Elizabeth A. Gerson

Ethanol synthesis, nitrogen, carbohydrates, and growth in tissues from nitrogen fertilized Pseudotsuga menziesii (Mirb.) Franco and Pinus ponderosa Dougl. ex Laws. seedlings

Abstract Seedlings of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and ponderosa pine, Pinus ponderosa Dougl. ex Laws., were grown in a controlled environment and fertilized with nutrient solutions containing 150 ppm (+N), or 0 ppm nitrogen (−N). These treatments greatly altered seedling growth, and the concentrations of N and carbohydrates in their tissues. Metabolically active tissues, such as roots, incubated with a limited supply of O2 became hypoxic faster and synthesized more ethanol than less active tissues, such as needles. All tissues that were incubated for 4 h in N2 synthesized ethanol. Needles incubated in N2 and light had much lower quantities of ethanol than needles in N2 and dark, suggesting that O2 from photosynthetsis limited internal anoxia. Most tissues from +N seedlings synthesized greater quantities of ethanol in N2 anoxia than tissues from −N seedlings, probably because they were able to produce more enzymes with a greater availability of N. However, this increase in ethanol synthesis between N treatments was most pronounced in the phloem. Ethanol and soluble sugar concentrations were negatively related in needles and positively related in roots of N+ seedlings, but not −N seedlings. Starch concentrations had no effect on the amount of ethanol produced by any tissue. Regardless of N treatments, all tissues from ponderosa pine produced more N2-induced ethanol than Douglas-fir, in part because its tissues contained different concentrations of soluble sugars and N as a consequence of phenological differences between the species. However, ponderosa pine tissues may also maintain greater quantities of anaerobic enzymes, or their isozymes than Douglas-fir.

Piperidine Alkaloids in Nitrogen Fertilized Pinus ponderosa

We fertilized individual, pole-size ponderosa pine trees at two low-quality sites and pine saplings at a relatively high-quality site, with ammonium nitrate. Six to 12 months later, we measured total %N and 2,6-disubstituted piperidine alkaloids in the foliage. The N additions raised foliar %N above deficiency levels (i.e., from 1.0–1.1% to 1.4–1.6%) at the low-quality sites, but did not elevate foliar %N in saplings at the higher quality site, where it was already (1.9%) well above critical levels. In control trees with foliar N below a threshold of 1.1%, we detected no more than trace levels of alkaloids, indicating that alkaloid production is highly constrained by N deficiency. The N additions increased mean concentrations of the predominant alkaloid, pinidine, at all three sites. Mean total alkaloid concentrations for fertilized trees at the two low-quality sites were 12 and 155 μg/g dry wt higher than controls (relative increases of 12× and 4.5×, respectively). For saplings at the high-quality site, the mean total increased by 584 μg/g dry wt (1.6×) with the N additions. Allocation of foliar N to alkaloids was highest in fertilized saplings (0.81%) compared to control saplings (0.53%). These findings demonstrate that foliar alkaloid concentrations can be increased by nitrogen fertilization of forest trees growing on both low- and high-quality sites. Fertilizing for the purpose of inhibiting potential herbivores may be more successful at higher quality sites where alkaloid levels are enhanced relative to food quality (foliar %N).

Piperidine Alkaloids in Sitka Spruce with Varying Levels of Resistance to White Pine Weevil (Coleoptera: Curculionidae)

Abstract Our objective was to evaluate piperidine alkaloids as potential resistance factors in Sitka spruce, Picea sitchensis (Bong.) Carr, at risk to attack by white pine weevils, Pissodes strobi (Peck). We sampled 72 seedlings in each of two replicated field trials in the Oregon Coast Range. The seedlings were grown from open-pollinated seeds of putatively “resistant” or “susceptible” off-site parental sources. Alkaloid concentrations in bark and foliage were measured in previously unattacked trees at the time of weevil host selection. Leader mortality was evaluated in the fall to gauge actual resistance in the sample trees. Five families had ≤25% topkill and seven sustained >50% topkill. Alkaloid concentrations differed significantly among families, but the major alkaloids did not appear to be functionally linked with topkill or useful indicators of resistance. However, our study design did not address all potential resistance mechanisms. Therefore, before concluding that Sitka spruce alkaloids have no influence on white pine weevils, complementary laboratory and field experiments are needed.

Variation of Piperidine Alkaloids in Ponderosa (Pinus poderosa) and Lodgepole Pine (P. contorta) Foliage from Central Oregon

We quantified 2,6-disubstituted piperidine alkaloids in Pinus ponderosa and P. contorta needles from three forest sites in April, June, August, and December. Alkaloids were detected on at least one date in 71% of the ponderosa pine and in 29% of the lodgepole pine trees sampled. Pinidine was the major alkaloid constituent of ponderosa pine, while euphococcinine was the predominant compound in lodgepole pine. For ponderosa pine, total alkaloid concentrations were very low at two sites on all dates. At the third site, concentrations were variable but significantly higher on all dates. Total alkaloid concentrations in previous-year foliage from this site were highest in April, then significantly lower from June through December. Current-year foliage collected in August and December had significantly higher alkaloid concentrations than previous-year foliage on the same dates. Variation in foliar nitrogen concentrations accounted for some of the alkaloid variation in current-year foliage sampled in August.

Foliar storage and extraction methods for quantitative analysis of piperidine alkaloids from ponderosa pine (Pinus ponderosa)

Yields of 2,6-disubstituted piperidine alkaloids from ponderosa pine (Pinus ponderosa) foliage were compared for frozen, air- and oven-dried samples stored for 3 days and for 5 weeks. Oven-drying provided the most stable alkaloid yields, but biological variation was greater than the variation between the storage methods. Alkaloid yields were also compared for the classical liquid–liquid partitioning method and a solid-phase partitioning (SPP) method using Extrelut™ columns. Under proper conditions, both methods were reasonably accurate, but biological variation in alkaloid content was much greater than experimental variation from either extraction method. In order to optimize the SPP method, it was necessary to use chloroform rather than dichloromethane as the eluting solvent, and to rinse the column more than the manufacturer directs. The SPP method requires less solvent and time per sample, thus it may be preferable for ecological studies where numerous samples are required to detect differences against high background variation. Zinc dust treatment, to reduce possible alkaloid N-oxides in SPP extracts, failed to increase yields, suggesting the absence of such compounds. Copyright

Attraction and direct mortality of pandora moths, Coloradia pandora (Lepidoptera: Saturniidae), by nocturnal fire

Abstract The attraction of nocturnal moths to candles and other sources of light has long been observed, but fire as a potential source of mortality to moths in ecosystems with frequent fire regimes has been overlooked. A prescribed burn was conducted shortly after dark in a central Oregon ponderosa pine forest during the flight period of the endemic defoliator Coloradia pandora (Blake). Attraction to the fire and partial consumption by flames caused direct mortality estimated at 2.2% to 17.1% of the local pandora moth population. In field tests with projected light, pandora moths did not discriminate among colors in the visible spectrum. Moths did not respond to projected light for at least 1 h after dusk, indicating that timing and duration of the prescribed fire may have limited the mortality.

Piperidine alkaloids in North American Pinus taxa: implications for chemosystematics

Foliage samples from 10 taxa of the genus Pinus occurring in Mexico and the southwestern US were extracted for piperidine alkaloids. Eight (P. cembroides, P. durangensis, P. engelmannii, P. leiophylla, P. leiophylla var. chihuahuana, P. lumholtzii, P. monophylla, and P. ponderosa) contained alkaloids; only a trace was detected in P. ponderosa var. arizonica; and no alkaloids were found in P. discolor. Relative concentrations of the two end products of piperidine synthesis were consistent among taxa within subsections: the Leiophyllae produced euphococcinine exclusively; the Ponderosae produced primarily pinidine; and the Cembroides produced appreciable quantities of both. Alkaloid profiles of P. leiophylla and P. l. chihuahuana were very similar, and in agreement with classification of chihuahuana as a variety of P. leiophylla. Among the Ponderosae, P. p. arizonica was unique in its lack of alkaloids, suggesting species-level distinction from P. ponderosa may be appropriate. The absence of alkaloids in P. discolor, contrary to its close relative P. cembroides, provides further evidence towards designation as a separate species. Alkaloids in a subset of seedlings subjected to water stress did not differ from controls.