Effects of Dormancy Regulating Chemicals on Innate and Salinity Induced Dormancy in the Invasive <Emphasis Type="Italic">Prosopis juliflora</Emphasis> (Sw.) DC. Shrub

The effect of different types and concentrations of dormancy regulating chemicals (DRCs) on innate and induced dormancy was evaluated under optimal germination conditions in the invasive Prosopis juliflora shrub. Lower concentrations of gibberellic acid (0.3 mM) and kinetin (0.05 mM) were more effective in enhancing germination % and rate at higher concentrations of NaCl, but the reverse was true for thiourea. None of the DRCs alleviated innate dormancy of P. juliflora. Germination % and rate decreased as salinity increased. Percent final germination of non-treated seeds was significantly reduced at 500 mM NaCl and virtually inhibited in 600 mM NaCl. Germination reduction in 500 mM NaCl was not alleviated by any of the DRCs, but inhibition induced at 600 mM NaCl was partially alleviated by all the DRCs. Gibberellic acid had a significantly greater effect than kinetin in alleviating germination inhibition. For restoration of saline soil through the use of P. juliflora, results suggest using DRCs, particularly gibberellic acid and thiourea, as a preseeding treatment can overcome the problem of reduced germination.     

Alleviation of Salinity-Induced Dormancy in Perennial Grasses

All seeds of Aeluropus lagopoides and Urochondra setulosa germinated under non-saline conditions except for Sporobolus ioclados which showed only 40 % germination. Increase in salinity substantially inhibited germination and few seeds germinated at 400 mM NaCl. Germination at 200 mM NaCl was alleviated in U. setulosa by the application of gibberellic acid and fusicoccin, in A. lagopoides by thiourea, betaine, kinetin, fusicoccin and ethephon, and in S. ioclados by gibberellin and ethephon. High salinity (400 mM NaCl) induced germination inhibition was alleviated by proline, kinetin, fusicoccin and ethephon only in A. lagopoides.     

Reversal of induced dormancy in lettuce by ethylene, kinetin, and gibberellic Acid

The germination of lettuce seeds (Lactuca sativa L., cv. Premier Great Lakes) was significantly inhibited by high temperature (32 C), 0.1 mM abscisic acid or 0.4 M mannitol. Ethylene (16 μl/1 of air) partially reversed the dormancy induced by all three inhibitors but only in the presence of 1 mM gibberellic acid (GA) or light. Neither ethylene plus GA nor ethylene plus light were able to promote germination when thermal inhibition was imposed at 36 C. Addition of 0.01 mM kinetin to the ethylene plus GA or light reversed thermodormancy at 36 C. The dormancy imposed by abscisic acid was also reversed by kinetin. Kinetin was unable to reverse the osmotic dormancy imposed by mannitol. The reversal of osmotic dormancy by ethylene or ethylene plus GA was actually inhibited by kinetin but only in the light. Kinetin apparently stimulates cotyledonary growth in the presence of light, and this growth may compete for certain metabolites critical to radicle growth and subsequent germination. Kinetin and ethylene, as demonstrated primarily in the thermodormancy at 36 C and in osmotic dormancy, appear to regulate a common event(s) leading to germination but through mechanisms unique to each respective growth regulator. The regulation of germination by ethylene is absolutely dependent upon an interaction with GA and/or light.     

Effects of Kinetin and Salinity on Germination of Tomato, Barley and Cotton Seeds

The effects of kinetin and the interaction between kinetin andsalinity on seed germination of three plant species namely Lycopersiconesculentum, Hordeum vulgare and Gossypium hirsutum were studiedKinetin was applied exogenously to the seeds in order to determinewhether this growth-promoting hormone would promote germinationand to see if osmotically-induced dormancy caused by NaCl couldbe alleviated The results indicate that kinetin is capable ofbreaking dormancy in these species and there is a significantinteraction with salinity in tomato and cotton Kinetin, germination, salinity, water stress, salt stress, Lycopersicon esculentum Mill, tomato, Hordeum vulgare L, barley, Gossypium hirsutum L, cotton     

Seeds of Kosteletzkya virginica (Malvaceae): their structure,germination, and salt tolerance. II. Germination and salt tolerance

Kosteletzkya virginica (L.) Presl. (Malvaceae) is a perennial that grows in saline or brackish water, and is salt-tolerant in its mature state, but less tolerant during germination. The seeds show a very low permeability to water that increases during storage. The permeability to water differs in seeds harvested in different years. Optimal temperature for germination is 28–30 C. The effect of salinity on imbibition is largely osmotic, but germination is inhibited, apparently, by the combined osmotic and “ionic” effects, especially at high NaCl concentrations. Inhibition of germination by high NaCl concentrations is relatively more severe in scarified than in intact seeds, indicating that the seed coat acts as a partial barrier to Na⁺ influx. External application of proline or betaine did not improve germination under saline conditions. Dry seeds contain a significant amount of betaine and low levels of proline, but during germination and in the presence of NaCl the betaine content decreased while the proline content increased. Thus, the likely compatible solute in the germinating seed seems to be proline.     

Influence of Salinity and Temperature on the Germination of Haloxylon recurvum Bunge ex. Boiss.

The stem succulent perennial halophyteHaloxylon recurvum Bungeex. Boiss. grows and produces seed under highly saline conditionsand seeds are deposited in saline soils. Experiments were conductedto determine the effect of salinity and temperature on the germinationof seeds. Results indicate that seeds can germinate at veryhigh salt concentrations (500 mM). However, highest germinationpercentages were obtained in distilled water. Cooler thermoperiodspromoted germination, while high temperatures significantlyinhibited the germination of seeds at all NaCl concentrationstested. Rate of germination decreased with increases in salinity.At higher thermoperiods the rate of germination was significantlylower in comparison to lower thermoperiods. Seeds recover afterbeing transferred to distilled water and recovery was higherfrom higher salinity concentrations and lower thermoperiods.Final recovery germination percentages in high salt treatmentswere significantly lower than non-saline controls, indicatingthat exposure to high concentration of NaCl permanently inhibitedgermination. Germination; halophyte; Haloxylon recurvum recovery of germination; salinity; temperature     

Seed Germination of Triglochin Maritima as Influenced by Salinity and Dormancy Relieving Compounds

Triglochin maritima had only 40 % germination in distilled water, but germination was substantially enhanced when seeds were exposed to ethephon, fusicoccin, proline, kinetin, and thiourea. Also, the effect of low salinity on germination was alleviated by fusicoccin, kinetin, nitrate and thiourea, whereas, the reduction in germination at high salinity was partially countered by ethephon, kinetin, thiourea and nitrate.     

The Effects of Kinetin and Gibberellin on the Germination of Dehusked Seeds of Indica and Japonica Rice (Oryza sativaL.) under Anaerobic and Aerobic Conditions

The effects of kinetin and gibberellin were examined under anaerobicconditions (0% oxygen) and aerobic conditions (20% oxygen) onthe germination of dehusked seeds of indica and japonica ricecultivars that had been harvested at different times duringthe formation of seeds. Surjamkhi was used as a representativeof deep dormant indica cultivars and Assam IV as a less dormantindica cultivar. Sasanishiki was used as the japonica rice cultivar.Both phytohormones were applied at a concentration of 10^-3Mwhichproved to have the greatest stimulatory effect in preliminarywork at concentrations of 10^-3–10^-5M. Under aerobic conditions,inhibition of germination by dehusking of Sasanishiki seedsthat had been harvested either 30 or 60 d after anthesis wasovercome by kinetin and all seeds germinated. Complete germinationinduced by kinetin under aerobic conditions was also achievedwith the dehusked seeds of the indica rice cultivar Assam IVthat had been harvested on two occasions and of Surjamkhi thathad been harvested 28 d after anthesis. In contrast, germinationof dehusked japonica seeds stimulated by anaerobiosis was inhibitedby kinetin. The stimulatory effects of gibberellin on the germinationof indica and japonica rice seeds were observed under aerobicand anaerobic conditions. Under anaerobic conditions, the responsesof dehusked indica and japonica rice seeds to kinetin and gibberellindiffered, being negative with kinetin and positive with gibberellin.Under aerobic conditions, the stimulatory effects of kinetinon germination of dehusked seeds were greater than those ofgibberellin. Thus, treatment with kinetin appears to be usefulfor breaking the considerable dormancy commonly observed inthe dehusked seeds of indica rice. Mechanisms are proposed toexplain the stimulatory effects of these phytohormones on thegermination of dehusked seeds of indica and japonica rice underaerobic and anaerobic conditions. Rice; Oryza sativaL.; seed germination; dehusking treatment; gibberellin; indica; japonica; kinetin; oxygen; dormancy; germination inhibition; seed formation     

Hormonal Control of Germination under Saline Conditions of Three Halophytic Taxa in the Genus Suaeda

The interaction between hormones and salinity on seed germination of three halophytic taxa in the genus Suaeda: S. maritima (L.) Dum. var. flexilis Focke and var. macrocarpa Moq., and S. depressa (Pursh) Wats, was studied. Exogenous applications of kinetin and gibberellic acid (GA3) were applied in order to determine if either of these growth-promoting hormones would promote germination in the two dormant taxa, Suaeda depressa and S. maritima var. flexilis and to see if osmotically induced dormancy by NaCl could be alleviated. Our results indicate that gibberellic acid is capable of breaking dormancy in these species with dormant seeds, but kinetin proved to be ineffective. A seed dormancy that was induced by osmotic stress could also be alleviated by treatments with gibberellic acid. Endogenous concentrations of both cytokinins and gibberellins were measured in seeds exposed to osmotic stress (0.85 M NaCl), and we found a reduction in cytokinin activity in these three taxa. Gibberellin-like activity was reduced in S. depressa when seeds were soaked in 0.85 M NaCl.     

Are Seasonal Dormancy Patterns in Arabidopsis thaliana Regulated by Changes in Seed Sensitivity to Light, Nitrate and Gibberellin?

Imbibed seeds of Arabidopsis thaliana (L.) Heynh., passed annuallythrough a pattern of changes in dormancy. Dormancy was brokenin summer and re-induced in autumn-winter. A second small germinationflush occurred in early spring. The role of sensitivity to light,nitrate and gibberellins (GAs) in regulating annual dormancypatterns and germination was studied with the use of GA-deficient(gal-2) and wild-type seeds. Dark-incubated seeds were exposedto a natural temperature regime for periods up to 18 monthsand at regular intervals germination capacity of portions ofseeds was tested at laboratory conditions. Germination datafitted as logistic dose response curves showed that sensitivityto light varied with the seasons in both genotypes. From interpretationof curve parameters, it is proposed that the observed sensitivitychanges involve alterations in the number of receptors, in thebinding characteristics of the receptors and/or in the responsechain initiated by ligand-receptor interaction. In this responsechain GA biosynthesis is stimulated (wild type) and sensitivityto GAs is enhanced (wild type, gal -2). GA sensitivity is alsodirectly influenced by temperature, thus without the interferenceof light. However, the significance of direct regulation ofGA requirement seemed to diminish with prolonged incubationoutdoors, whereas reversible changes in light sensitivity remainedclear. Therefore, we propose that seasonal dormancy patternsare mainly regulated by changes in sensitivity to light. GAsensitivity contributes to this pattern but is not primarilycontrolling dormancy. The GA requirement for germination isobvious as gal-2 seeds did not germinate at any time of theyear when deprived of applied GAs. However, GA biosynthesisis not required for dormancy control, as a dormancy patternwas also observed in the absence of the capacity to synthesizeGAs. Nitrate or sensitivity to nitrate did not contribute tothe regulation of dormancy and germination of this species.Copyright1994, 1999 Academic Press Arabidopsis thaliana (L.) Heynh., curve fitting, dormancy, fluence response curve, germination, gibberellin, gibberellin dose response curve, hormone mutant, light, mouse-ear-cress, nitrate, phytochrome, receptor, seasonal dormancy pattern, sensitivity     

Impact of dormancy regulating chemicals on salinity induced dormancy in Lasiurus scindicus and Panicum turgidum: two desert glycophytic grasses

The indigenous forage grasses Lasiurus scindicus and Panicum turgidum are candidate species for the restoration of degraded desert rangelands. The impact of five dormancy regulating chemicals on overcoming salinity-induced germination inhibition was assessed under the best germination conditions in the two species. Seeds were germinated in a series of NaCl concentrations: 0–200 mM NaCl for P. turgidum, and 0–300 mM NaCl for L. scindicus. Lasiurus scindicus seeds were more tolerant to salinity than those of P. turgidum. Twenty percent of P. turgidum seeds germinated in 100 mM NaCl and none in the higher levels, but 47.5% and 8.8% of L. scindicus seeds germinated in 100 and 200 mM NaCl, respectively. The five studied chemicals (fusicoccin, GA₃, kinetin, nitrate and thiourea) did not succeed in improving germination of non-saline treated seeds of the two species, compared to the control, except thiourea in P. turgidum. The salinity-induced germination inhibition in P. turgidum was completely alleviated by the application of gibberellic acid (GA₃), partially alleviated by the application of fusicoccin, kinetin and thiourea, but not affected by nitrate. In L. scindicus, the germination inhibition was completely alleviated by fusicoccin, GA₃, nitrate and thiourea, but partially alleviated by kinetin. For using the two grass species in restoration of degraded rangelands affected by higher salinity, the results suggest using fusicoccin, GA₃, nitrate and thiourea with L. scindicus and GA₃ with P. turgidum seeds as a preseeding treatment can overcome the problem of reduced germination.     

Effect of Dormancy Relieving Compounds on the Seed Germination of Non-dormantAllenrolfea occidentalisunder Salinity Stress

Allenrolfea occidentalis(Chenopodiaceae) is a highly salt tolerantplant species that is widely distributed in inland salt marshesand salt playas of the western United States. We investigatedthe influence of dormancy-relieving compounds (fusicoccin, ethephon,nitrate and thiourea) in alleviating salinity stress on theseed germination ofA. occidentalis. Seed germination decreasedwith an increase in salinity and no seed germinated at 800 mMNaCl.Fusicoccin (5 µM), ethephon (10 mM) and nitrogenous compounds(20 mMnitrate and 10 mMthiourea) were able to counteract theinhibition produced by salinity treatments. All dormancy relievingcompounds significantly (P<0.0001) promoted germination atall salinity concentations. Fusicoccin completely reversed theinhibitory effects of salinity on seed germination ofA. occidentalis.Ethephon application significantly promoted germination at allsalinities. Nitrate and thiourea were relatively less effectivein alleviating the effects of high salinity on germination.Copyright1998 Annals of Botany Company Allenrolfea occidentalis, ethephon, fusicoccin, halophyte, dormancy, nitrate, salinity, seed germination, thiourea.     

The Effect of Salinity on Germination and Its Correlation with K+, Na+, Cl- Accumulation in Germinating Seeds of Triticum aestivum L. cv. Akbar

NaCl salinity stress consistantly decreased the rate of germinationof wheat. GA alone or in combination with kinetin alleviatedthe inhibitory effect of salinity on germination. However, kinetinfurther decreased the rate of germination under NaCl salinitystress. NaCl salinity increased accumulation of Na⁺ and Cl^–while it decreased K⁺ accumulation in germinating seeds. GAcaused an increase in K⁺ accumulation and a decrease in Cl^–accumulation in the germinating seeds while kinetin increasedCl^– accumulation in salinity stressed plants. The co-relationbetween the effect of salinity on germination and that on accumulationof ions is discussed. (Received February 12, 1992; Accepted August 4, 1992)     

Light and temperature control of germination in Agropyron smithii seeds

In darkness, A. smithii seeds germinated poorly at constanttemperatures but well at alternating temperatures. Prolongedperiods on the high part of the temperature cycles reduced germination;the higher the temperature the shorter was the period requiredon the high part of the temperature cycles for optimum germination.Continuous, unfiltered, incandescent illumination and intermittentfar red at 15?–25?C alternation also inhibited germination;the inhibitory effects were similar to those caused by the highintensity reaction. Far red inhibited germination when appliedafter 1 and 2 complete 15?–25?C cycles in darkness butnot after 3 cycles. Less than 20% of the seeds were under phytochromecontrol at constant 20?C. When red light was applied directlyafter far red that was applied in intermittent cycles at 15?–25?C,however, 50% of the seeds caused to germinate by the alternatingtemperature were shown to be controlled by the reversible phytochromereaction. The induced high-temperature dormancy was overcome by gibberellicacid (GA₃) plus kinetin. The hormonal treatment was much moreeffective than light for breaking dormancy. Inhibition fromprolonged illumination was alleviated or eliminated by GA₃+kinetin.The failure of red light to promote good germination at 20?Cwas also overcome with GA₃+kinetin; effects of light plus thehormone treatments were more than additive. These data suggestthat optimum alternating temperatures facilitate a proper balanceand interaction of hormones, enzymes, substrates and possiblypreexistent P_fr so that the germination of A. smithii seedscan proceed without benefit of a light treatment. (Received July 7, 1976; )     

Salt stress enhanced antioxidant response in callus of three halophytes (Salsola baryosma, Trianthema triquetra, Zygophyllum simplex) of Thar Desert

Effects of salinity on growth, protein content, proline, catalase and antioxidant enzyme activity in callus of three halophytes of the Thar Desert; Salsola baryosma, Trianthema triquetra and Zygophyllum simplex were evaluated. Callus tissues were cultured on Murashige and Skoog’s medium containing different concentrations of NaCl (50, 100 and 200 mM). Increase in dry weight and soluble proteins were observed in the callus exposed to lower salinity (50 and 100 mM NaCl) in all the three species, whereas on the medium containing 200 mM NaCl, significant decrease in these two growth parameters was recorded. Under the salinity stress maximum proline accumulation was found in S. baryosma with parallel increase in soluble sugars. Among the three species, T. triquetra callus showed maximum CAT activity with 50 and 100 mM NaCl treatment, whereas the enzyme activity decreased at 200 mM NaCl treatment in all three species. The antioxidant potential steadily elevated under salt treatment in all the above three species using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant potential (FRAP) assay. Whereas, superoxide dismutase (SOD) quenching were recorded maximum at low (50 and 100 mM) concentrations in all the three species. However, T. triquetra callus showed maximum total phenolic content (TPC) 15 mg GAE g^?1 with the elevated concentration of NaCl up to 200 mM, and S. baryosma callus showed lower TPC as compared to both species. A significant correlation between antioxidant capacity and TPC was observed indicating that phenolic compounds are the major contributors to the antioxidant potential in these halophyte species. FRAP and DPPH activity of Z. simplex showed maximum correlation (R = 0.992), as compared to other two species. We can conclude that all the three species exhibit a protection mechanism by sustaining growth parameters and antioxidant capacity. Due to high antioxidant property of all these species, the plant extracts may be included in nutraceutical formulations.     

Synergistic and additive effects of kinetin and ethrel on the release of seed dormancy

Dormancy in scarified Indian rice grass seeds was partially released by kinetin. Germination percentage was highly dependent on the concentration of kinetin and peaked at 0.1 mM. Additional promotion, however, was observed in the presence of Ethrel. A synergistic or additive effect on germination by the two growth regulators was observed irrespective of whether they were applied in acetone solution or in water. ATP content, but not the activity of α-amylase or alkaline phosphatase, in the germinating seeds (24 hr) was enhanced by kinetin, ethrel or a combination of both. A synergistic effect of these two hormones on the release of dormancy in cocklebur seeds was also observed.     

Dormancy and germination responses of halophyte seeds to the application of ethylene

Ethylene is invariably produced during seed germination but its role in regulating seed dormancy and germination is poorly understood. Seeds of 22 halophytic species having different life forms – salt secreting dicots, salt secreting monocots, stem succulents and leaf succulents were germinated in Petri dishes kept in a growth chamber set at 20/30 °C (night/day) temperature and a 12 hr light period. Sodium chloride and ethephon were added to the medium from the beginning of the experiment. Seed germination was recorded every other day for twenty days. Application of ethylene did not have any significant effect on releasing seeds from innate dormancy. However, it appeared to have a role in alleviation of salinity effects which varied from negative in certain species to almost complete alleviation of high salinity effects in others.Our data indicates that ethylene appears to have little role in breaking innate seed dormancy however, in most halophyte seeds studied, application of ethylene alleviate the salinity effect to various degrees. Halophyte seeds which could germinate under saline conditions approaching twice the salinity of seawater may offer clues to understand management of seed germination under highly saline conditions. To cite this article: M.A. Khan et al., C. R. Biologies 332 (2009).     

Seed Dormancy in Acer: The Role of Testa-imposed and Embryo Dormancy in Acer velutinum

The embryo dormancy shown in freshly harvested samples of Acervelutinum seeds is weakly established and very short-lived.Loss of this embryo dormancy occurred during post-harvest fruitstorage at either 5 or 17 C. In contrast, the dormancy of intactfruits and seeds was overcome only during storage at the lowertemperature. Removal of the cotyledons from embryos of freshlyharvested fruits allowed more rapid germination of the embryonicaxes, indicating that the cotyledons exert an inhibitory effect,although the axes still retained a measure of innate dormancy.The inhibitory effect of the cotyledons became less marked withincreasing duration of fruit storage, this loss of inhibitoryeffect occurring at both storage temperatures. Applied ABA stronglysuppressed germinative capacity in intact embryos and isolatedembryonic axes from freshly harvested fruits, but when ABA wasapplied to embryos of fruits that had been stored for variousperiods at 5 or 17 C, the inhibitory effect was first weakenedand then lost with increased storage. Although dormancy in the seeds of A. velutinum may be describedas intermediate between testa-imposed dormancy and true dormancy,it is perhaps more properly included in the former category. Acer velutinum Boiss. var. vanvolxemii, abscisic acid, embryo dormancy, germination, seed storage, testa-imposed dormancy, tissue sensitivity     

Gibberellin A3 reverses the effect of salt stress in chickpea (Cicer arietinum L.) seedlings by enhancing amylase activity and mobilization of starch in cotyledons

The percentage germination of chickpea seeds (Cicer arietinum L.cv. PBG-1) gradually decreased with increasing concentration of NaCl in the growth medium and was completely inhibited with 200 mM NaCl. In the presence of 75 mM NaCl, only 51% of the seeds germinated. Gibberellic acid (GA3) and kinetin at 6 µM concentration induced the maximum increase in % germination and seedling growth under salt stress. However, IAA further inhibited both the germination and growth of stressed seedlings. The reduction in amylase activity in cotyledons of stressed seedlings was partially reversed with GA3 and kinetin whereas IAA did not show any positive effect. GA3 was more effective than kinetin in enhancing the reduced germination and seedling growth of chickpea seeds along with amylase activity in cotyledons under NaCl induced saline conditions. The reduced uptake of radiolabelled 14C sucrose by cotyledons and its reduced distribution in the shoots and roots of stressed seedlings was increased with addition of GA3 in the medium. Cotyledonary amylase was separated into amylase 1 and amylase 2 by sephadex G 150 column chromatography. The reduced activities of both amylase 1 and amylase 2 in cotyledons under salt stress was returned to near normal levels with GA3 and there was also an increase in starch utilization, resulting in its lower concentration in cotyledons of GA3-supplemented stressed cotyledons.     

Regeneration of plantlets of guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.) from somatic embryos developed under salt-stress condition

The present study demonstrates the regeneration of plantlets of guava (Psidium guajava L.) from somatic embryos developed under salt-stress conditions. With increasing concentrations of NaCl in induction medium (MS + 4.52 μM 2,4-d + 5% sucrose) from 0 to 200 mM, the number of somatic embryos per responsive explant decreased. Somatic embryos induced on 0–100 mM NaCl containing medium developed into torpedo stages, whereas, the development of somatic embryos that differentiated on 150 and 200 mM NaCl-supplemented medium was arrested prior to torpedo stage and did not undergo maturation phase. Somatic embryos that developed on NaCl-containing medium, showed better germination in the presence of NaCl as compared with those developed on medium without NaCl. The effect of increasing salt-stress was also investigated on plant growth, chlorophyll and carotenoids, Na⁺ and K⁺, and proline and glycine betaine accumulation in in vitro grown plantlets. The level of Na⁺ in leaves increased with increasing concentrations of NaCl in the medium. Accumulation of free proline and glycine betaine in leaves significantly increased with increasing salinity. The results suggest that accumulation of proline and glycine betaine may be important for osmotic adjustment in guava under salinity stress.