Interactive Effects of CO 2 and O 2 in Soil on Root and Top Growth of Barley and Peas

Abstract

Sunmmary. Barley and pea plants were grown tunder several regimens of different compositions of soil atmosphere, the 0., concentration varying from 0 to 21 % and the CO2 concentration from 0 to 8 %. In absence of CO, the effect of 09 on root length in barley was characterized by equal root lengths within the range of 21 to 7 % 0 and a steep decline between /7 and 0 %. In peas, while showing the same general response, the decline occturred between 14 and 7 % 02. Root numbers of the seminal roots of barley decreased already with reduction in 02 concentration from 21 to 14 %. Dry matter production was affected somewhat differently by 09 and C00 concentration. Dry matter production in barley was reduiced at 14 % 02 while root length decreased between 7 and 0 %. In peas, dry matter production was favored by low CO concentrations except where there was no oxygen. At 21 % O,, increasing CO concentrations did not seem to affect root length up to concentrations of 2 % 009. At 8 % CO2, root length was decreased. The interactive effects of CO and O., are characterized by a reduced susceptibility to CO at 02 valiues below 7 %, an(d a very deleteriouts effect of 8 % C002 at 7 % 02. Root length is affected by C09 and 02. Decreasing 02 concentrations and increasing CO concentrations cause a reduced root elongation (2, 3, 4,5, 6, 7, 8, 9). The stusceptibility and limits of tolerance to changes in the concentrations of these gases can be assumed plant specific (4, 5, 9). However, there is only limited information on the interactive effects of 02 and 002 on root morphology and dry matter produtction of tops and roots. Fuirthermore, the results seem to be contradicting , especially concerning the limits of tolerance to C00 at falling 02 concentrations. Some investigations show relatively high C02 concentrations tolerated by plants at low levels of 02 with the inhibiting effect occuirring when the C02