Effect of elevated atmospheric CO<sub>2</sub> concentrations on growth and yield of blackgram (Vigna mungo L. Hepper) - a rainfed pulse crop

Abstract

The response of blackgram (<i>Vigna mungo</i> L. Hepper) to two levels of elevated carbon dioxide (550 and 700 ppm) in terms of growth and yield was investigated and compared with ambient CO<sub>2</sub> level (365 ppm) using open-top chambers. The growth parameters viz., length and weight of root and shoot, root:shoot ratio, leaf area and weight significantly increased at 700 ppm CO2 when compared with 550 ppm. The percentage increase in total biomass at 700 and 550 ppm CO<sub>2</sub> was 65.4% and 39%, respectively compared to the ambient (chamber) control. The increase in total seed yield at 700 ppm (129%) was due to an increase in number of pods per plant and 100 seed weight, whereas at 550 ppm (88.7%) it was due to an increased number of pods/plant and seeds/pod. The results indicate variable responsive effects at different levels of CO<sub>2</sub> emphasizing the pertinence of research on elevated CO<sub>2</sub> in various agroecological inhabitations all over the world. The indication of higher responses for root and leaf at initial growth stages at the higher elevated level of CO<sub>2</sub> (700 ppm), which leads to better root establishment, achieving early photosynthetic efficiency and also better biomass production, and its improved partitioning can be reckoned as a positive aspect of increasing concentrations of CO<sub>2</sub> in atmosphere. The harvest index increased significantly to 35.7 and 38.4% at 550 and 700 ppm, respectively; it is a very important phenomenon in pulses for breaking the yield barrier.