Abstract
Effects of elevated CO2 on synthesis and degradation of Rubisco were examined in rice leaves from emergence to senescence. Rubisco content in control plants rapidly increased during leaf expansion, reached its maximum around full expansion, then declined. In elevated [CO2]-grown plants, Rubisco content was lower throughout lifetime of a leaf. Rubisco synthesis in control plants was active during leaf expansion, but declined just before full expansion, then Rubisco degradation occurred. For the elevated [CO2]-plants, Rubisco synthesis was lower in expanding leaves, but did not differ in senescent leaves. Although a slight stimulation of Rubisco degradation was found during the early stage of senescence, total amount of Rubisco degraded was slightly lower. Thus, a decline in Rubisco content by elevated [CO2] is the result of a repression of Rubisco synthesis during leaf expansion as well as a slight stimulation of Rubisco degradation during the early stage of senescence.
