| Stem cuttings are one of the most frequently used and successful methods of vegetative plant propagation. The understanding of unrooted cutting physiology, especially gas exchange and water flux, is crucial for successful propagation of healthy plants. Prior to root initiation, water uptake is limited and leafy stem cuttings are most vulnerable to wilting.;Experiments were carried out in the greenhouse with poinsettia cuttings to determine water uptake, photosynthesis, transpiration and stomatal conductance from the time of severing to rooting, including time spent in storage. Water uptake through the severed stem was investigated in the laboratory and growth chamber. Cutting gas exchange (i.e., photosynthesis, stomatal conductance and transpiration) sharply declined after severing and gradually recovered in propagation after root initiation. CIRAS-2, with optional integrated Chlorophyll Fluorescence Module (CFM) was used to assess chlorophyll fluorescence and photosynthesis of cuttings at different stages: freshly severed cuttings (Day 1), 3 day-old cuttings, callused cuttings (Day 7 and 10), and rooted cuttings (Day 21 and 28). There was no significant difference in chlorophyll fluorescence between the cuttings and stock plants hence we inferred no significant damage to photosynthetic reaction centers as a result of severing. Unrooted cuttings had relatively low photosynthetic rates compared to rooted cuttings with water as a possible limiting factor. Our data also suggest that water use efficiency increases during the first week in propagation prior to root initiation. The mechanism for this improved water use appears to be due to a return in normal stomatal function during the first week in propagation following severing the cutting from the stock plant. The results have implications for the management of mist in propagation environment. |
