| Popis: |
A series of studies were conducted with eastern redbud (Cercis canadensis L.) to identify clones with rooting potential, determine the optimum growth stage for taking stem cuttings, investigate the effect of auxin treatment on rooting of stem cuttings, and determine optimum nitrogen (N) nutrition for seedlings grown in containers. The first study consisted of two experiments, one utilizing softwood cuttings and the other semi-hardwood cuttings, to investigate the influence of growth stage and auxin treatment on rooting of four related clones of eastern redbud. The clones were âFlameâ, dwarf white, and two selections (NC99-6-1 and NC99-6-2) of an F1 generation of a cross of âFlameâ and dwarf white. At each growth stage, rooting responses of the clones varied and were influenced greatly by auxin treatment, demonstrating the variable rooting potential of the genotypes. In both experiments, âFlameâ rooted well [63% rooting in the softwood experiment when treated with the potassium (K) salt (K-salt) of indolebutyric acid at 5000 mgâ¢L-1(ppm), 83% rooting when treated in the semi-hardwood experiment with K-IBA at 10,000 mgâ¢L-1]. For the softwood cutting experiment, cuttings of dwarf white (46%) and NC99-6-2 (75%) rooted best when treated with K-IBA at 15,000 mgâ¢L-1. Softwood cuttings of NC99-6-1 rooted most successfully (46%) when treated with K-IBA at 10,000 mgâ¢L-1. Dwarf white and the F1s rooted poorly in the semi-hardwood experiment. In the second study, stem cuttings of four popular clones of eastern redbud (âAce of Heartsâ, âAppalachianâ, âForest Pansyâ, and âHearts of Goldâ) were taken on seven dates following budbreak during Spring and Summer 2007 and evaluated for rooting potential. Rooting was affected by a clone x cutting date interaction, indicating the optimum time to take cuttings was different for each clone. Cuttings of âAce of Heartsâ taken 6 weeks after budbreak (WAB) rooted at 75% and 71% when treated with K-IBA at 5000 mgâ¢L-1 and 15,000 mgâ¢L-1, respectively. In contrast, cuttings of âAppalachianâ rooted at 96% and 93% when taken 15 WAB, the last date tested for that clone, and treated with K-IBA at 5000 mgâ¢L-1 and 15,000 mgâ¢L-1, respectively. When taken 8 WAB and treated with K-IBA at 5000 mgâ¢L-1 or 15,000 mgâ¢L-1, cuttings of âHearts of Goldâ rooted at 42% and 58%, respectively. Cuttings of âForest Pansyâ rooted poorly no matter when they were collected or the K-IBA treatment. In the final study, containerized seedlings of eastern redbud were grown in a greenhouse for 10 weeks with N application rates (NARs) ranging from 0 to 300 mgâ¢L-1. Seedlings fertilized with N at 180 mgâ¢L-1 had the greatest leaf area, leaf dry weight, and total dry weight. Plants allocated more resources to root growth at NARs < 60 mgâ¢L-1. At NARs ⥠60 mgâ¢L-1, allocation of carbohydrates to roots and tops was constant, with a root:top ratio of 0.25. Foliar concentrations of nitrogen and phosphorus increased linearly with increasing NAR while concentrations of potassium were not affected by NAR. |
