Ecophysiology ofMycelis muralis(L.) Dumort in the Burren, Co. Clare, Ireland

Irradiance and nitrate‐dependent variation in growth and biomass allocation of Mycelis muralis. An analysis of its significance for a functional categorization of ‘sun’ and ‘shade’ plants

“…We have documented some aspects of the photosynthetic physiology oi Mycelis muralis (L.) Dumort and these results suggest a limited ability to adjust the biochemical and structural components of the photosynthetic apparatus to high irradiance (Osborne & Clabby, 1991;Clabby, 1992;Osborne et al, 1994). Specifically, light-saturated rates of photosynthesis were low and the chlorophyll a: b ratio did not change when plants were grown at different irradiances or when measurements were made on plants growing in contrasting natural light environments.…”

“…Specifically, light-saturated rates of photosynthesis were low and the chlorophyll a: b ratio did not change when plants were grown at different irradiances or when measurements were made on plants growing in contrasting natural light environments. Leaf and chloroplast structure were also relatively unresponsive to changes in growth irradiance (Osborne & Clabby, 1991;Clabby, 1992;Osborne et al, 1994).…”

“…It also occurs in shaded habitats in Ireland (Clabby & Osborne, 1991;Clabby & Osborne, 1994), which is in keeping with its status as a ' shade' species in Britain and continental Europe (Oberdorfer, 1970;Ellenberg, 1988;Grime, Hodgson & Hunt, 1988).…”

Mycelis muralis (L. ) Dumort. (Lactuca muralis (L. ) Gaertner)

“…The Asplenietum has generally been placed in the alliance Potentillion caulescentis, although some authors follow Segal (1969) and place it in the Cymbalario–Asplenion (White & Doyle 1982). In the Burren, M. muralis also occurs in grikes with species such as Asplenium ruta‐muraria , Geranium robertianum and Phyllitis scolopendrium (Osborne & Clabby 1991) and in Yorkshire with a range of species including Allium ursinum , Asplenium trichomanes , Epilobium montanum , Geranium robertianum , Mercurialis perennis , Oxalis acetosella , Phyllitis scolopendrium , Stachys sylvatica and Urtica dioica (Silvertown 1983). In shaded crevices and on ledges of lime‐rich bedrocks in western and northern Britain, M. muralis occurs in the Asplenium viride–Cystopteris fragilis community (NVC OV40) (A.J.C.…”

“…In a laboratory experiment withholding water until plant pots were reduced to 70% of their initial fully watered weight did not affect plant biomass over a 12‐week period (Manto 1995). Studies in the Burren, Co. Clare, Ireland, indicate that M. muralis may be more drought‐resistant than some co‐occurring species (Osborne & Clabby 1991). In open habitats the leaf lobes often curl inwards in periods of dry weather during the summer months.…”