Nucleotide and nucleic acid status in shoot tips from juvenile and mature clones of Sequoiadendron giganteum during rest and growth phases.

Nucleoside triphosphate and nucleic acid contents of shoot tips of juvenile and mature clones of Sequoiadendron giganteum Buchholz were analyzed during rest and growth phases. In both juvenile and mature clones, shoot growth activity was characterized by significant increases in ATP, non-adenylic nucleoside triphosphate (NTP) and RNA levels. During the rest period, both ATP/NTP and RNA/DNA ratios were significantly higher in the juvenile clone than in the mature clone. However, during the growth phase, only the ATP/NTP ratio was higher in the juvenile than in the mature clone. The results suggest that the physiological differences between shoot tips of juvenile and mature tissues during the rest phase tend to decline as active shoot growth commences. This conclusion is consistent with morphological observations and with the varying organogenetic capacities of in vitro cultures of explants removed from stock plants at different times.