Effect of abscisic acid, osmolarity and temperature onin vitro development of recalcitrant mango nucellar embryos

Development of cotyledonary-stage nucellar embryos of mango was arrestedin vitro by exposure to 750–1750 M ABA. The enlargement and germination of nucellar embryos was inhibited for as long as 4 weeks after subculture from ABA-containing medium. Mannitol at concentrations between 7.5 and 12.5% inhibited nucellar embryo development, presumably due to osmotic effects; however, there was no residual effect after subculture of somatic embryos onto medium without mannitol. Temperatures between 22.5 and 37.5°C stimulated embryo development, whereas lower temperatures (7.5 and 15°C) delayed germination. There was no germination 1 month after somatic embryos, pulsed for 8 weeks at 7.5°C, were transferred to 22.5°C; however, after 2 months, 86% of these somatic embryos germinated. These results indicate that it is possible to induce developmental arrest in recalcitrant mango embryos with high concentrations of ABA, mannitol or low temperature (7.5°C).Abbreviations ABA Abscisic acid - MM1 Mango maturation medium     

Inhibition of Gibberellic Acid-induced alpha-Amylase Formation by Polyethylene Glycol and Mannitol

Both polyethylene glycol (PEG) and mannitol inhibit gibberellic acid-induced α-amylase production in barley aleurone layers. The effect of the osmotic solution is on enzyme synthesis rather than α-amylase secretion. The inhibition of α-amylase synthesis does not appear to be mediated via an indirect effect on respiration or protein synthesis. Rather it seems that the osmotic solutions reduce the extent of proteolysis of the stored aleurone grain protein thus making available less substrate for new protein synthesis.     

Comparative study on seed germination characteristics of two species of Australia saltbush under salt stress

In order to examine the response characteristics and possible reasons of Atriplex lentiformis and Atriplex undulata under salt stress at stage of seed germination, the seeds were treated with different concentrations of NaCl (0, 50, 100, 200 and 300 mmol⋅L⁻¹), 20 mmol⋅L⁻¹ LiCl or mannitol whose iso-osmotic concentrations corresponding to 200 mmol⋅L⁻¹ NaCl. The results showed that the germination rate of two species of saltbush was depressed with the increase of NaCl concentration, and A. lentiformis showed greater salt tolerance compared with A. undulata. After removal of salt stress, the final germination ratio of A. lentiformis was over 93%, while that of A. undulata was only 56%. Evans blue staining revealed that 200 mmol⋅L⁻¹ NaCl did not damage membrane permeability of A. lentiformis seed embryos, but significantly increased the membrane permeability of A. undulata seed embryos and caused irreversible damage to them, especially radicles. The results on water uptake indicated that the inhibition of NaCl on seed germination was mainly due to osmotic stress instead of ionic toxicity, and A. lentiformis exhibited higher salt tolerance due to its greater resistance to osmotic stress.     

Effect of abscisic acid, osmolarity and partial desiccation on the development of recalcitrant mango somatic embryos

Inhibition of mango somatic embryo growth was inducedin vitro by treatments for 4 or more weeks with abscisic acid (0–100 M ABA) with and without high osmolarity provided by mannitol (0–10%). High osmolarity and ABA significantly affected somatic embryo length, precocious germination and the production of good quality secondary somatic embryos. High osmolarity also affected root elongation. Abscisic acid was more effective in suppressing growth and development of 0.5 cm-length somatic embryos than smaller somatic embryos. Development beyond the heart stage was significantly inhibited by both ABA and mannitol treatments. The recovery of good quality somatic embryos was enhanced by high levels of ABA (100 M) with and without mannitol (0–5%). Somatic embryos that had been pulsed with ABA were partially desiccated at different relative humidities. Weight loss was affected only by relative humidity; and ABA did not enhance desiccation tolerance.Abbreviations ABA Abscisic acid - 2,4-D 2,4-Dichlorophenoxyacetic acid - MM1 Mango maturation medium - RH Relative humidity     

Genetic analysis of involvement of ETR1 in plant response to salt and osmotic stress

The involvement of ethylene and ethylene receptor Ethylene Response 1 (ETR1) in plant stress responses has been highlighted. However, the physiological processes involved remain unclear. In this study, we have investigated the physiological response of two alleles etr1-1 and etr1-7 mutants during germination and post-germination seedling development in response to salt and osmotic stress. The etr1-1 mutants showed increased sensitivity to osmotic (200 mM or higher mannitol) and salt stress (50 mM NaCl or higher) during germination and seedling development, whereas the etr1-7 mutants displayed enhanced tolerance to the severe stresses (500 mM mannitol or 200 mM NaCl). These results provide physiological and genetic evidence that ethylene receptor ETR1 modulates plant response to abiotic stress. Furthermore, the etr1-1 and etr1-7 mutants showed different responses to exogenous abscisic acid (ABA) inhibition. The etr1-1 mutants were more sensitive to ABA than the wild type during germination, and young seedling development. In sharp contrast, the etr1-7 mutants showed enhanced insensitivity to ABA treatment (>1 μM ABA) in post-germination development including root elongation and greening of cotyledons of the treated seedlings, although the germination was not greatly altered at the tested doses of ABA. The results suggest that ETR1-modulated stress response may mediate ABA. Youning Wang and Tao Wang contributed equally to this report.     

等渗的盐分和水分胁迫对杠柳种子萌发的影响

通过等渗的NaCl和PEG溶液模拟盐分和水分胁迫,设置渗透梯度,在控制条件下对杠柳种子的萌发过程中总萌发率、幼苗鲜重、胚根生长、种子活力、发芽值等指标系统研究,对种子萌发率与渗透势之间关系进行回归分析,主要结果包括：（1）杠柳种子萌发过程中总萌发率、幼苗鲜重、活力指数和发芽值四项指标均随NaCl和PEG溶液的渗透势降低逐渐下降,综合研究活力指数和发芽值表明渗透势≥-0.5 MPa和≤-1.4 MPa时,PEG对种子萌发抑制作用大于NaCl,其他情况相反;（2）杠柳种子逐日萌发率和胚根日变化研究表明,与NaCl相比,PEG推迟杠柳种子萌发,并且对胚根增长抑制作用较大;（3）建立盐分和水分胁迫条件下种子萌发率与渗透势回归方程,发现杠柳种子在PEG胁迫下的萌发临界值和极限值为-1.0和-1.4 MPa,在NaCl胁迫下是-0.9和-1.3 MPa,解除胁迫条件,不同处理的杠柳种子复水萌发率均达到100%。说明杠柳具有良好的耐盐抗旱的特性。     

A Salt-Tolerant Cultivar of Wheat Maintains Photosynthetic Activity by Suppressing Sodium Uptake

The effects of NaCl treatment on the photosynthetic machinery in wheat (Triticum aestivum L.) cultivars differing in salt tolerance were investigated by comparison with iso-osmotic PEG treatment. Both cultivars similarly reduced the photosystem 2 (PS2) energy conversion efficiency (_PS2) rapidly when plants were exposed to a 100 mM NaCl solution, though no decline was detected under the iso-osmotic PEG treatment. There was no correlation between the reduction of the leaf relative water content (RWC) and the _PS2 in the two iso-osmotic stress treatments. In contrast, a decline of _PS2 along with the increase of the leaf sodium content above 4 % dry matter was detected under the NaCl treatment, while no such correlation was detected with other cations. The recovery of _PS2 after photoinhibitory irradiation was repressed by the NaCl treatment as the increase of the duration of the treatment. Norin 61 subjected to the 100 mM NaCl treatment for 10 d showed a decline of the _PS2 after 1 h moderate irradiation of 400 mol m^–2 s^–1 PPFD. Thus the concentrated Na⁺ within a leaf under salinity treatments may decrease the stability of PS2 functions and lead to photochemical inactivation.     

In vitro selection for salt tolerant lines in Lycopersicon peruvianum

A salt-tolerant callus line of Lycopersicon peruvianum has been obtained by exposing the cells, in suspension cultures and then in callus, to increasing concentrations of NaCl (50–350mM). This selected line grew better than the nonselected line at all levels of NaCl. Moreover, this selected line grew better in media containing salt than in those without it. It retained its tolerance after subculture for 3 passages (3 months) on salt-free medium. The growth of the selected line in mannitol was similar to that of the nonselected line, which suggested that the superiority of the selected line under salt stress was not due to osmotic stress tolerance. The ions SO ₄ ^–– and K⁺ were highly toxic to L. peruvianum root callus, while Na⁺, Mg⁺⁺ and Cl^– were less toxic.     

Growth and osmotic adjustment of two tomato cultivars during and after saline stress

The effect of a short period of saline stress was studied in two phenotypically different cultivars, one of normal fruit-size (L. esculentum cv. New Yorker) and one of cherry fruit-size (L. esculentum var.cerasiforme cv. PE-62). In both cultivars the relative growth rate (RGR) and the leaf area ratio (LAR) decreased following salinisation. The leaf turgor potential (_p) and the osmotic potential at full turgor (_os) decreased to the same extent in both cultivars. However, the contributions of organic and inorganic solutes to the osmotic adjustment was different between cultivars. New Yorker achieved the osmotic adjustment by means of the Cl^– and Na⁺ uptake from the substrate, and by synthesis of organic solutes. In the cherry cultivar organic solutes did not contribute to the osmotic adjustment, instead, their contribution decreased after salinisation. After the salt stress was removed, the water stress disappeared, the content of organic solutes decreased in plants of both cultivars and, therefore, their growth was not retarded by the diversion of resources for the synthesis of organic solutes. However, the toxic effects of the Cl^– and Na⁺ did not disappear after removal of the salt stress, and the net assimilation rate (NAR) and the rate of growth (RGR) did not recover.     

Effects of osmotic tension and salt stress on germination of three grass species

Effects of osmotic tension, salinity and alkalinity were studied on seed germination of three grasses of Karnal-Kurukshetra region with a view to evaluating their capacity to establish through seeds in saline and alkaline environments. Experiments were conducted under controlled conditions in petri dishes lined with blotting papers that were wetted with non-ionic osmotic solutions of mannitol (–2.5 to –15 bars); salinized solutions of NaCl, Na₂SO₄, MgCl₂ and CaSO₄ (Electrical conductivity, EC, ranging from 4 to 16 dS/m), alkaline solutions of Na₂CO₃ (pH 9 to 10) and also in dishes filled with alkali soil grades of the same pH range. Seed germination of all the three grasses was observed to be delayed and finally suppressed by the stress conditions, magnitude of reduction being related to the kind and level of stress as well as to the species. WhileSorghum halepense showed a strikingly superior stress-resistance,Panicum miliare did not appear to be suited to establishment through seeds.Diplachne fusca, on the other hand, was found to be remarkably adapted to alkalinity.     

Mannitol, polyethylene glycol and NaCl induced polypeptide changes during in vitro culture of three tomato cultivars

Three cultivars of tomato Pusa Ruby, Arka Vikas and Pusa Early Dwarf were subjected to osmotic stresses induced by mannitol, polyethylene glycol and NaCl in vitro. Polypeptide patterns were analyzed during each stress treatment to differentiate between tolerant and sensitive cultivars. The stresses induced more stress proteins in cv. Pusa Ruby compared to other two cultivars indicating it to be relatively osmotic stress tolerant.     

Osservazioni Sull'effetto Inibente di Elevate Pressioni Osmotiche su Diversi Tipi di Crescita

Abstract

On the inhibition of seeds germination and of growth by cell enlargement by the osmotic pressure of the medium. — The mechanism of inhibition by osmotic pressure (O.P.) of the medium on growth and respiration of germinating wheat, castor bean and lettuce sèeds and of etiolated pea internode segments was investigated.

The following results were obtained:

1 - External osmotic pressure (up to 0.3 M) of various substances such as mannitol, urea, glucose, NaCl, was shown to inhibit the germination and growth of lettuce, wheat and castor bean seeds.

2 - a) A remarkable decrease of the development of respiration during the first 48 h of germination was demonstrated in embryos of wheat seeds germinated and maintained in mannitol solutions at concentration from 0,2 to 0,3 M.

b) A slight but reproducible inhibition of óxygen uptake by O.P. was also observed in embryos isolated from wheat seeds germinated in water for 24 and 34 h and transported respectively in water or into 0,2 M mannitol solutions.

This is interpreted as indicating that high external O.P. inhibits both the respiratory metabolism and the development with time of enzyme systems supporting respiration.

3 - Mannitol solutions (0,2–0,3 M) inhibited completely growth by cell enlargement in pea internode sections, while they did not at all affect oxygen uptake and protein synthesis ( ¹⁴ C - leucine incorporation). The stimulatory effect of auxin on pea elongation was almost completely suppressed by mannitol, whereas the hormone stimulation of respiration remained unchanged.

These data are interpreted as indicating that in tissues, presenting an advanced differentiation, high external O.P. inhibits growth by a direct physico-chemical mechanism; while the inhibitory effect in embrional tissues seems to comprehend, besides this direct effect, a complicated metabolic component, apparently influencing protein synthesis.     

Enhanced germination of artificial seeds by marine cynobacterial extract

Summary We have developed an improved artificial seed system by using a hot-water extract from a marine cyanobacterium, Synechococcus sp. NKBG 042902. Carrot somatic embryos (Daucus carota L.) were divided into two size categories (> 800 m and 425–800 m). High frequency germination (91%) was obtained using the large somatic embryos encapsulated in calcium alginate gel containing 400 mg 1^–1 of extract. This compares to 35% without addition of the extract. A non-dialysate fraction of the extract showed strong germination-promoting activity compared with a dialysate fraction. The germination frequency of artificial seeds containing 100 mg 1^–1 of non-dialysate fraction was more than 90%. Almost all germinating artificial seeds developed into plantlets within 4 days. We also achieved high frequency germination (60%) of artificial seeds encapsulating small somatic embryos (425–800 m) that contained 100 mg 1^–1 of non-dialysate (control 9%). Although the small somatic embryos showed a lower germination frequency than the large embryos, the plantlet development process in these seeds was far more vigorous. Such a high germination frequency has not previously been reported for a carrot artificial seed system.     

Structure of the dehydrin tas 14 gene of tomato and its developmental and environmental regulation in transgenic tobacco

We have isolated a genomic clone encoding tomato TAS14, a dehydrin that accumulates in response to mannitol, NaCl or abscisic acid (ABA) treatment. A fragment of tas14 gene containing the region from –2591 to +162 fused to -glucuronidase gene drives ABA- and osmotic stress-induced GUS expression in transgenic tobacco. Histochemical analysis of salt-, mannitol-and ABA-treated plants showed GUS activity mainly localized to vascular tissues, outer cortex and adventitious root meristems, coinciding with the previously observed distribution of TAS14 protein in salt-stressed tomato plants. In addition, GUS activity was also observed in guard cells, trichomes and leaf axils. Developmentally regulated gus expression was studied in unstressed plants and found to occur not only in embryos, but also in flowers and pollen. Tas14 expression in floral organs was confirmed by northern blots of tomato flowers.     

Effects of 6-methoxy-2-benzoxazolinone on the germination and α-amylase activity in lettuce seeds

Germination of lettuce seeds was inhibited by 6-methoxy-2-benzoxazolinone (MBOA) at concentrations greater than 0.03 mmol/L. MBOA also inhibited the induction of α-amylase activity in the lettuce seeds at concentrations greater than 0.03 mmol/L. These two concentration–response curves for the germination and α-amylase indicate that the percentage of the germination was positively correlated with the activity of α-amylase in the seeds. Lettuce seeds germinated around 18 h after incubation and inhibition of α-amylase by MBOA occurred within 6 h after seed incubation. These results show that MBOA may inhibit the germination of lettuce seeds by inhibiting the induction of α-amylase activity.     

Germination of Prosopis juliflora (Sw.) D.C. seeds at different osmotic potentials and temperatures

The effects of osmolytes, osmotic potential (Ψ_s), temperature, and their interactions on the germinability, germination rate, and other germination parameters of the invasive shrub Prosopis juliflora, which grows in the semiarid environmental conditions of the Caatinga in northeast Brazil, were evaluated. To study the effects of polyethylene glycol (PEG) and NaCl stress and temperature on germination, two separate experiments were carried out at the Plant Ecophysiology Laboratory of the Federal University of Pernambuco in 2011. The overall germinability decreased significantly with increases in both PEG (one‐way anova , F_4,75 = 111.21, P ≤ 0.001) and NaCl (one‐way anova , F_4,75 = 12.82, P ≤ 0.001); however, the effects were more accentuated with PEG than NaCl. The PEG‐treated seeds maintained their germinability, even when they were subjected to a Ψ_s = ?1 MPa after being rinsed and allowed to germinate on deionized water. In contrast, NaCl‐treated seeds usually lost their ability to germinate; this fact was possibly linked to the accumulation of Na⁺ and Cl^? in the cells, which may have contributed to a loss of membrane function that led to the death of the embryos. Although numerous studies describing seed germination in the presence of osmolytes have been conducted, studies that show the interactions between osmolytes, osmotic potentials, and temperature are scarce. The present study is the first to describe these interactions for P. juliflora seeds.     

Salinity Induced Changes in α-Amylase Activity During Germination and Early Cotton Seedling Growth

Salinity induced changes in -amylase activity in three cotton cultivars (NIAB-Karishma, NIAB-86 and K-115) was studied during germination and early seedling growth under controlled conditions. The increase in NaCl concentration resulted in the decrease in -amylase activity and break down of starch into reducing and non-reducing sugars in all cultivars, however, it was more pronounced in NIAB-86. K-115 showed highest germination followed by NIAB-Karishma and NIAB-86.     

Isolation and characterization of α-amylase derived from starchgrownClostridium acetobutylicum ATCC 824

Summary An extracellular -amylase was purified to homogeneity from the culture supernatant ofClostridium acetobutylicum ATCC 824 grown in synthetic medium containing starch by using a combination of ammonium sulfate fractionation, anion exchange chromatography and HPLC-gel filtration. The molecular weight of the 160-fold purified -amylase was determined by SDS-PAGE to be 61 kDa. HPLC analysis of end-products of enzyme activity on various substrates indicated that the enzyme acted specifically in an endo-fashion on the -1,4-glucosidic linkages. Enzyme activity was optimal over a pH range of 4.5–5.0 and temperature of 55°C, but was rapidly inactivated at higher temperatures. Addition of calcium chloride (2–5 mM) increased -amylase activity by ca. 20%, while the addition of 19 g ml^–1 of acarbose (a differential inhibitor of amylases) resulted in 50% inhibition. TheV _max andK _m of -amylase were 2.17 mg min^–1 and 3.28 mg ml^–1 on amylose, and 1.67 mg min^–1 and 1.73 mg ml^–1 on soluble starch, respectively.     

Enhancement of phenylethanoid glycosides biosynthesis in cell cultures of <Emphasis Type="Italic">Cistanche deserticola</Emphasis> by osmotic stress

The effect of osmotic stress on cell growth and phenylethanoid glycosides (PeGs) biosynthesis was investigated in cell suspension cultures of Cistanche deserticola Y. C. Ma, a desert medicinal plant grown in west region of China. Various initial sucrose concentrations significantly affected cell growth and PeGs biosynthesis in the suspension cultures, and the highest dry weight and PeGs accumulation reached 15.9 g l⁻¹-DW and 20.7 mg g⁻¹-DW respectively at the initial osmotic stress of 300 mOsm kg⁻¹ where the sucrose concentration was 175.3 mM. Stoichiometric analysis with different combinations of sucrose and non-metabolic sugar (mannitol) or non-sugar osmotic agents (PEG and NaCl) revealed that osmotic stress itself was an important factor for enhancing PeGs biosynthesis in cell suspension cultures of C. deserticola. The maximum PeGs contents of 26.9 and 23.8 mg g⁻¹-DW were obtained after 21 days at the combinations of 87.6 mM sucrose with 164.7 mM mannitol (303 mOsm kg⁻¹) or 20 mM PEG respectively, which was higher than that of C. deserticola cell cultures grown under an initial sucrose concentration of 175.3 mM after 30 days. The stimulated PeGs accumulation in the cell suspension cultures was correlated to the increase of phenylalanine ammonium lyase (PAL) activity induced by osmotic stress.