Comparative gas exchange physiology in the Daucus carota complex
Rates of net photosynthesis, transpiration, and dark respiration of seven populations representing the diversity of the Daucus carota complex were measured. The two taxonomic groups of this complex proved physiologically distinguishable, with subspecies aggregate gingidium possessing lower capacities for photosynthesis and transpiration and a lower frequency of stomata than subspecies aggregate carota. In comparison with wild populations of the complex, cultivars manifested greater efficiency of photosynthesis with respect to water use, possibly the result of an increased demand for photosynthate in domesticated populations. The highest rate of photosynthesis was exhibited by a vigorous, primitive, Asian cultivar, which also possessed the highest stomatal frequency.