Ponderosa pine ( Pinus ponderosa Dougl. ex Laws), sometimes referred to as western yellow pine, is one of the most widely spread and important pines in the western United States, including Wyoming ( Barbour et al., 2008 ). It belongs to genus Pinus
Five year old container grown plants of Pinus ponderosa when treated with N6-BA at 500 and 1000 ppm during 1972 showed an increase in the number of dwarf shoots with developed buds on long shoots while lower concentrations used in 1971 were ineffective. Foliar applications of GA3 made during 1971 and 1972 were found not to increase bud development. Foliar applications of N6-BA applied in the spring of 1972 were more effective than fall applications. Removal of terminal buds also increased bud development within the dwarf shoot while combinations of N6-BA with removal of terminal buds was the most effective treatment.
Fertilization effects on mycorrhizal formation by Tricholoma virgatum with three pine species were studied. Inoculum was mixed into a 1 peat: 1 vermiculite media (1:9, v/v), prior to seeding in 160-cm3 “Leach Containers”. Four nutritional regimens were used: Full-strength Ingestad solution with 10% P, 10% Ingestad solution, modified-exponential Ingestad, and a slow-release fertilizer (Sierra TM, 17N-6P-1OK). Seedlings were harvested at 3, 4, and 5 months after sowing. Tricholoma inoculation resulted in 11% of the short roots of all species forming ectomycorrhizae (ECM) and 40% of the seedlings being colonized. P. sylvestris and P. nigra had significantly more ECM than did P. ponderosa, The number of ECM increased from the 3rd to the 4th month, but no increase occurred after the 4th month. Treatment with full-strength Ingestad/10% P yielded the largest seedlings and the least ECM, while exponential and 10% Ingestad produced smaller seedlings with the most ECM. The slow-release fertilizer treatment resulted in trees with intermediate growth and ECM formation. No differences in growth were found between inoculated and uninoculated trees.
Freezing woody stem segments of supercooling and non-supercooling species resulted in acoustic emissions in characteristic reproducible patterns. In the supercooling species examined (Fraxinus americana, Malus × ‘Dolgo’, Pyrus communis, and Fraxinus pennsylvanica), many acoustic emissions began after extracellular freezing, but before freezing of the supercooled fraction, and ended near −40°C. Acoustic emissions also occurred in species that did not supercool (Pinus edulis, Pinus ponderosa, and Cornus sericea), but to a much lesser extent. Cavitation of water within the cells during freezing is discussed as a source of acoustic emissions and possible cause of freezing injury.
Greenhouse-cultured, container-grown seedlings of interior Douglas fir [Pseudotsuga menziesii var. glauca (Beissn.) France], Engelmann spruce [Picea engelmannii (Parry) Engelm.], and ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) were acclimated and deacclimated to cold in growth chambers over 19 weeks. Heat tolerance and cold hardiness of needles, and bud dormancy, were measured weekly. Heat tolerance of Douglas fir and Engelmann spruce needles increased with development through the first complete annual cycle: new needles on actively growing plants; mature needles, not cold-hardy, on dormant plants; cold-hardy needles on dormant and quiescent plants; and mature, needles, not cold-hardy, on actively growing plants. Heat tolerance of ponderosa pine needles differed in two respects. New needles had an intermediate tolerance level to heat, and fully cold-hardy needles were the least tolerant. Thus, the physiological changes that conferred cold hardiness were not associated with greater heat tolerance in all the conifers tested. In none of these species did the timing of changes in heat tolerance coincide consistently with changes in cold hardiness or bud dormancy.
The formation of ozone in Los Angeles type (photochemical) smog was recognized by Haagen-Smit et al (1) in 1952. It soon became apparent that this compound could cause plant lesions identical to those which were seen on economic crops growing in many areas of the Los Angeles Basin. A “stipple” of grape leaves which occurred in midsummer in the field and which became progressively more severe with the season, was shown by Richards et al (4) to be very similar to lesions produced by ozone fumigation. Additional work with conifers (5) showed that a severe needle mottle of Pinus ponderosa and related species was caused by ozone in photochemical smog. Peroxy-acyl nitrates and oxides of nitrogen axe present in this mixture and are toxic to plants, but the separate effects of these pollutants have not been studied on grapes in detail.
Nine conifer species, including 3 selections of Scotch pine, were exposed to SO2 dosages of 1310 µg/m3 (0.5 ppm) for 5 hours, 2620 µg/m3 (1.0 ppm) for 4 hours, or 5240 µg/m3 (2.0 ppm) for 2 hours. Seedlings in the cotyledon and primary needle stages were utilized throughout the study. Significant injury occurred only at the highest concentration. Pine species (Pinus spp) were more susceptible to SO2 than were spruce (Picea spp.), fir (Abies spp.) or Douglas-fir (Pseudotsuga sp.). The 3 Scotch pine selections and ponderosa pine were more susceptible than Austrian pine species. Balsam fir, Douglas-fir, Fraser fir, white fir, blue spruce, and white spruce were not injured.
; Gjerstad and South, 1981 ). Even a preemergence rate of 1.7 kg a.i./ha failed to harm ponderosa pine ( Pinus ponderosa Laws. var. ponderosa ), although it did reduce germination of lodgepole pine ( Pinus contorta Dougl. var. latifolia Engelm
Sugar pine ( Pinus lambertiana Dougl.), a gymnosperm belonging to the family of Pinaceae prized for its economic and ecological value, is one of the most valuable softwood forest plant species in the western United States. Native to the region from
varied environments among populations of Pinus ponderosa For. Ecol. Mgt. 219 1 12