Growth rate, water relations and ion accumulation of soybean callus lines differing in salinity tolerance under salinity stress and its subsequent relief

A selected Glycine max (L.) salt-tolerant calluscell line (R100) was significantly more tolerant to salt than a salt-sensitiveline (S100) during exposure to salt stress. Growth (Fresh and Dry weights) ofthe R100 cell line declined significantly at NaCl concentrations greater than 75mM, while growth of the S100 cell line was already impaired at 25mM NaCl. Levels of Na⁺ and Cl^– inthe callus were elevated as the salt concentration increased, whileK⁺, Ca²⁺ and Mg²⁺ levels weremarkedly reduced. The lower s reduction and Na⁺accumulation found in the S100 callus corresponded with the higher callusdehydration during salinity. Calli grown on Miller's basal medium weresupplied with 100 mM NaCl for 12 days and then supplied with mediumwithout NaCl to relieve salinity stress. The Na⁺ andCl^– content decreased in both R100 and S100 cell lines duringthe first 24 h and reached normal levels four days after transferto the normal medium. This lower concentration was maintained until the end ofthe experiment. Concurrently, the K⁺ content andK⁺/Na⁺ ratio increased sharply and reached theirhighest levels within 24 h in both salt-sensitive and salt-tolerantcell lines. These data suggest that the inhibitory effects of salinization ongrowth and accumulation of potentially toxic ions (Na⁺,Cl^–) can be readily reversed when salinity is relieved.     

Growth, proline accumulation and ion content in sodium chloride-stressed callus of date palm

Summary Growth and physiological responses of date palm. Phoenix dactylifera L. cv. Barhee, callus to salinity stress were examined. Callus induced from shoot tips of offshoots was cultured on Murashige and Skoog medium supplemented with NaCl at concentrations ranging from 0 to 225 mM, in consective increments of 25 mM. Data obtained after 6 wk of exposure to salt have shown a significant increase in callus proliferation in response to 25 mM NaCl the lowest level tested, beyond which callus weight decreased. At 125 mM NaCl and higher, callus growth was nearly completely inhibited. Physiological studies on callus exposed to salt stress have shown an increase in proline accumulation in response to increased salinity. Proline accumulation was correlated to callus growth inhibition. Furthermore, increasing the concentration of NaCl in the culture medium generally resulted in a steady increase in Na⁺ and reduction in K⁺ concentrations. However, at 25 mM NaCl, the only level at which callus growth was significantly enhanced, an increase in K⁺ content was noted, in comparison to the NaCl free control. In response to increasing external NaCl level, the Na⁺/K⁺ ratio increased The Na⁺/K⁺ ratio was positively correlated to proline accumulation and hence callus growth inhibition. This study provides, an understanding of the response of date palm callus to salinity, which is important for future studies aimed at developing strategies for selecting and characterizing somaclonal variants tolerant to salt stress.     

Stage Development and Flowering in Dactylis glomerata L.

The results of pilot experiments lead to the conclusion thatD. glomerata exhibits a number of developmental stages: firstly,a juvenile stage during which the plant is insensitive to environmentalconditions which later stimulate flowering; secondly, an inductivestage, when the plant responds to periodic exposure to darknessat the conclusion of which it is fully induced or ripe to flower,and finally, a post-inductive stage during which inflorescencesare initiated and undergo further development; these are long-dayprocesses. In four populations studied the juvenile stage lasts about fiveweeks. In north European material daily exposure to seven hoursof darkness is near the minimum for induction although thereis considerable within-population variation. Further, it appearsthat the daily dark requirement becomes less as the plant ages. Comparisons are made of the flowering behaviour of D. glomerataand Lolium perenne. The differences between these species resultfrom the presence of a juvenile stage in Dactylis and the possibilityof satisfying its inductive requirement by long days. Inductionin Lolium requires short days or low temperature. The significance of these results is discussed in the lightof previous work on the environmental control of flowering inherbage grasses. The existence of three developmental stagescan explain the wide differences in interpretation of the floweringrequirements of Dactylis previously held. The possible evolutionof flowering requirements is also discussed.     

Effect of Light Intensity on Growth of Natural Populations of Dactylis glomerata L.

The growth of two natural populations of cocksfoot from contrastingclimatic regions, Norway and Portugal, was studied in two photoperiodsat three temperatures with three levels of light energy (48,144, and 240 W m^–2 in the wavelength interval 400–700nm). There was a consistent increase in relative growth-rate(RGR) in response to increased light energy up to 144 W m^–2,but above this energy level there was either no change, or,in some treatments, a decline. Net assimilation rate (NAR) increased,whilst leaf area ratio decreased from the lowest to the highestenergy level in most treatments. The decrease of LAR with increasedlight energy could be attributed to a decrease of both leafweight ratio (LWR) and specific leaf area (SLA), a greater proportionof dry matter being distributed to plant parts other than leaf.This effect occurred although there was a positive relationshipbetween light energy and relative leaf growth-rate (RLGR). Populationdifferences in these growth attributes were most marked in thetreatments with low-temperature and short-day conditions. Theefficiency of energy conversion of visible radiation declinedfrom 3–4 per cent at the lowest energy level to 1–2per cent at the highest energy level.     

The Effect of Temperature on the Growth of Cocksfoot (Dactylis glomerata L.)

The growth of cocksfoot at 14°, 22°, and 26° C wasmeasured at weekly intervals over a period of six weeks. Initially,the relative growth rates increased with increase in temperature,but during the final three weeks they were little differentat all three temperatures. The reduction in relative growthrates with time at 22° and 26° were associated withincreases in size which were partly reflected by reductionsin the leaf-area ratios. It is also likely that at 26° changesin the photosynthetic capacity of leaves, perhaps associatedwith decreasing concentrations of mineral nutrients, contributedto the decreased relative growth rates. Leaf expansion and increase in cell numbers were estimated overtwo-day periods at temperatures ranging from 5° to 30°C. Leaf expansion increased with increase in temperature throughoutthis range; extrapolation suggested that it would cease at temperaturesbelow 3° C. The optimum temperature for cell division appearedto be between 20° and 25°C. Different physiological processes appeared to be involved inthe temperature responses of plants of different sizes and histories.With young plants these responses resulted in a large overalleffect of temperature on the growth rate; with older plantsof the same size there appeared to be several compensatory responsesso that variation in temperature over an apprecaible range hadlittle overall effect.     

Drought survival,summer dormancy and dehydrin accumulation in contrasting cultivars of Dactylis glomerata

To study survival under prolonged and severe drought in the perennial grass Dactylis glomerata we compared dormant, resistant and sensitive cultivars (cvs.) in both field and glasshouse experiments. Water status, membrane stability and expression of dehydrins were assessed in the immature leaf bases, which are the last surviving organs. Analysis of leaf elongation and senescence of aerial tissues showed that dormancy was exhibited by the potentially dormant cultivar (cv.) only in the field. This cultivar exhibited a high survival rate, similar levels of dehydration and expression of a low-molecular weight (22–24 kDa) dehydrin in both drought and irrigated plants, whether fully dormant or not. At the same level of soil water deficit, there were no differences between the non-dormant drought resistant and drought sensitive cultivars in plant water status and membrane stability. However, the accumulation of dehydrins as drought progressed was markedly different between these cultivars and was associated with their contrasting survival. The possible role of the major low-molecular dehydrins in maintenance of cell integrity under dehydration is discussed with reference to both summer dormancy and survival under severe drought.     

Effect of Photoperiod on Vegetative Growth in Two Natural Populations of Dactylis glomerata L.

The growth of two natural populations of cocksfoot from contrastingclimatic regions (Norway and Portugal) was studied at four temperaturesand two photoperiods. Serial harvests were taken and quadraticcurves were fitted to log dry weight and leaf area for eachreplicate in order to calculate growth attributes at a constantplant weight for all treatments. Interactions of population,temperature, and photoperiod on relative growth-rate (RGR) werefound, with the greatest population differences at 5 and 30°C in an 8-h photoperiod. Leaf-area ratio (LAR) played alarger part than net assimilation rate (NAR) in determiningthe differential population responses in RGR to daylength, andthese differences in LAR were primarily the result of differentpatterns of dry-matter distribution within the plant.     

Plantlet formation from cultured inflorescences of Dactylis glomerata L.

The objective of this study was to demonstrate plantlet formation from cultured mature inflorescences of field-grown orchardgrass (Dactylis glomerata L.) plants. Whole tillers were collected and maintained in the dark at 4°C for either 19 or 25 days before panicle sections were plated on a Linsmaier and Skoog (LS) or Schenk and Hildebrandt (SH) agar medium containing 2,4-D. Generally, better results for both cell proliferation and plantlet formation were obtained with 1) large explants (many florets) on 9.1 μM 2,4-D compared to small explants (few florets) on 1.0 μM 2,4-D, 2) SH rather than LS medium and 3) when tillers were pretreated at 4°C for 25 days rather than 19 days. Chromosome counts of basal leaf cells in 94 regenerated plants showed that no plants possessed the gametic chromosome number of n=14.     

Phosphorus effect on the uptake,translocation and accumulation of the14C-urea in orchard grass (Dactylis glomerata L.)

Summary The effect of different phosphorus supplies on the uptake, translocation and accumulation of¹⁴C-urea by orchard grass was investigated. Phosphorus starvation inhibits the uptake, translocation and accumulation of the carbon of urea similarly to the nitrogen of urea. As compared with the uptake process the reduction of the accumulation is much more effected by the inhibition of the carbon translocation from roots to the aboveground parts. Lack of phosphorus also decreases the incorporation of the¹⁴C of urea into high-molecular compounds. The effect of phosphorus deficit on the accumulation of¹⁴C-urea increases with time of starvation.     

Diurnal Fluctuations in Growth and CO2 Exchange in Dactylis glomerata

Diurnal fluctuations in dry matter accumulation and leaf extensionof seedlings of Dactylis glomerata were followed through a 16-hlight period and a subsequent 8-h dark period at 20 °C.Themeasured increase in dry weight during the light period andthe decrease during the dark period showed a very good agreementwith calculated dry weight changes derived from the rates ofcarbon dioxide exchange of whole seedlings. Although dry weightof the leaf blades decreased during the dark period, leaf expansioncontinued throughout the 24-h period with associated changesin the ratio of fresh weight to dry weight of the leaf blades.     

Growth reductions in cocksfoot (Dactylis glomerata L.) as a result of SO2 pollution

The effects of exposing Dactylis glomerata L. to 11 pphm SO₂ for four weeks were investigated using a wind tunnel fumigation system. The pollutant was found to cause significant reductions in the numbers of tillers and green leaves, leaf area, root/shoot ratio and all dry weight fractions measured. The percentage yield reductions found for D. glomerata were compared with those previously found for Lolium perenne L. under the same conditions of exposure. It was concluded that D. glomerata may be slightly more sensitive to SO₂ than L. perenne. The magnitudes of the yield reductions found in these experiments are greater than those previously reported and this is discussed in relation to the rate of air movement through the fumigation system. It is concluded that the effects of SO₂ on plants in the field, and subsequent losses in the yields of crops, may have been under-rated in the past.     

Transgenic plants of Orchardgrass (Dactylis glomerata L.) from protoplasts

We have demonstrated the transfer and expression of a foreign chimeric gene in the grass species, Dactylis glomerata L. This species is a member of the Gramineae sub-family Pooideae, which includes the small grain cereals, from which transformed plants have not yet been obtained. A chimeric hygromycin-resistance gene was introduced into protoplasts isolated from an embryogenic suspension culture, using heat shock followed by electroporation or polyethylene glycol treatment. Cell colonies resistant to 20 g/ml hygromycin were selected in liquid medium using an agarose bead type culture system. Transformed calli were identified by Southern hybridization. Embryogenic callus was induced to regenerate plants and transformed plants were shown to contain the hygromycin resistance gene.Abbreviations 2,4-D 2,4-Dichloro-phenoxy-acetic acid - dicamba 3,6-dichloro-2-methoxy benzoic acid - PEG polyethylene glycol - SDS Sodium dodecyl sulfate - SH medium Medium of Schenk and Hildebrandt (1972)     

Phenotypic variation and performance of diploid subspecies of Dactylis glomerata L.

Dactylis glomerata L. is one of the best known examples of a polyploid complex that includes diploid (2n = 14), tetraploid (2n = 28) and hexaploid (2n = 42) types. The diploids, descending from the ancestors of the genus, are numerous, distinct forms adapted to specific environments and include all the morphological variation and ecological adaptation found in Dactylis. The objective of the present study was to shed more light on the differentiation of diploids and to obtain information for better exploiting the genetic resources of this species. To this end we carried out a discriminant analysis in the most widespread diploid subspecies based on a large number of morpho-physiological traits. We found that some characteristics, such as time to heading, time to flowering, vegetative regrowth, plant height and seed shattering are the most discriminant and enabled us to realize a more exact differentiation of the diploids with respect to the morphological criterion generally adopted. The results demonstrated that diploid taxa offer an interesting combination of relevant agronomical and ecological characteristics which could be useful in breeding programs to promote the use of this species in sustainable agriculture systems. We also performed cytological investigations and defined a general karyotype representative of the diploid Dactylis considered in this study.     

Embryoid and plantlet formation from leaf segments of Dactylis glomerata L.

Summary The purpose of this investigation was to demonstrate callus induction and plantlet formation from cultured leaf segments of 12–15 week-old Dactylis glomerata L. (orchardgrass) plants. Flat half-leaf sections, approximately 2–3 mm square, from the three innermost (youngest) leaves were isolated and individually plated serially beginning at the leaf base on a solid SH medium containing 30 M of 3,6-dichloro-oanisic acid (dicamba). Callus formed on leaf sections from all 50 plants used in the study. After transfer to SH medium with 1 M dicamba, plantlets formed from leaf sections of 9 of the 50 plants. In most cases plantlets formed from embryogenic callus but in a few cases embryoids formed directly on the leaf surface without an intervening callus state. These developed into plantlets when transferred to low auxin medium. The response for both callus and plantlet formation decreased with increasing distance both spatially and temporally from the shoot apex. Histological examination of embryogenic callus revealed the presence of non-zygotic embryos in various stages of development. The results provide further support for compentency (if not totipotency) of Gramineae leaf cells.     

放牧及刈割强度对鸭茅密度及能量积累的影响

1　引　　言放牧及刈割对牧草种群的影响 .一直是草地生态学研究的重点 .科学的放牧、刈割管理制度是保证草地畜牧业可持续发展的重要前提 .作为南方人工草地优势植物之一的鸭茅(Ｄａｃｔｙｌｉｓｇｌｏｍｅｒａｔａ) ,是一种经济效益高、生产价值大、在我国具有广泛应用前景的优良牧草 .通过对亚热带高山人工草地进行的梯度放牧及刈割实验 ,本文分析比较了不同放牧及刈割强度对鸭茅种群密度及能量积累的影响 ,旨在为该地区合理刈牧制度的建立提供理论依据 .2　研究地区与研究方法2 1　自然概况研究地点位于湖北长阳火烧坪 ,地理位置在 30…     

Embryogenic and callus-specific proteins in somatic embryogenesis of the grass,Dactylis glomerata L.

Somatic embryogenesis occurs spontaneously in some monocotyledoneous callus and cell suspension cultures maintained in suitable culture conditions. Nevertherless, the processes involved in somatic embryo development, and factors inducing this differentiation, are poorly understood. In order to study the changes in protein composition accompanying embryogenesis in cell suspension cultures of Dactylis glomerata L., embryos of various sizes and “undifferentiated” callus cells were separated and their total cellular protein extracts analyzed by two-dimensional polyacrylamide gel electrophoresis. Several proteins could be identified that are specific for embryos or callus under various culture conditions. Three independent detection methods were employed: silver-staining of proteins, in vivo labeling of proteins with [³⁵S]methionine, and in vitro translation of poly(A)⁺ RNA. All culture conditions tested, including those that induce embryonic proteins in carrot, fail to induce embryonic proteins in D. glomerata callus cells.     

鸭茅种质资源多样性研究进展

鸭茅是世界范围内广泛栽培的一种重要禾本科牧草,具有高产、优质、耐荫性强等特性。我国的野生鸭茅资源十分丰富,分布广泛,基因资源优良,但有关鸭茅的研究报导相对较少。为了更好地开发利用这一优良的牧草资源,本从形态学、细胞学和分子水平对国内外鸭茅种质资源多样性的研究进行了综述,并对今后我国的鸭茅研究工作提出了建议。     

Successful crosses between Festuca arundinacea Schreb. and Dactylis glomerata L.

Summary Five F₁ plants have been obtained after extensive crossing between different ecotypes or varieties of Festuca arundinacea Schreb. and Dactylis glomerata L. The success did not appear to depend on specific treatments (spraying with -aminocaproic acid or gibberellic acid or pre-pollination with killed pollen from the seed parent), but the crossability is limited to exceptional plants.F₁ hybrids showed characteristics of both the parents. In four hybrids various developmental disturbances were observed (low viability, aneusomaty, absence of development of inflorescences). Only one hybrid consistently showed 2n=35 chromosomes, good viability and growth, however, it was sterile. After clonal propagation, attempts for polyploidization were started.