Hormones-induced modifications in the response of wheat flag leaf to NaCl

A field experiment was carried out to investigate the effects of presoaking the wheat grains (Triticum aestivum L.) in 33 or 66 mM NaCl and indolyl-3-acetic acid (IAA at 50 g m⁻³), gibberellic acid (GA₃ at 100 g m⁻³) or kinetin (100 g m⁻³) on some tolerance criteria in wheat flag leaf at different stages of development. At various stages of flag leaf development pretreatment with 33 or 66 mM NaCl decreased degree of succulence (particularly 66 mM), relative growth rate, net assimilation rate, relative water content, K⁺ content and K⁺/Na⁺ ratio and at the same time induced accumulation of abscisic acid and Na⁺. In the majority of cases grain pretreatment with GA₃ or kinetin and to a lesser extent with IAA alleviated either partially or completely the deleterious effect of salinity on the above mentioned parameters.     

Effect of NaCl,water stress or both on gas exchange and growth of wheat

Responses of wheat (Triticum aestivum L.) to various concentrations of NaCl and levels of drought were followed. With the rise of NaCl or drought, or NaCl and drought together, growth was retarded. The water content of shoots and roots was mostly unchanged. The chlorophyll and carotenoid contents were increased in plants subjected to salinity or drought or both. Only high salinity level induced a considerable decrease in net photosynthetic rate (P_N) and dark respiration rate (R_D). P_N and R_D were decreased with the decrease of soil moisture content. The content of Na⁺ in the shoots and roots of wheat plants increased with increasing salinity or decreasing soil moisture content or both treatments. Considerable variations in the content of K⁺, Ca²⁺ or Mg²⁺ were induced by the NaCl, drought or both treatments.     

Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha^—1, 90 kg N + 60 kg P₂O₅ ha^—1, 120 kg N ha^—1 and 120 kg N + 60 kg P₂O₅ ha^—1. Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12—14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

Effect of genome, induction medium and temperature pretreatment on green plant production in durum ( Triticum turgidum var. durum ) x bread wheat ( Triticum aestivum L. em Thell) crosses

The recalcitrancy of durum wheat (Triticum turgidum var. durum) to anther culture, was attempted to be overcome by transferring the responsible genes form bread wheat B-genome to the respective on durum wheat, determining an appropriate induction medium and clarifying the necessity of cold pretreatment. For this, three durum wheat cultivars were crossed to two bread wheat (Triticum aestivum L. em Thell) cultivars. The resulting F₁ plants and their original cultivars were grown in the field and anthers at the appropriate microspore stage were cultured on potato-2 and W₁₄ media with and without low temperature pretreatment. No green plants were produced from the parental durum wheat cultivars. In contrast, green plants were produced from the F₁ plants. The best results in three of the four F₁ hybrids were recorded when potato-2 was used as induction medium. A more variable response of the examined genotypes was noticed with respect to temperature pretreatment. Regarding green plant production, a negative effect of cold pretreatment was observed in two of the F₁ hybrids when they were cultured on potato-2. Chromosome counts on root tips from the resulting green plants revealed that they all carried D-genome chromosomes. The last observation could suggest that D-genome chromosomes are necessary for anther culture response in wheat. Yet, the production of one green plant with 15 chromosomes may indicate that the development of extracted durum genotypes from bread wheat genotypes with good response to in vitro anther culture might be possible. Further work however, is needed for this to be verified.     

Development and function ofAzospirillum-inoculated roots

Summary The surface distribution ofAzospirillum on inoculated roots of maize and wheat is generally similar to that of other members of the rhizoplane microflora. During the first three days, colonization takes place mainly on the root elongation zone, on the base of root hairs and, to a lesser extent, on the surface of young root hairs.Azospirillum has been found in cortical tissues, in regions of lateral root emergence, along the inner cortex, inside xylem vessels and between pith cells. Inoculation of several cultivars of wheat, corn, sorghum and setaria with several strains ofAzospirillum caused morphological changes in root starting immediately after germination. Root length and surface area were differentially affected according to bacterial age and inoculum level. During the first three weeks after germination, the number of root hairs, root hair branches and lateral roots was increased by inoculation, but there was no change in root weight. Root biomass increased at later stages. Cross-sections of inoculated corn and wheat root showed an irregular arrangement of cells in the outer layers of the cortex. These effects on plant morphology may be due to the production of plant growth-promoting substances by the colonizing bacteria or by the plant as a reaction to colonization. Pectic enzymes may also be involved. Morphological changes had a physiological effect on inoculated roots. Specific activities of oxidative enzymes, and lipid and suberin content, were lower in extracts of inoculated roots than in uninoculated controls. This suggests that inoculated roots have a larger proportion of younger roots. The rate of NO^– ₃, K⁺ and H₂PO^– ₄ uptake was greater in inoculated seedlinds. In the field, dry matter, N, P and K accumulated at faster rates, and water content was higher inAzospirillum-inoculated corn, sorghum, wheat and setaria. The above improvements in root development and function lead in many cases to higher crop yield.     

Combined effect of salinity and hypoxia in wheat (Triticum aestivum L.) and wheat-Thinopyrum amphiploids

The effects of sodium chloride salinity and hypoxia were studied in eight wheat lines and three wheat-Thinopyrum amphiploids in vermiculite-gravel culture. The lines were treated with either 100 or 150 mol m^–3 NaCl with and without hypoxia. Saline hypoxic conditions significantly reduced the vegetative growth, water use, grain and straw yields for all wheat varieties except the amphiploids, whereas NaCl or hypoxia alone had less pronounced effects. In addition, saline hypoxic stress reduced K⁺ concentration and increased significantly the Na⁺ and Cl^– concentrations in cell sap expressed from leaves. There was more Na⁺ and Cl^– accumulation in wheats than the amphiploids in hypoxic conditions at 150 mol m^–3 NaCl. Of the wheats, Pato was the most sensitive at all stress levels while aTriticum aestivum cv. Chinese Spring ×Thinopyrum elongatum amphiploid was the most tolerant of the three amphiploids.     

Seed development and vivipary in Zea mays L.

Seed development was investigated in kernels of developing wild-type and viviparous (vp-1) Zea mays L. Embryos and endosperm of wild-type kernels began to dehydrate at approx. 35 d after pollination (DAP); viviparous embryos did not desiccate but accumulated fresh weight via coleoptile growth in the caryopses. Concentrations of endogenous abscisic acid (ABA) in the embryo were relatively high early in development, being approx. 150 ng·g^-1 fresh weight at 20 DAP. The ABA content declined thereafter, falling to approx. 50 ng·g^-1 at 30 DAP. Endosperm ABA content was always low, being less than 20 ng·g^-1. There were no differences between wild-type and vp-1 tissues. Immature kernels did not germinate when removed from the ear until late in development. The ability to germinate was correlated with decreasing moisture content in the endosperm at the time of removal; premature drying of immature kernels resulted in greatly increased germination following imbibition. Excised embryos germinated precociously when removed from the endosperm as early as 25 DAP. Such germination could be prevented by treatment with 10^-5 M ABA or by lowering the solute potential (_s) of the medium with 0.3 M mannitol. Treatment of excised embryos with ABA led to internal ABA concentrations comparable to those in embryos in which germination was inhibited in situ. Mannitol treatment did not have this effect, although water-deficit stress of excised embryos resulted in substantial ABA production. Germinated vp-1 embryos were less sensitive to growth inhibition by ABA or mannitol than germinating wild-type embryos. The vp-1 seedlings were not wilty and their transpiration rates were reduced in response to ABA or water shortage.Abbreviations and symbols ABA abscisic acid - DAP days after pollination - FW fresh weight - vp-1 viviparous genotype - _s solute potential     

Influence of Seed Size on Exploitation by the Rice Weevil, Sitophilus oryzae

Oviposition decisions and their fitness consequences for the seed parasite Sitophilus oryzae (L.) (Coleoptera: Curculionidae) were investigated. Female S. oryzae lay eggs inside seeds such as wheat [Triticum aestivum (L.)]. Because larvae develop to adult within a single seed, the resources available are determined by the behavior of the female parent and characteristics of the seed in which the egg was deposited. Females were demonstrated to lay more eggs in kernels 20 mg. Females initiated the chewing of oviposition holes in shriveled kernels but were less likely to oviposit in them. Progeny size increased with increasing seed size, but the probability of an adult emerging was not affected. Females accepted large kernels more quickly than small kernels and this contributed to increased oviposition in large kernels. The increase in the number of eggs per kernel appears to result from an increase in number of visits resulting in oviposition rather than an increase in the number of eggs laid during a visit.     

The integration of whole-root and cellular hydraulic conductivities in cereal roots

The hydraulic conductivities of excised whole root systems of wheat (Triticum aestivum L. cv. Atou) and of single excised roots of wheat and maize (Zea mays L. cv. Passat) were measured using an osmotically induced back-flow technique. Ninety minutes after excision the values for single excised roots ranged from 1.6·10^-8 to 5.5·10^-8 m·s^-1·MPa^-1 in wheat and from 0.9·10^-8 to 4.8·10^-8 m·s^-1·MPa^-1 in maize. The main source of variation was a decrease in the value as root length increased. The hydraulic conductivities of whole root systems, but not of single excised roots, were smaller 15 h after excision. This was not caused by occlusion of the xylem at the cut end of the coleoptile. The hydraulic conductivities of epidermal, cortical and endodermal cells were measured using a pressure probe. Epidermal and cortical cells of both wheat and maize roots gave mean values of 1.2·10^-7 m·s^-1·MPa^-1 but in endodermal cells (measured only in wheat) the mean value was 0.5·10^-7 m·s^-1·MPa^-1. The cellular hydraulic conductivities were used to calculate the root hydraulic conductivities expected if water flow across the root was via transcellular (vacuole-to-vacuole), apoplasmic or symplasmic pathways. The results indicate that, in freshly excised roots, the bulk of water flow is unlikely to be via the transcellular pathway. This is in contrast to our previous conclusion (H. Jones, A.D. Tomos, R.A. Leigh and R.G. Wyn Jones 1983, Planta 158, 230–236) which was based on results obtained with whole root systems of wheat measured 14–15 h after excision and which probably gave artefactually low values for root hydraulic conductivity. It is now concluded that, near the root tip, water flow could be through a symplasmic pathway in which the only substantial resistances to water flow are provided by the outer epidermal and the inner endodermal plasma membranes. Further from the tip, the measured hydraulic conductivities of the roots are consistent with flow either through the symplasmic or apoplasmic pathways.Symbols L _{p, cell} cell hydraulic conductivity - L _{p, root} root hydraulic conductivity - L _{p, root} calculated root hydraulic conductivity - root reflection coefficient     

Crop water availability in early agriculture: evidence from carbon isotope discrimination of seeds from a tenth millennium BP site on the Euphrates

The analysis of carbon isotope discrimination (Δ) in crop plant remains from archaeological sites may help to assess water availability for early agriculture. This study presents the analysis of Δ in seeds of naked wheat (Triticum aestivum/durum), lentil (Lens orientalis/culinaris), and flax (Linum sp.) found at the archaeological site of Tell Halula in the valley of the Middle Euphrates (Syria). This Neolithic site is the oldest in this region of the Fertile Crescent where the cultivation of domesticated plants has been reported, with seed remains ranging from 9550 to 8465 BP. Most of the seeds analysed showed Δ values greater than 16 ‰, reaching 20 ‰ for some samples of flax. For wheat, Δ values were much higher than those reported in present-day (1996) durum wheat crops cultivated under rainfed conditions in north-west Syria under environments with somewhat higher rainfall than Tell Halula. Similarly, grains of present-day (1997) barley cultivated in the archaeological site also showed lower values than those found in archaeological kernels. An empirical relationship between Δ of mature kernels and total precipitation (plus irrigation where applicable) from heading to maturity (r² = 0.82, n = 11) was established for durum wheat, currently cultivated in different environments of the Mediterranean basin. The resulting relationship was applied to the data on Δ of wheat fossil kernels from Tell Halula to estimate the accumulated water inputs during the time (about 6 weeks) the kernels were produced. Calculated water inputs for wheat during early agriculture were (over 110 mm) at least 5 times higher than current-day rainfall accumulated in Tell Halula during the same phenological period. These results strongly suggest that early agriculture wheat was cultivated at Tell Halula under much wetter conditions than are currently to be found in the area. The presence of flax and its very high Δ values also support this conclusion. Whether such humid conditions during cultivation were due to moister conditions prevailing at this time, by planting in alluvial areas or by irrigation works is discussed.     

水分胁迫下内生真菌球毛壳ND35对冬小麦苗期生长和抗旱性的影响

为明确不同水分条件下内生真菌对冬小麦苗期生长和抗旱性的影响,以抗旱型小麦品种山农16和水分敏感型小麦品种山农22为材料,利用荧光定量PCR技术检测小麦干旱诱导基因脱水素wzy2的表达量来了解冬小麦在干旱胁迫下相关基因的表达差异,通过测定相关生理指标与酶活性来判断小麦发育及其在干旱胁迫下的生理响应状况。结果表明,与正常水分ND35组相比,接种球毛壳菌(Chaetomium globosum)ND35的干旱处理组小麦的根冠比、总蛋白含量、脯氨酸含量及丙二醛含量等指标显著提高,小麦叶片含水量和可溶性糖含量有所降低。在干旱处理组中,球毛壳菌ND35可以显著提高小麦山农16的根长和山农22的株高,接种球毛壳ND35的山农16脯氨酸含量、可溶性糖含量、过氧化氢酶活性比对照组均显著提高,丙二醛含量比对照组降低9.0%,但差异不显著;山农22脯氨酸含量和过氧化氢酶活性比对照组显著提高,丙二醛含量和可溶性糖含量比对照组有所降低,但可溶性糖含量差异不显著;相对定量检测数据显示,接种球毛壳ND35后,两种小麦脱水素wzy2基因的表达量较对照组均能够显著提高。综合分析说明内生真菌球毛壳ND35可以促进冬小麦苗期根系和植株发育,小麦提前进入三叶期,增强小麦避旱性,同时提高小麦根系活力,增强小麦耐旱性;提高个体细胞内水分、糖分、脯氨酸含量,降低丙二醛的氧化性损伤,增强过氧化氢酶活性,从而提高两种冬小麦对干旱胁迫的耐受能力;球毛壳ND35促进小麦干旱诱导相关基因wzy2的表达量,进而提高抗旱相关蛋白的表达,从而提高两种冬小麦耐脱水性和对干旱胁迫的适应性。     

The influence of NO3 - and NH4 + nutrition on the carbon and nitrogen partitioning characteristics of wheat (Triticum aestivum L.) and maize (Zea mays L.) plants

The carbon and nitrogen partitioning characteristics of wheat (Triticum aestivum L.) and maize (Zea mays L.) grown hydroponically at a constant pH on either 4 mM or 12 mM NO₃ ^- or NH₄ ⁺ nutrition were investigated using either ¹⁴C or ¹⁵N techniques. Greater allocation of ¹⁴C to amino-N fractions occurred at the expense of allocation of ¹⁴C to carbohydrate fractions in NH₄ ⁺-compared to NO₃ ^--fed plants. The [¹⁴C]carbohydrate:[¹⁴C]amino-N ratios were 1.5-fold and 2.0-fold greater in shoots and roots respectively of 12 mM NO₃ ^--compared to 12 mM NH₄ ⁺-fed wheat. In both 4 mM and 12 mM N-fed maize the [¹⁴C]carbohydrate:[¹⁴C]amino-N ratios were approximately 1.7-fold and 2.0-fold greater in shoots and roots respectively of NO₃ ^--compared to NH₄ ⁺-fed plants. Similar results were observed in roots of wheat and maize grown in split-root culture with one root-half in NO₃ ^--and the other in NH₄ ⁺-containing nutrient media. Thus the allocation of carbon to the amino-N fractions occurred at the expense of carbohydrate fractions, particularly within the root. Allocation of ¹⁴N and ¹⁵N within separate sets of plants confirmed that NH₄ ^--fed plants accumulated more amino-N compounds than NO₃ ^--fed plants. Wheat roots supplied with ¹⁵NH₄ ⁺ for 8 h were found to accumulate ¹⁵NH₄ ⁺ (8.5 g ¹⁵N g^-1 h^-1) whereas in maize roots very little ¹⁵NH₄ ⁺ accumulated (1.5 g ¹⁵N g^-1 h^-1)It is proposed that the observed accumulation of ¹⁵NH₄ ⁺ in wheat roots in these experiments is the result of limited availability of carbon within the roots of the wheat plants for the detoxification of NH₄ ⁺, in contrast to the situation in maize. Higher photosynthetic capacity and lower shoot: root ratios of the C₄ maize plants ensure greater carbon availability to the root than in the C₃ wheat plants. These differences in carbon and nitrogen partitioning between NO₃ ^--and NH₄ ⁺-fed wheat and maize could be responsible for different responses of wheat and maize root growth to NO₃ ^- and NH₄ ⁺ nutrition.     

Transfer of Ph I genes promoting homoeologous pairing from Triticum speltoides to common wheat

Diploid-like chromosome pairing in polyploid wheat is controlled by several Ph (pairing homoeologous) genes with major and minor effects. Homoeologous pairing occurs in either the absence of these genes or their inhibition by genes from other species (Ph ^I genes). We transferred Ph ^I genes from Triticum speltoides (syn Aegilops speltoides) to T. aestivum, and on the basis of further analysis it appears that two duplicate and independent Ph ^I genes were transferred. Since Ph ^I genes are epistatic to the Ph genes of wheat, homoeologous pairing between the wheat and alien chromosomes occurs in the F₁ hybrids. Using the Ph ^I gene stock, we could demonstrate homoeologous pairing between the wheat and Haynaldia villosa chromosomes. Since homoeologous pairing occurs in F₁ hybrids and no cytogenetic manipulation is needed, the Ph ^I gene stock may be a versatile tool for effecting rapid and efficient alien genetic transfers to wheat.Contribution no. 93-435-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan, KS 66506-5502, USA     

Water-soluble phenolic compounds in the coat control germination and peroxidase reactivation in <Emphasis Type="Italic">Triticum aestivum</Emphasis> seeds

In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid equivalent g⁻¹ dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1% H₂O₂ reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H₂O₂ pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated. Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation.     

Microbial and enzymatic improvement of anaerobic digestion of waste biomass

Metabolic activities of different microorganisms (Bacillus subtilis, B. licheniformis and Aspergillus niger) and hydrolytic enzymes (concentrations: 1 to 200 mg enzyme solids g^–1 feed) were studied individually and in combinations with respect to H₂ and methane production from damaged wheat grains. Bacillus subtilis, B. licheniformis and pre-existing hydrogen producers (control) produced 45 to 64 l H₂ kg^–1 total solids and subsequently, with the help of added methanogens, 155 to 220 l methane kg^–1 total solids could be produced. H₂ production from damaged wheat grains could be decreased to 28% or enhanced up to 152% with respect to control, by employing various microbial and enzymatic treatments. Similarly, it has been made possible to vary methane production capacities from as low as 17% to as high as 110% with respect to control.     

Immunocytochemical localization of phosphoenolpyruvate carboxylase and photosynthetic gas-exchange characteristics in ears of Triticum durum Desf.

The presence and distribution of phosphoenolpyruvate carboxylase (PEPCase) in the glumes and immature grains of durum wheat (Triticum durum Desf.) were studied by electron-microscopical immunolabeling of PEPCase with polyclonal antibodies followed by protein A-gold. Plants were grown under mediterranean field conditions and samples were obtained two weeks after anthesis. In the kernels, high gold label was associated with the unstained areas of the protein bodies of aleurone cells, whereas labeling in the cytoplasm and chloroplasts of the pericarp was slight, although significantly above the background. In the glumes, high gold label was only located in cytoplasmic granules (vesicles) of the mesophyll cells, although labeling in the cytoplasm and chloroplasts was also significantly above the background. These observations in immature kernels and glumes are in accordance with the anaplerotic role of this enzyme, as evidenced in C₃ plants. Measurements of apparent photosynthesis and its O₂ dependence and CO₂ compensation concentration were made on ears and flag leaves of durum wheat. In addition, an analog of phosphoenolpyruvate, 3,3-dichloro-2-dihydroxy-phosphinoylmethyl-2-propenoate, was used to inhibit PEPCase and, thereby, to assess the contribution of the PEPCase to photosynthesis in detached ears. There was no effect of the inhibitor on the apparent photosynthesis of ears. Whereas inhibition of apparent photosynthesis by 210 mL · L^–1 O₂ in flag leaves was typical of C₃ species, inhibition in ears was even greater. The CO₂ compensation concentrations in different ear parts were similar to or higher than in flag leaves and the O₂ dependence was also comparable (about 70%). Therefore, gas-exchange data give further support to the assumption that a C₄ cycle is absent or limited to very low rates in ears of durum wheat.Abbreviations and Symbol AP apparent photosynthesis - BSA bovine serum albumin - DCDP 3,3-dichloro-2-dihydroxyphosphinoylmethyl-2-propenoate - PBS phosphate-buffered saline - PEP phosphoenolpyruvate - PEPCase PEP carboxylase - CO₂ compensation concentration We thank Dr. Sam Sun (University of Hawaii) for kindly providing the PEPCase antibodies and Drs. C.L.D. Jenkins and M.D. Hatch (Division of Plant Industry, CSIRO, Canberra, Australia) for supplying DCDP for these experiments. We are also grateful to Dr. Robert Bargalló and Mrs. Ana Ribero (Servei de Microscopia Electronica, Universitat de Barcelona) for technical assistance in electron-microscopy studies. Participation of Drs. J.L. Araus and J. Bort in this work was supported by the Research Project of CICYT AGF92-0301, Spain.     

Leaf–water relations and ion concentrations of the halophyte <Emphasis Type="Italic">Atriplex hortensis</Emphasis> in response to salinity and water stress

The impact of salinity and water stress was analyzed in the xero-halophyte Atriplex hortensis using two varieties: green orach (A. hortensis var. purpurea) and red orach (A. hortensis var. rubra). A. hortensis L. is a C₃ species well adapted to salt and drought conditions. To collect information on the physiological impact of different salt and water deficit levels on their water stress resistance, plants were exposed for 3 months to solution containing four levels of NaCl or to water stress regimes including four levels of field capacity. Osmotic potential at zero turgor Ψ_s⁰, osmotic potential at full turgor (Ψ_s¹⁰⁰), relative water content (RWC), ion concentration (Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl⁻), and malondialdehyde (MDA) were determined at the end of the treatment. The salinity and water stress induced a decrease in Ψ_s¹⁰⁰, Ψ_s⁰, and RWC in both varieties, recorded changes being higher in plants of red variety than those of green variety. Both varieties specifically accumulated Na⁺ in response to drought and salt stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. In contrast, the presence of NaCl and water stress induced a decrease in K⁺, Ca²⁺, and Mg²⁺ concentration in both varieties. Salinity clearly induced an increase in Cl^– concentration in all tissues, but water stress had no impact on this parameter. MDA concentration increased in response to water stress and exogenous NaCl. Based on these findings the more drought-tolerant red orach may be grown in water-limiting soils.     

Ion exchange properties of plant root cell walls

Acid-base properties and the swelling capacity of wheat, lupin and pea root cell walls were investigated. Roots of seedlings and green plants of different age were analysed by the potentiometric method. The ion exchange capacity (S _i) and the swelling coefficient (K ^cw) of root cell walls were estimated at various pH values (from 2 to 12) and at different ionic strength (between 0.3 and 1000 mM). To analyse the polysigmoid titration curves pH_i = f (S _i), the Gregor's equation was employed. It was shown that the Gregor's model fits well the experimental data. The total number of the cation exchange (S _t ^cat) and the anion exchange (S _t ^an) groups were determined in the root cell walls. The number of the functional group of each type (S ^j) was estimated, and the corresponding values of pK _a ^j were calculated. It was shown that for all types of cation exchangeable groups arranged in the cell wall structure the acid properties are enhanced by the increasing concentration of electrolyte. For each ionogenic group the coefficients of Helfferich's equation [pK _a ^j = f (C ^K+)] were determined. It was found that the swelling of root cell walls changes with pH, C ^K+ and strongly depends on plant species. Within the experimental pH and C ^K+ range the swelling coefficient changes as follows: lupin > pea > wheat. The obtained results show that for the plant species under investigation the differences in the swelling coefficients originate from (a) the differences in the cross-linking degrees of polymeric chains arranged in the cell wall structure, (b) the differences in the number of carboxyl groups and (c) the differences in the total number of functional groups. Based on the estimated swelling coefficients in water it could be inferred that for wheat the cross-linking degree of the polymeric chains in the root cell walls is higher than those for lupin or pea. It has been emphasized that the calculated parameters (S ^j, pK _a ^j, K ^cw), the equation {pK _a ^j = f (C^K+)} and the dependencies {K ^cw = f (C^K+, pH)} allow to estimate quantitatively the changes in the ion exchange capacity of the root cell walls in response to the changes in an ionic composition of an outer solution. The results of these estimations allow to suggest that (a) the root apoplast is a compartment where the accumulation of cations takes place during the first stage of cation uptake from an outer medium, and (b) the accumulation degree is defined by pH and ionic composition of an outer solution. On the basis of the literature review and the results of the present experimental study it was proposed that the changes in the cell wall swelling in response to variances of environmental or experimental conditions could lead to a change of the water flow through a root apoplast. It has been supported that there is direct relationship between the swelling of root cell walls and the water flow within the plant root apoplast.     

Selection and molecular characterization of imidazolinone resistant mutation-derived lines of Tritordeum HT621

Imidazolinone herbicides resistant varieties, induced by mutations at the AHAS gene (acetohydroxyacid synthase), have been developed in many crops. Hexaploid tritordeum (Tritordeum Asch. & Graebn.) is the amphiploid derived from the cross between Hordeum chilense (H^chH^ch) and durum wheat Triticum turgidum L. (Thell) (AABB). Tritordeums have the potential to become a new crop with high added-value for food or feed. Mutagenesis with EMS was conducted to obtain imidazolinone resistant lines derived of the tritordeum HT621. Eleven M₃ plants were selected after imidazolinone treatment and five descendants of two of these lines (HT621-M3R1-3 and HT621-M3R10-1) were analyzed at the molecular level. Partial sequences of the three homologous AHAS loci in genomes A, B, and H^ch were obtained as well as those of HT621. A partial sequence of the AHAS gene in Hordeum chilense is first described in this work, and the designation ahasL-H ^ch 1 is proposed. A single Ser-Asn₆₂₇ substitution at the AHAS locus in the B genome is responsible of resistance in both lines. We propose the name AhasL-B2 for this resistance allele. This is the first report of the selection of imidazolinone resistant lines of tritordeum and the molecular characterization of the mutation conferring this resistance.     

不同生境盐地碱蓬对氮饥饿的响应

为了探讨不同生境盐地碱蓬对低氮生境的适应机制,测定了盐渍环境下(200 mmol/L Na Cl)不同浓度硝态氮(0.3、5 mmol/L NO~-_3-N)预处理两种生境盐地碱蓬经氮饥饿后的NO~-_3含量、硝酸还原酶(NR)活性、光合特性及生长状况。结果表明,0.3和5 mmol/L NO~-_3-N处理以及进行氮饥饿时,潮间带生境盐地碱蓬叶片NO~-_3含量均高于内陆生境盐地碱蓬。与内陆生境盐地碱蓬相比,氮饥饿后,潮间带生境盐地碱蓬叶绿素含量、NR活性和光合放氧速率下降幅度均小于内陆生境盐地碱蓬,在0.3mmol/L NO~-_3-N预处理进行氮饥饿时趋势更加明显。0.3 mmol/L NO~-_3-N预处理后氮饥饿对潮间带生境盐地碱蓬根冠比没有影响,却降低内陆生境盐地碱蓬根冠比。上述结果表明,低氮条件下潮间带生境盐地碱蓬具有较高的NO~-_3储存能力,在环境持续氮素缺乏时具有较高的NO~-_3-N再利用能力,能更好地维持氮代谢以及光合性能。说明潮间带生境盐地碱蓬能更好地适应低氮生境。