Using leaf-mark material to monitor the morphology of white clover (Trifolium repens L.) at the clone and ramet level in grazed swards

Leaf markings are widespread in Trifolium spp. White clover (T. repens L.) material has been produced at the Institute of Grassland and Environmental Research (IGER) Aberystwyth, UK, which demonstrates the 'filled - V' leaf m ark as a subtle but clearly identifiable mark with little seasonal variatio n in expression. This paper describes how a population of genotypically ide ntical individual white clover plants (clones), created from this material, can be used in grazed swards to monitor changes in morphology at the clone and ramet level. In a pilot experiment, the effect of a late silage cut on the white clover component of grazed mixed swards was investigated. Leaf-m ark plants were introduced into known positions in a grass/clover sward in 1997 and monitored during 1998 under two grazing regimes: (1) continuous gr azing to a sward surface height of 4 cm (treatment G); and (2) grazing, fol lowed by a single late-season silage cut, a brief rest period, and a return to autumn sheep grazing (treatment GRG). The GRG treatment had a significa nt and rapid effect, producing larger clones with a larger number of ramets and higher proportions of complex ramets than the G treatment. As ramet co mplexity increased the treatment effect intensified, resulting in a four-fo ld increase in clone size, together with an enhanced ability to spread into the sward. The GRG treatment allowed a more widespread dispersal of indivi dual units and this is likely to enhance the opportunity for ramets to enco unter favourable micro-environments for survival and growth, The benefits a nd limitations of the procedures are discussed. (C) 2001 Annals of Botany C ompany.