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William R. Graves and Hongyi Zhang

Air temperature and photosynthetically active radiation (PAR) effects on relative water content (RWC), rooting percentage, root count, and root mass of unmisted, subirrigated stem cuttings of two taxa were determined. Leaf RWC of `Charm' chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] decreased until roots initiated and then increased, was lower for cuttings at 23 °C photoperiod/14 °C dark than for cuttings at 31 °C photoperiod/22 °C dark, and was lower at 193 than at 69 μmol·m–2·s–1 PAR. Neither temperature nor PAR affected leaf RWC of `Dollar Princess' fuchsia (Fuchsia ×hybrida Hort. ex Vilm.), which increased linearly before and after root initiation. Rooting percentage and root count were higher with photoperiods at 31 °C than at 23 °C for chrysanthemum after 7 days and for fuchsia after 10 days. Although all cuttings of both taxa had rooted after 14 days, root dry mass was higher with photoperiods at 31 °C than at 23 °C regardless of PAR for fuchsia and at 69 μmol·m–2·s–1 PAR for chrysanthemum. Propagators wishing to use subirrigation instead of mist, fog, or enclosure can minimize the decline in leaf RWC before root initiation and increase the number and dry mass of roots of chrysanthemum by using 69 μmol·m–2·s–1 PAR and a 31 °C photoperiod/22 °C dark cycle. Root dry mass of fuchsia also can be increased by the use of high temperature, but differences in rooting were independent of changes in leaf RWC.

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Hongyi Zhang and William R. Graves

A subirrigation method for rooting stem cuttings was compared to intermittent mist. Both methods resulted in 100% rooting of `Charm' chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura] and coleus (Coleus × hybridus Voss.) after 2 weeks. Subirrigated cuttings of `Charm' chrysanthemum had a lower mean root dry mass than misted cuttings, but root dry mass of coleus was not affected. Percentage rooting and mean root dry mass of subirrigated cuttings of `Franksred' red maple (Acer rubrum L.) were 95% and 321 mg, whereas the mean root dry mass of the 33% of cuttings that rooted under mist was 38 mg. For Japanese tree lilac [Syringa reticulata (Blume) Hara], the percentage of cuttings with living callus, mean callus diameter, and percentage rooting were higher for subirrigated cuttings than for misted cuttings. In a second study, cuttings of `Franksred' red maple were subirrigated with a solution containing 0 to 7.2 mol N/m3 and not misted. Cuttings given 3.6 or 7.2 mol N/m3 had > 90% rooting after 2 weeks, whereas only 8% of unfertilized cuttings had rooted, and root mass and chlorophyll content were highest for cuttings given 7.2 mol N/m3. Subirrigation can replace mist during propagation of some florist and nursery crops, and subirrigating with fertilizer solution improves rooting of `Franksred' red maple.

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Hongyi Zhang and William R. Graves

A rapid, easy, and economical way to root softwood cuttings of red maple (Acer rubrum L. and A. × freemanii E. Murray) has been developed. Single-node cuttings were treated with 8 g IBA/kg and inserted in flats of perlite. Flats were placed in larger trays without drainage holes. Cuttings were subirrigated by adding a complete solution with 100 mg N/L to trays, saturating perlite at the bottom of the flat, below the cuttings. After 3 weeks, 94, 98, 100, and 100% of cuttings of `Indian Summer', `Autumn Flame', `Red Sunset', and `Autumn Blaze' had rooted, respectively. Leaves on cuttings remained turgid without mist or fog. In a subsequent study of `Red Sunset', 0, 50, and 100 mg N/L in the subirrigation solution resulted in 37, 100, and 100% rooting with 8 g IBA/kg and 0, 43, and 67% rooting without IBA. Rooting was fastest and chlorophyll in leaves was highest with both IBA and nutrients. Subirrigation can replace mist or fog when rooting cuttings of red maple.

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Hongyi Zhang, William R. Graves, and Alden M. Townsend

Single-node cuttings of `Autumn Flame' and `Indian Summer' red maple (Acer rubrum L. and A. × freemanii E. Murray) were placed in subirrigated perlite that was kept at 29, 33, or 36 C at the cut ends for 3 weeks. Number and mass of roots and pigment quality and transpiration of leaves were greater for `Autumn Flame' than `Indian Summer' and decreased with increasing temperature for both cultivars. Rooting percentage at 29, 33, and 36 C was 75, 75, and 25 for `Autumn Flame' and 13, 13, and 0 for `Indian Summer'. Earlier work has shown > 90% of cuttings of both cultivars root at ≈ 22 C, and plants of `Autumn Flame' are more heat resistant than those of `Indian Summer'. Results of this experiment suggest the effect of heat on rooting of cuttings might be used to predict genotypic differences in heat resistance of whole plants.

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Hongyi Zhang, William R. Graves, and Alden M. Townsend

We determined transpiration rate, survival, and rooting of unmisted, softwood cuttings of `Autumn Flame' red maple (Acer rubrum L.) and `Indian Summer' Freeman maple (Acer ×freemanii E. Murray). Effects of perlite at 24, 30, and 33 °C were assessed to determine whether responses of cuttings would be consistent with cultivar differences in resistance to root-zone heat previously shown with whole plants. During 7 d, cutting fresh mass increased by ≈20% at all temperatures for `Autumn Flame' red maple, but fresh mass of `Indian Summer' Freeman maple decreased by 17% and 21% at 30 and 33 °C, respectively. The percentage of cuttings of `Indian Summer' that were alive decreased over time and with increasing temperature. Transpiration rate decreased during the first half of the treatment period and then increased to ≈1.1 and 0.3 mmol·m-2·s-1 for `Autumn Flame' 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 °C over both cultivars were 74%, 29%, and 25%, respectively. Over temperatures, mean root count per cutting was 41 and seven, and mean root dry mass per cutting was 4.9 and 0.4 mg, for `Autumn Flame' and `Indian Summer', respectively. Use of subirrigation without mist to root stem cuttings was more successful for `Autumn Flame' than for `Indian Summer'. Temperature × cultivar interactions for cutting fresh mass and the percentage of cuttings remaining alive during treatment were consistent with previous evidence that whole plants of `Autumn Flame' are more heat resistant than plants of `Indian Summer'. Mass and survival of stem cuttings during propagation in heated rooting medium may serve as tools for screening for whole-plant heat resistance among maple genotypes.