Interactive Effects of CO2 and O2 in Soil on Root and Top Growth of Barley and Peas

Abstract

Barley and pea plants were grown under several regimens of different compositions of soil atmosphere, the O2 concentration from 0 to 21% and the CO2, concentration from 0 to 8%. In absence of CO2 the effect of O2 on root length in barley was characterized by equal root lengths within the range of 21 to 7% O2 and a steep decline between 7 and 0%. Inpeas, the decline occurred between Hand 7% O2. Root numbers of seminal roots of barley decreased already with reduction in O2 concentration from 21 to 14%. Dry matter production in barley was reduced at 14% O2 while root length decreased between 7 and 0%. In peas, dry matter production was favored by low CO2 concentrations except where there was no oxygen. At 21% O2, increasing CO2 con-centrations did not seem to affect root length up to concentrations of 2%. At 8% CO2, root length was decreased. The interactive effects of CO2 and O2 are characterized by a reduced susceptibility to CO2 at O2 values below 7%, and a very deleterious effect of 8% CO2 at 7% O2.