Response of cow pea (Vigna unguiculata L.) to CO2 enrichment environment on growth, dry-matter production and yield components at different stages of vegetative and reproductive growth

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Abstract
SUMMARY: This study examines the effects of increased atmospheric carbon dioxide concentrations on vegetative and reproductive growth and partitioning of biomass during pod and seed development of cow pea in controlled environment chambers at 350, 675, and 1000μl CO2/l.The length of main stem and branches, the number of leaves and branches, and leaf area were all greater at high CO2 than at low CO2 concentration. The appearance of flowers was 10–12 days earlier in high CO2 than in ambient CO2 atmosphere. The senescence of leaves started about 7 days earlier in plants grown at 675 and 1000 μl CO2/l than in those grown at 350 μl CO2/l. The rate of leaf senescence was more rapid in 1000 μl/l than in 675 μl CO2/l. The dry weight of roots, stems and leaves increased with CO2 enrichment, being greater in 675 μl/l than in 1000 μl CO2/l. Plants grown in 675 and 1000 μ1/1 produced more pods and seeds than in 350 μl CO2/l. Total seed weight and number of pods, as well as number of seeds per pod, were significantly greater in CO2 enriched atmosphere than ambient CO2 level. Although CO2 enrichment caused a significant increase in the total number and weight of seeds as well as pods, it did not affect the ratio of seed dry weight to the total dry weight of above-ground plant parts (harvest index). It is concluded from the present investigation that CO2 enrichment significantly enhanced vegetative as well as reproductive growth resulting in the increase in yield and early plant maturation in this leguminous crop.