Effect of shade on the carbon and nitrogen allocation in a perennial tropical grass,Dichanthium aristatum
Journal of Experimental Botany
Changes in sward growth above ground by shade is a controversial subject for field experimentation because the differential allocation of carbon (C) to shoots and roots is difficult to measure. In this experiment the effect of three levels of irradiance (100%, 56% and 33% of full sunlight) on C and nitrogen (N) allocation in Dichanthium aristatum were studied under well-watered and well-fertilized conditions. Dry matter accumulation, weight ratio per organ and N allocation indices were studied
... dices were studied during two cycles of growth, after planting and after cutting. Shade had no effect on the C and N influxes into the whole plant, showing that the N absorption is regulated by the C assimilation. However, C, and principally N, were preferentially allocated to the laminae under reduced irradiance. Under 100% and 56% of full sunlight, more N was allocated to the stubble component. This situation was reversed in the lowest radiation level, indicating that N reserves, and not exclusively C reserves, may limit the regrowth of this perennial grass when growing under high levels of shade. The higher shoot: root ratio under shade shows the disadvantage in the use of radiation use efficiency calculated from aerial biomass data when comparing differents levels of shade. References AFNOR (Association Francaise de Normalization) 1987. Qualite des sols, methodes d'analyse. Afnor, Paris, 136 pp. Caloin M, El Khodre A, Atry M. 1980. Effect of nitrate concentration on the root: shoot ratio in Dactylis glomerata L. and on the kinetics of growth in the vegetative phase. Annals of Botany 46, 165-73. Cavagnaro JB, Passera CB. 1991. Water utilization by shrubs and grasses in the Monte ecosystem, Argentina. Proceedings IVth I.R.C., Montpellier, France, 255-8. Corre WJ. 1983. Growth and morphogenesis of sun and shade plants. 1. The influence of light intensity. Acta Botanica Neerlandica 32, 49-62. Cruz P. 1995. Use of the RUE concept for analysing growth of pure and mixed tropical forage crops. In: Sinoquet H, Cruz P, eds. The ecophysiology of tropical intercropping. Paris: 1NRA, Science Update, 319-30. Cruz P, Munier-Jolain NM, Tournebize R, Sinoquet H. 1993. Growth and mineral nutrition in a Dichanthium aristatum sward shaded by trees. Proceedings XVII I.G.C., New Zealand-Australia, 2056-7. Dale MP, Causton DR. 1992a. The ecophysiology of Veronica chamaedrys, V. montana and V officinalis. 1. Light quality and light quantity. Journal of Ecology 80, 483-92. Dale MP, Causton DR. 19926. The ecophysiology of Veronica clwmaedrys, V. montana and V. officinalis. III. Effect of shading on the phenology of biomass allocations-a field experiment. Journal of Ecology 80, 505-15. Dale MP, Causton DR. 1992c. The ecophysiology of Veronica chamaedrys, V. montana and V. officinalis. IV. Effects of shading on nutrient allocation-a field experiment.