Nine sugar beet lines were grown in a glasshouse on chernozem soil wat
ered to 35, 50 and 65% of maximal soil water capacity. After 12 d, pla
nt water potential, net photosynthetic rate, contents of soluble prote
ins, DNA and RNA, proportion of ribulose-1,5-bisphosphate carboxylase/
oxygenase (RUBISCO) protein, and carbonic anhydrase activity were meas
ured. As soil moisture decreased, the leaf water potential and net pho
tosynthetic rate decreased. DNA and RNA content and carbonic anhydrase
activity decreased under moderate drought, and increased with severe
drought. RUBISCO protein proportion did not change significantly under
decreased soil moisture, while the total soluble protein content decr
eased.