dynamics of rooting in Triplochiton scleroxylon cuttings: their relation to leaf area, node position, dry weight accumulation, leaf water potential and carbohydrate composition

Single-node, leafy stem cuttings of Triplochiton scleroxylon K. Schum. were collected from successive nodes down the uppermost shoot of 2-shoot stockplants. The leaves were trimmed to 10, 50 and 100 cm(2) before the cuttings were set under intermittent mist to root. Batches of cuttings were harvested after 0, 14, 28 and 42 days to assess leaf water potential, dry weight and carbohydrate content of their leaf and stem portions. Cuttings with leaf areas of 10, 50 and 100 cm(2) increased in total dry weight by 29, 61 and 90%, respectively, during the 6-week period. The increase in dry weight was accompanied by increases in reflux-extracted soluble carbohydrates (RSC), water-soluble carbohydrates (WSC) and starch. By contrast, increase in leaf area reduced leaf water potential of cuttings before root emergence. Fewer large-leaved cuttings rooted than smaller-leaved cuttings, suggesting that rooting ability is at least partially determined by the balance between photosynthesis and transpiration. Fewer roots per cutting were produced on cuttings with 10 cm(2) leaves than on cuttings with larger leaves. Node position affected increments in dry weight, carbohydrate content and leaf water potential, with differences between nodes on day 0 generally being lost or slightly reversed by day 14. Rooting ability was not related to initial (day 0) carbohydrate content, suggesting that rooting is dependent on carbohydrates formed after severance. During the rooting period, the proportions of total non-structural carbohydrate as WSC and starch were reversed, from mostly WSC on day 0 to mostly starch by day 42. These changes in WSC and starch occurred most rapidly in large-leaved cuttings.