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The effects of light conditions from patchy natural canopies on the growth and morphology of white clover clones Marcuvitz, Sheldon


In a community such as a pasture, the success of an individual plant might be affected by neighboring plants. One influence of neighbors on the environment of a plant is alteration of light conditions. Canopies in natural environments have only recently been recognized as heterogeneous in this regard, and responses of plants to alterations in light conditions under heterogeneous canopies are poorly understood. In this investigation, heterogeneity in canopy conditions experienced by white clover (Trifolium repens L.) in a pasture was acknowledged. Three natural canopy configurations were used to examine whether light conditions established by neighbors alter the growth and morphology of white clover clones. Live grass neighbors were used and at the same time, over one clover plant, patches of different light quality and/or quantity were provided. In the first set of experiments, light reflected from grass neighbors was provided simultaneously with direct light. There were. no consistent effects on white clover growth and morphology, but there was evidence of phototropic movement of plant structures, which became located in positions that might minimize the effects of grasses on more permanent features of the clones. In the second set of experiments, shade from three different species of grass was presented to different clover clones for parts of each day, with full sun around noon. The canopies reduced overall growth and branching of clones, while increasing length of, and biomass allocation to, petioles. Lolium perenne had different effects compared to Holcus lanatus or Dactylis glomerata, but between the latter two species, no differences were detected. In the final set of experiments, two interconnected portions of white clover clones, the apical and basal regions of a primary stolon, were subjected to local canopies. Basal region response was examined for independence from apical region conditions and vice versa. Basal regions responded to apical conditions only when they were themselves shaded, while apical regions responded to basal conditions regardless of their local illumination. The ways in which plants respond to neighboring vegetation are complex, and difficulty exists in interpreting plant morphology in terms that are ecologically relevant. If we could identify advantages to particular strategies or responses, and then selectively control plant performance, we might be able to improve our use of plants through more efficient production and management schemes.

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