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1.
V. Sivakumar R. Anandalakshmi R. R. Warrier B. G. Singh Mulualem Tigabu P. C. Odén 《New Forests》2007,34(3):281-291
The germination of Casuarina equisetifolia Forst seed lots is low (40–50%) even when freshly collected. This study aimed at upgrading the germination performance by
removing non-germinable seeds using petroleum flotation technique. Seeds collected from 19 individual trees in seedling seed
orchards in India were assessed using X-ray to determine the proportion of different seed lot fractions. The feasibility of
petroleum ether as a separation medium was tested. Morphological characters of floating and sunken seeds were further studied
using image analysis technique to examine their effects on the separation efficiency. The X-ray analysis revealed a large
quantity of shrivelled, empty and insect-damaged seeds, altogether accounting 50%, which were the causes of low percentage
germination of un-graded seed lots (48%). Petroleum flotation resulted in 90% germination in the sunken fraction and 4% in
the floating fraction. The separation was distinct for most seed lots, except few seed lots that had relatively low germination
in the sunken fractions and more than 10% germination in the floating fractions. As a whole, petroleum flotation appears to
be a feasible technique to upgrade the germination of C. equisetifolia seed lots, and its efficacy is influenced by wing surface area, seed density and wing quotient of filled and empty seeds. 相似文献
2.
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. 相似文献
3.
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. 相似文献
4.
Benigno González-Rivas Mulualem Tigabu Guillermo Castro-Marín Per Christer Odén 《林业研究》2009,20(2):99-104
A study was conducted to examine the germination requirements of Cedrela odorata, Guaiacum sanctum and Calycophyllum candidissimum seeds, and the effect of light intensity on survival and growth of C. Odorata and G. Sanctum seedlings planted on open, partially-open and beneath the canopy of a dry forest in Nicaragua. The results show that germination of C. Candidissimum seeds was significantly higher in light than darkness at constant temperatures ranging from 20–35oC. Both C. Odorata and G. Sanctum seeds germinated in light and darkness to a varying extent, and the optimal germination temperature was around 20-25oC. Alternating temperature regimes did not improve germination. Survival of G. Sanctum seedlings was 70% beneath the canopy and 80% in the open, and its relative growth rate in collar diameter was 1.88 mm/month in the open and 1.42 mm/month in the understory. Survival was generally poor for C. Odorata, particularly in the understory. We concluded that light is an absolute requirement for the germination of C. Candidissimum seeds while germination of C. Odorata and G. Sanctum seeds are more sensitive to temperature. Owing to its high survival rate on open site, G. Sanctum could serve as a candidate species for reforestation of degraded sites. 相似文献
5.
尼加拉瓜废弃农田次生演替后的土壤种子库 总被引：3，自引：0，他引：3
Benigno González-Rivas Mulualem Tigabu Guillermo Castro-Marín Per Christer Odén Benigno González-Rivas Mulualem Tigabu Guillermo Castro-Marín Per Christer Odén 《林业研究》2009,20(4):349-354
定量分析了被废弃4年、9年和14年的农田地上派生的次生林土壤中种子组成和密度,从而检测在次生林演替形成过程中,土壤种子库是否能随着植物种群的集成而集成。分别在废弃了4年、9年和14年的农田地里（15cm×15cm样方、9cm土层深）,掘取了18,37和48份土壤样品。在废弃了4,9和14年的农田地上,分别发现了3,5和9个物种。在这些不同的生命形态中,在9年和14年的迹地上,土壤种子树木占主要成分,分别为60%和33%,而4年废弃迹地主要被非木本植物所占领。三块废弃地里,4年废弃迹地植物种子的总数为327粒,相应可发育的种子密度为141粒/m2,14年废弃迹地种子的总数为46粒,相应的可发育种子的密度为26粒/m^2,指明种子数、种子密度随废弃地龄成下降趋势。在9年和14年龄废弃地上,土壤种子植物种类与立地木本植物种类的相似度较低,而4年龄地上两者比较则完全不同。我们认为：土壤种子库的物种构成是在次生演替过程中逐渐形成的,但是,所获得的总体种子密度太低,仅仅依赖于这些种子来实现树木自然再生是不可靠的。为了加快这些废弃地次生林的恢复,既要依靠自然集成的土壤种子库,还需要通过直播、所需物种的强化种植和设定人工生长环境以利于种子传播。 相似文献
6.
Abolfazl Daneshvar Mulualem Tigabu Asaddollah Karimidoost Per Christer Odén 《林业研究》2017,28(2):231-239
The germination of freshly collected Juniperus polycarpos (K. Koch) seeds is very low and attributed to the large proportion of nonviable seeds in the seed lots. Thus, the aim of this study was to improve seed lot quality by removing nonviable seeds using two flotation techniques: incubation-drying-separation (IDS) and modified specific gravity (MSG) separation. We examined different IDS conditions (the specific incubation time, subsequent drying time and sorting media) for effectively sorting out nonviable seeds; and tested the feasibility of modified SG separation, which involved soaking seeds in water for a certain period before sorting in different concentrations of sucrose solution. Viable seeds were expected to absorb and metabolically bind more water during soaking than dead seeds could, and hence be sorted effectively depending on the viscosity of the sucrose solution. The viability of the seeds that floated or sank was determined in a topographical tetrazolium chloride (TTC) test. For the IDS trial, 7 days incubation followed by 9 h of drying and sedimentation in pure water or 200 g·L?1 sucrose solution identified, respectively, 75 and 82 % of the seeds as viable (sunken) seeds. For the MSG trail, 77 % viable seeds were recovered in the sunken fraction when seeds were soaked for 48 h then immediately sorted in 600 g·L?1 sucrose solution. In both cases, the loss of viable seeds in the discarded floating fraction was only 4 %. The results demonstrate that both IDS and MSG separation techniques substantially improved seed lot viability, but MSG separation is simple and needs no modern seed handling facility, and its efficacy relies on seed mass (due to the initial soaking) and the specific density and viscosity of the flotation medium. 相似文献
7.
Sustainable forest production demands a continuous supply of high quality seeds for the production of seedlings in the nursery or for direct sowing. Here, we demonstrated the potential of near infrared spectroscopy as a rapid technique to discriminate viable and empty seeds of Pinus patula Schiede & Deppe. Near infrared spectra were collected from single seeds in transmittance and reflectance modes. To discriminate viable and empty seeds, multivariate classification models were developed with partial least squares (PLS) regression using the digitized spectra as a regressor and a y-vector of artificial values (1 for viable and –1 for empty seeds) as a regressand. Viable and empty seeds were perfectly distinguished by PLS models computed on full and selected transmittance spectroscopy data, while those derived from full NIR reflectance spectra recognized 96 % of viable and 88 % of empty seeds. Analyses made on selected NIR reflectance spectra improved the classification rate of empty seeds to 100%. Difference spectra and PLS weights indicated that the origin of spectral differences between viable and empty seeds was attributed to differences in fatty acids and proteins that were totally absent in empty seeds. The result shows the prospect of developing rapid filter-based sorting equipment that can easily be automated. 相似文献
8.
V. Sivakumar R. Anandalakshmi R. R. Warrier M. Tigabu P. C. Odén S. N. Vijayachandran S. Geetha B. G. Singh 《New Forests》2006,32(2):121-131
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. 相似文献
9.
Schelin Maria Tigabu Mulualem Eriksson Ingalill Sawadogo Louis Christer Odén Per 《New Forests》2004,27(3):251-267
Predispersal seed predation among individual Acacia macrostachya trees over two sites in Burkina Faso was assessed. In addition, the effects of seed predation on seed viability; germination responses to scarification (mechanical, hot water at 60, 70 and 80°C, and sulphuric acid for 10, 20 and 30 min) and dry heat (at 60, 70 and 80°C for 15, 30 and 60 min each) treatments were investigated under laboratory conditions. The results indicated a large difference in predation intensity among individual trees, as well as between sites. Predispersal predation significantly decreased seed germination, particularly when the number of insect larvae per seed increased. Scarified and unscarified seeds germinated equally well, except for hot water treatments of high temperature. This indicates lack of physical dormancy and dispersed seeds can readily germinate provided that conditions for germination are conducive. Seeds exposed to dry heat treatments also germinated close to 97% under low intensity and short exposure times. This suggests that fire, under natural condition, plays a key role in triggering germination of A. macrostachya seeds. 相似文献
10.
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. 相似文献