Germination and Dormancy of Themeda australis, Danthonia Spp., Stipa bigeniculata and Bothriochloa macra

1976 ◽  
Vol 24 (3) ◽  
pp. 319 ◽  
Author(s):  
MW Hagon
Keyword(s):  
Gibberellic Acid ◽  
Low Temperatures ◽  
Germination Capacity ◽  
Dry Storage ◽  
Temperature Regimes ◽  
Maximum Temperatures

The germination and dormancy of Themeda australis, Danthonia spp., Stipa bigeniculata and Bothriochloa macra were investigated in whole dispersal units or caryopses. Germination of non-dormant units of the four species was not affected by light but was delayed by low temperatures. Such temperature regimes depressed the germination capacity of Themeda while alternating temperatures with a range greater than 10°C depressed the germination of Bothriochloa. The level of germination of Danthonia and Stipa was not affected by any of the temperature regimes used. Dormancy was reduced either by the application of gibberellic acid at concentrations of 100 ppm to 1000 ppm or by stratification. In addition, application of kinetin ( 10 -4M ) or opening the lemma suture broke the dormancy of Stipa dispersal units. The breakdown of dormancy during dry storage was also examined. Temperature alternations with maximum temperatures greater than 40°C reduced the level of dormancy of Themeda and Stipa within 1-2 months.

GERMINATION RESPONSE OF DORMOAT SEEDS TO LOW TEMPERATURE AND GIBBERELLIN

1972 ◽  
Vol 52 (3) ◽  
pp. 295-303 ◽  
Author(s):  
C. J. ANDREWS ◽  
V. D. BURROWS
Keyword(s):  
Abscisic Acid ◽  
Low Temperature ◽  
Gibberellic Acid ◽  
Seed Dormancy ◽  
Avena Sativa ◽  
Low Temperatures ◽  
Dry Storage ◽  
Secondary Dormancy ◽  
Derivatives Of ◽  
Different Levels

Dormoats are derivatives of crosses between Avena sativa L. and A. fatua L., designed to be sown in the fall to germinate the following spring. Strains vary in levels of seed dormancy at harvest and in their rates of after-ripening in dry storage. Germination of the seeds is stimulated by gibberellic acid. Embryos isolated from dormant seeds exhibit no dormancy but their germination is prevented by abscisic acid. Low temperatures (ca. 7 C) stimulate germination to different levels in various strains. Seeds enter a secondary dormancy when they fail to germinate in the imbibed state due to primary domancy. Seeds with secondary dormancy are not stimulated to germinate by low temperatures until partial after-ripening of the seeds in the dry state has occurred, but germination is stimulated by gibberellic acid without after-ripening. Secondary dormancy is proposed as a factor in the maintenance of undergerminated seed in the soil from fall planting into winter.

Seed afterripening and germination photoinhibition in the genusCrocus(Iridaceae)

2015 ◽  
Vol 25 (3) ◽  
pp. 306-320 ◽  
Author(s):  
Evangelia Skourti ◽  
Costas A. Thanos
Keyword(s):  
Seed Germination ◽  
Gibberellic Acid ◽  
Low Temperatures ◽  
Temperate Climate ◽  
Optimal Temperature ◽  
Continuous Darkness ◽  
Dry Storage ◽  
The Mediterranean ◽  
Germination Experiments ◽  
First Time

AbstractMediterranean characteristics are attributed to the genusCrocus, which is inadequately studied in terms of seed germination. An afterripening requirement is very common in environments with warm and dry periods, and photoinhibition has been detected in many angiosperms inhabiting dry and open areas. The effects of afterripening and light on seed germination were investigated for the first time in 23 native GreekCrocustaxa, collected from various localities with either a Mediterranean or a temperate climate. Germination experiments were conducted in continuous darkness and in light at the optimal temperature for each taxon, with both freshly collected and afterripened seeds; warm stratification (20°C, darkness) was also examined in 22 taxa. A number of selected taxa were additionally investigated with respect to afterripening outdoors, afterripening and warm stratification at higher temperatures (35 and 25°C, respectively), stratification at 20/10°C, dry storage at low temperatures, response to gibberellic acid and phenology of embryo growth. It was postulated that an afterripening requirement is a characteristic of the genusCrocus, and we found that it can be fulfilled in nature during the Mediterranean dry summer. Also, for the vast majority of the taxa, warm stratification and stratification at 20/10°C can both meet the afterripening requirement. Embryos of the taxa studied are underdeveloped and have to grow prior to germination. Intrageneric differences of seed germination were observed only towards light, with photoinhibition being predominant in taxa from drier environments.

Infection of adventitious roots of Agrostis palustris by Pythium species at different temperature regimes

1994 ◽  
Vol 72 (3) ◽  
pp. 378-383 ◽  
Author(s):  
Clinton F. Hodges ◽  
Douglas A. Campbell
Keyword(s):  
Low Temperatures ◽  
Adventitious Roots ◽  
Root Hairs ◽  
Dry Weight ◽  
Agrostis Palustris ◽  
Pythium Species ◽  
Root Tips ◽  
Pythium Arrhenomanes ◽  
Temperature Regimes ◽  
Disease Complexes

Pathogenicity of several isolates of Pythium species to the adventitious roots of Agrostis palustris was evaluated at high (35:24, light:dark) and low (24:13 °C, light:dark) temperature regimes. Isolates of P. graminicola–arrhenomanes, P. rostratum, P. torulosum, P. vanterpoolii, and one unclassified species were evaluated. All isolates of all species infected roots. Some isolates of P. graminicola–arrhenomanes (PGA-5), P. torulosum (PT-1, PT-2, PT-3, PT-5), P. vanterpoolii (PV-1), and an unclassified species (UP-1) infected roots and decreased dry weight at both the high and low temperature regimes. Other isolates of P. graminicola–arrhenomanes (PGA-1, PGA-2, PGA-4, PGA-6, PGA-7) and P. torulosum (PT-4) infected roots and decreased dry weight only at the high temperatures. Isolate PGA-7 of P. graminicola–arrhenomanes also stimulated plant growth at low temperatures. The remaining isolates of P. graminicola–arrhenomanes (PGA-3), P. rostratum (PR-1), and P. vanterpoolii (PV-2) infected roots and decreased dry weight only at the low temperatures. Infection of roots was limited to root hairs, root tips, and epidermal and cortical tissues. The observations are discussed relative to the function of Pythium species as minor root pathogens and their potential function in disease complexes. Key words: disease complexes, infection, minor pathogens, pathogenesis, pathogenicity, Pythium arrhenomanes, P. graminicola, P. graminicola–arrhenomanes, P. rostratum, P. torulosum, P. vanterpoolii.

Agronomic studies on Vigna spp. in south-eastern Queensland. I. Phenological response of cultivars to sowing date

1979 ◽  
Vol 30 (5) ◽  
pp. 855 ◽  
Author(s):  
RJ Lawn
Keyword(s):  
Sowing Date ◽  
Reproductive Period ◽  
Day Length ◽  
Rate Of Development ◽  
South Eastern ◽  
Vigna Species ◽  
Reproductive Phase ◽  
Temperature Regimes ◽  
Sowing Dates ◽  
Maximum Temperatures

Phenological development of 16 cultivars from four Vigna species (V. radiata, green gram; V. mungo, black gram; V. angularis, adzuki bean; V. umbellata, rice bean) was studied over a range of 17 weekly sowing dates at Lawes in south-eastern Queensland. Cultivar and sowing date effects on phenology were large. In all cultivars, the rate of development during pre-flowering was associated negatively with mean day length and positively with mean maximum and/or mean minimum temperature. Cultivars differed in sensitivity to both photoperiod and temperature. Genetic lateness of flowering among cultivars was associated positively with increasing sensitivity to day length and negatively with the latitude of cultivar source. In the grams, early-flowering cultivars showed response to maximum temperatures, while the later-flowering lines responded to minimum temperatures. Rate of development in all four species during the reproductive phase was largely independent of cultivar and sowing date, per se, but rather appeared to depend on the day length and temperature regimes prevailing subsequent to the onset of flowering. The reproductive period in all species was shortest for those cultivar x sowing date combinations which commenced flowering in early autumn. Where flowering occurred in midsummer, i.e. for early sowings and for early cultivars, the reproductive period was extended as a consequence of prolonged flowering in response to the longer prevailing day lengths. As the date of flowering was delayed into mid or late autumn, the reproductive phase was extended owing to slower pod maturation rates in response to cooler prevailing temperatures. The implications of these responses on adaptation and agronomic utilization of these species are discussed.

Enhancement by Low Temperatures of the Anaerobic Induction of Cocklebur Seed Germination

1977 ◽  
Vol 4 (6) ◽  
pp. 849 ◽  
Author(s):  
Y Esashi ◽  
Y Ohhara
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
Gibberellic Acid ◽  
Low Temperatures ◽  
Anaerobic Treatment ◽  
Maximal Response ◽  
Benzyl Adenine ◽  
Anaerobic Induction ◽  
Time Period ◽  
Proportional Increase

Non-dormant, upper cocklebur (Xanthium pensylvanicum Wallr.) seeds, incapable of germinating under ordinary conditions, can germinate when previously subjected to anaerobiosis; this has been termed the anaerobic induction of seed germination. Aerobic presoaking of the seeds was also required for successful anaerobic induction, and exerted two counter-acting effects on seed germination. When the time period of aerobic presoaking was sufficiently prolonged, the increasing duration of an anaerobic treatment resulted in proportional increase of germination potential but, when it was short, the effect of the anaerobiosis was saturated in a few days. Prolonging the aerobic presoaking period caused less response of the seed to the anaerobic induction, suggesting the development of some germination-inhibiting system during the aerobic presoaking period. This system could not develop in the absence of O2 or at low temperature. Thus, low temperature during prolonged presoaking produced a maximal response to anaerobic induction. Various germination stimulants, CO2, ethylene, gibberellic acid and benzyl adenine, did not significantly alter the effects of the presoaking.

scholarly journals Long-term Effect of Temperature and Triadimefon on Proliferation of Uncinula necator: Implications for Fungicide Resistance and Disease Risk Assessment

Plant Disease ◽  
1997 ◽  
Vol 81 (10) ◽  
pp. 1187-1192 ◽  
Author(s):  
H. L. Ypema ◽  
W. D. Gubler
Keyword(s):  
Risk Assessment ◽  
Disease Risk ◽  
Resistant Isolate ◽  
Effect Of Temperature ◽  
Daily Maximum ◽  
Uncinula Necator ◽  
Risk Assessment Models ◽  
Temperature Regimes ◽  
Entire Duration ◽  
Maximum Temperatures

Triadimefon has been used in California to control Uncinula necator, causal agent of grape powdery mildew, since 1982. Instances of unsatisfactory control have occurred mainly in the cooler coastal areas of California. The effect of temperature and application of triadimefon was investigated over a 53-day-period on two U. necator isolates, sensitive and resistant to triadimefon. At 15°C, 25°C, or temperatures fluctuating between 15 and 25°C, in absence of triadimefon, the isolates continued to produce high numbers of conidia for the entire duration of the experiment. Sporulation declined at daily maximum temperatures of 32°C for 6 h, 36°C for 3 h, and 40°C for 1 h, but was detectable when the experiment was terminated. At these temperature regimes, sporulation of the triadimefon-treated sensitive isolate ceased after 23 days. When treated with triadimefon, sporulation of the resistant isolate was comparable to that of the water-treated control. At daily maximum temperatures of 32°C for 11 h, 36°C for 6 h, and 40°C for 3 h, sporulation of both isolates generally ceased after 23 days, regardless of triadimefon application. Triadimefon resistance is most likely to manifest itself under high disease pressure, which is in part a function of temperature. The duration of daily maximum temperatures may be a valuable addition to disease risk assessment models.

scholarly journals Seed dormancy in Camellia sinensis L. (Theaceae): effects of cold-stratification and exogenous gibberellic acid application on germination

Botany ◽  
2017 ◽  
Vol 95 (2) ◽  
pp. 147-152 ◽  
Author(s):  
Danping Song ◽  
Ganesh K. Jaganathan ◽  
Yingying Han ◽  
Baolin Liu
Keyword(s):  
Gibberellic Acid ◽  
Camellia Sinensis ◽  
Summer Temperature ◽  
Cold Stratification ◽  
Morphophysiological Dormancy ◽  
Temperature Regimes ◽  
Physiological Dormancy ◽  
Radicle Emergence ◽  
Persistent Seed Bank ◽  
Natural Dispersal

There are several different opinions regarding dormancy in tea (Camellia sinensis L.), but there is no strong evidence available to conclude whether or not these seeds are dormant. Freshly matured tea seeds collected from Hangzhou, China, at the natural dispersal time did not germinate in light at daily alternative temperature regimes of 10/15, 15/20, 20/25, or 25/35 °C, or at a constant temperature of 25 °C. Seeds were permeable to water and the embryos did not grow prior to radicle emergence, thus, the seeds have no physical, morphological, or morphophysiological dormancy. When cold-stratified at 4 °C for 1, 2, and 3 months, 64%, 88%, and 93% of the seeds germinated, respectively. Intact fresh seeds failed to germinate after treatment with 0, 10, 500, and 1000 ppm GA3, whereas 3%, 4%, 61%, and 86% of cracked seeds germinated, respectively. Thus, the seeds have nondeep and intermediate physiological dormancy. Seeds cold-stratified for 2 months that were buried at soil depths of 0, 1, and 5 cm in pots showed that seeds at 1 cm depth established significantly higher number of seedlings (P < 0.05) than at other two depths. Because tea seeds are susceptible to summer temperature drying, these seeds do not establish a persistent seed bank.

The effect of high temperature regimes or short periods of water stress on development of small fruiting saltana vines

1965 ◽  
Vol 16 (5) ◽  
pp. 817 ◽  
Author(s):  
D McEAlexander
Keyword(s):  
High Temperature ◽  
Water Stress ◽  
Shoot Growth ◽  
Fruit Set ◽  
Shoot Elongation ◽  
Night Temperature ◽  
Applied Water ◽  
Temperature Regimes ◽  
Controlled Environments ◽  
Maximum Temperatures

Poor fruit set of sultanas in the Murray Valley is sometimes attributed to excessively high temperatures around flowering time. Experiments with small fruiting sultana vines in pots suggest that water stress is the more important factor. Fruit set was significantly less when a 3-day period of water stress was imposed at flowering or 1, 2, or 4 weeks after flowering, but not when it was imposed 6 weeks after flowering. Three days with maximum temperatures above 45°C at or 1 week after flowering did not reduce fruit set when ample water was supplied. When controlled environments combining day temperatures between 21 and 30°C with night temperatures between 19 and 25° were used, no significant differences in fruit set were found, although shoot growth increased with increasing night temperature. Shoot elongation slowed down during periods of applied water stress but recovered, when the stress was ended, to a rate greater than that of plants which had not been stressed.

scholarly journals Reversal of Heat-induced Resetting in Eustoma grandiflorum with Low Temperatures

HortScience ◽  
1994 ◽  
Vol 29 (3) ◽  
pp. 165-166 ◽  
Author(s):  
Kiyoshi Ohkawa ◽  
T. Yoshizumi ◽  
M. Korenaga ◽  
K. Kanematsu
Keyword(s):  
Low Temperatures ◽  
Shoot Elongation ◽  
Rosette Formation ◽  
Continuous Illumination ◽  
Natural Light ◽  
Optimum Temperature ◽  
Eustoma Grandiflorum ◽  
Leaf Stage ◽  
True Leaf ◽  
Temperature Regimes

The effects of seedling age and temperature regimes and durations on the reversal of Eustoma grandiflorum (Raf.) Shin. heat-induced rosette formation were clarified. When E. grandiflorum seedlings were grown in a natural-light phytotron (600-800 μmol·m-2·s-1) for 4 weeks at 33/28C (12-h day/12-h night) from germination to the four true-leaf stage, the optimum temperature and duration required to break rosette formation was 15C for 4 weeks with continuous illumination (35 μmol·m-2·s-1). However, when seedlings were grown for 12 weeks at 33/28C from germination to the eight true-leaf stage. shoot elongation required 6 weeks at 10C.

scholarly journals The effect of achene heteromorphism on germination in the shaggy soldier [Galinsoga ciliata (Rafin) S.F. Blake]

2012 ◽  
Vol 64 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Magdalena Kucewicz ◽  
Aneta Wardzyńska ◽  
Anna Źróbek-Sokolnik
Keyword(s):  
Growing Season ◽  
Germination Percentage ◽  
Germination Capacity ◽  
Soil Storage ◽  
Dry Storage ◽  
Temperature Requirements ◽  
Similar Temperature ◽  
High Level ◽  
Galinsoga Ciliata ◽  
Over Time

Heteromorphic achenes are formed within each capitulum of <i>Galinsoga ciliata</i> (Rafin) S.F. Blake. We examined (1) the effects of the duration of dry storage on germination and (2) the effect of burial in soil on viability and germination of heteromorphic diaspores. Fresh harvested peripheral achenes remained dormant, while central achenes germinated at 60%. Both achene types became non-dormant after one month of dry storage. In successive months of dry storage, peripheral achenes demonstrated a higher germination percentage than central achenes. The peripheral and central achenes showed similar temperature requirements during dry storage. A similar germination pattern was observed in both achene types, with a germination peak in March (96% of peripheral achenes at 12, 26 and 34<sup>o</sup>C; 90% of central achenes at 26 and 34<sup>o</sup>C). The germination capacity deteriorated over time. After 19 months of dry storage, both achene morphs failed to germinate at 12oC. At a 26<sup>o</sup> and 34<sup>o</sup>C, the same group of achenes continued to germinate at a relatively high level. After six and seven months of soil storage, 90-95% of both achene types remained alive. Dimorphic achenes were characterized by similar germination percentage (89-99%) at all temperature intervals, whereas peripheral achenes exhumed in May were the fastest to germinate. After 18 months of storage in soil (successive growing season), most of the harvested achenes were dead. The studied achenes did not form a permanent seed bank.

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