Time in propagation and photosynthetic photon flux affect water demand of unrooted poinsettia cuttings prior to root initiation
2019
Alem, P. O. | Faust, J. E.
Commercial propagators reduce the frequency of mist provided to unrooted poinsettia (Euphorbia pulcherrima) cuttings on a daily basis during the first week in propagation prior to root initiation. This practice suggests that water regulation by the cuttings changes as the cuttings recover from being harvested from the stock plant. The first experiment demonstrated that when cuttings were removed from water, the time to wilt increased as time in propagation increased. For example, the cuttings wilted in the dark (0 µmol m(-2) s(‑1)) at 72, 130, 224 and 325 min. for cuttings that had previously been in propagation for 0, 2, 4, or 6 days, respectively. In the light (275 µmol m(-2) s(‑1)), the cuttings wilted much faster; however, the effect of cutting age was similar. The amount of water loss per cutting at the point of wilting was not affected by time in propagation. In a second experiment, water uptake was recorded on cuttings that had been in propagation for 0, 2, 4, or 6 days and then placed into vials of water. Time in propagation had no effect on water uptake in light (375 µmol m(‑2) s(‑1)), while the rate of water uptake during 8 h in the dark decreased from 2.38 to 1.64 mL cutting(‑1) for cuttings aged 0 to 6 d in propagation, respectively. The third experiment showed that desiccation of cuttings prior to propagation did not inhibit water uptake, but actually increased the rate of water uptake. These results demonstrate that water regulation of unrooted poinsettia cuttings increases during the first week in propagation before root initiation, thus increasing the water use efficiency of the cuttings and reducing the need for mist as cuttings mature in propagation.
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