Correlation between the rates of foliar dark respiration and net photosynthesis in some tropical dicot weeds

Abstract

The rates of foliar dark respiration and net photosynthesis in attached leaves of 25 C₃, C₄, and C₃-C₄ intermediate dicotyledonous weed species were determined using the infrared gas analyzer. The ratio of dark respiration to photosynthesis per unit leaf area in attached leaves of each species was inversely proportional to leaf age. Highly significant, positive linear correlation was observed between the rates of foliar dark respiration and net photosynthetic CO₂ uptake in dicot weeds irrespective of the photosynthetic type. The higher foliar dark respiration rate found in some of the weed species can be attributed in part to the higher carbohydrate levels as generated by a rapid photosynthetic CO₂ assimilation. The significance of higher dark respiration rate in relation to carbon and energy economy of weeds is discussed.