Flood tolerance of Glyceria fluitans: the importance of cuticle hydrophobicity, permeability and leaf gas films for underwater gas exchange

TY - JOUR

T1 - Flood tolerance of Glyceria fluitans

T2 - the importance of cuticle hydrophobicity, permeability and leaf gas films for underwater gas exchange

AU - Konnerup, Dennis

AU - Pedersen, Ole

PY - 2017/10/1

Y1 - 2017/10/1

N2 - Background and Aims Floating sweet-grass (Glyceria fluitans) can form aerial as well as floating leaves, and these both possess superhydrophobic cuticles, so that gas films are retained when submerged. However, only the adaxial side of the floating leaves is superhydrophobic, so the abaxial side is directly in contact with the water. The aim of this study was to assess the effect of these different gas films on underwater net photosynthesis (PN) and dark respiration (RD). Methods Evolution of O2 was used to measure underwater PN in relation to dissolved CO2 on leaf segments with or without gas films, and O2 microelectrodes were used to assess cuticle resistance of floating leaves to O2 uptake in the dark. Key Results The adaxial side of aerial leaves was more hydrophobic than the abaxial side and also initially retained a thicker gas film when submerged. Underwater PN vs. dissolved CO2 of aerial leaf segments with gas films had a Km of 172 mmol CO2 m-3 and a Pmax of 7-1 lmol O2 m-2 s-1, and the leaf gas films reduced the apparent resistance to CO2 uptake 12-fold. Underwater PN of floating leaves measured at 700 mmol CO2 m-3 was 1-5-fold higher than PN of aerial leaves. The floating leaves had significantly lower cuticle resistance to dark O2 uptake on the wettable abaxial side compared with the superhydrophobic adaxial side. Conclusions Glyceria fluitans showed high rates of underwater PN and these were obtained at environmentally relevant CO2 concentrations. It appears that the floating leaves possess both aquatic and terrestrial properties and thus have 'the best of both worlds' so that floating leaves are particularly adapted to situations where the plant is partially submerged and occasionally experiences complete submergence.

AB - Background and Aims Floating sweet-grass (Glyceria fluitans) can form aerial as well as floating leaves, and these both possess superhydrophobic cuticles, so that gas films are retained when submerged. However, only the adaxial side of the floating leaves is superhydrophobic, so the abaxial side is directly in contact with the water. The aim of this study was to assess the effect of these different gas films on underwater net photosynthesis (PN) and dark respiration (RD). Methods Evolution of O2 was used to measure underwater PN in relation to dissolved CO2 on leaf segments with or without gas films, and O2 microelectrodes were used to assess cuticle resistance of floating leaves to O2 uptake in the dark. Key Results The adaxial side of aerial leaves was more hydrophobic than the abaxial side and also initially retained a thicker gas film when submerged. Underwater PN vs. dissolved CO2 of aerial leaf segments with gas films had a Km of 172 mmol CO2 m-3 and a Pmax of 7-1 lmol O2 m-2 s-1, and the leaf gas films reduced the apparent resistance to CO2 uptake 12-fold. Underwater PN of floating leaves measured at 700 mmol CO2 m-3 was 1-5-fold higher than PN of aerial leaves. The floating leaves had significantly lower cuticle resistance to dark O2 uptake on the wettable abaxial side compared with the superhydrophobic adaxial side. Conclusions Glyceria fluitans showed high rates of underwater PN and these were obtained at environmentally relevant CO2 concentrations. It appears that the floating leaves possess both aquatic and terrestrial properties and thus have 'the best of both worlds' so that floating leaves are particularly adapted to situations where the plant is partially submerged and occasionally experiences complete submergence.

U2 - 10.1093/aob/mcx083

DO - 10.1093/aob/mcx083

M3 - Journal article

C2 - 29059317

SN - 0305-7364

VL - 120

SP - 521

EP - 528

JO - Annals of Botany

JF - Annals of Botany

IS - 4

ER -