AOBPreview originally published online on October 27, 2004
Annals of Botany 2004 94(6):831-842; doi:10.1093/aob/mch210
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Annals of Botany 94/6, © Annals of Botany Company 2004; all rights reserved
Nitrogen- and Storage-affected Carbohydrate Partitioning in High-light-adapted Pelargonium Cuttings in Relation to Survival and Adventitious Root Formation under Low Light
Institute of Vegetable and Ornamental Crops Grossbeeren/Erfurt e.V., Kuehnhaeuser Strasse 101, D-99189 Erfurt-Kuehnhausen, Germany
* For correspondence. E-mail Druege{at}erfurt.igzev.de
Received: 19 May 2004 Returned for revision: 4 August 2004 Accepted: 20 August 2004 Published electronically: 27 October 2004
• Background and Aims The aim of this study was to determine the role of nitrogen- and storage-affected carbohydrate availability in rooting of pelargonium cuttings, focusing on the environmental conditions of stock plant cultivation at low latitudes, transport of cuttings, and rooting under the low light that prevails during the winter rooting period in Central European greenhouses.
• Methods Carbohydrate partitioning in high-light-adapted cuttings of the cultivar ‘Isabell’ was studied in relation to survival and adventitious root formation under low light. Effects of a graduated supply of mineral nitrogen to stock plants and of cutting storage were examined.
• Key Results Nitrogen deficiency raised starch levels in excised cuttings, whereas the concentrations of glucose and total sugars in leaves and the basal stem were positively correlated with internal total nitrogen (Nt). Storage reduced starch to trace levels in all leaves, but sugar levels were only reduced in tissues of non-nitrogen deficient cuttings. Sugars accumulated in the leaf lamina of stored cuttings during the rooting period, whereas carbohydrates were simultaneously exhausted in all other cutting parts including the petioles, thereby promoting leaf senescence. The positive correlation between initial Nt and root number disappeared after storage. Irrespectively of storage, higher pre-rooting leaf glucose promoted subsequent sugar accumulation in the basal stem and final root number. The positive relationships between initial sugar levels in the stems with cutting survival and in leaves with root formation under low light were confirmed in a sample survey with 21 cultivars provided from different sources at low latitudes.
• Conclusions The results indicate that adventitious rooting of pelargonium cuttings can be limited by the initial amount of nitrogen reserves. However, this relationship reveals only small plasticity and is superimposed by a predominant effect of carbohydrate availability that depends on the initial leaf sugar levels, when high-light adaptation and low current light conditions impair net carbon assimilation.
Key words: Adventitious rooting, senescence, nitrogen, sugars, carbohydrates, quality, storage, cuttings, geranium, Pelargonium x hortorum