CHANGES IN PHOTOSYNTHETIC PARAMETERS DURING GRAFT UNION AND ADVENTITIOUS ROOT FORMATION IN CUTTING GRAFTS OF RHODODENDRON SUBG. HYMENANTHES
The cutting graft method is comparatively quick because during the process two different propagation events occur graft union formation and adventitious rooting. The method is based on grafting scions onto unrooted rootstocks. Less study has been done in order to find out, how the separation from stock plant and further graft union formation and adventitious rooting is connected to photosynthetic parameters like RC/ABS (total number of active reaction centers per absorption), PI (performance index, an indicator of plant or sample vitality), Fv/Fm (maximum quantum efficiency of photosystem II), photosynthetic rate, transpiration rate and starch content. Two Rhododendron subg. Hymenanthes cultivars were used, Cunninghams White as a rootstock and Baltais Brīnums as a scion. Cutting grafts with or without rootstock apical and lateral buds were used. Basal ends of all cutting grafts were dipped in 1% IBA talc powder. Chlorophyll fluorescence meter Handy PEA was used to measure chlorophyll fluorescence. LCi Portable Photosynthesis System was used for photosynthetic and transpiration rate measurements. Anatomical research and starch content analyses were done. Fv/Fm parameter decreased during the first 4 days of the experiment, but RC/ABS and PI increased. This could be related to renewal of processes in plant and stress provoked by wounding, leaf cutting and drought due to unavailability to water uptake. Further an increase in these 3 parameters was observed, which was followed by a decrease until day 13, when callus bridges in graft regions were anatomically observed. Further fluctuations were small and can be explained by root formation. These parameters were relatively higher in scions in both treatments. Contrary to decrease of transpiration rate during the whole experiment, the photosynthetic rate did increase. These parameters were relatively higher in rootstocks of cutting grafts. Starch content was higher in rootstock stem bases. There was a decrease during root initiation and graft union formation. Rootstock bud presence delayed successful graft union and adventitious root formation.
Dokane, K., Mertena, L., Megre, D. and Kondratovics, U. (2013). CHANGES IN PHOTOSYNTHETIC PARAMETERS DURING GRAFT UNION AND ADVENTITIOUS ROOT FORMATION IN CUTTING GRAFTS OF RHODODENDRON SUBG. HYMENANTHES. Acta Hortic. 990, 457-464
transpiration rate, photosynthetic rate, starch content, chlorophyll a fluorescence, anatomy