Drought tolerance and germination response to light and temperature for seeds of saline and non-saline habitats of the habitat-indifferent desert halophyte <Emphasis Type="Italic">Suaeda vermiculata</Emphasis>

Few plants are habitat-indifferent halophytes (i.e., grow well in both saline and non-saline soils). These plants offer a good opportunity to study drought and salinity tolerances during germination for seeds developed and matured in soils differ in salinity. Here, we assessed drought tolerance during germination, as simulated with PEG, and response of germination to light and temperature for Suaeda vermiculata, a habitat-indifferent shrub. Seeds matured in saline and non-saline soils were germinated in six PEG concentrations (0 to ? 1.0 MPa) and put in three incubators adjusted at different temperatures in both light and dark regimes. Drought tolerance was greater for seeds of the non-saline than those of saline soils, especially at higher temperatures. Seeds of the saline soils germinated in the lowest osmotic potentials (? 0.8 and ??1.0 MPa) only at lower temperatures, but seeds of the non-saline soils germinated to higher levels at all temperatures. Tolerances to drought and high temperatures were greater in light for seeds of saline soils, but in darkness for seeds of non-saline soils. Germination rate index did not differ significantly between seeds of the two soil types in higher osmotic potentials, but was significantly greater in seeds of non-saline at lower osmotic potentials. Most seeds that failed to germinate in the PEG concentrations recovered their germination when transferred to distilled water. Germination recovery levels and speeds increased with the decrease in osmotic potentials. Seeds of the saline soil postpone their germination until arrival of suitable temperatures and effective rainfalls that ensure seedling survival in salty habitats of the arid unpredictable deserts.     

Variation in temperature and light but not salinity invokes antioxidant enzyme activities in germinating seeds of Salsola drummondii

Seeds with efficient antioxidant defence system show higher germination under stress conditions; however, such information is limited for the halophyte seeds. We therefore studied lipid peroxidation and antioxidant responses of a leaf-succulent halophyte Salsola drummondii during seed germination under different salinity levels (0, 200 and 800 mM NaCl), temperature (10/20, 20/30 and 25/35°C) and light regimes. Seeds absorbed water and germinated in less than 1 h in non-saline control while increases in salinity decreased the rate of water uptake as well as seed germination. Non-optimal temperatures (10/20 and 25/35°C) and complete dark condition reduced seed germination in comparison to those seeds germinated under optimal temperature (20/30°C) and 12-h photoperiod, respectively. Generally, higher lipid peroxidation and antioxidant enzyme activities were observed in seeds at non-optimal temperature and in those seeds germinated in dark. Decrease in reduced ascorbic acid content was found in highest salinity and temperature treatments, while reduced glutathione content did not change significantly with changes in salinity, temperature and light regimes. These results indicate variation in temperature and light but not salinity enhances antioxidant enzyme activities in germinating seeds of Salsola drummondii.     

盐生植物角果碱蓬种子二型性对环境的适应策略

角果碱蓬(Suaeda corniculata)是藜科一年生盐生植物, 在我国分布于北方盐碱滩涂和盐碱荒漠地区。角果碱蓬具有棕色和黑色两种异型体种子(简称棕色和黑色种子)。对采自内蒙古鄂托克前旗盐渍化生境的角果碱蓬二型种子的形态、休眠和萌发特性开展对比研究, 测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应, 以揭示盐生植物异型种子对温带盐漠生境的适应对策。结果表明: (1)二型性种子在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比, 棕色种子个体较大, 种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感, 萌发率较高(84%-100%); 而新成熟的黑色种子萌发率较低(8%-78%), 萌发对光照敏感。(3)黑色种子具有浅度生理休眠, 种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)二型种子萌发对土壤盐分的胁迫具有不同的响应。与黑色种子相比, 棕色种子对盐分胁迫不敏感, 在较高的盐分浓度下仍有较高的萌发率, 低温层积处理能够降低黑色种子对盐胁迫的敏感性, 有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性, 提高了该物种在高度异质性生境中的适合度, 对种群成功地适应温带盐漠环境具有重要的意义。     

Effect of Salinity on Seed Germination,Growth, and Ion Accumulation of Atriplex patula (Chenopodiaceae)

Seeds and seedlings of the halophyte Atriplex patula were exposed to 0–2% NaCl to determine the effect of salt stress on germination and growth. Seeds germinated and plants survived and grew in solutions of up to 2.0% NaCl. Both seed germination and dry mass production were negatively affected by increased salinity. Dry mass production declined to 1% of controls and seed germination to 17% of controls in the 2% NaCl treatments, indicating that seeds were less inhibited than growing plants. Also, recovery treatments indicated that high salinity did not permanently injure seeds. Percent ash, and Na⁺ and Cl⁻ ions increased in shoots with each salt increment, while the K⁺ ion content decreased sharply. Atriplex patula is a facultative halophyte, and is limited to low and moderately saline sites because both seed germination and growth are severely reduced at salinities > 1% NaCl.     

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     

Effect of temperature, light and salinity on seed germination and radicle growth of the geographically widespread halophyte shrub Halocnemum strobilaceum

BACKGROUND AND AIMS: The small leafy succulent shrub Halocnemum strobilaceum occurs in saline habitats from northern Africa and Mediterranean Europe to western Asia, and it is a dominant species in salt deserts such as those of north-west China. The effects of temperature, light/darkness and NaCl salinity were tested on seed germination, and the effects of salinity were tested on seed germination recovery, radicle growth and radicle elongation recovery, using seeds from north-west China; the results were compared with those previously reported on this species from 'salt steppes' in the Mediterranean region of Spain. METHODS: Seed germination was tested over a range of temperatures in light and in darkness and over a range of salinities at 25 degrees C in the light. Seeds that did not germinate in the NaCl solutions were tested for germination in deionized water. Seeds from which radicles had barely emerged in deionized water were transferred to NaCl solutions for 10 d and then back to deionized water for 10 d to test for radicle growth and recovery. KEY RESULTS: Seeds germinated to higher percentages in light than in darkness and at high than at low temperatures. Germination percentages decreased with an increase in salinity from 0.1 to 0.75 M NaCl. Seeds that did not germinate in NaCl solutions did so after transfer to deionized water. Radicle elongation was increased by low salinity, and then it decreased with an increase in salinity, being completely inhibited by > or = 2.0 M NaCl. Elongation of radicles from salt solutions < 3.0 M resumed after seedlings were transferred to deionized water. CONCLUSIONS: The seed and early seedling growth stages of the life cycle of H. strobilaceum are very salt tolerant, and their physiological responses differ somewhat between the Mediterranean 'salt steppe' of Spain and the inland cold salt desert of north-west China.     

Effect of salinity on seed germination and seedling growth of the halophyte Suaeda japonica Makino

Seed germination and seedling growth of the annual halophyte species Suaeda japonica Makino were investigated in response to variable salinity of sediment pore water. The germination percentage of S. japonica’s soft brown seeds, which are dominant among dimorphic seeds, decreased with an increase in salinity, although germination was still observed at 1200‐mM NaCl concentration. The germination percentage and germination speed observed in April were higher than those observed in December when treated with sediment water with 400–1200 mM of NaCl concentrations. These data suggest that S. japonica seedlings could be established on sediments that experience high temperatures. Germination recovery of S. japonica seeds transferred from 600‐mM NaCl containing sediment (seawater equivalent) was lowest among 0–1200‐mM NaCl treatments, implying the low tolerance of seawater conditions of S. japonica seeds. Seeds germinated in 900‐ to 1200‐mM NaCl medium showed poor growth, but survived, in hypersaline conditions, and exhibited improvement in growth upon transfer to lower salinity.     

Effects of temperature,salinity and cold stratification on seed germination in halophytes

Salt tolerance of halophytes corresponds with the habitat requirement of the species. It is an important factor during the germination phase and it can determine successful establishment. This paper presents the effects of alternating temperature–light regimes (4/8°C, 10/20°C, 20/32°C; 12 h dark: 12 h light) and different salinity levels (0, 200, 400, 600 mmol l²¹ NaCl) on seed germination of five halophytes, Halimione pedunculata, Bupleurum tenuissimum, Aster tripolium, Triglochin maritimum and Armeria maritima. The five species differ with respect to family and life‐form and spatially correspond to a decreasing salt gradient (i.e. distance from salt water, with H. pedunculata being the most tolerant and A. maritima being the least). Armeria maritima, A. tripolium and T. maritimum seeds were additionally subjected to a cold stratification experiment. The results showed that Halimione pedunculata, an annual therophyte of year‐round heavily saline habitats, was dormant under all experimental conditions. Bupleurum tenuissimum, a species typical to sites of varying salinity prone to leaching during spring and autumn rainfall, germinated best under cold and warm temperatures, but only under non‐saline conditions. Aster tripolium and T. maritimum, close neighbours in salt marshes, showed very similar germination behaviour: seeds of both species tolerated high levels of salinity and germinated best in summer temperatures during periods of highest soil salinity, and germination was significantly promoted by cold. Armeria maritima, a species usually found on the marginal fringes of saline habitats, germinated only under low salt levels and maximum germination was under cold (spring) and warm (autumn) temperatures, with no significant effect of cold stratification.     

盐生植物种子萌发对环境的适应对策

盐生环境是一种严峻的胁迫环境,对植物的生长、发育、繁殖等生活史的各阶段都产生着重要的影响。盐生植物是生长在盐渍土壤上的一类天然植物区系,它们在长期的进化过程中形成了一系列适应盐生生境的特殊生存策略。一般情况下,盐生植物种子对环境的适应能力,是植物对盐生环境适应性的重要体现;而植物发育早期对盐度的适应能力又是决定物种分布和群落组成的关键因素。在对国内外相关文献进行分析归纳的基础上,从盐分对种子萌发的影响机理及植物种子萌发对盐生环境的适应对策两个方面综述了植物种子休眠萌发与盐生环境的关系。     

Effect of maturation conditions on light and temperature requirements during seed germination of Citrullus colocynthis from the Arabian Desert

• Seed germination of Citrullus colocynthis, as in many other species of Cucurbitaceae, is inhibited by light, particularly at low temperatures. Germination response to light and temperature has been attributed to day length and temperature during seed maturation. This study assessed the effects of these factors on the germination response of C. colocynthis to temperature and light quality.
• Ripe fruits were collected from natural habitats during December and February and germinated at three temperatures (15/25, 20/30 and 25/35 °C) in five light treatments (dark, white light and Red:Far Red (R:FR) ratios of 0.30, 0.87 and 1.19). Additionally, unripe fruits were also collected from natural habitats and completed their maturation in growth chambers under different day lengths (6, 16 and 24 h of darkness) at 10/20 °C, and in darkness at both 10/20 °C and 25/35 °C. Mature seeds of the different treatments were germinated in the same five light treatments at 15/25 °C.
• Germination was significantly higher in the dark than that in any light treatment. Seeds matured at higher temperatures (i.e. seeds from the December collection and those matured at 25/35 °C) had significantly higher germination than those matured at lower temperatures (i.e. seeds from the February collection and those matured at 10/20 °C). Dark germination was significantly higher for the December collection than for the February collection. Seeds of the two collections germinated in the dark only at 15/25 °C. However, seeds matured in a growth chamber at 10/20 °C in darkness germinated at 15/25 °C in all light treatments, except for the R:FR ratio 0.30. Seeds of the different treatments failed to germinate in FR‐rich light.
• This study demonstrates that both temperature and day length during seed maturation play significant roles in the germination response of C. colocynthis. Additionally, the dark requirement for germination is likely beneficial for species with the larger seeds, such as C. colocynthis, which produce bigger seedlings that are able to emerge from deep soils and are competitively superior under dense vegetation and resource‐limited conditions.

     

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 Germination of a Halophytic Grass Aeluropus lagopoides

Aeluropus lagopoides(Linn.) Trin. Ex Thw. (Poaceae) is a perennialgrass distributed from coastal Sindh and Balochistan to salineflats of Punjab, Pakistan. Seeds collected from an inland populationofA. lagopoides located on the University of Karachi campuswere germinated under various levels of salinity (0, 100, 200,300, 400 and 500 m M NaCl) and temperature regimes (10/20, 15/25,20/30 and 25/35 °C) in a 12 h dark/12 h light photoperiod.Highest germination was obtained under non-saline conditions,and an increase in NaCl concentration progressively inhibitedgermination. Inhibition of germination was greater at coolertemperatures (10/20 °C) when no seed germinated above aconcentration of 300 m M NaCl. The germination response at moderatetemperatures (20/30 °C) was optimal, with 30% of seeds germinatingin 500 m M NaCl. The rate of germination decreased as salinityincreased. Germination rate was highest at 20/30 °C andlowest at 10/20 °C. Seeds were transferred from salt solutionsto distilled water after 20 d and those from high salinitiesrecovered quickly at warmer temperatures with an optimal responseat 20/30 °C. Copyright 2001 Annals of Botany Company Aeluropus lagopoides, germination, halophyte, Karachi, salinity, temperature     

Variability on morphological and ecological seed traits of Limonium avei (De Not.) Brullo & Erben (Plumbaginaceae)

Limonium avei is an annual species occurring in the salt‐marshes and in limited surfaces of rocky areas around the Mediterranean coasts. Seed lots from five populations of this species, along a latitudinal gradient, were analyzed using an image analysis system to detect differences in seed morphology among populations. Germination requirements at constant (5–25°C) and alternating temperatures (25/10°C), both in light and in darkness, were evaluated for all populations, as well as the effect of the calyx removal on final seed germination and its rate. Morpho‐colorimetric analysis clearly identified seeds from different populations, habitats and substrates without misattributions among them. The calyx slowed the germination process, influencing both final germination and rate with respect to naked seeds. Seeds from all populations germinated with significantly higher percentages in the light, with respect to those incubated in the darkness, and showed rapid germination (time in days to reach 50% of germination: 0.5 days) at the warmer tested temperature (25°C). High germination (>80%) was also detected for seeds of all the investigated populations, except for those from the Apulian region (South Italy, ca. 60%). Our results highlight that L. avei has a high variability in seed morphology, probably habitat induced, and a fast germination response for all populations. Rapid germination may be an adaptive strategy that allows L. avei seeds to take advantage of transient favorable conditions during the germination stage, to ensure seedling establishment under the unpredictable rainfall pattern in the Mediterranean climate.     

Effects of seed maturation time and dry storage on light and temperature requirements during germination in invasive Prosopis juliflora

The effects of time of seed maturation and dry seed storage and of light and temperature requirements during seed incubation on final germination percentage and germination rate were assessed for the invasive shrub Prosopis juliflora (Sw.) D.C., grown under desert environmental conditions of the United Arab Emirates (UAE). Seeds were collected from Fujira on the northern coast of the UAE at different times during the growing seasons (autumn, winter and spring) and were germinated immediately and after 8 months of dry storage under room temperature (20±3 °C). Seeds were germinated at three temperatures (15, 25 and 40 °C) in both continuous light and darkness. The results showed significant effects for time of seed collection, seed storage, light and temperature of seed incubation and many of their interactions on both germination percentage and rate. Fresh seeds matured during autumn and winter germinated significantly greater at 40 °C and in light than at lower temperatures and in dark. Storage significantly increased germination percentage and rate; the increase was greater for seeds matured during winter than for seeds matured during spring. This indicates that dormancy breakage was greater in seeds of winter than seeds of spring. The need for high temperature to achieve greater germination was significantly reduced after seed storage, especially for seeds matured in autumn and winter.     

Accumulation of ions during seed development under controlled saline conditions of two Suaeda salsa populations is related to their adaptation to saline environments

Controlled conditions were used to investigate the relationship between ion distribution in developing seeds of two Suaeda salsa populations and seed germination and seedling emergence. Seeds were harvested from S. salsa plants that had been treated with 1 or 400 mM NaCl for 122 (saline inland population) or 135 days (intertidal zone population) in a glasshouse. Germination and seedling emergence were evaluated under salinity. In both populations, more ions were accumulated in the pericarps of plants cultured in 400 mM NaCl than in 1 mM NaCl. Pericarps accumulated much higher ion concentrations in the intertidal zone population than in the saline inland population, while the opposite trend occurred for ion accumulation in the embryos. Seeds of plants from the intertidal zone population germinated more rapidly than those from plants of the saline inland population, regardless of the NaCl concentration during seed germination. However, seedling emergence under high salinity was lower with seeds from the intertidal zone population than with seeds from the saline inland population. In conclusion, S. salsa in the intertidal zone employs superior control of ion compartmentalization in the pericarps to tolerate salinity but requires a minimal level of ions in embryos to ensure seedling establishment in highly saline environments. This indicates that euhalophytes require salts during the mature seed stage to maintain seed viability and to ensure seedling emergence and population establishment.     

Different ecological strategies during the seed germination phase of nine grasses inhabiting the hyper‐arid Arabian desert

The effect of photoperiod, thermoperiod and their interaction on seed germination and its rate was studied for nine grasses growing in the Arabian desert. Germination tests were conducted under two photoperiods and three thermoperiods. Germination of light‐incubated seeds of Hyparrhenia hirta, Pennisetum divisum, Stipacapensis, Centropodia forsskaolii, Stipagrostis plumosa, Cymbopogon parkeri and Panicum turgidum was significantly higher than that detected in the darkness. Photoperiod did not influence the seed germination of Aristida adscensionis and Imperata cylindrica. Seeds of all species, except P. divisum, C. parkeri and I. cylindrica, germinated indepen dently of the tested temperature. Our results indicate that species belonging to the same family and growing in the same hyper‐arid desert habitat may influence and act in different ways during the seed germination phase, causing species‐specific effects, and therefore might affect the ecology of each taxon in this harsh environment.     

The effects of salinity and osmotic stress on barley germination rate: sodium as an osmotic regulator

Background and Aims

Seed germination is negatively affected by salinity, which is thought to be due to both osmotic and ion-toxicity effects. We hypothesize that salt is absorbed by seeds, allowing them to generate additional osmotic potential, and to germinate in conditions under which they would otherwise not be able to germinate.

Methods

Seeds of barley, Hordeum vulgare, were germinated in the presence of either pure water or one of five iso-osmotic solutions of polyethylene-glycol (PEG) or NaCl at 5, 12, 20 or 27 °C. Germination time courses were recorded and germination indices were calculated. Dry mass, water content and sodium concentration of germinating and non-germinating seeds in the NaCl treatments at 12 °C were measured. Fifty supplemental seeds were used to evaluate the changes in seed properties with time.

Key Results

Seeds incubated in saline conditions were able to germinate at lower osmotic potentials than those incubated in iso-osmotic PEG solutions and generally germinated faster. A positive correlation existed between external salinity and seed salt content in the saline-incubated seeds. Water content and sodium concentration increased with time for seeds incubated in NaCl. At higher temperatures, germination percentage and dry mass decreased whereas germination index and sodium concentration increased.

Conclusions

The results suggest that barley seeds can take up sodium, allowing them to generate additional osmotic potential, absorb more water and germinate more rapidly in environments of lower water potential. This may have ecological implications, allowing halophytic species and varieties to out-compete glycophytes in saline soils.     

Do Conditions During Dormancy Influence Germination of Suaeda maritima?

Background and Aims

Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2–3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination.

Methods

Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination.

Key Results

A temperature of about 15 °C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry.

Conclusions

The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 °C and the salinity is reduced.Key words: Suaeda maritima, germination, pre-treatment, salinity, temperature     

Effects of salinity and nitrate on production and germination of dimorphic seeds applied both through the mother plant and exogenously during germination in Suaeda salsa

Salinity and nitrogen are two important environmental factors that affect the distribution of halophytes in their natural saline habitats. Seeds of the euhalophyte Suaeda salsa L. were harvested from plants that had been treated with 1 or 500 mm NaCl combined with 0.5 or 5 mm NO₃^?‐N (nitrate) for 115 days in a glasshouse. Germination was evaluated under different concentrations of NaCl and nitrate. Plants exposed to high salinity (500 mm ) and low nitrate (0.5 mm ) tended to produce heavy seeds. Either high salinity (500 mm ) or high nitrate (5 mm ) increased the brown/black seed ratio. The concentrations of Na⁺, K⁺, and Cl^? were higher in brown than in black seeds, and NO₃^? concentrations were higher in black than in brown seeds, regardless of NaCl and nitrate treatments during plant culture. Regardless of NaCl and nitrate concentrations during germination, seeds from plants grown with 0.5 mm nitrate generally germinated more rapidly than seeds from plants grown with 5 mm nitrate, and the difference was greater for black than for brown seeds. Exogenous nitrate during germination enhanced the germination of brown seeds less than that of black seeds. Producing more brown seeds and heavy black or brown seeds appears to be an adaptation of S. suaeda to saline environments. Producing more black seeds, which tend to remain dormant, should reduce competition for nitrogen and appears to be an adaptation to nitrogen‐limited environments. In conclusion, nitrate provided exogenously or by mother plants to black seeds may act as a signal molecule that enhances the germination of black S. suaeda seeds.     

Foliage colour influence on seed germination of Bienertia cycloptera in Arabian deserts

Bienertia cycloptera (Chenopodiaceae) produces two types of leaf foliage colour (reddish and yellowish). In order to determine the role of leaf colour variation in regulating the germination characteristics and salinity tolerance during germination, a study was conducted on seeds collected from plants of both colours. Seeds with and without pulp were germinated under two illumination conditions (12‐h light photoperiod and continuous dark), three alternating temperature regimes (15/25°C, 20/30°C and 25/35°C), and several salinity levels at 20/30°C. Germination percentage was significantly higher for seeds without pulp as compared to the seeds with pulp. The response of B. cycloptera seeds to salinity depended on the leaf colour. Thus, the seeds collected from reddish coloured plants were able to tolerate higher salinity compared to those of yellowish coloured plant. The germination recovery results indicate that the seeds from both coloured plants could remain viable in saline condition and they will be able to germinate once the salinity level are decreased by rain. The production of different foliage colours by B. cycloptera seems to be an adaptative strategy which increases the possibility for establishment in unpredictable environments by producing seeds with different germination requirements and salinity tolerance.