Abstract
The aim of the present study was to evaluate the applicability of maximal photochemical efficiency of photosystem II (Fv/Fm) as an early estimate of P. radiata micrografts viability coming from different position (basal vs. apical) in the ortets. We hypothesize that Fv/Fm variation is a good indicator of micrograft’s viability and phenological stage during micrograft development. The micrografts were established in QL medium supplemented whit 0.1 mg·L-1 IBA and 1 mg·L-1 BAP and cultured at 25°C ± 2°C and 80 μmol photons m-2s-1 of photosynthetic active radiation by 16 h per day. During the establishment and consolidation phase, we found significant differences in Fv/Fm with respect to time and buds positions provenience. During establishment, basal shoot tips have lower Fv/Fm than apical shoot tips, which agrees with the lowest viability (35%). However, during the consolidation phase, the trend changed and basal shoot tips presented higher Fv/Fm than apical shoot tips and showed an increase in ETR and NPQ, with respect to apical shoots and ortet. Although the measurement of fluorescence parameters implies the insertion of the fluorometer sonde in vitro, this implies aseptic considerations, but always conveies a contamination risk. We conclude that fluorescence (Fv/Fm, ETR, NPQ) can be indicators of the micrograft’s development according to the shoot tips position in the ortet and can be useful early-indicators of the scions’ physiological condition during micrograft transition from establishment to consolidation.
Highlights
IntroductionIn vitro propagation methods may induce reinvigoration of advanced physiological tissue and renewal of ontogenetically adult P. radiata [3] [6], and in this way avoid the problems associated to the lost of morphogenic capacity
It has been suggested that the decline in morphogenic capacity could be due to the loss in competence at the cellular level and it is highly likely that this phenomenon causes changes in gene transcription [8]
In vitro propagation methods may induce reinvigoration of advanced physiological tissue and renewal of ontogenetically adult P. radiata [3] [6], and in this way avoid the problems associated to the lost of morphogenic capacity
Summary
In vitro propagation methods may induce reinvigoration of advanced physiological tissue and renewal of ontogenetically adult P. radiata [3] [6], and in this way avoid the problems associated to the lost of morphogenic capacity. This reinvigoration includes anatomical, molecular and epigenetic changes which reflect characteristic juvenile individual’s protein patterns, DNA methylation and polyamine content [6] [9]. One tissue reinvigoration techniques is the in vitro micrograft, which has been tested to reinvigorate ontogenetically adult vegetative buds on juvenile rootstocks [11] and can be a solution for cloning adult trees of several species, in which sprouts present deficient rooting and lack of vigor [3] [4]
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