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Cycads are the most ancient living seed plants. Extant cycads exhibit high morphological diversity and grow in diverse habitats, but little is known of their physiology. We tested for a novel linkage of leaf water transport with nutrient concentrations in cycads, which could contribute to variation in photosynthesis and growth rate. We measured leaf hydraulic conductance, stomatal conductance, and nutrient concentrations of 11 cycad species grown in a tropical botanical garden. The leaf concentrations of chlorophyll, nitrogen, phosphorus, iron, and sulfur were positively associated with leaf hydraulic and stomatal conductance across the cycad species, suggesting that high leaf water transport and transpiration may promote greater leaf nutrient assimilation. The facilitation of nutrient accumulation by transpiratory flow is a long-standing hypothesis, here supported by our data for 11 cycad species, indicating an adaptive function of transpiration, especially for plants with low leaf water transport and nutrient use efficiency such as cycads.
Keywords: Cycadaceae, gymnosperms, Zamiaceae, leaf economics, leaf hydraulic conductance, nutrient transport