Two experiments investigated the relationship of light and temperature in seed germination of Fraser fir [Abies fraseri (Pursh) Poir.]. Irradiation during the warm portion of 9/15 hr thermoperiod of 20/10C and 30/20C increased germination percentages after 42 days, and the degree of stimulation depended on the timing of the light exposures. A 1-hr exposure was most effective during the latter part of the warm portion of the thermoperiods, and varying the time of irradiation had the greatest effect at 20/10C. The involvement of phytochrome in this photomorphogenic response was ascertained by demonstration of red/far-red reversibility.
Hardwood stem cuttings of eastern redcedar (Juniperus virginiana L.), taken from containerized stock plants fertilized weekly with 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N, were treated with 7500 ppm IBA and placed under intermittent mist for 12 weeks. Foliar starch and sucrose concentrations within cuttings at time of excision were significantly correlated with percent rooting and root length, respectively. Of the mineral nutrients analyzed (N, P, K, Ca, Mg, Mn, and B), only B and K were significantly correlated with rooting response. A threshold N level (20 ppm), applied weekly, maximized rooting; higher concentrations decreased response. Although N fertilization of stock plants affected adventitious rooting, there were no significant correlations between foliar N levels and measures of rooting response. Chemical name used: 1 H- indole-3-butyric acid (IBA).
Containerized seedlings of eastern redcedar (Juniperus virginiana L.) were fertilized weekly for 175 days with a solution containing 50 ppm P, 150 ppm K, and either 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N. Plant height, stem diameter, and shoot and root dry weights increased asymptotically with applied N; 640 ppm N diminished response. Growth after 175 (height, stem diameter) and 180 (shoot and root dry weights) days was optimal (90% of maximum) at N concentrations of 115, 155, 230, and 105 ppm, respectively, 1.5% foliar N optimized height growth. Foliar concentrations of N, P, and K increased in treated plants over the duration of the experiment, while Ca, Mg, and Mn decreased or remained constant. Starch concentration of fertilized plants decreased sharply after initiation of the experiment, but controls showed little change during the first 120 days. Sucrose concentration remained constant over the summer but increased sharply in late fall. At 180 days, foliar concentrations of starch, sucrose, hexose, N, P, K, and B increased asymptotically with applied N; concentrations of Ca, Mg, and Mn decreased.