Carbon — A plant nutrient, deficiency and sufficiency

Toxicity symptoms of carbon dioxide (CO2) have been observed at 10,000 ppm concentration after six days in seven species. Maize is an indicator plant for C-toxicity, developing zebra-like stripes. Full recovery from C-toxicity occurred only in wheat and maize plants. No deficiency symptoms of carbon have been determined. Root exposure during six days to 10,000 ppm CO2 or near zero CO2 had no visible effect, and plants develop normally.