Seed dormancy

Egamberdieva D.
Department of Biotechnology, National University of Uzbekistan, Vuzgorodok, Tashkent, 100174, Uzbekistan, e-mail: egamberdieva@yahoo.com

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.

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.

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.

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.

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.

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.

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 ...

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.