Salinity-yield response functions of barley genotypes assessed with a triple line source sprinkler system

Evaluation of the salt tolerance of crop cultivars under field conditions is greatly complicated by the typical temporal and spatial variability of soil salinity. We obtained the grain yield – salinity response functions of 124 barley genotypes by growing them in ten salinity treatments imposed by a Triple Line Source Sprinkler (TLS) system during five consecutive years. Additional objectives were to ascertain the consistency and reproducibility over years of these functions, to quantify the deleterious effects of saline sprinkling irrigations, and to assess correlations between salinity tolerance and leaf sap salt concentration. The consistency and reproducibility of the response functions within and between years were adequate (only 8% of the response functions were discarded for statistical reasons). The Y _m (grain yield without salinity) and the EC₅₀ (the EC _e that reduces yield by 50%) estimates were not correlated (P > 0.05) suggesting that the most productive genotypes were not necessarily less salinity tolerant. Y _m was positively and significantly (P < 0.01) correlated with Y₆ and Y₁₂ (fitted grain yields at EC _e values of 6 dS m^-1, and 12 dS m^-1, respectively), indicating that it is a useful statistic in the selection of barley genotypes most productive under medium and high salinities. Foliar salt uptake due to saline sprinkling irrigations decreased the EC₅₀ by around 50% as compared with the salinity tolerance obtained with surface irrigation systems. No consistent relationships were found between either Y _m or EC₅₀ and the leaf sap osmotic potential, Cl, Ca, Na and K concentrations. They could not therefore be used in screening for salinity tolerance of barley. On the basis of the evidence from the present study, Y _m is the best statistic for predicting the most productive barley genotypes in salt-affected soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of gibberellic acid and different salt concentrations on germination percentage and physiological parameters of oat cultivars

Gibberellic acid (GA₃) is one of the plant growth regulators which improve salt tolerance and mitigate the salt stress impact on plants. The extant analysis was carried out to study the effect of GA₃ and different salt concentrations on seed germination and physiological parameters of oat cultivars. Oats is substantially less tolerant to salt than wheat and barley. Experimentation was conducted as factorial with Completely Randomized Block Design with three replicates. Different concentration of NaCl salt ((25, 50, 75 and 100 mM) were used in test control group and 100 and 150 ppm of GA₃ were used in two group by pre-treated (after 24 h of the seed soaking) and plants were analyzed on 15th day. Results indicate that increasing salinity would decrease the germination percentage and growth parameter in three oat cultivars. Quotes data indicating a 13%, 19.9% and 32.48% in cultivars NDO-2, UPO-212 and UPO-94 germination reduction when soil salinity reaches 50 mM. A 36.02%, 47.33% and 56.365 reduction in germination is likely when soil salinity reaches 100 mM respectively same cultivars. Seeds treated with GA₃ significantly promoted the percentage of germination, shoot and root length, total fresh and dry weight of seedling, tissue water content and seedling vigor index by NDO-2 and UPO-212 under different saline concentration. The maximum average of germination and growth parameters were observed from 150 ppm GA₃ treated seeds. But this concentration was significantly inhibited root length in sensitive cultivar UPO-94 at 75 and 100 mM salt as compared to 100 ppm. We observed that, the high concentration of GA₃ was not suitable for sensitive oat cultivars. Because the plant root are the real workforce behind any plants success. Thus, it may be concluding that, GA₃ treatment could curtail the toxic effect of salinity by increasing germination percentage and shoot and root length, total fresh and dry weight, tissue water content and seedling vigor index in tolerant cultivar.     

Salinity and salt composition effects on seed germination and root length of four sugar beet cultivars

Salinization is one of the most important factors affecting agricultural land in the world. Salinization occurs naturally in arid and semiarid regions where evaporation is higher than rainfall. Sugar beet yield declines with an increase in salinity, but the sensitivity to salts varies with salt composition in water and sugar beet growth stage. The aim of this study was to determine the effect of water salinity levels and salt composition on germination and seedling root length of four sugar beet cultivars (PP22, IC2, PP36, and 7233). The experiments were undertaken with irrigation water with two salt compositions (NaCl alone and mixture of MgSO₄ + NaCl + Na₂SO₄ + CaCl₂) in three replicates. Thirteen salinity levels with electrical conductivity (EC) of the irrigation water ranging from 0 to 30 dS/m were applied to each cultivar in both experiments. Seed germination percentage and seedling root length growth were determined in 13 days. Statistical analysis revealed that germination and root length were significantly affected by salt composition, cultivars and salinity levels. Regardless of salt composition, seed germination and seedling root length were significantly affected by the irrigation water with EC up to 8 dS/m and 4 dS/m, respectively. Except for cultivar PP22, the adverse effect of salinity of the irrigation water on seed germination and seedling root length was higher for NaCl alone than for the salt mixture, which refers to lower salt stress in field conditions with natural salt composition. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

Studies on the salt tolerance of some flower crops grown under glass

Summary The salt sensitivity of carnations, gerberas, anthuriums, chrysanthemums and hippeastrums was studied in an investigation. The crops were grown in basins filled with soil and irrigated with the aid of low level sprinklers. Two different cultivars of each crop were included in the experiments. The crops were irrigated with water containing different levels of salts. The EC of the irrigation water (EC_w) ranged between 0.2 and 3.9 mS.cm^–1 at 25°C.The salt applications had a deleterious effect on the development of all the flower crops used in the investigation. Carnations and chrysanthemums proved to be the least sensitive. Gerberas and hippeastrums showed a medium sensitivity and anthuriums proved to be the most salt sensitive. The latter crop also showed a specific sensitivity to sodium chloride.The salinity threshold values were low for most crops,i.e. EC_w<0.6. Slightly higher values were found for carnations only. The salinity decrease values of EC_w showed very wide variations and ranged from 6 to 34%. A method is proposed for the conversion of EC_w values into EC values for the saturation extract (EC_e) with the aid of the soil analytical results.The results of tissue analyses showed that the sodium and chloride contents in particular were affected by the salt applications. The effects of the salt applications on the uptake of the major nutrient elements varied from crop to crop.     

Terpenes from the Red Alga <Emphasis Type="Italic">Sphaerococcus coronopifolius</Emphasis> Inhibit the Settlement of Barnacles

In this study, we screened eight terpenes isolated from the organic extract of Sphaerococcus coronopifolius for their antifouling activity in order to find possible new sources of non-toxic or less toxic bioactive antifoulants. The anti-settlement activity (EC₅₀) and the degree of toxicity (LC₅₀) of S. coronopifolius metabolites was evaluated using larvae of the cirriped crustacean Amphibalanus (Balanus) amphitrite (cyprids and nauplii) as model organism. For five of eight tested metabolites EC₅₀ was lower than 5 mg/L. The most promising results were observed for bromosphaerol (3), which expressed an EC₅₀ value of 0.23 mg/L, in combination with low toxicity levels (LC₅₀ > 100 mg/L). The therapeutic ratio—an index used to estimate whether settlement inhibition is due to toxicity or other mechanisms—is also calculated and discussed.     

Variation in cardinal temperatures for germination among wheat (Triticum aestivum) genotypes

In most tropical regions where wheat is grown under irrigation, high temperatures at sowing adversely affect crop establishment and subsequent seedling survival. The objective of this study was to compare wheat (Triticum aestivum) genotypes for their ability to germinate and grow at high temperatures during the seedling stage. Twenty-five seeds each of 14 spring wheat cultivars were placed on moist filter paper at different temperatures (5°C to 40°C) in a one-way thermogradient plate to determine the cardinal temperatures for germination. Rate of germination at each temperature for each genotype was computed as the inverse of time taken for 50% of the seeds to germinate. Rate of germination for each genotype at different temperatures was modelled with temperature to determine the base (t_b), and optimum (t_opt) temperatures. Response of germination to temperature for each genotype was calculated as the slope of a linear regression of the rate of germination on temperature below t_opt. Genotypes differed in their optimum temperatures and Mexipak (= Kalyansona) had the lowest. Range in base temperature among the genotypes was between 0°C and 2°C differences but were not statistically significant though they might be biologically significant. Genotypes differed in their response to temperature with Gomam having the lowest rate, implying that it was slow to respond to increasing temperatures. Debeira and Cham 6 showed a similar response. Three lines which had performed well in spring wheat evaluation trials for moderate rainfall areas under heat stress had the highest response rate. It is concluded that combining higher optimum temperatures with faster response rates would result in better-adapted germplasm for regions where high temperatures persist at sowing.     

Asymptotics of the total net direct pharmacological effect for large drug doses

The direct pharmacological effect E is described by the E _max model relating E to the drug plasma concentration C _p . The area under the effect vs. time curve (AUC _E ) is used as the measurement of the total net pharmacological effect. The drug plasma concentrations are solutions of compartmental systems of ordinary differential equations with the input terminated after a finite time and controlled in a proportional manner by a single dose-like parameter. The asymptotics of the time derivative of C _p for large doses are derived and used as conditions which have to be satisfied by functions for which the asymptotics of the integral defining AUC _E are derived. The AUC _E is proportional to the time T _C>EC50 for which the drug concentration stays above the threshold level EC ₅₀. The threshold EC ₅₀ denotes the drug plasma concentration which elicits 50% of the maximum effect. The parameter T _C>EC50 is proportional to the logarithm of drug dose for large doses and its asymptotics is calculated up to the order o(1) as dose increases to infinity. The results are applied to basic pharmacokinetic systems. Received: 7 December 1999 / Revised version: 23 May 2000 / Published online: 23 October 2000     

Salinity tolerance in different cultivars of barley (Hordeum vulgare L.)

Seven barley(Hordeum vulgäre L.) cultivars tested varied greatly in their responses to root medium salinity (electrical conductivity of 3, 5, 10, 15 and 20 dS nr^-1)-lant growth was relatively more adversely affected than seed germination. Dry/fresh mass ratio increased at higher salinity levels in all barley cultivars indicating reduced water uptake. Higher K/Na ratio in plant shoots compared to that in the root medium solution indicated selective uptake of K that seems to be among processes involved in tolerance of cultivars to salinity stress.     

Seed yield of soybeans with daytime or continuous elevation of carbon dioxide under field conditions

Some studies of responses of plants to elevated concentrations of carbon dioxide (EC) added CO₂ only in the daytime, while others supplied CO₂ continuously. I tested whether these two methods of EC treatments produced differences in the seed yield of soybeans. Tests were conducted for four growing seasons, using open top chambers, with soybeans rooted in the ground in field plots. One third of the chambers were flushed with air at the current ambient [CO₂] (AC), one third had [CO₂] 350 μmol mol⁻¹ above ambient during the daytime (EC_d), while one third had [CO₂] 350 μmol mol⁻¹ above ambient for 24 h per day (EC_dn). EC_dn increased seed yield by an average of 62 % over the four years compared with the AC treatment, while EC_d increased seed yield by 34 %. Higher seed yield for EC_dn compared with EC_d occurred each year. In comparing years, the relative yield disadvantage of EC_d decreased with increasing overall seed yield. On days with high water vapor pressure deficits, soybean canopies with EC_d had smaller midday extinction coefficients for photosynthetically active radiation than canopies with EC_dn, because of a more vertical leaf orientation. Hence the seed yield of soybean at EC varied depending on whether EC was also provided at night, with much greater yield stimulation for EC_dn than for EC_d in some years.     

HIV spread in the San Francisco cohort: Scaling of the effective logistic rate for seropositivity

A simple scaling (semigroup) property is manifest in the functional form of the effective logistic rate for the increase in the HIV seropositive fraction in the San Francisco (City Clinic) cohort. Witht _i=4.5 years, this scaling property—r→λ^-2r undert→[λt+(λ−1)t _i] for all parameter values λ≧1—encapsulates the effects of relevant biological and sociological changes in the key epidemiological variables during the 8-year seropositive rise period, 1978–1985 inclusive.     

Salt stress response in tomato beyond the salinity tolerance threshold

Crop salt tolerance is generally assessed as the relative yield response to increasing root zone salinity, expressed as soil (EC_e) or irrigation water (EC_w) electrical conductivity. Alternatively, the dynamic process of salt accumulation into the shoot relative to the shoot biomass has also been considered as a tolerance index. These relationships are graphically represented by two intersecting linear regions, which identify (1) a specific threshold tolerance, at which yield begins to decrease, and (2) a declining region, which defines the yield reduction rate. Although the salinity threshold is intuitively a critical parameter for establishing plant salt tolerance, we focused our interest on physiological modifications that may occur in the plant at salinity higher than the so-called tolerance threshold. For this purpose, we exposed hydroponically grown tomato plants to eight different salinity levels (EC = 2.5 (non-salinized control); 4.2; 6.0; 7.8; 9.6; 11.4; 13.2; 15.0 dS m⁻¹). Based on biomass production, water relations, leaf ions accumulation, leaf and root abscisic acid and stomatal conductance measurements, we were able to identify a specific EC value (approximately 9.6 dS m⁻¹) at which a sharp increase of the shoot and root ABA levels coincided with (1) a decreased sensitivity of stomatal response to ABA; (2) a different partitioning of Na⁺ ions between young and mature leaves; (3) a remarkable increase of the root-to-shoot ratio. The specificity and functional significance of this response in salt stress adaptation is discussed.     

Response of wheat to subsoil salinity and temporary water stress at different stages of the reproductive phase

To examine the effects of subsoil NaCl salinity in relation to water stress imposed at different growth stages, wheat was grown in a heavy texture clay soil (vertosol) under glasshouse conditions in polythene lined cylindrical PVC pots (100 cm long with 10.5 cm diameter) with very low salinity level (EC_e 1.0 dS/m; ESP 1.0 and Cl 30 mg/kg soil) in top 10 cm soil (10–20 cm pot zone) and low salinity level (EC_e 2.5 dS/m, ESP 5, and Cl 100 mg/kg soil) in top 10–20 cm soil (20–30 cm pot zone). The plants were exposed to three subsoil salinity levels in the 20–90 cm subsoil (30–100 cm pot zone) namely low salinity (EC_e: 2.5 dS/m, ESP: 5, Cl: 100 mg/kg soil), medium salinity (EC_e: 4.0 dS/m, ESP: 10, Cl: 400 mg/kg) and high salinity (EC_e: 11.5 dS/m, ESP: 20, Cl: 1950 mg/kg) in the subsoil (20–90 cm soil layer: 30–100 cm pot zone). Watering of plants was withheld for 20 days commencing at either early booting or anthesis or mid grain filling, and then resumed until maturity, and these treatments were compared with no water stress. Water stress commencing at anthesis stage had the most depressing effect on grain yield and water use efficiency of wheat followed by water stress at grain filling stage and early booting stage. High subsoil salinity reduced grain yield by 39.1, 24.3%, and 13.4% respectively in plants water-stressed around anthesis, early booting, and mid grain filling compared with 36.6% in well-watered plants. There was a significant reduction in root biomass, rooting depth, water uptake and water use efficiency of wheat with increasing subsoil salinity irrespective of water regimes. Plants at high subsoil salinity had 64% of their root biomass in the top 0–30 cm soil and there was a marked reduction in subsoil water uptake. Roots also penetrated below the non-saline surface into salinised subsoil and led to attain high concentration of Na and Cl and reduced Ca/Na and K/Na ratio of flag leaf at anthesis stage. Results suggest that high subsoil salinity affects root growth and water uptake, grain yield and water use efficiency even in well water plants. Water stress at anthesis stage had the most depressing effect on wheat.     

RFLP mapping of QTLs conferring salt tolerance during germination in an interspecific cross of tomato

 Most cultivars of tomato (Lycopersicon esculentum) are sensitive to salinity during seed germination and at later stages. Genetic resources for salt tolerance have been identified within the related wild species of tomato. The purpose of the present study was to identify quantitative trait loci (QTLs) for salt tolerance during germination in an inbred backcross (BC₁S₁) population of an interspecific cross between a salt-sensitive tomato breeding line (NC84173, maternal and recurrent parent) and a salt-tolerant Lycopersicon pimpinellifolium accession (LA722). Onehundred and nineteen BC₁ individuals were genotyped for 151 restriction fragment length polymorphism (RFLP) markers and a genetic linkage map was constructed. The parental lines and 119 BC₁S₁ families (self-pollinated progeny of 119 BC₁ individuals) were evaluated for germination at an intermediate salt-stress level (150 mM NaCl+15 mM CaCl₂, water potential approximately −850 kPa). Germination was scored visually as radicle protrusion at 8-h intervals for 28 consecutive days. Germination response was analyzed by survival analysis and the time to 25, 50, and 75% germination was determined. In addition, a germination index (GI) was calculated as the weighted mean of the time from imbibition to germination for each family/line. Interval mapping, single-marker analysis and distributional extreme analysis, were used to identify QTLs and the results of all three mapping methods were generally similar. Seven chromosomal locations with significant effects on salt tolerance were identified. The L. pimpinellifolium accession had favorable QTL alleles at six locations. The percentage of phenotypic variation explained (PVE) by individual QTLs ranged from 6.5 to 15.6%. Multilocus analysis indicated that the cumulative action of all significant QTLs accounted for 44.5% of the total phenotypic variance. A total of 12 pairwise epistatic interactions were identified, including four between QTL-linked and QTL-unlinked regions and eight between QTL-unlinked regions. Transgressive phenotypes were observed in the direction of salt sensitivity. The graphical genotyping indicated a high correspondence between the phenotypes of the extreme families and their QTL genotypes. The results indicate that tomato salt tolerance during germination can be improved by marker-assisted selection using interspecific variation. Received: 29 January 1998 / Accepted: 4 June 1998     

Novel Fungitoxicity Assays for Inhibition of Germination-Associated Adhesion of Botrytis cinerea and Puccinia recondita Spores

Botrytis cinerea and Puccinia recondita spores adhere strongly to polystyrene microtiter plates coincident with germination. We developed assays for inhibition of spore adhesion in 96-well microtiter plates by using sulforhodamine B staining to quantify the adherent spores. In both organisms, fungicides that inhibited germination strongly inhibited spore adhesion, with 50% effective concentrations (EC₅₀s) comparable to those for inhibition of germination. In contrast, fungicides that acted after germination in B. cinerea inhibited spore adhesion to microtiter plates only at concentrations much higher than their EC₅₀s for inhibition of mycelial growth. Similarly, in P. recondita the ergosterol biosynthesis inhibitors myclobutanil and fenbuconazole acted after germination and did not inhibit spore adhesion. The assays provide a rapid, high-throughput alternative to traditional spore germination assays and may be applicable to other fungi.     

Molecular analysis of somatic embryogenesis through proteomic approach and optimization of protocol in recalcitrant Musa spp.

Somatic embryogenesis (SE) is a complex stress related process regulated by numerous biological factors. SE is mainly applicable to mass propagation and genetic improvement of plants through gene transfer technology and induced mutations. In banana, SE is highly genome dependent as the efficiency varies with cultivars. To understand the molecular mechanism of SE, a proteomics approach was carried out to identify proteins expressed during embryogenic calli (EC) induction, regeneration and germination of somatic embryos in the banana cultivar cv. Rasthali (AAB). In total, 70 spots were differentially expressed in various developmental stages of SE, of which 16 were uniquely expressed and 17 were highly abundant in EC compared to non‐embryogenic calli and explants. Also, four spots were uniquely expressed in germinating somatic embryos. The functional annotation of identified proteins revealed that calcium signaling along with stress and endogenous hormones related proteins played a vital role in EC induction and germination of somatic embryos. Thus, based on this outcome, the callus induction media was modified and tested in five cultivars. Among them, cultivars Grand Naine (AAA), Monthan (ABB) and Ney Poovan (AB) showed a better response in tryptophan added media, whereas Red Banana (AAA) and Karpuravalli (ABB) showed maximum EC induction in kinetin and CaCl₂ supplemented media respectively. Simultaneously, germination media were modified to induce proteins responsible for germination. In cv. Rasthali, media supplemented with 10 mM CaCl₂ showed a maximum increase in germination (51.79%) over control plants. Thus, the present study revealed that media modification based on proteomic analysis can induce SE in recalcitrant cultivars and also enhance germination in cultivars amenable for SE.     

Salt tolerance of two differently drought-tolerant wheat genotypes during germination and early seedling growth

Summary Osmotic and specific ion effect are the most frequently mentioned mechanisms by which saline substrates reduce plant growth. However, the relative importance of osmotic and specific ion effect on plant growth seems to vary depending on the drought and/or salt tolerance of the plant under study. We studied the effects of several single salts of Na⁺ and Ca²⁺−NaCl, NaNO₃, Na₂SO₄, NaHCO₃, Na₂CO₃, and Ca(NO₃)₂—on the germination and root and coleoptile growth of two wheat (Triticum aestivum L.) cultivars, TAM W-101 and Sturdy, the former being more drought tolerant than the latter. The concentrations used were: 0, 0.02, 0.04, 0.08, 0.16, and 0.32 mol L⁻¹. Significant two- and three-way interactions were observed between cultivar, kind of salt, and salt concentration for germination, growth of coleoptile and root, and root/coleoptile ratio. Salts differed significantly (P<0.001) in their effect on seed germination, coleoptile and root growth of both cultivars. Germination of TAM W-101 seeds was consistently more tolerant than that of Sturdy to NaCl, CaCl₂, Ca(NO₃)₂, and NaHCO₃ salts at concentrations of 0.02, 0.04, 0.08, 0.16 mol L⁻¹. The osmotic potential, at which the germination of wheat seeds was reduced to 50% of that of the control, was different depending on the kind of salt used in the germination medium. NaCl at low concentrations (0.02 and 0.04 mol L⁻¹) stimulated the germination of both wheat cultivars. At concentrations of 0.02 to 0.16 mol L⁻¹, Ca²⁺ salts (CaCl₂ and Ca(NO₃)₂) were consistently more inhibitory than the respective Na⁺ salts (NaCl and NaNO₃) for germination of Sturdy. This did not consistently hold true for TAM W-101. Among the Na⁺ salts, NaCl was the least toxic and NaHCO₃ and Na₂CO₃ were the most toxic for seed germination. Root and coleoptile (in both wheat cultivars) differed in their response to salts. This differential response of coleoptile and root to each salt resulted in seedlings with a wide range of root/coleoptile ratios. For example, the root/coleoptile ratio of cultivar TAM W-101 changed from 2.09 (in the control) to 3.77, 3.19, 2.8, 2.44, 1.31, 0.32, and 0.0 when subjected to 0.08 mol L⁻¹ of Na₂SO₄, NaCl, CaCl₂, NaNO₃, Ca(NO₃)₂, NaHCO₃, and Na₂CO₃, respectively. Na₂CO₃ at 0.08 mol L⁻¹ inhibited root growth to such an extent that germinated wheat seeds contained coleoptile but no roots. The data indicate that, apart from the clear and more toxic effects of NaHCO₃ and Na₂CO₃ and lesser toxic effect of NaCl on germination and seedling growth, any toxicity-ranking of other salts done at a given concentration and for a given tissue growth may not hold true for other salt concentrations, other tissues and/or other cultivars. The more drought-tolerant TAM W-101, when compared to the less drought tolerant Sturdy, showed higher tolerance (at most concentrations) to NaCl, CaCl₂, Ca(NO₃)₂ and NaHCO₃ during its seed germination and to Na₂SO₄ and CaCl₂ for its root growth. This supports other reports that some drought-tolerant wheat cultivars are more tolerant to NaCl. In contrast, the coleoptile growth of drought-sensitive Sturdy was noticeably more tolerant to NaNO₃, Ca(NO₃)₂ and NaHCO₃ than that of drought-tolerant TAM W-101. Based on the above and the different root/coleoptile ratios observed in the presence of various salts, it is concluded that in these wheat cultivars: a) coleoptile and root tissues are differently sensitive to various salts, and b) at the germination stage, tolerance to certain salts is higher in the more drought-tolerant cultivar.     

Response of Photosynthetic Apparatus of Spring Barley (Hordeum vulgare L.) to Combined Effect of Elevated CO2 Concentration and Different Growth Irradiance

The response of barley (Hordeum vulgare L. cv. Akcent) to various photosynthetic photon flux densities (PPFDs) and elevated [CO₂] [700 μmol (CO₂) mol⁻¹; EC] was studied by gas exchange, chlorophyll (Chl) a fluorescence, and pigment analysis. In comparison with barley grown under ambient [CO₂] [350 μmol (CO₂) mol⁻¹; AC] the EC acclimation resulted in a decrease in photosynthetic capacity, reduced stomatal conductance, and decreased total Chl content. The extent of acclimation depression of photosynthesis, the most pronounced for the plants grown at 730 μmol m⁻² s⁻¹ (PPFD₇₃₀), may be related to the degree of sink-limitation. The increased non-radiative dissipation of absorbed photon energy for all EC plants corresponded to the higher de-epoxidation state of xanthophylls only for PPFD₇₃₀ barley. Further, a pronounced decrease in photosystem 2 (PS2) photochemical efficiency (given as F_V/F_M) for EC plants grown at 730 and 1 200 μmol m⁻² s⁻¹ in comparison with AC barley was related to the reduced epoxidation of antheraxanthin and zeaxanthin back to violaxanthin in darkness. Thus the EC conditions sensitise the photosynthetic apparatus of high-irradiance acclimated barley plants (particularly PPFD₇₃₀) to the photoinactivation of PS2. This revised version was published online in August 2006 with corrections to the Cover Date.     

陆地棉萌发至三叶期不同生育阶段耐盐特性

摘要：土壤盐渍化是一个世界性的资源问题和生态问题,盐分胁迫几乎会影响棉花所有重要的生命活动, 造成棉花的减产或其他不利影响。本试验通过对14个品棉花种（系）的萌发期耐盐性、芽期耐盐性以及两个耐盐性不同的品种（系）三叶期的耐盐性,对棉花不同时期的耐盐特性进行了研究,结果表明：棉花在不同生育阶段耐盐能力是不同的,棉花盐敏感时间是在萌发出苗期。随着生育期的延长,棉花的耐盐性是逐步提高的,进行耐盐性鉴定的最佳时期在是萌发出苗期。在三叶期,随着盐分浓度的提高,棉花苗受伤害程度逐渐增加,盐敏感性品种受伤害大于耐盐品种,在同样盐浓度胁迫条件下,耐盐性不同的品种各部分受到的伤害不同,耐盐品种（系）中棉所35受伤害程度由高到低依次为：真叶>上胚轴>子叶;盐敏感品种（系）Tamcot CAB-CS受伤害程度由高到低依次为：真叶> 子叶>上胚轴。     

Assessment of polyembryony in lemon: rescue and in vitro culture of immature embryos

The 27 lemon cultivars analysed could be considered slightly or moderately polyembryonic, with 25 to 43% of seeds being polyembryonic and from 1.3 to 1.6 embryos per seed. On this basis, it is necessary to rescue zygotic embryos at an immature stage. Rescue and in vitro embryo development have been studied in two Citrus limon polyembryonic cultivars. Sucrose (50 and 70 g/l) was combined with Murashige and Skoog and Gamborg’s B5 media and tested for optimal growth response. An important effect of genotype was observed: embryos from cultivar ‘Eureka’ had greater survival, germination percentage, and radical development. While the sucrose concentration in the medium did not have an effect on germination, the medium affected the embryo survival and root development of the seedlings, Gamborg’s B5 medium giving the best results. The ability to form plants in vitro was affected by an increase of embryo developmental stage. The germination and seedling height were greater with embryos of seeds collected 135–150 days after anthesis.