Martínez-Berdeja A., Valverde T., Growth response of three globose cacti to radiation and soil moisture: An experimental test of the mechanism behind the nurse effect, Journal of Arid Environments, 2008, 72(10):1766-1774, doi: 10.1016/j.jaridenv.2008.04.010
A six-month experiment on seedlings of three cacti separates the effects of light and water availability on dry biomass growth and root and shoot proportions. Obregonia denegrii was compared at two substrate hydration levels crossed with two light levels. Greater water availability increased relative growth rate and reduced the root-to-shoot biomass ratio. The authors discuss the significance of these responses for nurse plant effects.