Stockplants of Eucalyptus grandis were pruned to a height of 7- 10 cm and after 3 weeks were placed in growth cabinets set at a photon flux density (PFD) of 200 mu mol m(-2) s(-1) and red to far-red ratios of 0.4, 0.7, 1.3, 3.5 or 6.5. Experiments tested the effects of light quality on growth and gas exchange of stockplants. Light quality did not affect the total shoot dry weight (DW), root DW or shoot to root ratio of stockplants or their total leaf area. However, there were significant effects of light quality on: (i) plant height, which was greatest at red:far-red (R:FR) ratios of 0.3 and 0.7; (ii) partitioning of DW between leaves and stems, with greater stem DW and less leaf DW at low R:FR ratios (0.4 and 0.7); (iii) partitioning of DW and leaf area between the most dominant shoot and all other (non-dominant) shoots; (iv) specific leaf area, which was greatest at low R:FR ratios. In the above characters, the dominance ratio (ratio of most dominant shoot to sum of all other shoots) was greatest at low R:FR ratios and least at ratios of 3.5 and 6.5. Photosynthetic rate per unit leaf area and leaf chlorophyll concentration significantly increased with increasing R:FR ratio. However, photosynthesis per unit chlorophyll concentration was significantly greater at low R:FR ratios. Generally, light quality had no significant effect on photosynthetic rate per leaf or per unit dry weight, but rates of transpiration, stomatal conductance and water use efficiency increased with an increase in R:FR ratio. These data indicate that compensatory changes in plant morphology and gas exchange caused equality in total dry weight per plant between treatments. The above effects of light quality on dry matter partitioning and gas exchange had important effects on the size, number, morphology and physiology of subsequently collected cuttings for vegetative propagation.

Two-leaf, two-node cuttings were taken from Eucalyptus grandis stockplants grown under different light qualities (red to far- red ratios of 0.4, 0.7, 1.3, 3.5 and 6.5) at a constant photon flux density (200 mu mol m(-2) s(-1)). Two experiments tested effects of pre-severance light quality on cutting morphology, post-severance gas exchange, carbohydrate status and rooting of cuttings. The best rooting percentage was achieved by cuttings with longer stems and greater stem volume from stockplants grown at lower red to far-red (R:FR) ratios. Generally, rooting success was associated with low pre-severance starch and water- soluble sugar concentrations, and a greater total water-soluble carbohydrate (TWSC) content per cutting. Rooting was associated with well maintained stem starch and an increase in stem TWSC during the propagation period. Gas exchange of cuttings was measured between 28 and 33 days after severance. Rooting percentages at 35 days after severance were positively and linearly related to net photosynthetic rate and stomatal conductance. In unrooted cuttings there was a net release of CO2 which increased significantly with an increase in pre- severance R:FR ratio. These results demonstrate that stockplant environment may significantly modify the morphology and physiology of subsequent cuttings, and that cutting morphology, and stored and current photosynthates have a significant influence on rooting.

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