Secondary Dormancy In Seeds Research Articles

Breaking Seed Dormancy during Dry Storage: A Useful Tool or Major Problem for Successful Restoration via Direct Seeding?

To facilitate the restoration of disturbed vegetation, seeds of wild species are collected and held in dry storage, but often there is a shortage of seeds for this purpose. Thus, much research effort is expended to maximize the use of the available seeds and to ensure that they are nondormant when sown. Sowing nondormant (versus dormant) seeds in the field should increase the success of the restoration. Of the various treatments available to break seed dormancy, afterripening, that is, dormancy break during dry storage, is the most cost-effective. Seeds that can undergo afterripening have nondeep physiological dormancy, and this includes members of common families such as Asteraceae and Poaceae. In this review, we consider differences between species in terms of seed moisture content, temperature and time required for afterripening and discuss the conditions in which afterripening is rapid but could lead to seed aging and death if storage is too long. Attention is given to the induction of secondary dormancy in seeds that have become nondormant via afterripening and to the biochemical and molecular changes occurring in seeds during dry storage. Some recommendations are made for managing afterripening so that seeds are nondormant at the time for sowing. The most important recommendation probably is that germination responses of the seeds need to be monitored for germinability/viability during the storage period.

Seed dormancy regulates germination response to smoke and temperature in a rhizomatous evergreen perennial.

Seed dormancy status regulates the response of seeds to environmental cues that can trigger germination. Anigozanthos flavidus (Haemodoraceae) produces seeds with morphophysiological dormancy (MPD) that are known to germinate in response to smoke, but embryo growth dynamics and germination traits in response to temperatures and after-ripening have not been well characterized. Seeds of A. flavidus, after-ripened for 28 months at 15 °C/15 % relative humidity, were incubated on water agar, water agar containing 1 μM karrikinolide (KAR1) or 50 μM glyceronitrile at 5, 10, 15, 20, 25, 20/10 and 25/15 °C for 28 days. After incubation at 5, 10 and 25 °C for 28 days, seeds were transferred to 15 °C for another 28 days. Embryo growth dynamics were tested at 5, 10, 15 and 25 °C. Results demonstrated that fresh seeds of A. flavidus had MPD and the physiological dormancy (PD) component could be broken by either glyceronitrile or dry after-ripening. After-ripened seeds germinated to ≥80 % at 15–20 °C while no additional benefit of germination was observed in the presence of the KAR1 or glyceronitrile. Embryo length significantly increased at 10 °C, and only slightly increased at 5 °C, while growth did not occur at 25 °C. When un-germinated seeds were moved from 5–10 °C to 15 °C for a further 28 days, germination increased from 0 to >80 % in significantly less time indicating that cold stratification may play a key role in the germination process during winter and early spring in A. flavidus. The lower germination (<50 %) of seeds moved from 25 to 15 °C was produced by the induction of secondary dormancy. Induction of secondary dormancy in seeds exposed to warm stratification, a first report for Anigozanthos species, suggests that cycling of PD may be an important mechanism of controlling germination timing in the field.

Environmental conditions and endogenous mechanisms involved in secondary dormancy of seeds

ABSTRACT Secondary dormancy, is defined as the dormancy developing in seeds after harvest or dispersal. Under field conditions secondary dormancy is part of cyclic changes in the level of dormancy that often follow a seasonal pattern. It develops when germination is inhibited, e.g. by burial in soil. Temperature, absence of light or oxygen, presence of volatile or allelopathic inhibitors and moisture conditions are among the factors which may contribute to inhibition of germination and thus to development of dormancy. Decreasing light sensitivity is part of the development of secondary dormancy. It is partly attributed to photo- or dark-reversion of the far-red absorbing form of phytochrome (Pfr), pre-existing in the seeds or newly formed, to Pr. Changing levels of Pfr at its primary site of action, possibly being a membrane, are also held responsible for the decreasing light-sensitivity. Secondary dormancy is not related to a deterioration of the seeds. A specific relationship with any particular metabol...

Identification of Late Embryogenesis Abundant (LEA) protein putative interactors using phage display.

Arabidopsis thaliana seeds without functional SEED MATURATION PROTEIN1 (SMP1), a boiling soluble protein predicted to be of intrinsic disorder, presumed to be a LATE EMBRYOGENESIS ABUNDANT (LEA) family protein based on sequence homology, do not enter secondary dormancy after 3 days at 40 °C. We hypothesized that SMP1 may protect a heat labile protein involved in the promotion of secondary dormancy. Recombinant SMP1 and GmPM28, its soybean (Glycine max), LEA4 homologue, protected the labile GLUCOSE-6-PHOSPHATE DEHYROGENASE enzyme from heat stress, as did a known protectant, Bovine Serum Albumin, whether the LEA protein was in solution or attached to the bottom of microtiter plates. Maintenance of a biological function for both recombinant LEA proteins when immobilized encouraged a biopanning approach to screen for potential protein interactors. Phage display with two Arabidopsis seed, T7 phage, cDNA libraries, normalized for transcripts present in the mature, dehydrated, 12-, 24-, or 36-h imbibed seeds, were used in biopans against recombinant SMP1 and GmPM28. Phage titer increased considerably over four rounds of biopanning for both LEA proteins, but not for BSA, at both 25 and at 41 °C, regardless of the library used. The prevalence of multiple, independent clones encoding portions of specific proteins repeatedly retrieved from different libraries, temperatures and baits, provides evidence suggesting these LEA proteins are discriminating which proteins they protect, a novel finding. The identification of putative LEA-interacting proteins provides targets for reverse genetic approaches to further dissect the induction of secondary dormancy in seeds in response to heat stress.

Secondary Seed Dormancy of Rhododendron catawbiense and Rhododendron maximum

Abstract Seeds of Rhododendron catawbiense Michx. (Catawba rhododendron) and Rhododendron maximum L. (rosebay rhododendron) were germinated at 25C (77F) or an 8/16 hr thermoperiod of 25/15C (77/59F) with constant light after imbibed seeds were maintained in total darkness for 0, 9, 18, 27, 36, 45, 54 or 63 days at the same temperatures. Maintenance of imbibed seeds of R. catawbiense in darkness at 25C (77F) for up to 63 days caused no induction of secondary dormancy while induction occurred for seeds in darkness at 25/15C (77/59F). When imbibed seeds of R. catawbiense were subjected immediately to light following imbibition, 30-day germination at 25C (77F) was 98% compared to 95% for imbibed seeds maintained in darkness for 63 days and then exposed to light. If germinated at 25/15C (77/59F), immediate light exposure resulted in 99% germination which decreased significantly to 76% after 63 days of dark treatment. Seeds of R. maximum maintained in darkness developed secondary dormancy at both temperatures. Thirty day germination of seeds subjected immediately to light following imbibition at 25C (77F) was 82% which decreased to 29% after dark treatment for 9 days. Further reductions in germination continued as the length of dark treatment increased with &amp;lt; 10% germination after maintenance in darkness for 27 days. At 25/15C (77/59F) induction of secondary dormancy was not as dramatic as that at 25C (77F). Without dark treatment, 30-day germination at 25/15C (77/59F) was 99% which decreased significantly to 88% after dark treatment for 18 days. Reductions in germination continued up to 63 days with 67% germination. Partial removal of secondary dormancy in seeds of R. maximum was achieved by subjecting seeds to moist-chilling.

Real-time assessment of seed dormancy and seedling growth for weed management

AbstractComputer software called WeedCast was developed to simulate weed seed dormancy, timing of seedling emergence, and seedling height growth in crop environments in real-time and using actual or forecasted weather data. Weather data include daily rainfall and minimum and maximum air temperatures. Air temperatures are converted to average daily soil temperature at 5-cm soil depth using a series of equations that are specific for soil type, tillage system and previous year's crop-residue type. Daily rainfall and soil temperature estimates are combined to determine soil water potential (in megapascals) at 5-cm depth. Daily estimated soil water potential or soil temperatures are matched to empirically-derived threshold values that induce secondary dormancy in seeds of certain species. Soil growing degree days (GDD), calculated from soil temperatures, are used to project maximum emergence rates of weed seedlings. Emergence ceases on days when soil water potential falls below threshold values specific to each species. GDD based on air temperatures are used to estimate post-emergence seedling height growth. All three types of simulation provide information that allows users to answer important weed management questions in real-time. These types of questions include but are not limited to the following: (1) Are soil-applied treatments necessary? (2) How late can pre-emergence herbicides be applied? (3) When should mechanical control be implemented? (4) When should field-scouting commence and end? (5) When should post-emergence herbicides be applied?

Seed Germination Ecophysiology of Meadow Salsify (Tragopogon pratensis) and Western Salsify (T. dubius)

To understand persistence strategies of meadow and western salsify, ecophysiological characteristics of their seed germination were studied. Anaerobiosis (immersion in deoxygenated water) induced secondary dormancy in seeds of both species. Dormancy could be induced in 86% of meadow salsify seeds and in 65% of western salsify seeds by a 1-d anaerobiosis treatment. The induced dormancy was gradually released during storage of air-dried secondary dormant meadow salsify seeds, and the rate of this release was influenced by storage temperature; 30 C was more effective than 10 or 20 C in releasing secondary dormancy. These results suggest that the two species may rely on induced dormancy as an option in their persistence strategy. The optimum temperature for germination of nondormant seeds of both species was 15 C. Maximum germination percentages for both species were established within 4 to 6 d of incubation at 15 C and within 14 to 28 d of incubation at 25 C. Nondormant seeds did not germinate below 10 or above 30 C. Stratification (at 5 C for 2 to 10 wk) stimulated germination of secondary dormant seeds of meadow salsify. This stratification requirement can be important in preventing germination of dormant salsify seeds in the fall, thereby avoiding high seedling mortality in the winter. Light (red and far-red) had no effect on germination of seeds in secondary dormancy. In a separate study, seeds of both species were planted in pots at depths of 2 to 14 cm and seedling emergence was observed. Maximum emergence occurred when seeds were buried 2 cm deep. Seeds planted 8 cm or deeper germinated but did not emerge.

Effect of Acetone on the Induction and Breakage of Secondary Dormancy in Seeds of Cucumber

The dark-germinating seeds of cucumber (Cucumis sativus L. cv. Saharanpur Long green) developed secondary dormancy when given two brief far-red light (FR) irradiations during a 4 d incubation in osmoticum at 20 °C. Acetone treatment of seeds was found not only to break FR-induced dormancy but also to prevent its development. The progressive effect of increasing the duration of treatment or the concentrations of acetone, as well as an appreciable activity of the latter, irrespective of its application to dry or hydrated seeds, is consistent with the Taylorson hypothesis of anaesthetic action at the membrane level. Contrary to the general consensus that it is only the cells of the embryo which respond to an active dormancy-breaking factor, termination of dormancy as well as prevention of its development by acetone in cucumber seeds was accompanied by a striking change in the permeability of the cell membranes of the perisperm-endosperm envelope enclosing the embryo. This change in the permeability of the cell membranes brought about by acetone appeared to be permanent in nature as it was not affected by hydration or dehydration of the treated seeds.

Induction of secondary dormancy in seeds ofBarbarea strictaandB. vulgarisby chlormequat and daminozide, and its termination by gibberellic acid

SummaryGermination in the laboratory of seeds ofBarbarea strictaandB. vulgariswas inhibited by 20–200 mg l−1chlormequat chloride or daminozide. Seeds treated with chlormequat and then washed with water and kept on moist quartz sand remained dormant for up to 1 year, but dormancy could be broken at any time by treatment with gibberellic acid. Similar results were obtained withCapsella bursa‐pastorisandThlaspi arvense.In contrast, germination of other weed species, such asSpergula arvensisandMatrkaria perforata, took place in the presence of chlormequat and daminozide in concentrations of 5000–10000 mg 1−1. The relevance of the results to the duration of seed dormancy in the soil is discussed.

Ecophysiology of Secondary Dormancy in Seeds of Ambrosia Artemisiifolia

As buried seeds of Ambrosia artemisiifolia came out of primary and secondary dormancy, they showed similar germination responses. In early spring at simulated habitat temperatures, seeds germinated well in light but not in darkness, but they germinated well in darkness at temperatures characteristic of the habitat in late spring and summer. By late spring, seeds had entered secondary dormancy and did not germinate at any temperature in light (14—h daily photoperiod) or darkness. Prolonged exposure to 5°C in darkness did not decrease germination in either light or darkness at a 12—h alternating temperature regime of 30°/15°C, but seeds subsequently kept at 15°/6°C in darkness for 1 mo required light for germination. Seeds then lost the ability to germinate in light as they were exposed sequentially to 20°/10°, 25°C/15°C, and 30°C/15°C in darkness. Thus, upon exposure to the sequence of natural temperature regimes in spring, induction of secondary dormancy of seeds in darkness occurs in two physiological stages. While buried seeds are at low marginal temperatures for germination they lose the ability to germinate in darkness, and then at higher temperatures they lose the ability to germinate in light.

Secondary Dormancy in Seeds: Effects of Substrate Hydration

When hydration of the substrate is low while seeds of Lactuca sativa L. (cv. Grand Rapids) and Phacelia tanacetifolia Benth. are under non-inductive conditions for a sufficient time to induce secondary dormancy, the depth of this dormancy is reduced. It is suggested that a low degree of hydration is suboptimal for the initiation of an inhibition which otherwise would become established under the non-inductive conditions.

Secondary Dormancy in Seeds

Secondary Dormancy in Seeds