Effects of elevated CO2 and paternal family on stomatal index and size in wild radish (Raphanus raphanistrum).

Abstract

Rising atmospheric carbon dioxide may become a stronger selection force in a future environment if certain genotypes exhibit differential responses to elevated CO2. Heritable variation must be present within natural populations for a given trait, and such variation must convey greater fitness for adaptive changes to occur. I tested for heritable variation in stomatal traits in a weedy annual, Raphanus raphanistrum. Effects on stomatal index (# stomata/total # epidermal cells), stomatal length, and frequencies of both stomata and epidermal cells were addressed. Progeny from 12 paternal families and three maternal families were grown at ambient and twice ambient CO2 using open-top chambers (144 plants per treatment). Across treatments, elevated CO2 increased stomatal index by 6% and decreased stomatal size by 10%. Within treatments, paternal families differed in their responses to elevated CO2, showing significant genotype x environment interactions. Our results indicate the presence of intrapopulational genetic variation in stomatal traits and differential responses of these traits to elevated CO2.