Sugar Pine Seeds Research Articles

Factors Affecting Seed Germination and Establishment of an Efficient Germination Method in Sugar Pine (Pinus lambertiana Dougl.)

Mature sugar pine (Pinus lambertiana Dougl.) trees produce large amounts of viable seeds but have seed dormancy. In this study, we used three sugar pine genotypes, 8877, 9306, and 9375, to test seed germination response. Seed germination from local sources varied greatly, and germination percentages were poor. There was a large variation in seed size and seed weight among the genotypes. Seeds of 9375 and 9306 were significantly larger and heavier (30.7 and 28.8 g/100 seeds, respectively) than 8877 (23.6 g/100 seeds). Three types of seeds—intact seeds, hulled seeds, and naked embryos—were examined for germination. Intact seeds failed to germinate due to the physical restraint and water impermeability of the seed. Chemical scarification with 5 m hydrochloric acid and 5 m sodium hydroxide did not soften the hard seedcoat and also failed to induce any germination of intact seeds. Hulled seeds resulted in an extremely low germination percentage (≤5%) with abnormal seedling development even though the endosperm was water permeable. Germination of the hulled seeds was not increased by adding 1 mg·L−1 gibberellic acid to the culture medium. Artificial opening of the hulled seeds created by longitudinal or horizontal cuts on the endosperm after removal of the seedcoat to avoid physical restraint and allow air exchange also failed to improve germination, indicating that inhibitors related to germination were present in the endosperm. However, naked embryos of all three genotypes germinated rapidly and uniformly with 70% to 95% germination percentage regardless of cold stratification treatment. Our data indicate that sugar pine seeds from the current source did not have physiological dormancy of embryos themselves, but dormancy was imposed by the seedcoat and endosperm. Using the naked embryos as donor explants, we have successfully established an efficient in vitro culture system. The protocol described here can be applied for the tissue culture and genetic transformation of sugar pine.

Implications of the variable availability of seasonal foods on the home ranges of black bears, Ursus americanus, in the Sierra Nevada of California

Background: Sugar pine (Pinus lambertiana) seeds and oak (Quercus spp.) acorns are both important fall food sources for a variety of wildlife in the Sierra Nevada, but both have variable mast production and are in decline. Sugar pines are in decline due to white pine blister rust (Cronartium ribicola) infection and oaks are in decline due to fire exclusion and mule deer (Odocoileus hemionus) predation. To examine how a change in availability of seed and acorn crops from these trees could have a cascading effect on associated wildlife, we studied their relationship to black bear (Ursus americanus) fall ranges in Sequoia National Park, California. The distribution of seed-bearing sugar pines overlaps with the bears’ summer range, whereas acorn-bearing oaks occur at lower elevations. We used GPS collars and field observations to collect location data on ten wild, adult, female bears during the summer and fall of both 2005 and 2006, and then compared these data on habitat use with the Park’s vegetation map of available habitat. Results: Our results indicate that the inter-annual variability in the availability of these natural foods is closely related to the seasonal ranges of black bears. In the fall of 2005, when blue and black oak acorns were scarce but other acorns were abundant, bears remained within their summer ranges to feed on sugar pine seeds. In the fall of 2006, when blue oak acorns were abundant, bears shifted out of their summer ranges to feed on acorns and forego sugar pine seeds, even though the seeds were more abundant than in 2005. Incidents between humans and black bears were highest in 2006 while bears were moving between their summer ranges and the oak belt. Conclusion: In the fall, black bears make heavy use of both sugar pines and oaks. Although they prefer acorns to sugar pine seeds, the loss of either food source would lead to an increased dependence on the other. When both are unavailable due to continued decline or simultaneously low mast crops, an increase in human-bear incidents is likely.

Clark's Nutcrackers Harvest Sugar Pine Seeds from Cones

ABSTRACT. This is the first report of Clark's Nutcrackers (Nucifraga columbiana) harvesting seeds from the cones of sugar pine (Pinus lambertiana), based on observations over several years in Crater Lake National Park, Oregon. The harvesting period in late September corresponded to peak cone-opening dates. Nutcrackers placed harvested seeds in their throat pouches, a behavior associated with seed caching.

ON THE RELATIVE CONTRIBUTIONS OF WIND VS. ANIMALS TO SEED DISPERSAL OF FOUR SIERRA NEVADA PINES

Selective pressures that influence the form of seed dispersal syndromes are poorly understood. Morphology of plant propagules is often used to infer the means of dispersal, but morphology can be misleading. Several species of pines, for example, have winged seeds adapted for wind dispersal but owe much of their establishment to scatter-hoarding animals. Here the relative importance of wind vs. animal dispersal is assessed for four species of pines of the eastern Sierra Nevada that have winged seeds but differed in seed size: lodgepole pine (Pinus contorta murrayana, 8 mg); ponderosa pine (Pinus ponderosa ponderosa, 56 mg); Jeffrey pine (Pinus jeffreyi, 160 mg); and sugar pine (Pinus lambertiana, 231 mg). Pre-dispersal seed mortality eliminated much of the ponderosa pine seed crop (66%), but had much less effect on Jeffrey pine (32% of seeds destroyed), lodgepole pine (29%), and sugar pine (7%). When cones opened most filled seeds were dispersed by wind. Animals removed > 99% of wind-dispersed Jeffrey and sugar pine seeds from the ground within 60 days, but animals gathered only 93% of lodgepole pine seeds and 38% of ponderosa pine seeds during the same period. Animals gathered and scatter hoarded radioactively labeled ponderosa, Jeffrey, and sugar pine seeds, making a total of 2103 caches over three years of study. Only three lodgepole pine caches were found. Caches typically contained 1-4 seeds buried 5-20 mm deep, depths suitable for seedling emergence. Although Jeffrey and sugar pine seeds are initially wind dispersed, nearly all seedlings arise from animal caches. Lodgepole pine is almost exclusively wind dispersed, with animals acting as seed predators. Animals treated ponderosa pine in an intermediate fashion. Two-phased dispersal of large, winged pine seeds appears adaptive; initial wind dispersal helps to minimize pre-dispersal seed mortality whereas scatter hoarding by animals places seeds in sites with a higher probability of seedling establishment.

Interactions between Steller's jays and yellow pine chipmunks over scatter‐hoarded sugar pine seeds

Summary Sugar pine (Pinus lambertiana Douglas) seeds are dispersed by wind, but yellow pine chipmunks (Tamias amoenus Allen) and Steller's jays (Cyanocitta stelleri Gmelin) gather the seeds and scatter‐hoard them. Chipmunks and jays store seeds in a similar manner, and during cache recovery they appear to compete for stored seeds. A series of aviary studies and radioactive seed studies in the field were used to examine how chipmunks and jays interact over stored seeds. Aviary studies revealed that chipmunks use spatial memory and olfaction to find seeds, including those stored by conspecifics and jays, whereas jays use spatial memory and observational learning, so they usually find only the seeds that they have stored. Use of olfaction makes chipmunks much better pilferers than jays. In the field, both chipmunks and jays have a recovery advantage (they retrieve their own caches 3·6 faster than do pilferers), and chipmunk caches disappear 3·4 faster than jay caches. Steller's jays appear to avoid chipmunk pilferage by caching seeds in closed‐canopy pine forests with little shrub understorey where chipmunks seldom forage, whereas chipmunks cache under shrubs in forest openings. The risk of pilferage by chipmunks appears to force jays to cache in forests. Competition between chipmunks and jays for stored seeds might have indirect effects on sugar pine seedling establishment because seedlings survive better when under shrubs.

Effects of seed size of wind‐dispersed pines (Pinus) on secondary seed dispersal and the caching behavior of rodents

Seeds and nuts dispersed by scatter‐hoarding animals are relatively large compared to propagules dispersed by other means. Possible selective forces in the evolution of large seed size include the selectivity of foraging animals and the ways that food‐storing animals treat seeds and nuts after harvest. Treatment by rodents, primarily yellow pine chipmunks (Tamias amoenus), of four species of pine seeds that vary in size was studied in the Carson Range of western Nevada. The pines, lodgepole pine (Pinus contorta, 8.7 mg), ponderosa pine (P. ponderosa, 55 mg), Jeffrey pine (P. jeffreyi, 157 mg), and sugar pine (P. lambertiana, 213 mg), produce winged seeds that are initially wind‐dispersed but are gathered by rodents and cached in the soil. Radioactive scandium‐46 was used to follow the fates of seeds of all fours species placed around three source trees during autumn 1998 to 2000. Rodents gathered the seeds of all four species, but they took fewer of the lodgepole pine seeds and only six lodgepole seed caches (n=2106 total caches) were found during the three years. Among the other three species, number of seeds per cache decreased with increasing seed mass. However, the product of number of seeds per cache and seed mass was similar for all species. Sugar pine seeds were cached slightly deeper than ponderosa and Jeffrey pine seeds. For the species examined, seed size appeared to have had little effect on several other attributes, including mean dispersal distance, substrate choice, and microhabitat choice. Large size decreases wind dispersibility of pine seeds, but secondary dispersal by scatter‐hoarding rodents compensates for poor wind dispersal so that total dispersibility of large‐seeded pines is not compromised.

Somatic Polyembryogenesis from Callus of Mature Sugar Pine Embryos

An embryogenic callus was isolated from suspensor cells of 5–year–old sugar pine seeds. With a newly formulated basal medium and by removal of 2,4–D followed by an addition of BAP, globular somatic embryos were induced having elongated suspensors. In darkness, embryos elongated and formed numerous cotyledons in a repetitive and true–to–type polyembryonic process. When separated from one another, none of the embryos showed overt evidence of lethal or competitive effects under in vitro conditions.

Protein Synthesis and Aminopeptidase Activity in Dormant Sugar Pine Seeds During Stratification and Warm Incubation

Summary The capacity for protein synthesis, the activity of leucine-tyrosine aminopeptidase, and the pattern of soluble native proteins were determined for embryos and megagametophyte tissue from dormant sugar pine ( Pinus lambertiana Dougl.) seeds during 90 d of 25 °C warm, moist incubation or 5 °C stratification. The capacity for protein synthesis increased rapidly during the first 7 d in 25 °C embryos and megagametophytes and then decreased gradually through the rest of the 90-d treatment period. However, this protein synthesis at 25 °C occurred independently of germination, as these seeds maintained their dormancy. The capacity for protein synthesis in the 5 °C embryos eventually surpassed the capacity in 25 °C embryos after 60 d but remained significantly lower in the 5 °C than the 25 °C megagametophytes throughout the 90-d period. The pattern of increase in the capacity for protein synthesis in the 5 °C embryos generally paralleled increases in germinability. After about 14 d, the rate of leucine-tyrosine aminopeptidase activity remained higher in both embryos and megagametophytes at 5 °C than at 25 °C. A decline in activity occurred towards the end of the 90-d period. Patterns of native protein bands, as determined by polyacrylamide gel electrophoresis, remained the same in 5 °C and 25 °C embryos and megagametophytes throughout the 90-d period. However, the staining intensity of several individual bands appeared greater in 25 °C embryos than in 5 °C embryos.

Temperature Effects on Oxidative Metabolism of Dormant Sugar Pine Seeds

When dormant sugar pine (Pinus lambertiana L.) seeds were imbibed at 5 degrees C, they showed a rapid increase in O(2) uptake, ATP level, and moisture content during the first 4 days. This was followed by a plateau phase until 60 days, after which a second significant increase in all three features occurred as dormancy was broken. During the plateau phase, conventional CN-sensitive respiration accounted for 74 to 79% of the total O(2) uptake. When dormant sugar pine seeds were imbibed at and maintained at 25 degrees C, a different pattern occurred. Water uptake was much more rapid during the first 4 days and no second increase occurred after 60 days because the seeds did not break dormancy. There was an initial burst of O(2) uptake and ATP formation, but these both declined abruptly after 24 to 48 hours. Levels about half those of seeds at 5 degrees C were maintained through the rest of a 90-day period. CN-sensitive respiration declined during imbibition at 25 degrees C, and accounted for only 55 to 61% of the total O(2) uptake. The inability of dormant sugar pine seeds to germinate at temperatures above about 17 degrees C may therefore result from initial temperature effects on membrane properties, leading to reduced O(2) uptake, reduced cytochrome oxidase electron transport activity, and lowered ATP levels.

Changes in phenolic acids and abscisic acid in sugar pine seed coats during stratification

The phenolic acids and abscisic acid (ABA) of sugar pine (Pinus lambertiana Dougl.) seeds coats, separated by high‐pressure liquid chromatography, were analyzed during 90 days stratification of the seeds. Although levels of seed coat phenolic acids and ABA declined significantly during, stratification, this decrease did not appear to be responsible for the loss of dormancy due to stratification. Lack of improved germination following washing, cracking, or removal of the seed coats, plus additional evidence, did not support a significant role for the seed coat in the dormancy of sugar pine seeds.

Activity of L-Phenylalanine Ammonia-Lyase during Stratification and Germination of Sugar Pine Seeds

Following a two-week lag period, during which time the majority of seed hydrationoccurred, PAL activity of sugar pine embryos increased four-fold during a 90-day stratification period at 5 °C. PAL activity of the female gametophyte tissue increased by 50 % over the same period, its level being one-third that of the embryos. Soluble protein content of the embryos did not change during stratification, while that of the female gametophytes decreased by 10 %. During germination, the embryo PAL level initially dropped to half that attained during stratification, then increased rapidly to a level on day six twice the initial, and finally decreased to about 35 % of the maximum rate of activity. PAL activity of the female gametophytes changed only slightly during germination. Soluble protein content of the embryos decreased by 60 % over 21 days germination, while soluble protein in the female gametophytes increased 2.5 times over the same period. The pattern and conditions for PAL activity during stratification and germination of sugar pine seeds suggests a temperature-sensitive balance between PAL-activation and PAL-inactivation systems.

MOISTURE AND TEMPERATURE IN RELATION TO SEED STRUCTURE AND GERMINATION OF SUGAR PINE (PINUS LAMBERTIANA DOUGL.)

The typical, irregular, delayed germination of sugar pine seeds was studied under different conditions of environment and seed dissection. Individual seeds showed a 3‐phase pattern of water uptake which was obscured when average values for groups of seeds were used. Stratification at 5 C slowed the rate of imbibition as well as the growth rate, but when followed after 3 months by return to 20 C, germination was uniformly rapid. Complete removal of the seed coats yielded prompt germination without stratification. The thin layer of the inner coat was a critical factor. Slitting this layer indicated less significance for gas exchange or mechanical restraint than for a restriction upon the rate of water uptake. Regardless of the method of seed treatment, the visible stages of germination consistently occurred within well‐defined levels of water uptake. The delicate balance between water entry and use as well as the internal distribution of water within seed components should be evaluated, rather than a mere expression of the total amount of water in a seed.

Moisture and Temperature in Relation to Seed Structure and Germination of Sugar Pine (Pinus Lambertiana Dougl.)

The typical, irregular, delayed germination of sugar pine seeds was studied under different conditions of environment and seed dissection. Individual seeds showed a 3-phase pattern of water uptake which was obscured when average values for groups of seeds were used. Stratification at 5 C slowed the rate of imbibition as well as the growth rate, but when followed after 3 months by return to 20 C, germination was uniformly rapid. Complete removal of the seed coats yielded prompt germination without stratification. The thin layer of the inner coat was a critical factor. Slitting this layer indicated less significance for gas exchange or mechanical restraint than for a restriction upon the rate of water uptake. Regardless of the method of seed treatment, the visible stages of germination consistently occurred within well-defined levels of water uptake. The delicate balance between water entry and use as well as the internal distribution of water within seed components should be evaluated, rather than a mere expression of the total amount of water in a seed.

Possible Relation of Linolenic Acid to the Longevity and Germination of Pine Seed

SEEDS of some pines, such as Jeffrey pine (Pinus jeffreyi), can be stored in air-tight jars at room temperature for a long time. Even after ten years of storage one may expect as much as 40 per cent of viable seed. When the seeds of Jeffrey pine are sown in a greenhouse they germinate rapidly and abundantly. Many other pines, as, for example, sugar pine (Pinus lambertiana), have short-lived seed. Under ordinary storage conditions sugar pine seeds lose their viability rapidly, and after five years of storage their germination is usually nil. At 5° C. the viability of sugar pine seed is maintained for a long time; in one case, after eight years of cold storage, germination amounted to 86 per cent of the original. Normally seeds of sugar pine sown in a greenhouse either fail to germinate completely or give a very small percentage of germination. When, however, the seeds are chilled in some moist medium for three months at 5° C, they germinate as well as those of Jeffrey pine. This prolonged period at a low temperature, necessary for germination of refractory seeds, can be designated as the period of incipient germination.