THE WATER STATUS OF LEAFY CUTTINGS OF 4 TROPICAL TREE SPECIES IN MIST AND NON-MIST PROPAGATION SYSTEMS

Variation in the water status of leafy cuttings of four tropical tree species was assessed in both mist and non-mist propagation systems, by measurement of stomatal conductance, relative water content (RWC) and water potential during the first three weeks after insertion in the propagators. Significant water deficits developed in all four species, with a minimum water potential of -3.1 MPa recorded for Triplochiton scleroxylon K. Schum. However, unrooted cuttings in both propagation systems were able to recover turgor, with peak RWCs over 90% recorded for all four species. Stomatal conductances were generally above 0.4 cm s-1, with a maximum of over 1.2 cm s-1 recorded for Terminalia spinosa Engl. These results support the suggestion that leafy cuttings actively photosynthesize during propagation. The two propagation systems had a contrasting effect on the water status of the cuttings, but this effect differed between the two experiments, and there was no overall effect of propagation system on rooting performance. Stomatal conductances and RWCs were negatively correlated with mean VPD in a number of cases, enabling critical values of VPD for the maintenance of leaf turgor to be estimated.