Quantification of endogenous aromatic cytokinins in Pinus radiata embryonal masses after application of heat stress during initiation of somatic embryogenesis

Short-term exposure to high temperatures modulates the aromatic cytokinin profile of radiata pine embryonal masses when measured 8 weeks after initiation. Abstract Recent research has demonstrated that cytokinins could be involved in abiotic stress responses. However, little research has been published about the role of endogenous aromatic cytokinins during these processes. Therefore, in this study, different temperature and incubation periods (23 oC, 8 weeks; 40 oC, 4 h; 50 oC, 30 min; 60 oC, 5 min) were applied during induction of radiata pine somatic embryogenesis and the aromatic cytokinin content of the resulting embryonal masses was measured. Results indicated that temperature during induction had a significant effect on the profile of most of the aromatic cytokinins detected. All tested higher temperatures than control provoked a decline in some free bases, including N6-benzyladenine, ortho-Topolin and para-Topolin. On the other hand, the values of N6-benzyladenine nucleotides, ribosides and irreversible metabolites (9G), as well as para-Topolin ribosides, increased in embryonal masses originating from 40 oC treatment. These results suggest that despite not being traditionally considered part of the stress response machinery, aromatic cytokinins might be involved in heat-stress responses during early stages of somatic embryogenesis in radiata pine.