Relation between Nitrogen Status, Carbohydrate Distribution and Subsequent Rooting of Chrysanthemum Cuttings as Affected by Pre-harvest Nitrogen Supply and Cold-storage

This study investigated the relationship between internal nitrogenand carbohydrate distribution in chrysanthemum cuttings of twocultivars (‘Puma’, ‘Cassa’) when affectedby nitrogen supply to stock plants (0.6, 1.5, or 4.0 g N m^-2week^-1)and different periods (2, 3, or 4 weeks) of dark cold-storage(0.5 or 5°C), and adventitious rooting. Concentrations oftotal nitrogen (N_t) and nitrate in cuttings and the levels ofsugars, starch and fructan in different cutting parts (leaves,upper stem, and basal stem) were studied in relation to subsequentadventitious rooting at natural radiation in a greenhouse. Increasingnitrogen supply resulted in substantially lower starch levelsand higher sucrose concentrations in leaves when cuttings wereexcised. Fructan concentrations were low and decreased withincreasing nitrogen levels. Starch completely disappeared fromleaves and to a large extent from stems within the shorteststorage period. A less pronounced decrease in sugar concentrationwas observed, particularly in low-nitrogen cuttings and thecuttings of ‘Puma’. The number and length of adventitiousroots subsequently formed by unstored and stored cuttings waspositively correlated with initial N_t, and to a lesser extentwith initial nitrate concentrations in cuttings. Whereas rootingwas not limited by pre-rooting concentrations of carbohydratesin the different cutting parts, the generally higher rootingcapability of nitrogen-rich cuttings, a stronger nitrogen responseof ‘Cassa’, and increased rooting at a particularharvest date, were associated with higher sucrose:starch ratiosin leaves at harvest. This reflected an increased assimilateexport. By using this characteristic in a linear regressionmodel, total variability of root numbers, ranging from three–35per cutting, could be predicted to 57% for the unstored andto 40% for all cuttings. Increased basipetal transport of carbohydrates,of nitrogen compounds, and of auxins may be causally involvedin these associations. Copyright 2000 Annals of Botany Company Adventitious rooting, nitrogen, sugars, carbohydrates, source-sink, partitioning, quality, storage, cuttings, stock plants, chrysanthemum, Dendranthema grandiflorum