text: It was determined, according to Sefcik et al ., that "the magnitude of enhancement from exposure to elevated CO 2 was similar for both shade-tolerance groups," with the elevated CO 2 treatment increasing the mean light-saturated net photosynthetic rate by 63% in the shade-tolerant species and by 67% in the shade-intolerant species. More importantly, however, they found that "seedlings grown in deep shade, regardless of shade-tolerance group, showed a greater long-term photosynthetic enhancement to elevated CO 2 than those grown in moderate shade," with the mean long-term enhancement being 47% in moderate shade and a whopping 97% in deep shade. What it means