ISHS Acta Horticulturae 227: International Symposium on Vegetative Propagation of Woody Species
EFFECTS OF WATER STATUS ON ROOTING AND ESTABLISHMENT OF LEAFLESS WINTER (HARDWOOD) CUTTINGS |
| Authors: | B.H. Howard, R.S. Harrison-Murray |
| Abstract:
Broadleaved deciduous fruit and ornamental species can sometimes be propagated by winter cuttings, typically 60 cm long in the method developed at East Malling. These are stimulated to root in beds of compost over bottom heat and later transferred outside to the nursery. During the critical pre-rooting stage water is absorbed from the rooting medium and lost to the atmosphere. Cuttings may experience net gains or losses in water content depending on the water available in the compost, the aerial humidity and the area of cutting surface exposed to the atmosphere. Using a granulated bark medium with 15 cm suction provided by a sand-bed, the water status of cuttings was modified by exposing them to relative humidities between about 60 and 100%. In general, highest rooting frequency by the fourth week was associated with no change or a small decrease in water content during the first nine days of propagation. Changes of the order of 3% FW were often detrimental, but whether or not this was so depended on other factors. Cuttings were affected adversely by water loss in autumn and late winter/spring, and by water gain during mid-winter. Conventional seasonal rooting curves for M.26 apple were inverted by counteracting these tendencies. Loss of water at low aerial RH was reduced by wrapping bundles of cuttings in polythene, but this was often detrimental to rooting, probably because water condensed on the inner surface and ran to the cutting base. The effect of the polythene, therefore, was to increase water uptake while reducing water loss. The establishment of Tilia clones four to five months after propagation was related to the effects of aerial RH on cutting water content during the first nine days of the rooting phase. Treatment responses were clone-specific. | |
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