Seed dormancy

Egamberdieva D.
Department of Biotechnology, National University of Uzbekistan, Vuzgorodok, Tashkent, 100174, Uzbekistan, e-mail: [email protected]

The action of phytohormone producing bacteria and plant growth regulators on germination and seedling growth of wheat under saline conditions were studied. Seed dormancy enforced by salinity (100 mM NaCl) was substantially alleviated and the germination was promoted by gibberelin, auxin, zeatin and ethephon from 54 to 97%. The IAA producing bacterial strains Pseudomonas aureantiaca TSAU22, Pseudomonas extremorientalis TSAU6 and Pseudomonas extremorientalis TSAU20 significantly increased seedling root growth up to 25% in non salinated conditions and up to 52% at 100mM NaCl, compared to control plants. It is concluded that growth regulators considerably alleviated salinity-induced dormancy of wheat seeds. The facts mentioned above make it possible to recommend root colonizing bacteria that produce phytohormone to alleviate salt stress of wheat grown under conditions of soil salinity.

Many species of Western Australian Cyperaceae (sedges) are vital components of the indigenous flora but commonly display low seed set, poor seed quality and intractable seed dormancy. We report the effects of incubation temperature and in vitro growth media on whole seed germination compared with extracted zygotic embryo growth in Tetraria capillaris, T. octandra, Lepidosperma drummondii and L. tenue. No germination was observed from intact whole seeds of all test species regardless of the treatment evaluated. In contrast, excised zygotic embryos of all study species exhibited significant increases in growth when cultured at 15°C compared to embryos incubated at 25°C; however, optimal media for embryo growth were genera specific. Extracted embryos of T. capillaris and T. octandra exhibited maximum percentage growth (30 and 40%, respectively) at 15°C on MS medium with no plant growth regulators required. In the case of L. drummondii and L. tenue 1 lM thidiazuron was a necessary addition to the MS medium resulting in 40 and 77% growth of embryos (at 15°C), respectively. Incubation of extracted embryos at 25°C (regardless of medium treatment) resulted in \10% embryo growth for T. octandra and L. tenue, while the remaining two species (L. drummondii, T. capillaris) showed no embryo growth at 25°C on any medium treatment. Keywords Lepidosperma drummondii Á Lepidosperma tenue Á Temperature Á Tetraria capillaris Á Tetraria octandra Á Seed germination Abbreviations 2,4-D 2,4-Dichlorophenoxyacetic acid. TDZ Thidiazuron K Kinetin (6-furfurylaminopurine) BA 6-Benzylaminopurine MES 2-(N-morpholino) ethanesulfonic acid TTC Triphenyl tetrazolium chloride Ca(OCl) 2 Calcium hypochlorite

This study confirmed the significant role of phenolics in the dormancy of cereal caryopses. Investigations were conducted on two cultivars of wheat (Elena and Alba), rye (Amilo and Dań kowskie Złote), and triticale (Ugo and Bogo), with characteristic deeper or shallow dormancy, respectively. In germination studies, cultivars susceptible to sprouting (Alba, Dańkowskie Złote and Bogo) displayed higher germination percentages than those resistant to sprouting (Elena, Amilo and Ugo). The phenolic acid contents (i.e. free, liberated from soluble esters, and liberated from soluble glycosides) in caryopses were determined by an HPLC method. Caffeic, p-coumaric, ferulic and sinapic acids were the dominant phenolic acids detected. The majority of phenolic acids were found in the form of soluble esters. For all species examined, the levels of phenolic acids liberated from soluble esters and the total phenolic acid contents in caryopses showing shallow dormancy were higher than in those showing deeper dormancy. Slight differences in the UV spectra of extracts of phenolic compounds from caryopses showing shallow or deeper dormancy were noted.

Fire is a key ecological factor affecting plant dynamics. In the last few decades, fire occurrence in the Chaco region has increased noticeably, challenging the adaptive capacity of plants to regenerate after a fire. Broad-leaved forb species have been much less studied than woody and graminoids, although they are an important component of fire dynamics. Here we analysed the germination response to heat shock of 70 and 110°C, smoke and their combination in 10 broad-leaved herbaceous species frequently occurring in the Chaco Serrano of C ordoba province, central Argentina, including five annual (Bidens subalternans, Conyza bonariensis, Schkuhria pinnata, Tagetes minuta and Zinnia peruviana) and five perennial species (Borreria eryngioides, Sida rhombifolia, Sol-idago chilensis, Taraxacum officinale and Verbena litoralis). We also compared the response of annual versus perennial species. Six species had highest germination when treated with heat and smoke combined, whereas two had lowest germination under this treatment, indicating synergistic and antagonistic interaction of these factors respectively. Most of the species tolerated heat shock (i.e. germination was similar to that in control treatment), whereas others had higher germination in response to heat shock, especially under the moderate 70°C treatment. Germination was higher than control (i.e. no heat and no smoke) after smoke treatment in four species. Perennial species showed higher average germination than annuals in both heat treatments and in the control. Annual species had higher average germination for all treatments involving smoke. The high variability observed at the species level, and the limited number of species studied calls for precaution in interpreting and extrapolating results. Nevertheless, our study shows a general positive response of both perennial and annual species to fire cues, suggesting an advantage of these species for colonizing post-fire environments, and being favoured under scenarios of increasingly frequent low-to-medium intensity fires.

This study examined germination and dormancy in Galeopsis speciosa (Lamiaceae), a common summer annual weed in cold-temperate areas. Seeds collected in southern Sweden were subjected to several experiments. The seeds were dormant at maturity. Seeds sown outdoors after collection produced a small number of seedlings that emerged early in the spring. After long cold stratification or stratification outdoors over two winters, the maximum germination was 40-50%; germination occurring over a wide range of temperatures. Warm stratification preceding cold stratification had no effect on germination, but repeated warm and cold periods seemed to promote germination. Gibberellic acid (GA) stimulated germination, but full germination was only achieved after more than 2 months of incuba-tion at the most suitable temperature regime tested. Excised embryos grew and developed into normal seedlings. With these results, the species does not fit into the currently used system for seed dormancy classifications. The response to GA and the growth of excised embryos indicate non-deep or intermediate physiological dormancy, but dormancy alleviation by stratification was not in line with the guiding principles for these classifications. Galeopsis speciosa has a strong dormancy that is sufficiently alleviated during the winter to allow germination of only part of a seed batch each year; hence a stepwise germination pattern occurs over a period of several years.

By selecting for germinating seeds in the progeny of mutagen-treated non-germinating gibberellin responsive dwarf mutants of the ga-1 locus in Arabidopsis thaliana, germinating lines (revertants) could be isolated. About half of the revertants were homozygous recessive for a gene (aba), which probably regulates the presence of abscisic acid (ABA). Arguments for the function of this gene were obtained from lines homozygous recessive for this locus only, obtained by selection from the F2 progeny of revertant X wild-type crosses. These lines are characterized by a reduced seed dormancy, symptoms of withering, increased transpiration and a lowered ABA content in developing and ripe seeds and leaves.

Since Prosopis ferox seeds have a hard coat, scarification is needed in order to liberate seeds from their physical dormancy. We analysed the effect of mechanical and chemical scarification agents, and assessed whether the passage through goat and donkey digestive tracts is a scarifying mechanism. We found that the best germination rates are obtained with mechanical treatment, and that the biological treatments had very low germination rates. With subsequent mechanical scarification, seeds from the biological treatments that did not germinate had high germination rates, showing that the seeds are viable but still dormant. This confirm that the passage through digestive animal tracts does not brake physical dormancy, but act as a mechanism of seed liberation from their indehiscent fruit.

Seed dormancy allows seeds to overcome periods that are unfavourable for seedling established and is therefore important for plant ecology and agriculture. Several processes are known to be involved in the induction of dormancy and in the switch from the dormant to the germinating state. The role of plant hormones, the different tissues and genes involved, including newly identified genes in dormancy and germination are described in this chapter, as well as the use transcriptome, proteome and metabolome analyses to study these mechanistically not well understood processes.

We investigated the germination requirements of the species Stachys germanica L. subsp. bithynica (Boiss.) Bhattacharjee (Lamiaceae). We studied the effects of scarification, short-time moist chilling (+4 • C) for 15 and 30 days, and various doses of gibberellic acid (GA 3 ; 0, 100, 150 and 250 ppm), Kinetin (KIN; 50 ppm) and a combination of 250 ppm GA 3 and 50 ppm KIN. The hormone and moist chilling treatments were carried out under both continuous darkness (20 • C) and photoperiodic (20/10 • C; 12/12 h, respectively) conditions. Seeds failed to germinate in response to short-time moist chilling treatments with distilled water under both continuous darkness and photoperiodic conditions. Seeds were found to have dormancy. Treatments with GA 3 or a combination of GA 3 and KIN were successful at breaking seed dormancy. A maximum of 37% of the seeds germinated after GA 3 application in all series. When only KIN was applied at a 50 ppm concentration, germination (12%) was found only with moist chilling for 30 days under continuous darkness. The highest germination rates were found in seeds treated with combination of 250 ppm GA 3 and 50 ppm KIN. In the combination treatments, while the moist chilling treatments for 15 days resulted in 68 and 73% germination, respectively, these rates were up to 95% in the moist chilling treatments for 30 days under continuous darkness and photoperiodic conditions. Mean germination time (MGT) in GA 3 and KIN combinations was lower than in other treatments. Scarification with 80% sulphuric acid did not promote germination. The characteristics of physiological dormancy of S. germanica ssp. bithynica seeds are consistent with conditions of existence in the in alpine habitat of this species.

Church forests are sanctuaries for different organisms, ranging from microbes to large animals, which have almost disappeared in most parts of northern Ethiopia. Despite the actual and potential significance of these forests, studies and documented information on their bio-physical features and socio-economic setting are either scanty or totally lacking. A study was, therefore, carried out in seven of these church forests, namely Hiruy, Zahara, Gibtsawit, Gelawdiwos, Dengolt, Debresena and Ascha with the objective of assessing the composition, densities and spatial heterogeneity of soil seed banks. The number of viable seeds in the soil samples, from both germination and sieving, corresponded to a seed bank density down to 9 cm in the soil of 7594 seeds m À2 at Ascha, 2064 seeds m À2 at Debresena, 4208 seeds m À2 at Dengolt, 3158 seeds m À2 at Gelawdiwos, 2754 seeds m À2 at Gibtsawit, 2759 seeds m À2 at Hiruy, and 1909 seeds m À2 at Zahra. The total number of species recorded was 50, representing at least 22 plant families, in the seven church forests, of which 13 were recorded from Ascha, 29 from Debresena, 26 from Dengolt, 19 from Gibtsawit, 22 from Gelawdiwos, 20 from Hiruy and 21 from Zahra. There was a significant difference in seed densities and number of species recovered from the soil seed banks of the seven church forests. Ascha had a significantly higher seed bank density than all other church forests. Dengolt exhibited a significantly higher number of species compared with other church forests. Of the identified species recorded from the seven church forests, 83% were herbs, 11% trees and 6% shrubs. Our results revealed that church forests accumulate large quantities of persistent seeds of herbaceous species in the soil while only five (6%) of the 91 woody species recorded in the standing vegetation of the seven church forests were represented in the soil seed banks. The fact that most of the dominant tree species do not accumulate seeds in the soil suggests that their regeneration from seeds would be prevented by removal of mature individuals in the standing vegetation. The results also provided further evidences that consolidate the conclusions of previous studies, i.e. the future existence of the woody flora characteristic of dry Afromontane areas in Ethiopia depends on the conservation and sustainable utilization of the few remnant natural forests.

Seed dormancy in wild cucurbit species very often interferes with the results of routine germination tests conducted by genebanks. Seed coat impermeability to water causes physical dormancy in Momordica cochinchinensis. To ensure conservation of rare and important germplasm, it is important to determine the most suitable means of overcoming physical dormancy which can promote rapid and uniform germination, freshly harvested, dried seeds of M. cochinchinensis were subjected to different dormancy breaking treatments. Removal of the entire seed coat increased germination from 0% (control) to 89%. This increase may be due to the removal of the restriction of water entry by the seed coat into the seed. Chemical scarification with concentrated sulphuric acid and hot water treatment were less effective in promoting germination.

Till today chilli seeds are separated manually and there is no specific machine designed to separate seed from its pulp. The manual process is carried out by hammering chilli fruits with wooden stick, separating the husk using hand separator. This manual method is quite tiresome mainly due to the inhalation of fine particles of chilli fruits by labours. Its pungency results in continuous sneezing and irritation for labours. Hence, it is necessary to eliminate laborious work and time consumption. The automated process of chilli seed extraction will be the better solution for this problem, which helps farmers. This automated method can also be adopted by food industries for large scale extraction of chilli seed, as well.

Berdasarkan tingkat kadar air di dalam benih terdapat dua tipe benih yakni benih ortodoks dan benih rekalsitran. Benih ortodoks adalah benih yang dapat disimpan lama dengan kadar air dapat diturunkan sampai di bawah 10%, dan dapat disimpan pada suhu dan kelembapan rendah. Benih rekalsitran yaitu benih yang tidak dapat disimpan dalam waktu lama, tidak tahan atau mati jika disimpan pada suhu dingin, dan tidak tahan disimpan bila kadar airnya diturunkan sampai di bawah kadar air kritis. Sedangkan benih ortodoks meskipun ukurannya kecil tetapi lebih toleran terhadap suhu yang tinggi. Berdasarkan hal tersebut maka perlu dipelajari bagaimana benih ortodoks dan rekalsitran dapat berkecambah pada penurunan kadar air benih.

1. Recent models on bet-hedging germination in annual plants assume a negative relationship between the proportion of offspring that germinate and the quality of the maternal environment. An increase in the proportion of seeds remaining dormant in the next year, when produced in seasons with high reproduction may result from selection that avoids overcrowding in the following year. 2. We present the first empirical test of this prediction by utilizing a field experiment in Israel which manipulated the entire maternal environment. We subjected semi-arid and Mediterranean annual plant communities to different rainfall treatments: control, reduced and increased rainfall. We then related maternal environment quality to offspring germination fractions for three focal species in two consecutive seasons. 3. There was a negative relationship between the quality of the maternal environment and offspring germination fraction in four out of twelve cases. The negative relationship was stronger for the least competitive species and in the environment with high competition intensity, supporting the role of competition for the observed pattern. 4. Our results suggest that competition with all neighbours is more likely to explain the pattern than sib competition. 5. Synthesis. Our findings provide the first experimental evidence of a highly reliable cue (productivity of maternal environment) that allows for plants to respond to their future biotic environment. There is an urgent need for testing predictions of theoretical models in natural populations and for incorporating the role of density dependence in studies of bet-hedging germination.

The germination rate in the nursery of Pomaderris hamiltonii and P. kumeraho has been observed to be low. Poor germination for a number of species can be due to a range of seed dormancy mechanisms. Five different dormancy-breaking treatments were trialled. Scarification using boiling water and sulphuric acid significantly improved germination in both species (for P. hamiltonii the germination percentages were 9.3 for the control, 14 for boiling water, and 32.6 for acid; for P. kumeraho the germination percentages were 3.4 for the control, 27.3 for boiling water, and 59.3 for acid), by breaking the impervious coat. The most successful treatments achieved 97% germination (acid plus warmth during germination) for P. kumeraho and 50% germination (boiling water plus warmth during germination) for P. hamiltonii. Smoke exposure followed by pre-sowing heat significantly (P < 0.011) improved germination for P. hamiltonii, but not for P. kumeraho, suggesting different dormancy-breaking stimuli. The response of both species to treatments which break physical dormancy may indicate an ecological role for high heat events such as fire.

Sudah banyak upaya manusia yang dilakukan dalam penjagaan benih agar
tetap memiliki tingkat kelangsungan hidup atau viabilitas yang tinggi dari
berbagai macam gangguan lingkungan. Salah satu yang menjadi perhatian dalam
penjagaan benih adalah kemasan. Sifat dari kemasan tersebut haruslah
mendukung kelangsungan hidup benih, yakni dari sisi ketahanan terhadap panas,
permukaan yang halus, kuat terhadap tekanan dari luar, pori yang kecil, tingkat
elastisitas dan keempukan yang tinggi dan kuat terhadap senyawa-senyawa korosi
lainnya. Perlu diperhatikan pula keekonomisan dari bahan dasar kemasan.
Globalisasi yang menuntut kuantitas transfer produk yang tinggi juga menuntut
perusahaan pengelola benih untuk menjaga kualitas benih tersebut selama proses
ekspor-impor. Sehingga diperlukannya suatu penggantian bahan kemasan yang
lebih tepat dibandingkan bahan yang telah ada sebelumnya yaitu stainless steel.
Karet reklim diduga dapat menggantikan peran dari kemasan berbahan
stainless steel. Karena karet reklim sendiri berasal dari proses daur ulang materi
karet alami ataupun sintesis, berbeda dengan material stainless steel yang memang
material proses pabrikasi non-recycle. Sehingga ekonomi hijau dari perusahaan
pengguna karet reklim dapat dilaksanakan. Ekonomi hijau yang terdiri atas aspek
ekosistem, biomassa, energi dan materi harus mulai diterapkan sejak dini karena
keadaan bumi yang saat ini tengah terancam secara menyeluruh. Menyeluruh di
sini baik dari segi geografi ataupun demografi karena pada intinya ekonomi hijau
bertujuan untuk kesejahteraan rakyat yang kedua aspek tersebut dapat saling
bersangkutan satu sama lain.

A protocol for micropropagation of Arbutus andrachne from seeds was developed. Results indicated that none of the seeds cultured on Murashige and Skoog (MS) medium, with or without plant growth regulators (PGRs), germinated. Seeds soaked in 250 mg l -1 gibberellic acid (GA 3 ) at 4°C for 3 days, then cultured on water-agar medium containing 2.0 mg l -1 GA 3 exhibited 80-100% germination and developed into usable seedlings. Shoot proliferation was tested on MS or B5 medium containing different concentrations of cytokinin. No shoot proliferation was observed on PGR-free medium. Proliferation was more successful on MS than on B5 medium. On both media, the most successful proliferation was obtained using zeatin as a cytokinin type. Rooting was tested on MS medium containing different concentrations of auxin. Rooting failed on PGR-free medium and on medium containing indole-3acetic acid (IAA), 0.25 or 0.5 mg l -1 indole-3-butyric acid (IBA), or 0.25, 0.5 or 2.0 mg l -1 a-naphthaleneacetic acid (NAA). Rooting (40%) was most successful with 1.0 mg l -1 NAA. Rooted plantlets exhibited 80% survival in all mixtures of peatmoss and perlite, and acclimatized plants were successfully grown in the greenhouse. Quantitative analysis of arbutin performed on in vivo and in vitro leaves using high-performance liquid chromatography (HPLC) revealed that in vivo leaves contained higher arbutin content (0.3-0.81% w/w) than in vitro leaves (0.09% w/w). The highest yield of arbutin in vivo was detected in leaves collected in August, and the lowest yield in leaves collected in December.

Predispersal seed predation may have implications for plant population dynamics and the evolution of plant traits, but assessing the level of seed predation for an individual plant is not always straightforward. Seeds of Lotus corniculatus (Fabaceae) are often only partially eaten by a weevil seed predator, Apion loti. Samples of these seeds were tested for viability and subsequent seedling vigour. A large proportion of these damaged seeds were viable, and the resulting seedlings almost as vigorous as those from undamaged seeds. The ubiquity of these findings, and their ecological significance, is discussed.(Received January 31 1996)(Accepted February 28 1996)

Breaking physical dormancy in some forest seeds is a challenge for scientists and forest managers to obtain a homogeneous germination for larger seed samples. The role played by the seed coat in seed dormancy of six trees with great interest in agroforestry (Robinia pseudoacacia, Leucaena leucocephala, Erythrostemon gilliesii, Styphnolobium japonicum, Acacia dealbata and Brachychiton populneus) was tested by the effects of the pretreatment and its duration on the performance of seed germination, by considering the final germination percentage (FGP) and the mean germination time (MGT). These parameters are estimated at various times of incubation (5, 10 and 15 days) in Petri dishes and stored in darkness at (25 ± 2°C). The pretreatment consists of an immersion of seeds in concentrated sulphuric acid during 30, 60 and 90 minutes. Sowing without pretreatment (control) revealed no germination induction for B. populneus and A. dealbata, except for R. pseudoacacia, L. leucocephala and S. japonica where the germination does not exceed 12% for all the experience duration. Generally, pretreatments were very useful to improve seed germination. The time of immersion into sulphuric acid significantly affected (P < 0.0001) the FGP and the MGT in all studied species. A duration of 30 minutes of soaking was adequate to give a very high rate of germination for L. leucocephala, E. gilliesii, S. japonica and A. dealbata with respective FGP of 100%, 95%, 100% and 82,5%. However, an extended duration of pretreatment of 60 minutes was necessary for a maximal germination for R. pseudoacacia and B. populneus with FGP of 85% and 100%, respectively. A prolonged duration of 90 minutes of presowing was very fatal for L. leucocephala, A. dealbata and B. populneus. An excellent germinative strength is characterized by a higher FGP and a reduced MGT.

The present work demonstrates the effects of moist cold stratification on seed dormancy breaking in Hawthorn (Crataegus monogyna Jacq.). We also examined the fruit and seed morphology. Mature and ripe fruits were collected, the pulp removed and the seeds (stones) left in the sun to dry for three days. Four temperature regimes viz. 4°C, 6.5°C (natural conditions where the fruits were harvested), 10°C and 20°C were used for stimulating seed germination under total darkness. For each treatment, there were four replicates with 50 seeds incubated in a plastic container between two layers of moist sand at 15%. At the end of the experiment, non-germinating seeds were tested for viability using Tetrazolium chloride (TZ). After 4 months, the final germination (FGP) was expressed as a percentage of the total number of seeds in each treatment. The fruits of Hawthorn were 14.9 ± 0.73 mm long and 15.1 ± 0.84 mm in diameter and weigh 2.05 ± 0.28 g. The seeds were 8.29 ± 0.43 mm long and 6.75 ± 0.39 mm in diameter and weigh (0.25 ± 0.04) g. The thousand-fruit weight was 2,000 g and of the thousand-seeds weight was 280 g. The statistical analysis indicated significant effect (p < 0.0001) of treatment on seed germination. Dormancy in this species was broken most effectively by cold stratification at 4°C and under natural conditions with 76% and 67.5% of FGP, respectively. Most of the nongerminated seeds of C. monogyna were viable (dormant) as judged by TZ.

Seeds of many tree-species possess a hard seed coat which is impervious to water. These seeds often take a long time to germinate, resulting in heterogeneity and a delay in seedlings development which is an inconvenience for reforestation success. The aim of the present work was to determine the possibilities to improve the germination of five leguminous trees of the genus Acacia that have been recorded in the arid and the desert region of Algeria using sulphuric acid. A duration of 30 min of immersion in sulphuric acid improved the seed germination up to 97.5% and 99% for A. albida and A. laeta, respectively. Increasing the time of immersion (from 30 to 90 min) improved the germination percentages for A. ehrenbergiana and A. seyal seeds to 92.5% and 93.7%, respectively. Increasing this duration to 120 min had a positive effect on A. tortilis seed germination, improving the final germination rate up to 97%. Understanding of seed germination requirements is very important for regeneration and successful tree establishment in forest nurseries as well as for direct plantation in arid and semi-arid lands.

Acacia niloticaest un ligneux fourrager de la famille des Fabaceae (légumineuses). Cet arbre est d'une grande importance agro-forestière, sylvo-pastorale et nutritionnelle dans les régions arides et semi-arides où le couvert végétal ne cesse de reculer. La première cause est le manque de projets de reboisement. En outre, chez les légumineuses, la dormance tégumentaire (vernalisation) et le réchauffement climatique limitent la germination et l'établissement d'une population végétale importante. Le taux de germination dans la nature n'est maintenant que de 5 à 10% selon les services forestiers. L'effet d'un prétraitement chimique pour améliorer la germination a été étudié en analysant 3 paramètres (cinétique de germination ; TMG : temps moyen de germination en jours et ITG : indice du taux de germination) après 4 temps d'incubation (4, 8, 12 et 16 jours) en boîte de Pétri. Le prétraitement consistait en l'immersion des graines dans de l'acide sulfurique concentré (98%) pendant 7 durées : 0 (témoin), 20, 40, 60, 80, 100 et 120 minutes. Chez toutes les graines d'A. nilotica prétraitées dans cette étude, la durée croissante d'immersion dans l'acide sulfurique a amélioré significativement (p < 0,001) la germination en réduisant le TMG et en augmentant l'ITG. La meilleure germination a atteint un taux de 95%, avec une valeur de TMG réduite (1 jour) et une valeur d'ITG élevée (47,3±2,6) pour une immersion de 100 min dans l'acide sulfurique. Par contre, l'immersion de 120 min a réduit l'ITG à (26,5±1,9). Un tel prétraitement de 100 min est donc recommandé pour augmenter le taux de germination des acacias implantés par les services forestiers en Algérie. Abstract Acacia nilotica is a ligneous forage tree of the family of Fabaceae (Legumes). This tree has a great agro-forester, sylvo-pastoral and nutritional importance in the arid and semi-arid regions where the plants cover is in a permanent reduction. The first cause is the lack of reforestation project. In addition, the stage of germination for the legume trees meets the problem of the integumentary dormancy (vernalization) and the global warming which

Aims: Seed dormancy has been an impeding factor in seedling recruitment. In this study we
examined the performance of Faidherbia albida (Delile) A. Chev. seeds when exposed to the hot
water + nicking pre-sowing treatment by evaluating the Cumulative Germination Percentage (CGP),
Germination Velocities (GV) and Survival Percentages (SP).
Place and Duration of Study: This study was carried out in the shade house of the Department of
Botany and Plant Physiology, Faculty of Science, University of Buea between November 2014 and
December 2014.
Methodology: One hundred and eighty viable seeds were exposed to the hot water, nicking, hot
water + nicking combination and control treatments, respectively, in germination boxes watered (8
litres) once a week for the duration of the experiment (40 days).
Results: We found significant differences between the type of pre-sowing treatment and resulting
Daily Germination Percentages (DGP) (χ2 = 261.299, P <.001). The highest CGP (74.4%), GV (16)
and SP (93.3%) were obtained using the nicking treatment with the hot water + nicking combination treatment performance as CGP (56.1%), GV (13) and SP (63.4%) and the control, interestingly,
produced the second best performance CGP (60.6%). The lowest CGP (51.1%) and GV (6) were
obtained with the hot water treatment (51.1%).
Conclusion: Combining the two pre-sowing treatments does not positively influence germination.
Nicking is the best pre-sowing treatment method that should be preferred and adopted in the
propagation of F. albida.

Seeds of forty species of medicinal plants produced in the Medicinal Plant Garden of the Faculty of Agriculture; Ferdowsi University of Mashhad, Iran were obtained to assess their germination. Germination tests were performed in H 2 O and then dormancy breaking treatments (removing mucilage and seed coat, scarification, pre-chilling, GA 3 and KNO 3) applied on the species which showed germination below 70% in H 2 O. Seeds of 17 species (i.e. Linum usitatissamum and Amaranthus annus) had high germination (over 70%) in H 2 O. Dormancy breaking treatments were effective on 13 species (i.e. Ocimum basalicum and Echinacea purpurea) out of 23 species.

Requirements for germination and establishment of mycorrhiza Hanne N. Rasmnssen Rasmussen, H. N. 1992. Seed dormancy patterns in Epipactis palustris (Orchidaceae): Requirements for germination and establishment of mycorrhiza. -Physiol. Plant. 86: 161-167.

Cycling of physically dormant (PY) seeds between states insensitive and sensitive to dormancy-breaking factors in the environment has recently been demonstrated in Fabaceae and Convolvulaceae, and it may be a common phenomenon in seeds with water-impermeable seed coats. In contrast to seeds of many species with physiological dormancy (PD), those with PY cannot cycle between dormancy and non-dormancy (ND). In this paper, we evaluate the role of sensitivity cycling in controlling the timing of germination of seeds with PY in nature, and show that sensitivity cycling in seeds with PY serves the same ecological role as dormancy cycling in seeds with PD. Thus, sensitivity cycling in seeds with PYensures that germination in nature occurs only at (a) time(s) of the year when environmental conditions for growth are, and are likely to remain, suitable long enough for the plant to complete its life cycle or to form a perennating structure. Further, we describe the experimental procedures necessary to determine whether sensitivity cycling is occurring, and discuss briefly the possible relevance of sensitivity cycling to dormancy classification.

Seagrasses have received considerable attention over the past 2 decades because of the multiple ecological roles they play in estuarine and coastal ecosystems and concerns over worldwide losses of seagrass habitat due to direct and indirect human impacts. Restoration and conservation efforts are underway in some areas of the world, but progress may be limited by the paucity of information on the role of seeds in bed dynamics. Although flowering occurs in most of the 58 seagrass species, seed germination data exist for only 19 of the 42 species that have some period of dormancy, with only 93 published references to field and/or laboratory studies. This review addresses critical issues in conservation and restoration of seagrasses involving seed dormancy (e.g. environmental vs physiological), existence and type of seed bank (transient or persistent), and factors influencing seed germination (e.g. salinity, temperature, light). Results of many earlier published studies relating seed germination to various environmental factors may need re-examination given more recent published data which show a confounding influence of oxygen level on the germination process. We highlight the importance of conducting ecologically meaningful germination studies, including germination experiments conducted in sediments. We also identify questions for future research that may figure prominently in landscape level questions regarding protected marine or estuarine reserves, habitat fragmentation, and restoration.

Although seeds have been the subject of extensive studies for many years, their seed coats are just beginning to be examined from the perspective of molecular genetics and control of development. The seed coat plays a vital role in the life cycle of plants by controlling the development of the embryo and determining seed dormancy and germination. Within the seed coat are a number of unique tissues that undergo differentiation to serve specific functions in the seed. A large number of genes are known to be specifically expressed within the seed coat tissues; however, very few of them are understood functionally. The seed coat synthesizes a wide range of novel compounds that may serve the plant in diverse ways, including defense and control of development. Many of the compounds are sources of industrial products and are components of food and feeds. The use of seed coat biotechnology to enhance seed quality and yield, or to generate novel components has not been exploited, largely because of lack of knowledge of the genetic systems that govern seed coat development and composition. In this review, we will examine the recent advances in seed coat biology from the perspective of structure, composition and molecular genetics. We will consider the diverse avenues that are possible for seed coat biotechnology in the future. This review will focus principally on the seed coats of the Brassicaceae and Fabaceae as they allow us to merge the areas of molecular biology, physiology and structure to gain a perspective on the possibilities for seed coat modifications in the future.

In a ®eld experiment, watermelons (cv.``Sugar Baby'') were grown in the Newe Ya'ar Research Center (northern Israel). Fruits were harvested 21, 28, 35, 42 and 49 days past anthesis (DPA) and seeds were fermented or not fermented in the extraction procedure. After washing, the seeds were dried either in ambient air or at 40, 20 or 10 8C, to form four replicates of 40 different seed lots. Germinability (percentage and rate of germination) was examined during 10 years of storage at 10 8C and 45% RH.

Indigofera glandulosa Wendl., (Barbada) belongs to the family Leguminosae, subfamily-Papilionoidae and tribe Indigoferae is widely distributed as weed in India, Indonesia and North Australia. It is an annual herb or sub-shrub growing along roadside and open grassland areas. The plant produce seeds rich in valuable food ingredients such as proteins, carbohydrates, essential amino acids and vitamins. The plant is described as nourishing food for human beings and is believed to possess the qualities of a tonic in Indian medicine. It is highly palatable forage legume; green plants are generally appreciated by domestic animals. Environmentally, it is utilized for the nitrogen enrichment in degraded soil, as the roots produce nodules fixing atmospheric nitrogen. It can be grown in dry regions, therefore appears to drought resistant and at low cost. The plant species remains unexploited although it has high forage and nutritious value. The meagre information on I. glandulosa lead us to explore this neglected and underutilized species to utilize it as food for human beings, forage for animals and for nitrogen enrichment of the soil. The seed viability and seed germination data revealed seed dormancy associated with the hard and impermeable seed coat and it could be overcome by treating the seeds with concentrated sulphuric acid for 10-15 min thus improving the seed germination percentage up to 75%. The result of the present investigation provides preliminary information on agronomical and morphological traits related to yield and biomass production of I. glandulosa from its natural habitat. In addition the detailed survey about taxonomic characters, distribution, cultivation and utilization of I. glandulosa has been documented. Keywords Forage plant Á Indigofera glandulosa Á Neglected and underutilized species Á Nitrogen fixation Á Nutritious food

Convolvulaceae is the most advanced plant family (asterid clade) that produces seeds with physical dormancy (water-impermeable seed coat). There are several different opinions about the nature of the specialized structure (&#39;water gap&#39;) in the seed coat through which water initially enters seeds of Convolvulaceae, but none of them has been documented clearly. The primary aim of the study was to identify the water gap in seeds of Ipomoea lacunosa (Convolvulaceae) and to describe its morphology, anatomy and function. Light microscopy, scanning electron microscopy, tissue-sectioning, dye-tracking and blocking experiments were used to describe the morphology, anatomy and function of the water gap in seeds of I. lacunosa. Dormancy-breaking treatments caused slits to form around the two bulges on the seed coat adjacent to the hilum, and dye entered the seed only via the disrupted bulges. Bulge anatomy differs from that of the rest of the seed coat. Sclereid cells of the bulges are ...

In this study, we investigated the effect of light regimen (white light vs. darkness) on the germination of 12 species of the Echinopsis genus (tribe Trichocereeae, Cactaceae). This genus presents a variety of growth forms and relatively small and uniform seed size. These traits allowed us to test, within the same linage and removing seed mass effect, the hypothesis that the germination response to light (indifferent to light or positive photoblastic) is related to growth form. Our results reject this hypothesis since no seeds germinated in darkness, so all of the species can be classified as being positively photoblastic. The proportion of seed germination with white light was significantly different among cactus growth forms. Columnar cacti (arborescent, creeping and short) showed a greater proportion of seed germination than barrel and globose cacti. The germination rate differed among growth forms and species. At constant temperatures, creeping columnar cacti presented a significantly higher germination rate than the other growth forms. With alternating temperatures, columnar cacti showed higher germination rates than the other growth forms. The low proportion of seeds that germinated for some species indicates that they show seed dormancy. Our results suggest that germination responses to light in the cactus family could be related to seed mass and phylogenetic constraints.

Studies of genome expression in Arabidopsis have provided important new information about mechanisms controlling germination and suggest new avenues to explore. Unexpectedly, changes in transcription and protein metabolism were observed in the ‘dry’ 1 quiescent seed state, suggesting that careful controls are required for seed expression-profiling experiments. Changes in the transcriptome following seed imbibition suggest a dynamic relationship between RNAs ‘stored’ from seed maturation, and synthesis of new RNAs related to post-imbibition germinating- or dormant-seed states. Recent post-genomics approaches suggest that RNA translation or post-translation are the major levels of control for germination completion and that transcriptome changes might reflect alteration in dormancy status or enhancement of germination vigour and effects on post-germination functions that relate to seedling growth.

In order to recognize, identify and determine the relative dominance of weed species distributed in wheat fields of Tabriz county-Iran, a total 118 weed species belonging to 24 plant family were observed. Ermopyrum bonaepartis (Spreng.) Nevski, Acroptilon repens (L.) DC., Cardria Draba (L.) Desv., Chenopodium album L., Polygonum aviculare L., and Convolvulus arvensis L. with relative dominance (RD) index equal 30, 20.2, 19.1, 18.1, 17.5, and 17.5 respectively were dominant weed species. Poaceae, Brassicaceae and Asteraceae with Family Dominance Index (FDI) equal 63.08, 45.54, and 45.46 were dominant plant families observed in wheat fields. A. repens (L.) DC., C. Draba (L.) Desv., C. album L., P. aviculare L., and C. arvensis L. with frequency level 82.2, 75.6, 62.2, 64.4 and 64.4 respectively were the main disturbing weeds prior to harvesting wheat in Tabriz county. Eighty-nine percent of weeds were below average, because they founded below thirty percent of wheat fields. However, nearly four percent of weeds were assertive and distributed in more than sixty percent of wheat fields. So, the revised management procedure about these weeds in different districts of this county is very important.