Seed production of western larch in seed-tree systems in the southern interior of British Columbia

A series of surveys and experiments were conducted on four sites to identify constraints to seed production and natural regeneration in western larch seed-tree systems in the southwestern interior of British Columbia, Canada. These surveys included pollen monitoring, a cone analysis to evaluate seed production potential, seed trapping to estimate seed rain and the installation of field germination trials to assess the effects of germination substrate and seed losses due to bird and rodent predators. Pollen shedding was found to be adequate for moderate seed production with filled seed counts ranging from 9 to 30 per cone (10–34% of all seeds/cone). No significant differences in seed yields per cone and cone characteristics were observed between uncut control stands and seed-tree stands. Seed rain was generally good in 1995, ranging from 70,000 to 4.6 million seed/ha. For the four seed-tree stands, the average filled seed percentage of the trapped seeds ranged from 9–30%. Seed rain and seed quality were much reduced in 1996. Field germination trials showed western larch seeds germinated and survived best (15–70%) on mineral soil but rodent and/or bird predation reduced germination success significantly. Germination/germinant survival on undisturbed forest floor, covered with predator exclusion screens, was intermediate.     

Germination and storage characteristics of Prunus africana seeds

Prunus africana, from the moist highlands of sub-Saharan Africa, is subject to great exploitation because its bark is used in the treatment of prostate-related diseases. A better understanding of the biology of its seed could help the ex situ and in situ conservation of the species. Fifty per cent of fresh seeds (46.8% MC) from mature purple fruits harvested in Kenya germinated after 10 days incubation at 25°C. The germination rate was linearly related to constant temperature, giving a prediction for the minimum temperature for germination at ca. 0.6°C. All seeds germinated at 5°C during 4 months fully hydrated storage. P. africana seed is, thus, neither dormant nor chilling sensitive. The relationship between equilibrium moisture content and relative humidity was used to construct a sorption isotherm, against which seed desiccation and storage responses were assessed. Seventy six per cent of mature seeds survived drying to 4.5% MC (22% RH) compared to 17% of seeds from immature purple-green fruits. Although, 25–45% of mature seeds survived at 8–12% MC after 2 months, only 10% remained viable after 6-month storage at 5°C. This study proposes optimum conditions for the artificial regeneration of P. africana seeds and highlights the need for further experiments storing dry seeds at sub-zero temperatures.     

杉木球果和种子发育节律的研究初报

杉木为我国南方主要造林树种,研究也较充分,但对球果和种子发育的研究比较薄弱。蒋恕(1980年)和华中农学院植物教研组(1975年)等从解剖学角度研究过杉木的受精过程。中国科学院林业土壤研究所(1973年)和唐午庆等(1964年)从物候学角度报告过杉木球果的大小和重量变化。我们则想从种子生产角度观察球果,特别是种子的发育过程,了解不同季节的种子品质变化,以便为最适采种期找到一些客观指标,并为种子园适时管理提供一些依据。     

Effects of storage conditions on dormancy and vigor of Picea abies seeds

The dormancy and vigor of Picea abies seeds were studied after five months of storage at 25 and 75% relative humidity (RH) and 5 and 12 °C. Dormancy was evaluated by studying germination response to light and moist chilling at 12 and 21 °C. Dormancy causing germination reduction in the dark was induced in seeds during storage at 25% RH (5–6% moisture content, MC) in darkness. The dormancy was greater when seeds were germinated at 12 than at 21 °C and after storage at 12 than at 5 °C. The effective dormancy relief by light indicates that germination was under phytochrome control. Moist chilling could partly replace light. According to accelerated aging and leachate conductivity tests, dry seeds could be stored at 12 °C for five months without affecting their vigor. After storage at 75% RH (11% MC) and 5 °C, the seeds germinated slowly and incompletely. The decreased germination response to light indicates that other processes than those mediated directly by phytochrome restricted germination of these seeds. The positive germination response to moist chilling suggested that secondary dormancy was induced in the seeds. However, vigor tests gave some evidence of simultaneous decrease of vigor. Storage at 75% RH and 12 °C decreased germination nearly to 0%. Germination of seeds stored at 75% RH could be stimulated by a short accelerated aging period.     

Effect of Seed Maturity and Pretreatment on Dormancy and Germination of Sorbus mougeotii Seeds

The effect of harvest time on seed germination, desiccation tolerance and level of dormancy is not known in Sorbus mougeotii (Soyer-Will. & Godron). Dry weight (DW), moisture content (MC) and leakage conductivity (LC) were tested on seeds from six harvest times. Chilling requirement and germinability were tested on seeds without drying and after drying and rehydration. The effect of postharvest ripening of seeds with or without drying was also tested. The DW was stable during the last 6 weeks of maturation, whereas MC initially decreased but later increased simultaneously with an increase in LC. Seeds were desiccation tolerant, deeply dormant and after a chilling treatment germinated to a high percentage at all harvest times. The chilling requirement decreased significantly with later harvest, suggesting a decrease in level of dormancy. Drying and postharvest ripening reduced and synchronized the chilling requirement.     

Enhancing germinability of Schinus molle L. seed lot from Ethiopia with specific gravity and IDS techniques

The IDS (Incubation, Drying and Separation) method was tested on Schinus molle L. seeds collected from Ethiopia in an attempt to sort non-viable from viable seeds. Seeds were incubated for 24 h followed by one, three, four, five, six, nine and twelve hours of drying and then separated in water. All IDS treatments gave 80.5–93.5% germination in the sunken fraction compared with 61% for untreated seeds. The mean germination time of sunken seeds reduced from 11.2 (control) to 8.9–9.2 days (IDS-treated). Specific gravity separation in water of untreated seeds was also tested, and the germination capacity of sunken fraction was 83.5% with a mean germination time of 9.3 days. IDS method can, therefore, be used to enhance both percentage and rate of germination of a seed lot of Schinus molle, which is desirable to produce uniform and vigorous seedlings in the nursery or out in the field.     

Storage of non-dormant seeds of Fraxinus angustifolia Vahl

The effects of drying and storage on the quality of Fraxinus angustifolia non-dormant seeds have been investigated. Mature seeds subjected to a 2-week warm stratification (20 °C) followed by a 2-week cold stratification (3 °C), were exposed to a gentle air stream at room temperature to dry them to 9.5% moisture content. After 4, 8 and 12 months of storage at –3 °C, in hermetically sealed containers, germination tests were conducted in darkness at 30/20 °C and 25/5 °C to evaluate possible changes in seed quality. The results obtained suggest the feasibility of drying non-dormant seeds. In fact, though causing a slight decrease in seed quality, such a process enables storage of ready to sow seeds for at least 12 months without any further loss. The temperature regime of 30/20 °C, prescribed by the International Seed Testing Association (ISTA), was found to be suboptimal for the particular conditions tested in this trial, the 25/5 °C cycle being more stimulating for germination.     

不同引发处理对了哥王种子萌发的影响

以了哥王种子为材料,通过比较不同浓度的GA3、PEG、NaCl、复合盐KNO3·KH2PO4预浸种处理后种子发芽率、发芽势、发芽指数、活力指数等指标,研究不同引发剂对了哥王种子萌发的影响,结果表明：4种引发剂浸种处理均显著促进了哥王种子的萌发及幼苗生长,各指标提高效果均以GA3处理最好,PEG次之,再之为复合盐KNO3·KH2PO4, NaCl引发效果较差,并且随着引发剂浓度的升高呈先升高后降低的趋势。     

Effects of osmopriming and hydropriming on vigour and germination of China aster (Callistephus chinensis (L.) Nees.) seeds

The aim of this research was to evaluate the effects of osmopriming and different hydropriming treatments on the vigour and germination of China aster (Callistephus chinensis) seeds. Seed vigour and germination tests were conducted at 10, 20 and 30°C in darkness for untreated, osmoprimed and hydroprimed seeds. The following parameters and categories of seeds and seedlings were evaluated: the mean germination time (MGT), T10, T50, U75–25, U90–10, the percentage of germinating seeds (Gmax), germination capacity, percentage of abnormal seedlings and dead seeds. The results showed that osmopriming accelerated seed germination to the largest extent and improved the uniformity of germination at 10 and 30°C. Among the hydropriming treatments the highest speed of germination was observed for seeds hydrated in 500 μL of water per 1 g of seeds for 48 h at 15°C. This treatment accelerated seed germination at 10°C compared with the control. Osmopriming increased seed germination capacity at 30°C. None of the applied hydropriming treatments improved this parameter.     

Seed biology and germination ecophysiology of Camellia nitidissima

Camellia nitidissima Chi (Theaceae) is a famous ornamental species with golden-yellow flowers. Due to deforestation and destructive collection of seedlings, its natural population size has been reduced greatly in recent decades. To provide basic information for its conservation, we studied the morphological and physiological characteristics of seeds and the environmental factors influencing germination. The seed production of C. nitidissima was of low yield, which caused lack of seed resource. The seeds were big and heavy, so they did not spread far from the mother trees and did not enter soil after falling down. Optimal temperatures for seed germination were 25–30 °C. The fresh-harvested seeds had high moisture content and weak desiccation-tolerance, so they tended to be recalcitrant. Soaking for 24 h in 10–30% PEG solution could significantly reduce the seed germination percentage. The imbibed seeds placed on the soil surface mostly could germinate, but some of them could not develop into seedlings because the embryo roots did not grow into soil. When the seeds were sowed at the depth of 1 cm, the seedling emergence reached over 70%, but then decreased with increased sowing depth, and reached about 50% when at the depth of 5 cm. The seeds sowed in sandy soil had higher emergence than those in clayed soil. It is feasible for seedling nursing to harvest seeds in time, harvesting prematurely or postmaturely may reduce seed quality.     

Desiccation and storage behavior of bay laurel (Laurus nobilis L.) seeds

The effect of seed moisture content (m.c.) and seed storage conditions of bay laurel (Laurus nobilis L.) was investigated in relation to seed viability. In the first experiment, the effect of drying rate on seed moisture and seed germination was investigated. Fresh seeds, with their original moisture content displayed a germination percentage of 55.1%. When the seed moisture content was reduced by 2.0% in an oven, the germination percentage rose to 81.0%. When the seed moisture content was reduced even more by using the same method, the germination percentages decreased dramatically. Reducing the seed moisture content to 28.7 and 23.5% by drying the seeds in alternating room conditions resulted in an increase of seed germinability to 84.3 and 90.9%, respectively. The drying of the seeds for 45, 60 and 75 days reduced their seed germination to 66.8, 49.4 and 48.0%, respectively. Reducing seed moisture content below 15.0% resulted in practically nullifying seed germinability. The fact that bay laurel seeds cannot retain their germinability at lower moisture contents demonstrates that it is a species with recalcitrant seeds. In the second experiment, moist and dry storage conditions were tested under different temperatures and moisture contents. The storage experiment showed that the most effective way of conserving the bay laurel seeds is moist storage at 0 ± 1°C for 4 months without previous drying of the seeds.     

Culling phenotypically inferior trees in seed production area enhances seed and seedling quality of <Emphasis Type="Italic">Acacia auriculiformis</Emphasis>

Improvement in seed and seedling quality of Acacia auriculiformis after culling phenotypically inferior trees was studied in a 6-year old seed production area (SPA). A 5-ha plantation was identified, of which 2.3 ha was converted into SPA. The initial stocking, 1 612 trees·ha⁻¹, was thinned down to 982 trees·ha⁻¹ based on growth characteristics. The following fruiting season, seeds were collected from 10 randomly selected trees in culled and non-culled stands, and seed physical characters, germination and seedling traits were assessed. Seed weight, seed thickness and percentage germination increased by 32.1%, 4.43% and 22.37%, respectively in the culled stand compared to the non-culled stand. Culling also increased the speed of germination, seedling dry weight and seedling vigor index. Heritability values were high for seed weight (0.974) and seed thickness (0.948) while medium values were observed for percentage germination (0.577) and total dry weight (0.534). Predicted genetic gain was 11.13% and 11.22% for seed weight and percentage germination, respectively. The actual gain was 32.1, 51.9 and 22.9% for seed weight, percentage germination and total dry matter, respectively. In conclusion, SPAs established by culling inferior trees could serve as sources of good quality seeds for reforestation programs until genetically improved seeds are made available.     

Variation in seed traits and seedling vigour of <Emphasis Type="Italic">Cordia africana</Emphasis> Lam. provenances in Ethiopia

Cordia africana is a very important indigenous tree species for timber and other products and services in Ethiopia. Seed traits and seedling vigour of seeds from 12 provenances of the species were compared. Mean seed mass for each provenance was assessed for 1000 seeds in 10 replications, and seed length and width were measured for 100 seeds in four replications per provenance. Germination was assessed in a glasshouse taking 400 seeds from each provenance. Root collar diameter and height of 440 seedlings grown in a nursery for 290 days in Addis Ababa were measured. Seed length, seed width, seed mass, and shoot height and root collar diameter of seedlings showed significant differences (P < 0.001) among provenances. Correlation analysis between seed and seedling traits and environmental variables revealed significant positive correlations between seed width and germination percentage, seed width and altitude, seed width and longitude and seed length and latitude. Negative correlations were obtained between seed width and temperature, seed width and rainfall, seed mass and temperature, and germination and temperature of the seed source. As expected, differences in seed trait did not explain the variability in seedling vigour. Determining quantitative variations in seed traits and seedling vigour among provenances and the patterns along environmental gradients are essential for informing decisions on the tree improvement programme of the species.     

自然脱水过程中七叶树种子生理特性的变化

于 2003 年研究了自然脱水过程中七叶树种子生理特性的变化。结果表明:七叶树种子对脱水高度敏感,为顽拗性种子。种子成熟采收时含水量高达 60.3%,种子在室温下自然干燥 30 天后,含水量下降到 30.2%,此时种子生活力完全丧失。在脱水初期,种子发芽率有所上升,但随后种子发芽率迅速降低。随着含水量的下降,种子浸出液相对电导率上升,但当含水量在 53.7% 到 50.9%之间时,种子浸出液相对电导率出现异常升高。同时种子超氧化物歧化酶(SOD)的活性随脱水时间的延长而下降,只有种子含水量在 53.7% 到 50.9%之间时出现例外。丙二醛(MDA)含量在脱水初期缓慢上升,在含水量下降到低于 50.9%时,丙二醛(MDA)含量快速上升。可溶性糖含量随脱水时间的延长缓慢上升。当种子含水量为 47%–60%时,种子发芽率较高,说明这一含水量区间有利于种子生活力的保持。图 6 参 13。     

处理方法对杏种子发芽率的影响初报

对不同成熟期杏品种的种子进行了常规层积和鲜种低温保鲜贮藏（简称鲜种鲜贮）两个处理。结果表明：供试极早熟杏品种的种子常规层积均不发芽,而对其鲜种进行长达１９０ｄ左右的低温保鲜贮藏,均有一定的发芽率。无论哪种方法处理,种子的发芽率均随其果实发育日数的增加而提高,但常规层积这种规律表现更为明显。鲜种鲜贮不同成熟期的杏种子,果实发育日数越少,需时间越长,果实发育日数在６０ｄ以内的极早熟品种,需要比中晚熟品     

Effects of presowing treatments, desiccation and storage conditions on germination of Strychnos nux-vomica seeds, a valuable medicinal plant

Seeds of Strychnos nux-vomica have slow and erratic germination; thus different presowing treatments were applied to enhance the germination of its seeds collected from Tamaraikulam, Tamil Nadu, India. In addition, the effects of desiccation and different storage conditions on the germination of S. nux-vomica seeds were investigated. The results show that soaking in 500 ppm gibberellic acid (GA₃) for 24 h, incubation of seeds at 40 °C for 3 days and alternate water soaking (16 h) and drying (8 h) for 14 days significantly increased the percentage germination compared to the control. Desiccation of seeds down to 10% moisture content resulted in better germination. Germination of S. nux-vomica seeds differed significantly between different storage periods, moisture contents of the seed and for first and second order interactions (p<0.001). The highest germination (92%) was achieved when seeds with 10% moisture content were stored at ambient temperature for 30 weeks. Evidence from the present study indicates that S. nux-vomica seeds possess physiological dormancy that can be broken effectively by after-ripening. As seeds of S. nux-vomica are found to be desiccation tolerant, dry seed (10% moisture content) can be hermitically stored at ambient temperature for 30 weeks without losing their viability.     

Natural Variation in Seed Characteristics of Eastern White Pine (Pinus strobus L.)

Natural variation in seed characteristics of eastern white pine (Pinus strobus L.) trees and its relationship with the size, form, and crown class of parent trees was examined in second-growth, white pine mixedwood stands in Ontario. Cones were collected prior to and following partial harvesting of two stands during 2 years of above-average seed production. Fully enlarged seed extracted from mature cones was X-rayed to determine seed yield per cone, the percentage of sound, partially filled, and empty seed, and the sound seed mass for each tree. Variation in seed yield per cone, the proportion of sound, partially filled, and empty seed, and seed mass was much greater among individuals than between stands or seed years. The strength and significance of the relationship of seed mass with sound seed yield differed with stand and seed year. In uncut stands, seed mass was higher for trees with dominant crown class, larger live crown ratios, and smaller height to diameter ratios, suggesting tree vigour and microsite quality influence seed mass. Proportion of partially filled seeds was significantly reduced in both stands in the second year likely due to increased growing degree days during female gametophyte development. The implications of these results to natural and artificial regeneration of white pine are discussed.     

Predicting anatomical maturity of Pinus sylvestris L. Seeds in northern Fennoscandia

The hypothesis tested was that it should be possible to predict maximum attainable level of anatomical maturity of Pinus sylvestris L. seeds, and thus the germination capacity, using only one x‐ray based sample value of anatomical potential (Ap) in combination with a time function. This sample should be taken after commencement and before cessation of embryo growth. Since this predictive model should be independent of temperature, it was validated by repeatedly collecting seeds from several localities with presumably different temperatures during ripening. Although the temperature sums differed between localities, the rate of increase in Ap was almost identical in August. According to multiple linear regression analysis, the highest coefficient of determination (0.81) was achieved if Ap values from collections made in August were used in the regression. The average absolute deviation for the different localities between actual and predicted maximum Ap was 2%, and the highest deviation 7.2%. Thus, it should be possible to make a good prediction of the maximum germination capacity as early as in August. The practical consequence of this is that cone collection and possible artificial ripening could be started very close to the optimal time. Furthermore, soil scarification could be done in seed tree stands before seedfall when high seed quality is predicted.     

The effect of different pre-sowing seed treatments, temperature and light on the germination of five Senna species from Ethiopia

The germination requirements of five Senna species: S. bicapsularis, S. didymobotrya, S. multiglandulosa, S. occidentalis and S. septemtrionalis have been investigated. Seeds possess dormancy which is caused by their hard seed coats hampering maximum, uniform and rapid germination. To overcome this dormancy, seeds of the five species were pre-treated with (a) mechanical scarification, (b) concentrated sulphuric acid for 15, 30, 45 and 60 minutes and (c) boiling water for 15, 30, 45 and 60 seconds. To determine the effects of temperature on the germination of seeds, pre-treated seeds from each species were incubated at 10, 15, 20, 25 and 30°C. Germination was also tested in the dark. Both acid treatment and mechanical scarification resulted in fast and uniform germination. The highest germination (95–100%) for all species was obtained from seeds treated with sulphuric acid for 60 minutes. Mechanical scarification resulted in 100% germination in all the species except S. septemtrionalis (59%). Boiling water improved germination significantly in S. didymobotrya (98%), S. occidentalis (82%) and S. septemtrionalis (97%), but had very little effect on S. multiglandulosa and reduced germination in S. bicapsularis. Senna seeds germinated over a wide range of temperatures with the optimum temperatures for germination falling around 20–25°C. Germination was either completely inhibited or very low at 10°C. Seeds of all species germinated both in light and dark conditions.     

“Target moisture content” prechill overcomes the dormancy of temperate conifer seeds

Temperate conifer seeds are often considered to be shallowly dormant because a dormancy breakage treatment such as incubation of moist seeds at 4°C (prechilling) for 3–6 weeks improves germination. However, longer prechill durations can induce germination during the cold phase. Since the delicate radicles of prematurely germinated seeds are easily damaged and killed during sowing, potential benefits of extended prechilling are unknown.Described here for the first time is a target moisture content (TMC) prechill. In this dormancy breakage method the seeds are chilled at moisture contents high enough for removal of dormancy but low enough to produce surface dry, free flowing seeds that do not germinate during chilling. The method is a simple, effective and practical way to restrict the amount of water available to seeds from the start of a prechill treatment. The TMC prechill was applied to three conifer species, Douglas fir (Pseudotsuga menziesii (Mirbel) Franco), Lodgepole pine (Pinus contorta Douglas), and Sitka spruce (Picea sitchensis (Bongard) Carrière). All three species benefited from the TMC prechill. Extending the prechill period progressively improved germination by widening the range of temperatures over which germination occurred, raising germination capacity at most temperatures and increasing germination rate at all temperatures. The optimum prechill period combining high germination capacity and low mean germination time was 36 weeks for Douglas fir, from 36 to 76 weeks for Lodgepole pine and 36 or 76 weeks for Sitka spruce depending on incubation temperature. None of the seeds of any of the species germinated during the TMC prechill of up to 76 weeks at 4°C.This work is Crown copyright, reproduced by Kluwer Academic Publishers by permission of the Forestry Commission.