Provenance and pretreatment effect on seed germination of six provenances of <Emphasis Type="Italic">Faidherbia albida</Emphasis> (Delile) A. Chev

A nursery experiment was conducted to determine the effects of seed pretreatment methods on the germination of Faidherbia albida at ICRAF, Nairobi from six provenances consisting of Awassa, Taveta, Lake Koka, Maseno, Chinzombo and Wagingombe. Seeds were subjected to five pretreatment methods namely nicking, soaking in acid, hot water, cold water and control. Germination percentages (GP), mean germination time (MGT) and germination index (GI) were calculated and the data was subjected to ANOVA. The study revealed significant (p ≤ 0.05) differences in seed treatments among provenances in all studied parameters. Highest germination among pretreatments in Awassa (99 %) and Wagingombe (80 %) was observed in nicked seeds, Chinzombo (81 %) in nicked and acid treated seeds, Lake Koka (90 %) in acid treated seeds and Taveta (28 %) and Maseno (64 %) in cold water treated seeds. Nicking gave the highest cumulative GP (69.67) while lowest GP was observed in hot water treated seeds (23.17). Acid treatment exhibited lowest MGT (8.85 days) and highest GI (2.29) while highest MGT (24.35 days) and lowest GI (0.31) were observed in control and hot water treatment respectively. Although acid treatment gave a high GP and lowest MGT and GI, nicking and soaking in cold water for 24 h is being recommended as cheaper and less hazardous pretreatment methods to improve germination in F. albida since sulphuric acid is expensive and requires proper handling techniques. Significant correlation between geo-climatic data and germination parameters of seeds subjected to different pretreatments indicates that provenances are as important as pretreatments in germination of the species.     

The soil seed bank of the threatened plant <Emphasis Type="Italic">Magnolia stellata</Emphasis> is subordinate to the emergence of current-year seedlings

We studied seed bank formation of the threatened star magnolia, Magnolia stellata, to examine the early stage of regeneration. Forty-five seedling plots (2 × 2 m), each including a soil-sampling quadrat (40 × 40 cm), were established randomly under or around the crowns of mature M. stellata trees. Seeds of M. stellata were collected from each quadrat to a depth of 5 cm. Only four seeds of M. stellata were found (0.56 seeds/m²) and all were located under mature crowns. Current-year seedlings were abundant in water channels, on moss, or under mature crowns, suggesting that the seeds may require wet soil conditions for germination. Magnolia stellata seeds show considerable germination below the crowns of mature trees in the year following masting, while some seeds remain dormant in the soil. Considering the soil seed bank and the current-year seedling bank of M. stellata, a frequent supply of seed is essential for the regeneration of this species. Thus, it is important to maintain mature trees in addition to promoting seed production.     

Effects of fire on germination of Pterocarpus angolensis

Pterocarpus angolensis (Fabaceae) is a leguminous tree species of the miombo region of sub-Saharan Africa that is highly prized for its wood value. We use both experimental exposure to fire, as well as classification of field burned seeds, to predict germination rates in seeds from both husked and unhusked fruits. We find that seed germination and seed persistence in unhusked fruits are maximized by moderate exposure to fire. Germinating seeds had heavier fruit and seeds than those that did not. Finally, seeds without husks persisted in the soil yet continued to germinate even after 18 months in wet soil, indicating potentially long soil longevity. Using these results, we support an intermediate fire exposure model wherein repeated moderate exposure to fire enhances the capability of seeds to emerge from fruits. Seeds from unburned and unhusked fruits were never observed to germinate and had poorer soil longevity than those exposed to moderate fire. Similarly, extreme exposure to fire resulted in poor seed germination rates, often as a consequence of direct fire mortality of seeds. We suggest that early burning resulting in cool fires may augment germination and recruitment in wild populations.     

Inhibition by pulp juice and enhancement by ingestion on germination of bird-dispersedPrunus seeds

To evaluate what prevents seed germination and why ingestion by birds enhances germination, we carried out germination experiments using bird-dispersed seeds of twoPrunus species (Prunus sargentii andP. ssiori) in the laboratory. Germination of seeds with following four treatments was compared: “Ingested seeds” excreted after feeding of fruits to birds; “Extracted seeds” deliberately extracted from the fruit pulp; “Juiced seeds” which were supplemented with the juice of the pulp after seeds had been deliberately extracted from the pulp; and “Intact seeds” in untreated whole fruits. Many ingested (27%, 23% inP. sargentii, 18% inP. ssiori) and extracted seeds (24% inP. sargentii, 17% inP. ssiori) germinated, and difference in germination percentages between ingested and extracted seeds were not significant, for eitherPrunus species. The Juiced seeds rarely germinated (2% inP. sargentii, 6% inP. ssiori), and seeds within intact fruits did not germinate. These results suggest that the fruit pulp and the juice of the pulp inhibit germination and the seeds could germinate without ingestion by birds once they had been manually extracted from pulp. Therefore, it is considered that bird ingestion enahnces germination by removing pulp, especially juice of the pulp, in these twoPrunus species.     

Seed bank and regeneration dynamics of <Emphasis Type="Italic">Emmenopterys henryi</Emphasis> population on the western side of Wuyi Mountain,South China

Emmenopterys henryi Oliv. (Rubiaceae) is an endangered tree species that is native to China. The wild populations of E. henryi have declined rapidly because of its poor natural regeneration, but the actual regeneration processes are not yet understood. In field tracking surveys and experiments in the Wuyishan Nature Reserve in Southeast China to determine the most important stage that affects the regeneration process, seed bank characteristics, seed germination, and seedling growth dynamics were studied in the typical habitats of E. henryi, Phyllostachys pubescens and broad-leaved forests. Results showed that in both P. pubescens and broad-leaved forests, more than 70% of the E. henryi seeds were distributed in moss and litter layers, and few were found in the soil beneath them. However, seed germination in the soil layer was significantly higher than in the moss and litter layers. Seed density, overall seed quality, and germination rate in the broad-leaved forest were significantly higher than in P. pubescens forest. Seed germination was highest in the microsites around the edge of the crown projection area of E. henryi mother trees. The order of survival rate of the seedlings on different ground surfaces was soil > moss > litter. In both habitats, the average seed density was 24.9 seeds m^?2, and the total germination rate was less than 3.5‰. However, seedlings developed from only 1% of the germinated seeds, indicating that the seed germination is the most important stage in the natural regeneration of E. henryi.     

Germination traits and adaptive regeneration strategies of the threeCarpinus species

Germination tests in the three sympatricCarpinus species,C. laxiflora, C. tshonoskii, andC. cordata, were carried out to clarify their germination traits in relation to the regeneration strategies. Seeds did not germinate just after ripening under any conditions in the three species. After one or two rounds of cold stratification, however,C. laxiflora andC. tshonoskii showed high germination percentages (>80%) at alternating temperature in light whileC. cordata did not. After a long-term (10 months) cold stratification, about 100% ofC. cordata seeds germinated, although about 70% of these seeds were in “conditional dormancy” and cannot germinate in the dark. Seed germination in the threeCarpinus species was enhanced by alternating temperature, but not by light exposure. These results suggest that the seeds of the three species are dormant just after ripening and the dormancy is broken by cold stratification. with intra-generic variations in the breakage. Germination traits in each species may be closely related to the regeneration strategy;C. cordata maintains a persistent seed bank with seed dormancy and regenerates after disturbances as a seed bank strategist, whereas the other two species germinate in the next spring after seedfall and regenerate depending either on existing disturbed-sites or sites of recent disturbances after seedling establishment as a seed rain strategist (C. tschonoskii) or seedling bank strategist (C. laxiflora). This study was supported by grants from the Ministry of Agriculture, Forestry and Fisheries (BCP-97-III-A).     

Pre-sowing treatments for improved germination and growth of two rare native species of Bangladesh

Pre-sowing treatments are expected to increase seed germination. This evaluates response to pre-sowing treatments and the growth performance of two native and rare tree species, Garuga pinnata Roxb. and Vitex glabrata R. Br. The hard seed coats were treated by rubbing with sand paper, nail clipping, and immersion in water and acid (H₂SO₄). Results indicate that G. pinnata showed a 90% germination rate and 30% germination energy when seed coats were nicked with a nail clipper. Rubbing with sand paper was the best pre-sowing treatment for V. glabrata, resulting a 80% germination rate and 30% germination energy. G. pinnata and V. glabrata seedlings from seeds soaked 24 h in water resulted in maximum heights and collar diameters. These were significantly higher (at p < 0.05) than those of other treatments. The results indicate that scarification or nicking of seeds may have some negative impacts on seedling growth. Therefore, it is difficult to recommend a pre-sowing treatment of seeds for achieving both maximum germination and good early seedling growth.     

Effect of harvest date,drying, short-term storage and freezing after chilling on the germination of rowan seeds

The effects of seed pretreatment and harvest date on the germination of European rowan (Sorbus aucuparia L) seeds were examined. In one experiment, seeds were subjected to drying, storage, soaking, warm and chilling treatments after harvesting in mid- and late August. In another experiment, fully imbibed (FI) seeds were given warm treatment for six weeks and then various durations of chilling (4?±?1°C) for up to 24 weeks. Thereafter, the seeds were adjusted to target moisture content of 35% and 30% or remained in the FI state and were then subjected to either subsequent chilling or freezing (?3°C) for up to 32 weeks. The treated seeds were allowed to germinate at a constant 15°C with 8 hours of lighting per day. Treatment effects were generally consistent for each harvest date. Seeds did not germinate unless they were chilled and germination rates were low unless the seeds were soaked. Warm treatment applied before chilling appeared to induce dormancy. The effect of storage varied with harvest date and storage treatment, with germination being highest for seeds harvested in late August. Mild freezing of ≥16 weeks duration following 16–24 weeks initial chilling resulted in >80% germination, more than could be achieved using chilling alone.     

Seed dormancy in bay laurel (Laurus nobilis L.)

The germination of bay laurel (Laurus nobilis L.) seeds wasexamined both in the laboratory and in the field during twoyears. Seeds were collected from a grove in a garden in the townof Drama, Northern Greece, by mid November in the first year andby late November in the second year. The seeds with and withoutpericarp were given a warm-moist (20 °C day/12 °C night) oncold-moist (4±1 °C) treatment in peat or sand. After treatment theseeds were placed in the germinator along with controls. Thegermination of seeds with and without pericarp was alsoinvestigated in the field (late fall sowing). It was found thatthe pericarp caused dormancy. In seeds without pericarp,cold-moist and warm-moist stratification both proved to besuccessful in breaking embryo dormancy (100% and 96% successrespectively). The required stratification duration was 50 daysfor the warm-moist and 60 days for the cold-moist treatments.During the cold-moist stratification no germination was observed.On the other hand, seeds started to germinate during thewarm-moist stratification by about the 50th day. In the fallsowing germination was 20% for seeds with pericarp and 41% for seeds without pericarp. Drying bay laurel seeds caused areduction of the seed germination.     

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.     

Germination and early seedling growth of <Emphasis Type="Italic">Pinus densata</Emphasis> Mast. provenances

We studied seed germination and early seedling growth of Pinus densata to explore the range of variability within the species and to inform afforestation practices. Phenotypes were evaluated at a forest tree nursery under conditions that support Pinus yunnanensis, one of the presumed parental species of P. densata. Seeds were collected from 20 open-pollinated trees within each of eight autochthonous populations representing the natural distribution of P. densata in China to assess variation in germination traits and early seedling growth, and to examine the relationships among these traits. Results showed that seeds from all populations germinated and seedlings established successfully. There were significant differences among populations in 13 of 14 traits evaluated. Seed germination and early seedling growth were strongly related to seed size and seed weight. Bigger seeds germinated earlier and faster than small seeds, and seedling size was positively correlated with seed size. Some germination traits were strongly and significantly correlated with climatic variables associated with the provenance of the studied populations. Based on these observations, we conclude there were large, significant, and biologically important differences among P. densata populations in seed germination and seedling growth traits. The observed variability probably reflects a high degree of adaptive differentiation among populations that is likely to be relevant for future afforestation.     

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.     

Germination of <Emphasis Type="Italic">Juniperus procera</Emphasis> seeds in response to stratification and smoke treatments,and detection of insect-damaged seeds with VIS + NIR spectroscopy

Seeds of Juniperus procera collected from five provenances across its geographic range in Ethiopia were subjected to cold-moist stratification at 5°C or 10°C for 6–12 weeks. The effect of aqueous smoke solution in overcoming the light requirement for germination, and the potential of visible (VIS) and near infrared reflectance (NIR) spectroscopy for sorting sound and insect-damaged seeds were also investigated. Highly significant differences in germination were detected among provenances (P < 0.0001) and stratification periods (P < 0.0001), but not between temperature regimes (P=0.111). Seeds from the south and southeast distribution ranges had higher percentage germination after 6 weeks of stratification than seeds collected from north, northwest and central ranges of distribution. The smoke treatment did not affect germination regardless of whether the seeds were exposed to light. Exposure to light increased germination capacity three fold. Sound and damaged seeds were distinguished with 90% accuracy using VIS + NIR spectroscopy. It can be concluded that dormancy in juniper seeds varies with provenances, and cold stratification for 6 weeks alleviates dormancy in some seed lots. Tentatively, smoke treatment seems ineffective in overcoming photo-dormancy in juniper seeds. VIS + NIR spectroscopy has demonstrated a great potential for sorting damaged seeds, thereby upgrading seed lot purity.     

果翅、盐分及干旱胁迫对白梭梭种子萌发的影响

从生态学角度研究了果翅、温度、盐分和干旱胁迫等因素对白梭梭种子萌发的影响,结果表明:去除种翅能显著促进种子萌发,无翅种子比有翅种子萌发速率快(P<0.05),提早1 d达最高萌发率。变温条件有利于种子萌发。白梭梭种了萌发率随着NaCl浓度增加而降低,但在0.9 mol.L-1的浓度中仍有2%的种子萌发;将未萌发的种子移至蒸馏水中后,部分种子可以萌发,在较低浓度盐溶液(0.05～0.6 mol.L-1)中培养的种子其萌发恢复率低,而高浓度(0.7～1.0 mol.L-1)中培养的种子其萌发恢复率高。在较低程度的干旱胁迫下,白梭梭种子迅速萌发,而较高程度的干旱胁迫下种子萌发受抑制,在PEG浓度50%时不萌发;同等干旱胁迫程度下,无翅种子比有翅种子萌发率高。     

Breaking seed dormancy in European rowan seeds and its implications for regeneration

The effects of the presence of a medium, seed moisture content, warm and chilling treatments on the germination response of European rowan (Sorbus aucuparia L.) seeds of Irish origin were investigated with the aim of reducing precocious (or premature) germination and maximising germination after pretreatment. After adjusting seed moisture content, seeds of two lots were subjected to warm treatment for 0–6 weeks followed by 0–50 weeks of chilling. The seeds then were allowed to germinate at a constant 15 °C with 8 h lighting per day or 20 (dark)/30 °C (light). Some seeds were treated in the fully imbibed (FI) state in a medium (standard operational treatment). Seed lot effects were evident, but treatment effects were consistent in each lot. Warm treatment greatly increased germination and reduced precocious germination. The presence of a medium was not required to achieve high germination and seed moisture content close to the FI state was needed to maximise germination. Climate change may reduce the ability of this species to regenerate naturally, favouring other species that require less chilling.     

Identification of pests and assessment of their damage on <Emphasis Type="Italic">Carapa procera</Emphasis> and <Emphasis Type="Italic">Lophira lanceolata</Emphasis> in Burkina Faso,West Africa

Nontimber forest products are a source of income for women in rural African communities. However, these products are frequently damaged by insect pests. The present study investigates the diversity and damage rates of insect pests that attack Carapa procera seeds and Lophira lanceolata fruits. The experiment was set up in western Burkina Faso and, for C. carapa, consisted of pests collected from seeds that had fallen to the ground and from stockpiled seeds. For L. lanceolata, pests were collected from fruits on the trees, and on the ground. The collected samples were sent to the laboratory to estimate the proportion of damaged seeds/fruits and rear the insects. The results showed that Ephestia spp., Tribolium castaneum, Oryzeaphilus spp., and Tenebroides mauritanicus were the pests of Carapa procera seeds and Lophira lanceolata fruits. Ephestia spp. was recorded as the main pest of both C. procera and L. lanceolata, whereas T. castaneum was only detected from seeds of L. lanceolata. For C. procera, the stocks were the most infested (29 %) by Ephestia spp. The infestation rate of fruits of L. lanceolata by Ephestia spp. on trees (31.42 ± 3.75 %) was less than the rate of fruits by T. castaneum on the ground (44.00 ± 3.5 %). The different body sizes of Ephestia spp. may indicate the occurrence of two putative species, one from C. procera and another one from L. lanceolata. This work provides important information that could contribute to the setting up of a local-scale sustainable management framework for oil tree pests in Burkina Faso and surrounding countries.     

Variation in germination character of Robinia pseudoacacia L. (Leguminosae) seeds at individual tree level

To demonstrate the seed dormancy and germination characters of Robinia pseudoacacia L., an exotic tall tree species in Japan, we applied scarification, cold stratification, diurnal thermal regime, heat shock, and/or winter weathering treatments to the seeds. These characters differed markedly among three seed sources (Trees K, B, and I). Scarification revealed that most seeds from Tree K showed physical dormancy, whereas those from Tree B had no physical dormancy. The seeds from Tree I showed weak physical dormancy so that the seeds eventually germinate without any treatments as time goes by. The physical dormancy in Tree K was broken by a long, high heat shock treatment. The results imply that seeds from Tree K respond to fire in natural conditions. Seeds from Tree I responded to a wide range of thermal regimes, except for long, high heat shock. In contrast, most seeds from Tree B absorbed water during cold stratification and some germinated. However, many seeds from Tree B died in the soil during the winter, presumably because of microbial and fungal infections. Seeds from Trees I and B acquired physical dormancy by weathering during the winter, implying that seedpods that remain in the crown function as an aerial seed bank. R. pseudoacacia may be able to produce various levels in dormancy with respect to the winter condition.     

Breaking Seed Dormancy of Laurel (Laurus nobilis L.)

Laurel (Laurus nobilis L.) seeds were collected from the west part of Turkey in the fall of 2002. Seeds with pericarp (+) or without pericarp (−) were treated with 1000 mg/l, 2000 mg/l and 3000 mg/l GA₃ concentrations, cold stratified at +4 ± 1°C for 25 and 50 days, punctured and seed coat removed to overcome and assess the mechanism of laurel seed dormancy. A period of 50 days cold stratification and removing seed coat significantly increased germination rate to 55% ± 1.91 (Mean ± SE) and 85% ± 3.00, respectively. None of the seeds with pericarp germinated regardless of treatment they underwent. Results suggested that seed dormancy was mainly due to pericarp and perhaps inhibitors linked to seed coat.     

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).     

Nursery soil cover influences germination of Thujopsis dolabrata var. hondai seeds

We examined the influence of nursery soil cover on germination of Thujopsis dolabrata var. hondai. Seeds were sown under seeding bed conditions: (1) nursery soil (andosol) without soil cover, (2) Kanuma pumice without soil cover, (3) nursery soil with nursery soil cover, and (4) nursery soil with sterilized sand cover. Germination percentages were compared between these conditions. The germination percentage (8.8%) at 10 weeks after sowing under condition 3 was significantly lower than under conditions 1, 2, and 4 (56.8%, 52.0%, and 47.2%, respectively). Of the nongerminated seeds under condition 3, 75.0% were decayed and several fungi were isolated from decayed seeds. An inoculation test of isolated fungi Cylindrocarpon tenue, Cylindrocarpon sp., Fusarium oxysporum, and Botrytis sp. to seeds showed that these fungi caused seed decay. Our results indicated that nursery soil cover may not be suitable for T. dolabrata var. hondai seeds sown in nursery soil because of seed decay by pathogens.