WATER-LOSS AND SURVIVAL OF STEM CUTTINGS OF 2-MAPLE CULTIVARS HELD INSUBIRRIGATED MEDIUM AT 24 TO 33 DEGREES-C

We determined transpiration rate, survival, and rooting of unmisted, s oftwood cuttings of 'Autumn Flame' red maple (Acer rubrum L.) and 'Ind ian Summer' Freeman maple (Acer xfreemanii E. Murray). Effects of perl ite at 24, 30, and 33 degrees C were assessed to determine whether res ponses of cuttings would be consistent with cultivar differences in re sistance to root-zone heat previously shown with whole plants. During 7 d, cutting fresh mass increased by approximate to 20% at all tempera tures for 'Autumn Flame' red maple, but fresh mass of 'Indian Summer' Freeman maple decreased by 17% and 21% at 30 and 33 degrees C, respect ively. The percentage of cuttings of 'Indian Summer' that mere alive d ecreased over time and with increasing temperature. Transpiration rate decreased during the first half of the treatment period and then incr eased to approximate to 1.1 and 0.3 mmol . m(-2). s(-1) for 'Autumn Fl ame' and 'Indian Summer', respectively. Mean rooting percentages over temperatures for 'Autumn Flame' and 'Indian Summer' were 69% and 16%, respectively. Mean rooting percentages at 24, 30, and 33 degrees C ove r both cultivars were 74%, 29%, and 25%, respectively. Over temperatur es, mean root count per cutting was 41 and seven, and mean root dry ma ss per cutting was 4.9 and 0.4 mg, for 'Autumn Flame' and 'Indian Summ er', respectively. Use of subirrigation without mist to root stem cutt ings was more successful for 'Autumn Flame' than for 'Indian Summer'. Temperature x cultivar interactions for cutting fresh mass and the per centage of cuttings remaining alive during treatment were consistent w ith previous evidence that whole plants of 'Autumn Flame' are more hea t resistant than plants of 'Indian Summer'. Mass and survival of stem cuttings during propagation in heated rooting medium may serve as tool s for screening for whole-plant heat resistance among maple genotypes.