The results from a rather global experiment have just been accepted in New Phytologist. It was a collaboration between Estonian, Japanese, Spanish and Chilean researchers, who measured the photosynthetic capacity of 35 fern species growing in different continents. It´s more or less a leaf economics spectrum for ferns. More elaborated blog post about this paper is soon to follow. When the paper will be available.
Not yet full citation: Tosens T, Nishida K, Gago J, Coopman RE, Cabrera HM, Carriquí M, Laanisto L, Morales L, Nadal M, Rojas R, Talts E, Tomas M, Hanba YT, Niinemets Ü, Flexas J (2015) The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait. New Phytologist (in press)
* Ferns and fern allies have low photosynthetic rates compared to seed plants. Their photosynthesis is thought to be limited principally by physical CO2 diffusion from the atmosphere to chloroplasts.
* The aim of this study was to understand the reasons for low photosynthesis in species of ferns and fern allies (Lycopodiopsida and Polypodiopsida). We performed a comprehensive assessment of the foliar gas-exchange and mesophyll structural traits involved in photosynthetic function for 35 species of ferns and fern allies. Additionally, the leaf economics spectrum (the interrelationships between photosynthetic capacity and leaf/frond traits such as LMA or nitrogen content) was tested.
* Low mesophyll conductance to CO2 was the main cause for low photosynthesis in ferns and fern allies, which in turn was associated with thick cell walls and reduced chloroplast distribution towards intercellular mesophyll air spaces.
* Generally, the leaf economics spectrum in ferns follows a trend similar to that in seed plants. Nevertheless, ferns and allies had less nitrogen per unit of dry weight than seed plants (i.e. the same slope but a different intercept) and lower photosynthesis rates per leaf mass area and per unit of nitrogen.