface features such as hairs or papillae surrounding the stomata, or encryption of stomata, may affect the diffusion through stomata, and especially will influence the boundary layer, which in addition to stomatal conductance determines overall diffusional conductance and therefore gas exchange (Kenzo et al, 2008;Hassiotou et al, 2009;Maricle et al, 2009). Clearly, much more research is needed to establish models that include all the factors that determine the anatomical influence of stomata on gas exchange rates and to validate these against a wide diversity of plants, yet the anatomical maximum defined as in Equations 1 and 2 is a strong constraint: g max correlates across diverse species with g op and lightsaturated photosynthetic rate (McElwain et al, 2016), and scales up, in combination with leaf area allocation, to the determination of ecosystem net primary productivity (Wang et al, 2015a).…”

Physiological responses of Spartina alterniflora to varying environmental conditions in Virginia marshes

“…The results are consistent with several studies suggesting atypical C 4 pathways. Although greenhouse studies (Maricle et al, 2009) found that S. alterniflora plants displayed traits of the C 4 carboxylation pathway, field studies (Dai & Wiegert, 1997;Barlocher et al, 2003) also reported Fig. 6 The relationship between maximum electron transport rate (J max ) and leaf temperature.…”