White clover morphology changes with stress treatments

The plasticity of white clover (Trifolium repens L.) results in changes in plant habit in response to different environmental stresses. The objective of this research was to characterize those morphological changes associated with plasticity in white clover clones derived from 'Osceola', 'Grassland Huia', and SRVR germplasm. Clones were exposed to treatments in the following two-way factorial design: no clipping or clipping on 7-d intervals and barrier to stolon rooting or no barrier. In a three-season greenhouse test, 90 clones were measured for leaf dry weight (DW), stolon DW, stolon length, root DW, and apex number. Generated parameters were herbage DW (leaf DW + stolon DW), biomass DW (root DW + herbage DW), leaf-to-stem ratio (leaf DW + stolon DW), and herbage-to-root ratio (herbage DW divided by root DW). Plant means were significantly reduced for all traits and ratios with repeated clipping. The rooting barrier significantly reduced apex number, root DW, and the leaf-to-stem ratio while increasing the stolon DW and the herbage-to-root ratio. The interaction of root barrier and repeated clipping was significant for apex number, root DW, and the herbage-to-root ratio. Near zero correlations for the same measurements made on the same clone grown with different stress treatments suggest genetic differences in the magnitude of plasticity. Path analysis further described changes in relationships among traits for plants exposed to different stresses. The magnitude of plasticity appeared to be a clone-specific phenomenon that may frustrate verifying gain with selection for progenies of selections evaluated in different environments.