Effects of warming basal ends of Carolina poplar (Populus x canadensis Moench.) softwood cuttings at controlled low-air-temperature on their root growth and leaf damage after planting

We investigated the effects of warming the basal ends of Carolina poplar (Populus x canadensis Moench.) softwood cuttings at controlled low-air-temperature on their root growth and leaf damage after planting. The warming treatment was applied to the cuttings by soaking 10 mm beyond the cut end in warmed water maintained at 30 A degrees C in a cold chamber maintained at an air temperature of 10 A degrees C and a photosynthetic photon flux density (PPFD) of 10 mu mol m(-2) s(-1) (near the light compensation point at 10 A degrees C) until rooting was observed. The warmed cuttings were then grown in a growth chamber at an air temperature of 30 A degrees C, relative humidity 85-90 %, and a PPFD of 100 mu mol m(-2) s(-1). Control cuttings were grown in the growth chamber throughout the experiment. Rooting occurred simultaneously for both warmed and control cuttings, irrespective of air temperature. Root development was greater and leaf damage, evaluated on the basis of extent of necrosis, was less for warmed cuttings than for control cuttings. The reduction of leaf damage for warmed cuttings probably resulted from reduced post-planting water stress and leaf senescence, because of improved root development as a result of the pre-planting warming treatment. This technique could improve the propagation of cuttings of woody plants, because it would ensure that the cuttings are ready to develop roots with minimum loss of carbohydrates, irrespective of weather conditions.