ECOPHYSIOLOGY OF SEED GERMINATION IN ENDEMIC LABIATES OF CRETE

1995 ◽  
Vol 43 (3) ◽  
pp. 227-237 ◽  
Author(s):  
Costas A. Thanos ◽  
Maria A. Doussi
Keyword(s):  
Seed Germination ◽  
Slow Rate ◽  
Narrow Range ◽  
Seedling Emergence ◽  
Red Light ◽  
Significant Inhibition ◽  
Light Conditions ◽  
Salvia Fruticosa ◽  
Intermediate Response ◽  
Alpine Distribution

Ecophysiological aspects of seed germination were investigated in four aromatic labiate plants of Crete Origanum dictamnus (dittany), Sideritis syriaca L. ssp. syriaca (Cretan mountain tea), Salvia pomifera L. ssp. pomifera (gall-bearing sage), and Salvia fruticosa (three-lobed sage). Experiments were performed both at constant temperatures and darkness as well as under temperature and light conditions simulating those prevailing in nature during the main germination periods (i.e., start and middle of the rainy season, November and February-March, respectively). In three out of the four species, no particular dormancy was revealed and germination occurred rather promptly, although in a rather narrow range of cool temperatures and at a relatively slow rate; both characteristics determine and/or support an early, autumn seed germination and seedling establishment. In the fourth plant, Sideritis syriaca, germination was manifested at relatively warm temperatures and at a considerably faster rate, in accordance with its alpine distribution favoring spring seedling emergence and establishment. All four species tested showed an intermediate response towards light, as a result of their intermediate levels of active phytochrome maintained in darkness. Therefore seed germination was partially manifested in darkness but it was significantly enhanced (particularly at suboptimal temperatures) by white or red light; on the other hand, illumination with far-red light (simulating light conditions under a canopy) resulted in significant inhibition compared to dark controls.

scholarly journals Ecophysiology of seed germination in Mediterranean geophytes. 1. Muscari spp

2002 ◽  
Vol 12 (3) ◽  
pp. 193-201 ◽  
Author(s):  
Maria A. Doussi ◽  
Costas A. Thanos
Keyword(s):  
Seed Germination ◽  
White Light ◽  
Mediterranean Climate ◽  
Germination Rate ◽  
Red Light ◽  
Rainfall Regime ◽  
Light Conditions ◽  
Rainy Period ◽  
Germination Characteristics ◽  
The Mediterranean

Ecophysiological aspects of seed germination were investigated in four Mediterranean geophytes of the genus Muscari (Liliaceae): M. comosum (tassel hyacinth), M. neglectum (common grape hyacinth), M. commutatum and M. weissii. Experiments were performed at constant temperatures in the dark and under temperature and light conditions simulating those prevailing in nature during November–January, i.e. well into the rainy season of the Mediterranean climate. In all species, no primary dormancy was revealed, and germination occurred in a rather narrow range of cool temperatures (optimum at 10 or 15°C) and at a remarkably slow rate; both germination characteristics seem to be associated with autumn/winter seed germination and seedling establishment. Such a postulated strategy is ecologically advantageous within an unpredictable rainfall regime, known to prevail during the start of the rainy period of the Mediterranean climate. This strategy may also explain the spread of germination of M. comosum seeds over two consecutive years, observed by Theophrastus. Far-red light, simulating light conditions under a dense canopy, resulted in only a slight delay of germination compared to dark controls. Diurnal white light, qualitatively simulating natural daylight, caused a significant decrease of the germination rate in all four species studied. Moreover, white light was found to suppress considerably final seed germination (photoinhibition) in M. weissii and M. neglectum; in the latter species, prolonged imbibition under white light also led to the induction of secondary dormancy.

Seed stratification and germination strategy in the Mediterranean pines Pinus brutia and P. halepensis

1995 ◽  
Vol 5 (3) ◽  
pp. 151-160 ◽  
Author(s):  
Antonis Skordilis ◽  
Costas A. Thanos
Keyword(s):  
Seed Germination ◽  
Germination Rate ◽  
Seedling Emergence ◽  
Red Light ◽  
Pinus Brutia ◽  
Temperature Range ◽  
Promotive Effect ◽  
Germination Behaviour ◽  
Mediterranean Pine ◽  
Of Greece

AbstractThe ecophysiology of germination in Pinus brutia and P. halepensis was studied in seeds collected from different areas of Greece. In regard to the temperature range of germination, both P. halepensis and the southern provenance (Lasithi, Crete) of the East Mediterranean pine, P. brutia, follow a typical Mediterranean pattern. In the latter species, dramatic differences in the degree of dormancy were noted among the three provenances investigated; in all seed lots however, 20°C was clearly the optimal temperature for germination. Stratification resulted in a considerable promotion of P. brutia seed germination. Nevertheless, the inductive effect of stratification was shown to differ among the three provenances used, escalating from a simple increase of germination rate (in the southern seed lot from Lasithi, Crete) through a broadening of the temperature range of germination (in the intermediate lot from Thasos Island) to, finally, a dramatic release from a particularly deep dormancy (in the northern lot from Soufli). These deeply dormant seeds of the latter provenance displayed an absolute stratification requirement; prolonged illumination or seed coat scarification could not substitute for the promotive effect of prechilling. A considerable interaction between far-red light and stratification was revealed in the dormant seeds of P. brutia (Soufli provenance); far-red pulses during stratification could either cancel or diminish the germination promotion induced by low temperatures. The differences observed in the germination behaviour among the various P. brutia provenances may be attributed to a variable ecophysiological strategy in regard to the temporal pattern of seedling emergence and establishment. According to the variants of this strategy, seed germination is timed to occur during either spring (in regions with relatively cold and moist climates), or autumn and early winter (in southern, mild and dry areas) or both (in intermediate conditions).

Water constraints on the photoinduction of weed seed germination during tillage

2000 ◽  
Vol 27 (5) ◽  
pp. 463 ◽  
Author(s):  
Javier F. Botto ◽  
Ana L. Scopel ◽  
Rodolfo A. Sánchez
Keyword(s):  
Seed Germination ◽  
Soil Water ◽  
Seedling Emergence ◽  
Red Light ◽  
Soil Water Potential ◽  
Laboratory Data ◽  
Soil Disturbance ◽  
Light Signal ◽  
Weed Species ◽  
Night Time

Germination of light-requiring seeds may be induced by very brief exposure to sunlight during soil disturbance through the very-low fluence (VLF) mode of phytochrome action. We studied the effect of soil water availability after cultivation on the photoinduction of seed germination in two important weed species, Datura ferox andChenopodium album. In daily-irrigated plots, seedling density was 1- to 4-fold greater in plots cultivated during daytime than in those tilled at night. In contrast, when plots were not irrigated soon after tillage and rainfall was excluded, no significant differences were observed between seed germination in daytime vs night-time cultivated plots, although seedling emergence in night-time cultivated plots was higher than in non-cultivated controls. The average critical value of soil water potential required for the expression of VLF-induced germination was higher than –0.5 MPa (at 3-cm depth during the 6 d following cultivation). Dark germination was less sensitive to decreasing soil moisture than light-induced seed germination. The promotive effect of the light signal perceived by the seeds during daytime cultivation is maintained for several days (ca 6) in drying soil, even though laboratory data suggest that the far-red-light absorbing form of the phytochrome inducing the VLF photoresponse is unstable, disappearing in less than 24 h. These results reveal the complexity of interactions between the light signal and other environmental factors that control seed germination under natural conditions.

Seed Germination Ecology of Purple-Leaf Button Weed (Borreria ocymoides) and Indian Heliotrope (Heliotropium indicum): Two Common Weeds of Rain-Fed Rice

Weed Science ◽  
2008 ◽  
Vol 56 (5) ◽  
pp. 670-675 ◽  
Author(s):  
Bhagirath S. Chauhan ◽  
David E. Johnson
Keyword(s):  
Seed Germination ◽  
Seedling Emergence ◽  
Soil Layer ◽  
Soil Surface ◽  
Burial Depth ◽  
Light Conditions ◽  
Weed Species ◽  
Heliotropium Indicum ◽  
High Level ◽  
Purple Leaf

Purple-leaf button weed and Indian heliotrope are widespread and common weed species of rain-fed rice in many tropical countries. The influence of various environmental factors on seed germination of these species was studied. Seeds of both species germinated at a range of alternating temperatures (25/15, 30/20, and 35/25 C day/night). Germination of purple-leaf button weed was similar among light conditions after an after-ripening period of 3 mo, whereas germination of Indian heliotrope was always greater in light. Seed germination of both species was not affected by a high level of salt and a range of pH between 5 and 9, but was sensitive to high degrees of water stress. Seed burial strongly inhibited germination and emergence of these species. Seedling emergence of purple-leaf button weed (82 to 86%) and Indian heliotrope (70%) was optimal when seeds were sown in the top 0.2-cm soil layer. A burial depth of 2 cm completely inhibited emergence of Indian heliotrope, whereas, for purple-leaf button weed, this depth was 5 cm. Most of these seeds germinated, however, when brought to the soil surface. The information gained from this study would help in predicting the potential of these species for spreading into new areas, and could contribute to their control.

scholarly journals MOTHER-OF-FT-AND-TFL1 represses seed germination under far-red light by modulating phytohormone responses in Arabidopsis thaliana

2018 ◽  
Vol 115 (33) ◽  
pp. 8442-8447 ◽  
Author(s):  
Fabián E. Vaistij ◽  
Thiago Barros-Galvão ◽  
Adama F. Cole ◽  
Alison D. Gilday ◽  
Zhesi He ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Seed Germination ◽  
Signaling Pathways ◽  
Red Light ◽  
Dependent Manner ◽  
Light Conditions ◽  
Ga Signaling ◽  
Expression Of Genes ◽  
Genes Encoding

Seed germination in many plant species is triggered by sunlight, which is rich in the red (R) wavelength and repressed by under-the-canopy light rich in far red (FR). R:FR ratios are sensed by phytochromes to regulate levels of gibberellins (GAs) and abscisic acid (ABA), which induce and inhibit germination respectively. In this study we have discovered that, under FR light conditions, germination is repressed by MOTHER-OF-FT-AND-TFL1 (MFT) through the regulation of the ABA and GA signaling pathways. We also show that MFT gene expression is tightly regulated by light quality. Previous work has shown that under FR light conditions the transcription factor PHYOCHROME-INTERACTING-FACTOR1 (PIF1) accumulates and promotes expression of SOMNUS (SOM) that, in turn, leads to increased ABA and decreased GA levels. PIF1 also promotes expression of genes encoding ABA-INSENSITIVE5 (ABI5) and DELLA growth-repressor proteins, which act in the ABA and GA signaling pathways, respectively. Here we show that MFT gene expression is promoted by FR light through the PIF1/SOM/ABI5/DELLA pathway and is repressed by R light via the transcription factor SPATULA (SPT). Consistent with this, we also show that SPT gene expression is repressed under FR light in a PIF1-dependent manner. Furthermore, transcriptomic analyses presented in this study indicate that MFT exerts its function by promoting expression of known ABA-induced genes and repressing cell wall expansion-related genes.

Soil water thresholds for photoinduction of redroot pigweed germination

Weed Science ◽  
1997 ◽  
Vol 45 (3) ◽  
pp. 414-418 ◽  
Author(s):  
Robert S. Gallagher ◽  
John Cardina
Keyword(s):  
Seed Germination ◽  
Soil Water ◽  
Light Stimulus ◽  
Seedling Emergence ◽  
Red Light ◽  
Soil Disturbance ◽  
Redroot Pigweed ◽  
Seed Population ◽  
Potential Gradients ◽  
Water Contents

Perception of light by phytochrome is a mechanism that triggers weed seed germination in response to soil disturbance. Photoconversion of phytochrome from the red light absorbing form to the active far-red absorbing form depends on hydration of phytochrome. This research was conducted to determine the soil water threshold for the photoinduction of germination by the brief exposure of light that occurs during soil disturbance, and to determine how this threshold is affected by the fluence of the light stimulus and fluence sensitivity of the seed population. Redroot pigweed seedling emergence and germination response to red light (R) was studied for a range of water potentials. Water potential gradients were established by incubating seeds in soils wetted to various water contents, or in polyethylene glycol 8000 (PEG) solutions. After imposing the light treatments, seeds were returned to a fully hydrated state. Seedling emergence in response to R increased as the volumetric water content (θv) of soils increased. At volumetric water contents of 4.0%, R-induced seedling emergence was inhibited 50% compared to photoinduced seedling emergence at the highest soil water contents tested. Attenuation of photoinduction was more pronounced at low vs. high R fluences in freshly imbibed seeds, but was unaffected in seeds that exhibited enhanced fluence sensitivity. In ecosystems where seasonal soil moisture extremes are prevalent, the photoinduction of seed germination may be limited in dry microsites such as surface crusts or under extreme drought conditions.

scholarly journals Cranberry Germination and Emergence Response to Environmental Factors and Seeding Depth

HortScience ◽  
2021 ◽  
pp. 1-8
Author(s):  
Thierry E. Besançon
Keyword(s):  
Water Stress ◽  
Seed Germination ◽  
Seedling Emergence ◽  
Red Light ◽  
Soil Surface ◽  
Average Maximum ◽  
Fruit Productivity ◽  
Diurnal Temperatures ◽  
Residual Herbicide ◽  
Over Time

Cranberry (Vaccinium macrocarpon Ait.) cultivars are clonally propagated. Germination of cranberry seeds produces off-type varieties that are generally characterized by lower fruit productivity and higher vegetative vigor. Over time, the productivity of cranberry beds decreases as off-type frequency increases over time. Improved knowledge of cranberry germination biology would facilitate the use of targeted agronomic practices to reduce the emergence and growth of less productive off-types. The influences of light, temperature regime, pH, and water potential on cranberry seed germination were assessed in a growth chamber, whereas the effect of seeding depth on seedling emergence was evaluated in a greenhouse. Seeds stratified for 6 months at 3 °C were used for these experiments. Cranberry germination was influenced by light quality, with maximum germination reaching 95% after 15 minutes of exposure to red light but decreasing to 89% under far-red light. However, light was not required for inducing germination. Cranberry seeds germinated over a range of alternating diurnal/nocturnal temperatures between 5 and 30 °C, with an average maximum germination of 97% occurring for diurnal temperatures of 20 to 25 °C. The length of emerged seedlings was reduced by an average of 75% for pH 6 to 8 compared with pH 3 to 5. Seedlings that emerged at pH greater than 5 showed increasing chlorotic and necrotic injuries and were not considered viable at pH 7 or 8. Germination at 15 °C was reduced when seeds were subjected to water stress as low as −0.2 MPa, and no germination occurred below −0.4 MPa. Seeds incubated at 25 °C were more tolerant to water stress, with at least 70% maximum germination for osmotic potential (ψS) −0.6 MPa or greater. The average seedling emergence was 91% for seeds left on the soil surface or buried at a maximum depth of 1 cm; however, it was null at a burying depth of 4 cm. These results indicate that germination of cranberry seeds in cultivated beds in the northeastern United States likely occurs during the summer months, when temperatures are optimal and the moisture requirement is supported by irrigation. However, timely application of residual herbicide or sanding (a traditional cranberry agronomic practice) of open areas in cranberry beds could help prevent seed germination and reduce minimizing the onset of off-type varieties.

Germination biology of dimorphic seeds of the annual halophyte common seepweed (Suaeda glauca)

Weed Science ◽  
2019 ◽  
Vol 68 (2) ◽  
pp. 143-150
Author(s):  
Hongfei Wang ◽  
Lin Kong ◽  
Rui Gao ◽  
Buhailiqiemu Abudureheman ◽  
Xinyang Li ◽  
...  
Keyword(s):  
Seed Germination ◽  
Salt Concentration ◽  
Seedling Emergence ◽  
Germination Percentage ◽  
Common Salt ◽  
Light Conditions ◽  
Effective Measure ◽  
Temperature Regimes ◽  
Suaeda Glauca ◽  
Black Seeds

AbstractCommon seepweed [Suaeda glauca (Bunge) Bunge] is a common salt-tolerant weed species distributed across the agricultural regions of northern China. It produces dimorphic seeds with different phenotypic characteristics and seed sizes. However, there is no information regarding the germination biology of these dimorphic seeds. Studies were conducted to evaluate the effects of ecological factors such as temperature, light, pH, osmotic stress, salt concentration, and planting depth on seed germination and seedling emergence. The results showed that brown seeds were nondormant, whereas black seeds had an intermediate physiological dormancy. The germination percentage of brown seeds was more than 80% at all temperature regimes and light conditions, but the optimum germination occurred at the cold thermoperiod of 20/10 C. In contrast, less than 6% of black seeds germinated at all temperature regimes and light conditions. Eight weeks of cold stratification did not break the dormancy of black seeds, whereas low concentrations of gibberellic acid (0.1 and 1.0 mM) significantly increased seed germination. Removal of the testa of black seeds also promoted germination and produced normal seedlings. Brown seeds showed moderate tolerance to salt stress, with 16% germination percentage at a salt concentration of 600 mM NaCl. The germination of brown seeds was 38% at an osmotic potential stress of −0.8 MPa; above that, no germination was obtained. Brown seeds germinated well in a wide pH range (4 to 10), with a germination percentage higher than 95%. Seedling emergence percentage was higher than 90% at burial depths of 0 to 2 cm, while germination percentage severely decreased for brown seeds with burial depths >2 cm, indicating that shallow tillage could be an effective measure to minimize seed germination. Information gathered from this study will help to develop an effective protocols for controlling S. glauca.

African mustard (Brassica tournefortii) germination in southern Australia

Weed Science ◽  
2006 ◽  
Vol 54 (5) ◽  
pp. 891-897 ◽  
Author(s):  
Bhagirath S. Chauhan ◽  
Gurjeet Gill ◽  
Christopher Preston
Keyword(s):  
Seed Germination ◽  
Seedling Emergence ◽  
Potassium Nitrate ◽  
Light Conditions ◽  
Seed Decay ◽  
Brassica Tournefortii ◽  
Dark Conditions ◽  
Lower Temperature ◽  
Mustard Seeds ◽  
Salt And Osmotic Stress

Germination of African mustard seeds collected from southern Australia was not influenced by light conditions at the optimum temperature of 20/12 C. However, seed germination was inhibited by light at the lower temperature (15/9 C). Presence of light increased the sensitivity of seeds to low temperature, as well as salt and osmotic stress. In dark conditions, seed germination was relatively unaffected at a low level of salinity (80 mM NaCl) but decreased even at 10 mM NaCl in light/dark conditions. In the dark, seed germination was unaffected up to an osmotic potential of −0.6 MPa but declined thereafter. Seeds of African mustard germinated over a broad range of pH from 4 to 10. Seed germination was stimulated by potassium nitrate (from 0.005 to 0.04 M) and gibberellic acid (0.001 M). Seedling emergence of African mustard was the greatest (51%) for seeds buried at 1 cm but no seedlings emerged from seeds placed at a depth of 5 cm. At the end of the growing season, seed decay (77 to 87%) and dormant (12 to 18%) components were similar among different seed burial depths. Information gained in this study will be important in developing a better understanding of the requirements for African mustard germination and emergence.

Variable regeneration behaviour of Ulmus davidiana var. Japonica in response to disturbance regime for risk spreading

1997 ◽  
Vol 7 (2) ◽  
pp. 195-207 ◽  
Author(s):  
Kenji Seiwa
Keyword(s):  
Seedling Emergence ◽  
Red Light ◽  
Bare Soil ◽  
Forest Edge ◽  
Light Conditions ◽  
Growth And Survival ◽  
Litter Accumulation ◽  
Ulmus Davidiana ◽  
And Control ◽  
Soil Level

AbstractRecruitment-related traits (development and dispersal of seeds, emergence, leaf dynamics, growth and survival of seedlings) were studied in Japanese elm (Ulmus davidiana var. japonica) in relation to disturbance at the soil level (bare soil, litter and control) or the canopy level (forest edge (FE), small gaps (SG) and forest understorey (FU)), or both, in a riverside forest from 1990 to 1993. Seed germination was also tested in the laboratory. Litter accumulation severely inhibited seedling emergence. Seedling emergence from a single seed rain occurred in summer immediately after seed dissemination and in the following spring. In summer, seedling emergence was higher in FE than in FU. In the following spring more seedlings emerged in FU than in FE and SG, resulting in non-significant differences in the percentage emergence among the three sites in bare soil. Darkness or far-red light induced seed dormancy, but after chilling they started to germinate again under white or red light conditions. These results explained emergence phenology under changing light conditions in the field. In FU, the spring emerging cohort grew and survived better than the summer emerging one. In FE the reverse was true. Japanese elm avoids unfavourable periods by escaping either in time (dormancy) or in space (dispersal). Such traits compensate for late and compressed seed dissemination, and improve seedling growth and survival not only when disturbance occurs at both canopy and soil level (bare soil in FE) but also only at soil level (bare soil in FU), which may occur more frequently in riverside forests.

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