What does the Net Assimilation Rate (NAR) measure?

The Net Assimilation Rate (NAR) measures the rate of dry matter production per unit area of time, reflecting the efficiency of a plant in converting absorbed light and nutrients into biomass while considering losses due to respiration. By calculating the NAR, one can assess the growth performance of plants, indicating how effectively they are synthesizing new tissue. It is an important metric because it helps to evaluate not just growth quantity (which can be influenced by size and environmental factors) but also the efficiency of photosynthesis and nutrient usage over time.

When plants are assessed for their growth through NAR, it allows for a more nuanced understanding of their health and productivity compared to simply measuring overall plant growth or glucose production, which might not accurately reflect the overall dry-matter accumulation and plant efficiency in resource use.