Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/17/2003
Publication Date: 10/1/2003
Citation: Seker, H., Rowe, D.E., Brink, G.E. 2003. White clover morphology changes with stress treatments. Agronomy Journal. 43:2218-2225. Interpretive Summary: Unlike most plants, white clover, when it is stressed by competition, by animal feeding on its leaves, or by drought doesn't just get smaller but changes its structure so the relative sizes of roots, stems, leaves, and leaf petioles change with each stress. This change in plant appearance is thought to help it survive in diverse environments. Results of this research shows the range of changes that can occur when the same plant is grown in different environments. The relative performance of different plants changed so much from one environment to the next that the growth of a plant in one environment did not describe how well that same plant would grow in another environment. Statistical tests showed that different plants had different levels of plasticity and that genetic factors controlling growth of the white clover could be separate from those affecting plasticity. For plant breeders, this is a serious problem because selection of best plant at one location or in one environment could improve white clover growth for that location but not improve that white clover when it is grown in a multitude of other environments across the country.
Technical Abstract: The plasticity of white clover (Trifolium repens L.) results in morphological changes in plant habit in response to different environmental stresses. This research characterized morphological changes in white clover clones derived either from two cultivars and a germplasm exposed to treatments in 2-way factorial: no clipping or clipping on 7 da intervals, and a rooting barrier or no barrier. In a greenhouse test in three different seasons, 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 ÷ stem DW) and herbage-to-root (herbage DW ÷ root DW). The season of evaluation greatly affected the leaf-to-stem ratio (varied from 1.16 to 1.79) but had little effect on herbage-to-root ratio (3.62 to 3.83). For the treatments, the leaf-to-stem ratio ranged from 1.92 for no clipping and no rooting barrier to 0.61 for clipped plants with a rooting barrier. The herbage-to-root ratio was minimal (2.91) for clipped plants and no rooting barrier and maximal (5.08) for unclipped plant with a rooting barrier. Path analysis estimates of the magnitude of indirect and direct effects on leaf DW, root DW, and herbage DW showed the relationships among the measured traits varied greatly across the four treatment environments. Plasticity appeared to be a clone genotype phenomena and may be inherited separate from other factors contributing to yield and persistence.