Production of a new generation of seeds through the use of somatic clones in controlled crosses of black spruce (Picea mariana)

To assess the potential to integrate somatic clones (SC) of desired characteristics in production of high genetic quality seed, controlled crosses between different SCs of black spruce (Picea mariana (Mill) B.S.P.) were used to assess their suitability for the production of viable pollen, cones, seeds and seedlings. These SC produced male and female strobili at an early stage. Pollen, cones and seeds produced were characterized (mass, size, germination); their characteristics were similar to those produced by trees in natural forests or seed orchards. A maternal effect was demonstrated for the cone size and seed mass. Although seeds had excellent germination rates, the somatic biparental crosses were divided into three distinct groups with different germination curves using the Weibull function. Seeds from controlled crosses between different SC enabled the production of high morpho-physiological quality seedlings in a forest nursery. Using black spruce as a model, we showed, for the first time, that SC can be used as seed producers. These encouraging results open new perspectives on the tangible integration of somatic embryogenesis (SE) in the chain of seed, vegetative propagation (cuttings and SE) and production of plants for high productivity plantations. Controlled crosses can be made between SC with the desired characteristics (fewer large branches, fewer nodes, good growth, high wood density, performance, improved yield, etc.), vegetative propagules produced and deployed to clonal tests. After elimination of the worst performing SC, clonal tests can be converted into seed orchards that produce a new generation of seeds of high genetic quality. This will allow the rapid introduction of new materials in elite breeding programs of forest species.     

Seed germination and seedling establishment of the monocarpic dwarf bamboo Sasa veitchii var. hirsuta

In order to determine the influences of environmental factors on seed germination and to identify the effects of germination characteristics on seedling establishment for Sasa veitchii var. hirsuta, germination experiments and a survey on current seedling dynamics were conducted in a natural habitat after mass flowering. The results of the germination experiments revealed that the seeds require a low-temperature environment for germination; those exposed to low-temperature conditions for a time similar to the length of winter (4 months of low-temperature conditions) germinated gradually, while those exposed for longer (>4 months of low-temperature conditions) germinated rapidly. These results were compatible with field observations indicating that seedlings emerged from June to October in the year after mass flowering, and they suggested this germination characteristic (i.e., variation of germination timing due to seed dormancy) may play an ecological function in spreading risk (although it may also increase the potential for seed predation). The results also revealed that stronger light and alternating temperature conditions had no effect on germination, whereas high temperatures and drying had negative effects. The outcomes of the survey on current seedling dynamics revealed that the seedling establishment ratio was high in a forest understory compared to that seen at a site where solar radiation was strong and soil water content was low. This implies that germination characteristics may promote seedling establishment in forest understory.     

The effect of timing of forest fire on phenology and seed production in the fire-dependent herbs Geranium bohemicum and G. lanuginosum in Sweden

The seasonal distribution of fires is one fire regime variable which has received little attention with regard to its effects on plants. For species with a short life-span that recruits after fire, the seasonal timing of a fire can be expected to be important due to effects on potential growth period and reproduction. We observed phenology and reproductive output in two annual and fire-dependent Geranium spp. in the southern part of the European boreal forest. In a garden experiment with the two species under two levels of nutrition, we established cohorts of seedlings at several dates over three summers. Time from germination to flowering and first mature seed differed little between the two species and levels of nutrition; i.e. plant size or level of nutrition had almost no effect on phenology. However, emergence time controlled the timing of reproduction. Most plants emerging before the second week of July in the garden experiment bolted the same year. Plants emerging later behaved as winter-annuals and started to flower in June the following year. A similar dichotomy was observed for populations of Geranium spp. at a number of burnt forest sites that differed in date of fire. This response is likely controlled by photoperiod. Nevertheless, at sites that burnt early some plants did not bolt in the same season; probably an effect of variable seedling emergence dates in the populations. In both the field and garden experiment, there were plants entering reproduction too late to produce mature seeds. Our results indicate that management fires should be conducted either very early, or during July and August to achieve a high seed production in these rare forest plants.     

大娄山区金佛山方竹种子营养成分与播种育苗

调查了大娄山区金佛山方竹的开花结实历程,并采集8个不同地点的金佛山方竹种子分析其营养成分,同时进行种子育苗试验。结果显示：1）大娄山区金佛山方竹在11月前后产生花枝,翌年2月初至3月中旬开花,4月中旬至5月初种子成熟;2）鲜种子千粒质量为230.9~342.5 g,种子含有丰富的蛋白质、脂肪、多糖、碳水化合物、多种氨基酸和矿质元素;3）种子成熟后不耐储藏,40 d后便失去发芽力,种子育苗应随采随播;4）人工异地播种其苗木质量优于原生林落种形成的苗木质量。     

Grazing exclosure increases fruit and seed production but reduces seed viability in <Emphasis Type="Italic">Myrtus communis</Emphasis>

Plants have compensating mechanisms to alleviate the loss of vegetative and reproductive tissues by herbivores. In this study, we evaluated how reproductive traits (size and production of fruit and seed, as well as germination and viability of seeds) of Myrtus communis (myrtle) were affected by goat grazing exclosure of forest understory in the Doñana Natural Park. One hundred and fifty myrtles were selected in three sites with similar environmental characteristics, although with a different length of grazing exclusion: (1) exclosure for 2 years (GE2); (2) exclosure for 3 years (GE3); and (3) long ago grazed plots (GE15): non-accessible to goat for at least 15 years. Fruit production, fruit and seed morphology and seed viability and germination were evaluated. Length of exclosure to goats increased fruit production, mass and volume of the fruits and seed, and endocarp mass. However, seed viability was higher in more recently grazed plots (70–90%) than in GE15 plots (51%). The final balance of viable/germinable seeds produced by an average sized myrtle in each treatment showed that the recently grazed myrtles (GE2) produced nearly five times less seeds (1200) than the myrtles grazed 15 years ago (5500). However, myrtles recovered the ability to produce viable seeds quickly, almost tripling, each year of non-grazing the number of viable/germinable seeds. The results of this study indicated that goat grazing could affect regeneration of myrtle because it reduced reproduction output and the number of viable propagules. Future studies should evaluate other related ecological aspects, such as fruit consumption by potential frugivores and seed dispersal (distance and place of seed deposition).     

Mechanical but not physical dormancy is a cause of poor germination in teak (Tectona grandis L.f.)

Poor seed germination is a significant problem for propagation of teak and it particularly hampers the deployment of genetically improved material into plantations. Seed dormancy is the putative cause for delayed and sporadic germination of teak seed but specific dormancy mechanisms have not been proven. In this paper we investigate whether physical or mechanical dormancy could affect teak germination. Physical dormancy was disproved when we observed water in every examined locule of fruit which had been immersed for 12–24 h (n = 1,700 fruits from six diverse sources). Mechanical dormancy was found to affect teak seed germination by means of valve structures which must open for the radicle to emerge. All 1,450 germinating seeds in 16 samples emerged from the endocarp via the detachment of a valve. Germination over 16 days was compared between extracted seeds (ex situ) and seeds within their endocarp (in situ) to determine the effect of mechanical dormancy on germination. Significantly greater germination of the ex situ seeds (62 ± 2% SE; n = 486) than of the in situ seeds (32 ± 2% SE; n = 564) indicated that mechanical dormancy is an important factor in the poor germination of teak.     

Inheritance of male flower production in Cryptomeria japonica (sugi) estimated from analysis of a diallel mating test

Context

Clonal variation of flower production has been investigated thoroughly in coniferous tree species because of the importance of flowering in seed production from seed orchards. However, the inheritance of flower production by progeny test has not been previously studied well, so the heritability of male flower production of Cryptomeria japonica, the most important species for forestry and the main cause of pollinosis in Japan, was estimated to provide fundamental data for pollen control in seed orchards and plantation forests.

Methods

Male flower production in C. japonica was investigated for three years using 20 full-sib families created by a diallel mating design with six parents using gibberellin treatment to promote flowering.

Results

The narrow-sense individual tree heritability of male flower production in each year was estimated as ranging from 0.777?±?0.339 to 1.050?±?0.346 by sib analyses. The contribution of general combining ability to the total variance varied from 24.1 to 35.6?%. The highest contribution of specific combining ability was 1.42?%. By selecting the top 50?% of parental clones for reduced male flower production, the genetic gain in lowering male flower productivity was predicted as 46.1?C53.0?%.

Conclusion

Our results suggest that male flower production in C. japonica is under strong genetic control and that control of male flowering by breeding is possible with a well-designed program.     

Enhancement of seed germination in Macaranga peltata for use in tropical forest restoration

We used pre-sowing treatments v/z., soaking seeds in concen- trated sulphudc acid （CSA）, gibberellic acid （GA）, combined treatment of CSA ＋ GA and mechanical scarification to overcome seed dormancy and enhance synchronous germination of Macaranga peltata seeds. We analysed percent seed germination data by logistic regression and con- finned that except in GA treatment, time and acid concentration together were crucial for enhancing germination. The combination treatment of CSA and GA resulted in higher percent germination （up to 74%） than either treatment used separately, but produced defective seedlings （26%）. Mechanical scarification of seed coat had the greatest impact in enhanc- ing germination （78%） and reducing imbibition time （6 days） against the control （0%）. Germination studies and SEM analysis confirmed that seed germination in M. peltata was inhibited by seed coat dormancy.     

Flower induction treatments have no effects on seed traits and transmission of alleles in Picea glauca

Flower induction methods-hormone application or exposure to physiological stress, or both-are used routinely for shortening breeding cycles and increasing seed production in white spruce (Picea glauca (Moench) Voss). The objectives of this study were: (1) to evaluate the effects of flower induction on seed yield and quality in white spruce; and (2) to determine if flower induction treatments affect the maternal contribution to offspring. We assessed the effects of flower induction treatments, which consisted of gibberellin A(4/7) (GA(4/7)) and naphthaleneacetic acid (NAA) stem injections, on allele segregation for 28 clones, number of seeds per cone, number of sound seeds per cone, seed weight, and the germination rate of a subset of clones. Flower induction treatments did not affect any of the phenotypic traits examined. No increase in segregation distortion in allozyme loci following flower induction treatments was observed.     

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.     

Effects of submergence in water on seed germination and vigor of the Copaifera lucens （Fabaceae） seedlings

We analyzed the tolerance of Copaifera lucens seeds to sub- mersion in water to assess the use of this species for direct seeding in riparian forest restoration programs. Seeds were submerged in water for 2, 4, 8, 16 and 32 days or not submerged （control = 0 days of submer- gence）. For the control and at the end of each period of submersion, germination and seedling vigor tests were carried out. For germination tests, seeds were sown in plastic pots containing sand and kept in labora- tory conditions. The percentage of seed germination, the germination rate and the average germination time were analyzed. For seedlings, total biomass, leaf area, leaf mass per area and leaf area ratio were analyzed. Submersion time drastically affected the dissolved oxygen content and seed germination. Between 4 and 8 days of submersion there was a de- crease from 83.8% to 15.6% in the germination percentage. No seed germination occurred after 16 days of submersion. Although there was a significant decrease in the percentage of seed germination between 4 and 8 days of submersion, seedling vigor was not affected. Seeds of this species were partially tolerant to submersion in water, suggesting that C. lucens is a promising species for direct seeding in riparian forest restora- tion projects.     

Seed Size as a Predictor of Germination Success and Early Seedling Growth in ‘Hollong’ (Dipterocarpus macrocarpus Vesque)

In species with seeds losing viability shortly after dispersal and exhibiting inherently low germination, quick decisions are required with respect to seeds that should be selected to maximize germination success and vigorous growth of seedlings. In ‘hollong’ (Dipterocarpus macrocarpus Vesque), I address the following questions: (a) are seeds that germinate randomly distributed within a seed population, (b) are subpopulations of viable and non-viable seeds separable, (c) does seed size predict which seeds germinate and (d) does seed size predict time required for germination and seedling vigour? Two estimators of seed size, diameter and weight, demonstrated a significant positive linear relationship endorsing assumption that accumulation of mass increases with increase in diameter of seeds. A threshold for selection of potential seeds for germination could not be derived from diameter measurements since seeds in an entire range of diameter did or did not germinate. All seeds <11 g did not germinate, but this threshold lies at the far lower end of the weight range and allows rejection of only a few seeds and acceptance of many seeds that will not germinate. A risk of potential seeds being rejected or non-viable seeds being picked exists if selection was derived from either diameter or weight. However, viable seeds could be better predicted from a scatter-plot of diameter on x-axis and weight on y-axis. Seeds showed a fan-shaped scatter and those developing the lower blade of the fan did not germinate while those following the handle were successful. Hence, two subpopulations segregated, but with a fuzzy edge. Mean diameter and mean weight of germinated seeds were significantly greater than those of ungerminated seeds. Most ungerminated seeds were those that had relatively smaller weight compared to their diameter. Although some large diameter seeds with small weight did germinate, but failed to develop into seedlings. Germination time and seedling vigour parameters (height, leaf number and collar diameter) were correlated both with diameter and weight. However, weight appears to have mattered more than diameter in germination success and early seedling growth.     

Effect of water-spray cooling treatment in a Douglas-fir seed orchard on seed germination

Overhead-cooling treatment used to delay flowering produced non-significant effects on germination capacity, germination rate, germination value, and abnormal germination of seeds from a 13-year-old Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] seedling seed orchard. The percentage of variation accounted for by cooling treatment ranged from 0.0 to 1.0%. In contrast, variation among trees within treatments ranged from 28 to 46%. These effects were significant, indicating that each tree has an individual germination pattern. The temporal delay of reproductive phenology caused by temperature manipulation as a result of the cooling treatment was judged to be within the species' biological limits.     

Seed germination of six mature neotropical rain forest species in response to dehydration

We studied effects of dehydration and rehydration on germination of seeds of six mature tropical rain forest species-Cupania glabra Swartz, Cymbopetalum baillonii Fries, Poulsenia armata (Miq.) Standl., Stemmadenia donnell-smithii (Rose) Woodson, Rheedia edulis Triana & Planch. and an understory palm Chamaedorea alternans H. Wendl.-from Veracruz, México. Before the seeds were sown, their water content was reduced by 0 (control), 30, 54 and 72% of their original water content. Dehydration affects the ability of seeds to rehydrate, as well as the rate and final percentage of germination when seeds are subsequently rehydrated. Seed survival and germination behavior showed three patterns: (1) C. baillonii, P. armata and S. donnell-smithii had greater tolerance to seed dehydration than C. glabra, C. alternans and R. edulis; (2) partial dehydration enhanced germinability of C. glabra and C. baillonii seeds; and (3) partial dehydration of C. alternans and R. edulis seeds resulted in delayed or sporadic germination. A relationship was found between the effects of dehydration on germination and the seasonality of seed production.     

Reproductive biology of the critically endangered tropical tree Talbotiella gentii

Talbotiella gentii is a critically endangered caesalpiniaceous legume endemic to Ghana, restricted in distribution to the margins of the forest zone where there has been extensive fire damage in recent decades. It occurs as isolated, near-monospecific populations, some of which show little seedling regeneration. We studied its reproduction to determine limitations that might inform efforts to prevent its extinction. We report on flowering phenology, pollen dispersal and germination, fruit and seed set, seed size and germination, and seedling survival, using controlled and open pollination. Talbotiella gentii flowers profusely in most years. Although the flowers are coloured and scented, no animal pollinators were observed but pollen can be dispersed by wind. In open pollination, the number of pollen grains on stigmas and their germination was sufficient to fertilise the three ovules, despite competition from heavy stigmatic infestation by fungal spores and hyphae. Fruit set and seed set were low due to high flower losses and fruit abortion during development but ripe seeds showed high germination. Controlled pollination experiments (self, supplemented self, and intra- and inter-population crosses) showed that, while the species is self-compatible, selfing was the least successful treatment in all of the above steps of reproduction, whereas cross-pollination enhanced most steps, the more so for inter-population crosses. Seed size was notably greater in inter-population crosses and was positively correlated with genetic distance of the cross. The larger seeds associated with cross-pollination showed higher germination and seedling survival in the nursery. We conclude that limitations to natural reproduction in T. gentii are principally due to processes between pollen germination and fruit and seed set, including pollen quality (low genetic diversity and inbreeding), fertilisation rates, flower and fruit abortion, and resource limitation. Low seed size in open and self pollination may have implications for seedling establishment. Species fitness might be improved by introducing other genotypes to existing populations, but in situ protection of the populations is essential in the medium term.     

Pre-sowing treatment for breaking dormancy in Acer velutinum Boiss. seed lots

Acer velutinum Boiss is a valuable tree species native to Iran, and its seeds possess physiological dormancy that hampers seedling production in the nursery for large-scale reforestation efforts. The aim of this study was to determine the optimal dormancy breaking treatments for A. velutinum seeds. We conducted a factorial experiment involving six seed lots collected along an elevation gradient from 300 to 1800 m at 300 m interval and four cold-moist stratification periods (0, 4, 8 and 16 weeks) at 4℃ and 70% relative humidity. The result shows that the germination of cold-moist stratified seeds was significantly (p < 0.0001) higher than the control for all seed lots. The highest germination capacity was recorded after 16 weeks of cold-moist stratification for all seed lots (68% 88% depending on the seed lot) except those collected from mid altitude sites (600 and 900 m) that germinated equally well (≥ 75%) after 4and 8-week of clod-moist stratification compared to the other seed lots. The mean germination time was significantly shorter (12 to 19 days, depending on the seed lot) for seeds stratified for 16 weeks than for untreated seeds. It can be concluded that: (1) cold-moist stratification for 16 weeks is the best pre-sowing treatment for breaking dormancy in A. velutinum seeds; and (2) seeds should be collected from mid altitude sites (600 and 900 m) to get more than 80% germination within 15 days, and these seed lots even required shorter cold-moist stratification period(eight weeks) than other seed lots.     

Variation of seed mass and its effects on germination in <Emphasis Type="Italic">Polylepis australis</Emphasis>: implications for seed collection

South American Polylepis mountain forests are recognised as being one of the most endangered forest ecosystems in the world. Reforestation measures have been strongly recommended but may be hampered due to the very low seed germination reported for several Polylepis species. In order to facilitate reforestation we analysed the influence of seed mass on germination probability for Polylepis australis seeds in the Córdoba mountains (central Argentina). We collected seeds from 43 trees distributed throughout five woodland fragments located within two regions differing in size, topographical position, and altitude (1,900 m a.s.l. and 2,200 m a.s.l.). Seeds of Polylepis australis exhibited a great variation in terms of mass and percent seed germination among individual trees and among geographical regions. The results of logistic regression showed that germination probability was highly correlated with seed mass. However, the explained deviance significantly increased by including the region, the woodland fragment and especially the individual tree in addition to seed mass in the regression models. We conclude that selecting seeds on the basis of mass is an appropriate way to enhance germination prospects for reforestation projects. However, no absolute mass values are applicable in this context as the highest germination probabilities were reached at varying seed mass values depending on geographical region, woodland fragment or individual tree. We suggest collecting the relatively heaviest available seeds, even though the absolute seed mass may be low.     

Effects of seed mass and emergence time on seedling performance in Castanopsis chinensis

Seed mass and emergence time may influence fitness of plants. The experiments were conducted to investigate the effects of seed mass and emergence time on the performance of seedlings of Castanopsis chinensis, a large evergreen tree species with limited tolerance of shade. The treatment consisted of three light regimes: 100%, 15% and 2% of full sunlight. Germination rate and germination time showed a significant correlation with seed mass. Germination rate differed among the three light regimes. Early-emerging large-seeded seedlings in 100% light produced the heaviest seedlings, while those resulting from smaller late-emerging seeds and grown under 2% light regime produced the lightest seedlings. Relative growth rate (RGR) decreased with seed mass in all three light regimes, and seedlings of C. chinensis have a higher RGR in high and intermediate light levels compared to low light. In contrast, the effect of emergence time on RGR was not significant. The growth of C. chinensis seedlings were significantly influenced by seed size, emergence time, and light conditions. For each month, the mean height of seedlings was significantly greatest for large-seeded seedlings and significantly lowest for small-seeded ones, irrespective of emergence time and light conditions. Regeneration success of C. chinensis appears to be regulated by the interactive effect of seed mass, emergence time and light regime.     

Seed Development, Maturation and Storage Behaviour of Mimusops elengi L.

Mass maturity (end of the seed-filling phase) occurred at about 72 days after flowering (DAF) in developing seeds of Mimusops elengi, at which time seed moisture content had declined to about 55%. The onset of ability to germinate was detected at 56 DAF and seeds showed 98% germination by 84 DAF. Tolerance of desiccation to 10% moisture content was first detected at 70 DAF and was maximal by 84 DAF. Delaying collection by a further 14 days to 98 DAF, when fruits began to be shed, reduced seed viability, particularly for seeds first dried to 10% moisture content. Hence the best time for seed collection appears to be about 14 days before fruits shed. In a separate investigation with six different seed lots, desiccation below about 8–12% moisture content reduced viability (considerably in some lots). The viability of dry seeds (below about 10% moisture content) stored hermetically was reduced at cool temperatures (5 °C and below), and none survived storage at sub-zero temperatures. The results suggest that Mimusops elengi shows intermediate seed storage behaviour and that the optimal hermetic seed storage environment is about 10% moisture content at 10 °C, while short-term, moist, aerated storage at high (40%) moisture content is also feasible.     

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.