ISHS Acta Horticulturae 751: IV International Symposium on Rose Research and Cultivation
ANATOMY AND MORPHOLOGY OF ROOTING IN LEAFY ROSE STEM CUTTINGS AND STARCH DYNAMICS FOLLOWING SEVERANCE |
| Authors: | J.M. Costa, E. Heuvelink, P.A. Van de Pol, H.M.C. Put |
| Keywords: | propagation, Rosa hybrida, cuttings, anatomy, rooting, carbohydrate, callus |
| Abstract:
Carbohydrates influence survival and rooting of leafy rose stem cuttings. However, to what extent the anatomical changes occurring during rooting (e.g., callus formation) are related with changes or limitations in carbohydrates is not well described. Therefore, the anatomy and morphology of rooting and carbohydrate concentrations in cuttings were followed during the first 21 days of propagation. Single node leafy stem cuttings of Rosa hybrida Madelon® were propagated in climate chamber (23-25ºC, 85 µmol m-2 s-1, 16 h day-1) and subjected to two CO2 levels: ambient (~ 350ppm) and low (80-100 ppm). Callus formation, number and dry weight of roots and stem were measured. Cross and longitudinal sections of the most basal 14-15mm of the stem (rooting zone) were made and carbohydrates were assayed by iodine staining and chromatography. Under ambient CO2 cambial activity was noticed by day 3 through proliferation of undifferentiated parenchyma cells (callus) between the cambium and the sclerenchyma, and at day 7 meristematic centers and root primordia were observed. Roots emerged and started elongating between days 11 and 14 in ambient CO2 and new xylem vessels were visible by day 14. Under low CO2 callus proliferation and rooting (number of roots formed) were delayed and strongly diminished. In ambient CO2 the stem tissues close to the basal callus showed weak staining of pith cells and medular rays, in contrast to the dark bluish staining observed for the remaining upper part of the stem. Carbohydrate extraction and chromatography analysis confirmed the heterogeneous accumulation of starch in the stem under ambient CO2 and showed that low CO2 drastically reduced starch concentrations most likely due to suppressed photosynthesis. We conclude that callus formation is a pre-requisite for root formation in rose cuttings and that carbohydrates have a major influence on callus proliferation that precedes root formation. | |
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