盐地碱蓬二型性种子及其幼苗对盐渍环境的适应性

研究了盐地碱蓬二型性种子中离子含量与刚萌发幼苗耐盐性之间的关系,以及盐分对砂培盐地碱蓬二型性种子的幼苗生长、离子含量及光合特性的影响.棕色种子中离子含量显著高于黑色种子.与对照相比,100和400 mmol/L NaCl对棕色种子幼苗伸长没有抑制作用,却显著抑制黑色种子幼苗的伸长.NaCl处理下棕色种子的幼苗地上部分干重和主茎一级分枝数比黑色种子幼苗高,但二型性种子的幼苗叶片中离子含量、叶绿素含量及光合放氧速率却没有明显差异.上述结果说明盐地碱蓬棕色种子较高的离子含量可能是棕色种子刚萌发幼苗耐盐性较强的重要原因.棕色种子幼苗较高的生物量可能与其较多的分枝数有关.二型种子的这些特征可能决定了其在群落建成中所起到的不同作用.     

The effects of seed weight on growth and competitive ability of Rumex acetosella from two successional old-fields

Summary The effects of seed size on growth, biomass allocation and competitive ability of Rumex acetosella plants grown either individually or in competition were studied in two populations (6 months and 15 years old respectively) sampled from a postcultivation successional gradient. For plants grown individually there were highly significant effects of seed weight on growth after 43 days, with a higher relative growth rate (RGR) observed for plants raised from heavier seeds. However at the end of the experiment, seedlings developed from lighter seeds had a RGR 2 times greater than those from heavier seeds. Final biomass of the two types was not significantly different after 73 days of growth. When plants were grown individually, there were only slight differences between populations, but when grown in monocultures of 4 plants per pot, plants from the old population had higher root and leaf biomass per pot whereas those from the young population had a higher reproductive effort per pot. This suggests that a trade-off between allocation to sexual and vegetative reproduction occurs over successional time. In mixtures of light and heavy seeds, plants from light seeds were shorter, had fewer leaves and lower biomass than plants from heavy seeds, which were also taller and produced more dry matter than plants grown from heavy seeds in monoculture. The significant effects of seed weight and population on biomass parameters persisted unit the end of the experiment. Seedlings from heavy seeds were strong competitors: those from the young population grew better in the presence of neighbors than in monoculture and those from the late successional population suppressed the more the growth of their partners. Seedlings from light seeds were subordinate competitors. These results suggest that seedlings from seeds of different sizes benefit from contrasting ecological conditions and that selection acts on reproductive output along successional gradients.     

Gamma radiation effects on seed germination, growth and pigment content, and ESR study of induced free radicals in maize (Zea mays)

The effects of gamma radiation are investigated by studying plant germination, growth and development, and biochemical characteristics of maize. Maize dry seeds are exposed to a gamma source at doses ranging from 0.1 to 1 kGy. Our results show that the germination potential, expressed through the final germination percentage and the germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose. Moreover, plants derived from seeds exposed at higher doses (≤0.5 kGy) did not survive more than 10 days. Biochemical differences based on photosynthetic pigment (chlorophyll a, chlorophyll b, carotenoids) content revealed an inversely proportional relationship to doses of exposure. Furthermore, the concentration of chlorophyll a was higher than chlorophyll b in both irradiated and non-irradiated seedlings. Electron spin resonance spectroscopy used to evaluate the amount of free radicals induced by gamma ray treatment demonstrates that the relative concentration of radiation-induced free radicals depends linearly on the absorbed doses.     

GENETIC HISTORY AND GENERAL COMPARISONS OF TWO ALBINO MUTATIONS OF HELIANTHUS ANNUUS

Wallace , Raymond H. (U. Connecticut, Storrs.), and Helen M. Habermann . Genetic history and general comparisons of two albino mutations of Helianthus annuus. Amer. Jour. Bot. 46(3) : 157-162. Illus. 1959.—The genetic history of the progeny of a single ultrasonically-treated seedling of Helianthus annuus L. has been summarized for the 6 generations for which quantitative data are available. A yellow mutation was found in the F₂ generation and later in the F₅, a second, white mutation occurred. Both mutants have been grown to maturity by grafting them onto normal green host plants and they have set viable seeds. Both pigment-deficient conditions are inherited as single recessive factors. These albino strains form chlorophyll during their seedling stages if they are grown at low light intensities. Chlorophyll is destroyed, however, under bright illumination and, once bleached, the capacity for chlorophyll formation appears to be lost. The yellow mutant contains xanthophyll but no traces of carotene have been found. In the white mutant, neither carotene nor xanthophyll have been detected. Flower color in the yellow mutant is normal while the flowers of the white mutant have no apparent pigmentation. The growth pattern of grafted yellow mutants is normal, save for a stiffer and woodier condition and a greater resistance to wilting. These characteristics have also been observed in grafted white mutants. In addition, there is a pronounced reduction in leaf size in the white mutant.     

In Planta visual monitoring of green fluorescent protein in transgenic rice plants

The green fluorescent protein (GFP) from the jellyfish Aequorea victoria is a widely used reporter that can be directly visualized in the living cells in both animals and plants. We inserted a synthetic gene (sgfp) encoding a modified form of the GFP into expression vector, Act1-sgfp for the direct expression of GFP which is easily detectable in rice plants. Green fluorescence emitted from GFP could be visualized in calli, dry seeds, roots and seedlings with green shoots of transgenic rice plants. In our visualization system with a charge-coupled device camera, band-pass filters and a light source, the presence of red chlorophyll autofluorescence from chloroplasts did not alter the green fluorescence of GFP. These results demonstrate that GFP could be used as a non-destructive visual selection marker for examining gene expression in transformed calli, dry seeds and young plants.     

Oak seedlings grown in different light qualities

Oak seedlings (Quercus robur L.) were germinated in darkness for 3 weeks and then given continuous long wavelength far-red light (LFR; wavelengths longer than 700 nm). A control group of seedlings was kept in darkness. After 2 additional weeks the chlorophyll formation ability in red light was examined in the different seedlings. The stability of the protochlorophyll(ide) and chlorophyll(ide) forms to high intensity red irradiation was also measured. Oak seedlings grown in darkness accumulated protochlorophyll(ide) (6 μg per g fresh matter). Absorption spectra and fluorescence spectra indicated the presence of more protochlorophyll(ide)_628–632 than protochlorophyllide_650–657. The level of protochlorophyll(ide) was higher in leaves of plants cultivated in LFR light (13 μg per g fresh matter) than in leaves of dark grown plants. 12% of the protochlorophyll(ide) was esterified in both cases. The level of protochlorophyll(ide)_628–632 in LFR grown oaks varied with the age of the leaves, being higher in the older (basal) leaves, but also in the very youngest (top-most) leaves. The ability of the leaves to form photostable chlorophyll in red light showed a similar age dependence, being low in rather young and in older leaves. A low ability to form photostable chlorophyll thus appears to be correlated with a high content of protochlorophyll(ide)_628–632. Upon irradiation only the protochlorophyllide_650–657 was transformed to chlorophyllide. After this phototransformation the chlorophyllide peak at 684 nm shifted to 671 nm within about 30 min in darkness. This shift took place without any accompanying change in photostability of the chlorophyll(ide). Upon irradiation with strong red light a similar shift took place within one minute. This indicates that the chlorophyllide after phototransformation was rather loosely bound to the photoreducing enzyme. The development towards photostable chlorophyll forms consists of three phases and is discussed.     

Density-dependent responses of Picea purpurea seedlings for plant growth and resource allocation under elevated temperature

This study was conducted to determine whether plants in the presence or absence of competition differ in their responses to warming, and whether density modifies the effect of warming. Picea purourea seedlings were grown under ambient and warming (ambient +2.2 °C) conditions in climate control chambers with two different planting densities. After 4 years, seedlings were harvested and measured for height, stem diameter, leaf area, structural biomass, carbon, nitrogen, chlorophyll and carbohydrate levels of needles, branches, stem and roots. At low density, warming increased height, stem diameter, total leaf area biomass production and carbohydrate concentration per seedling, while it decreased C/N ratio for all plant parts, but did not affect chlorophyll content. By contrast, at high density, although warming increased biomass and total leaf area, it did not affect plant height and stem diameter. At the same time, it had different effects on chlorophyll content, C/N ratio and carbohydrate levels among plant parts. On the other hand, high density limited plant growth and altered resource allocation pattern. Our study demonstrates that planting densities decreased the temperature-induced growth enhancement of P. purpurea seedlings and the effects of warming on resource allocation not only showed density-dependence, but also vary with tissue age classes and root diameter; the responses of plants to elevated temperature, acquired from plants growing as individuals, may not be applicable to plants grown under intraspecific competition as typically found in the field.     

The role of salinity in seed maturation of the euhalophyte Suaeda salsa

Controlled conditions were used to investigate how salinity maintains the salt tolerance of seeds and seedlings of the euhalophyte Suaeda salsa. Seeds were harvested from S. salsa plants that had been treated with 1 or 500 mM NaCl for 113 days in a glasshouse. The results showed that high salinity (500 mM NaCl) increased chlorophyll concentration and oxygen production in embryos of maturing seeds. At 500 mM NaCl, the phosphatidylglycerol and sulfoquinovosyldiacylglycerol levels and the digalactosyldiacylglycerol/monogalactosyldiacylglycerol ratio were higher in young seedlings derived from seeds whose source plants were cultured in 500 mM rather than in 1 mM NaCl. When seeds were incubated with 600 mM NaCl, the conductivity and malondialdehyde concentration in the embryos was greater if the source plants had been cultured in 1 mM rather than in 500 mM NaCl. The opposite pattern was evident for seedling survival and shoot weight. In conclusion, salinity during seed maturation may increase the salt tolerance of seeds and seedlings by increasing the oxygen production in the embryos of the maturing seeds and by changing the lipid composition of membranes in the seedlings.     

Restoring Populations of the Endangered Plant Scorzonera humilis: Influence of Site Conditions,Seed Source,and Plant Stage

Changes in land‐use have resulted in the decline of many formerly common plants of nutrient‐poor grasslands in Europe. Recently, extensification schemes have been applied at sites in order to restore former habitat conditions. However, the establishment of rare and endangered plants is often severely limited by the lack of propagules both in the seed bank and in the surrounding landscape. For such species deliberate introductions may be necessary to overcome these limitations. In a 7‐year study, we assessed the importance of gaps created by sod cutting, of plant stage, and of plant origin for the restoration of populations of Scorzonera humilis, a threatened long‐lived plant of nutrient‐poor, wet grasslands. The effect of gaps on seedling emergence and survival varied strongly among the 12 sites. Gaps increased survival at nutrient‐rich, but reduced it at nutrient‐poor sites. Remarkably, young plants grown for only 5 weeks in the laboratory and transplanted into the same sites had much higher survival than seedlings from seeds sown and there were no differences in survival between nutrient‐rich and nutrient‐poor sites. The field performance of the plants from the various populations of origin varied depending on the site into which they were transplanted, indicating genotype by environment interactions and genetic differentiation among populations, but there was no home‐site advantage. While sowing only succeeded in producing adult plants in five sites, transplanting succeeded at 10 sites. Our results suggest that transplanting young plants could be a much more effective and faster way to establish new populations than sowing seeds.     

The Role of Sprouts in the Restoration of Atlantic Rainforest in Southern Brazil

The relative importance of sexual reproduction (seed) and sprouting as sources for regeneration in Brazilian Atlantic Forest was evaluated in three different successional forest stages: young forest, immature forest, and late‐successional forest. Young plants (10–100 cm tall) of tree species were classified into the following categories: (1) seedlings that are nonsprouting—plants that originated through sexual reproduction as seeds; (2) stem base sprouting—plants that sprouted at the base of an existing plant; and (3) underground stem sprouting—plants that sprouted from subterranean stems of an existing plant. A total of 1,030 individuals of 48 species were collected. Underground stem sprouting is the rarest form of propagation, with stem base sprouting somewhat more common and possibly associated with recovery of damaged parts. The greatest contribution to regeneration was due to seeds: 92% of the individuals counted in 67% of the plant species. However, 13 species were “facultative” sprouters as seedlings and sprouters were observed in this group. The three forest ages differed in the proportion of regeneration strategies; in immature forest, sprouting was more common (15%) than in young (7%) and late‐successional (3%; p < 0.05) forest. In these three forest stages, germinating seeds are the major source of new plants; although sprouting as a reproductive strategy is rare, it is related to recovery after damage of an already existing plant and may be due to previous land use history (agriculture) and low soil fertility. Restoration using natural regeneration should consider these factors to understand seed arrival as seed is the main source of regeneration.     

Respiratory potential and Se compounds in pea (Pisum sativum L.) plants grown from Se-enriched seeds

Selenium (Se) has been proved to be an essential element for humans and animals. However, less is known about its effects on plants. Pea plants were treated foliarly once (OT) and twice (TT) with Se solution during their flowering period. Seeds obtained from these plants contained 383 and 743 ng Se g(-1), respectively, and, together with control seeds from untreated plants (UT) containing 21 ng Se g(-1), were sown in soil in a greenhouse. Se content and its chemical form in young plants were studied, and its impact on plant respiratory potential, measured as terminal electron transport system (ETS) activity, determined. ETS activity was highest in young pea leaves with the highest Se content. Higher ETS activity possibly reflected increased glutathione peroxidase (GSH-Px) activity in mitochondria. The Se content of leaves and stems of plants grown from control seeds was similar to that in the seed, being around 40 ng Se g(-1). Se concentration in leaves of young plants grown from OT and TT seeds was 605%, and 1340% higher, respectively, than the control, and in their stems 355%, and 680% higher, respectively. The ratio of Se concentrations in OT and TT seeds was the same as in the leaves and stems in the young plants grown from them. SeMet was the major Se compound in Se-rich pea seeds and leaves, comprising 49% and 67% of the total Se content in OT and TT seeds, respectively, and 85% and 79% in the corresponding leaves.     

Effects of clonal integration on allelopathy of invasive plant Wedelia trilobata under heterogeneous light conditions

异质光照条件下克隆整合对入侵植物南美蟛蜞菊化感作用的影响 植物入侵已成为全球生态系统最严重的威胁之一。当具有克隆生长能力的入侵植物入侵或定殖到新的生境时,它们相互连接的分株可能受到异质光照的影响。在异质光照条件下,克隆整合对入侵植物化感作用的影响尚不清楚。为研究异质光照条件下克隆整合对入侵植物南美蟛蜞菊(Wedelia trilobata) 化感作用的影响,采用两个连续分株的克隆片段进行了盆栽试验。较老的分株暴露在全光下,而年轻的分株则受到20%的全光照。同时,每个克隆片段的年轻分株与目标植株(一个番茄苗)在盆栽中相邻生长。南美蟛蜞菊的两个连续分株之间的匍匐茎设置切断和不切断两种处理。另外,两株番茄幼苗 (一株作为目标植株)在盆栽中相邻生长作为对照。研究结果表明,当与目标植物相邻生长的南美蟛蜞菊分株之间的匍匐茎保持完整时,目标植株的生物量积累、叶片叶绿素和氮含量、叶绿素荧光参数和净光合速率及其根长和活性相较于匍匐茎切断处理显著降低。异质光照条件下连续两个分株之间碳水化合物的运输或共享可以增强20%全光处理下年轻分株的化感作用。克隆整合在异质光照条件下对具有克隆生长能力的入侵植物的入侵或定殖具有重要意义。     

Effect of light conditions of wheat growing on sensitivity of photosynthetic machinery to salt stress

Sensitivity of wheat (Triticum aestivum L.) seedlings to salt stress was investigated as dependent on light conditions of plant growing. In two-week-old seedlings grown on salt-free medium, aboveground organs were detached from the roots and subjected to a brief stress at different concentrations of NaCl. The extent of salt stress effect expressed as a decrease in the rate of the photosynthetic release of oxygen and the relative content of water and chlorophyll in the leaves greatly depended on light conditions of growing. The plants grown at low light intensity were notable for a greater sensitivity to NaCl in the medium. Plant responses to salt stress were different at low and high salt concentrations. At low NaCl concentrations (0.05–0.10 M) in the solution, in plants grown at low light intensity, the rate of photosynthesis calculated per unit of chlorophyll increased. This effect was not observed in plants grown at the higher light intensity. At high NaCl concentrations (0.2–0.4 M) in the medium, the rate of photosynthesis rapidly decreased in all the types of treatment, with the effect being most pronounced in plants grown at low light intensity. The obtained results suggest a narrow range of NaCl concentrations with an optimum at 0.1 M positively affecting the wheat seedlings physiological state upon salt stress development depending on light conditions of plant growing.     

Restoration Ecology of an Endangered Plant Species: Establishment of New Populations of Cirsium pitcheri

We determined the effects of shade, burial by sand, simulated herbivory, and fertilizers on the survival and growth of artificially planted population of Cirsium pitcheri—an endangered plant species of the sand dunes along Lake Huron. Sand burial experiments showed that greenhouse grown plants should optimally be transplanted into areas receiving 5 cm of sand deposition: burial at this depth maximized emergence, survivorship, and below‐ground biomass. Under field conditions, simulated herbivory of up to 50% of the plant height produced a slight increase in biomass after one year of growth. Field observations showed that when white‐tailed deer removed more than 50% of the transplant's leaf tissue, the plant died. The application of a 20:20:20 (N:P:K) water‐soluble fertilizer produced a significant increase in the dry leaf biomass, total leaf area, and total dry biomass relative to control plants. We also tested for the presence or absence of a persistent seed bank. Few seeds were recovered from soil samples collected from Pinery Provincial Park and Providence Bay. However, C. pitcheri has the ability to form a persistent seed bank under field conditions but only at soil depths of 15 cm. Cirsium pitcheri seeds are able to germinate and seedlings can emerge from a burial depth of up to 6 cm. Thus, seeds planted in open, sunny areas will probably maximize emergence, growth, and survivorship of seedlings. Populations of C. pitcheri can be restored by planting seeds at shallow depths, transplanting greenhouse‐grown plants, applying water soluble fertilizers, and protecting plants from herbivores.     

Some Physiological Parameters and Seed Lipid Composition of Transgenic Tobacco Plant

To see the effects of foreign gene introduction on the physiological performance and the quality and quantity of seed lipids, we studied transgenic tobacco plant as a model system, as tobacco seeds are oil seeds. Using Agrobacterium Ti plasmid based vectors, tobacco plants cv Petit Havana were transformed by NPT II gene as selectable marker. Transformed T₀ generation plants raised in tissue culture were transferred to pots and selfed. From the seeds, T₁ generation plants were grown in pots and their physiological performance was assessed. The transgenic plants showed slightly slower rates of germination and growth. Total chlorophyll content, chlorophyll a/b ratio and specific leaf weight, however, remained unchanged. The transgenic plants also had delayed flowering. However, total protein, lipid content and fatty acid composition of lipids of seeds in transgenic plants did not show appreciable difference from the seeds from control plants. Thus the physiological cost of transgenic plant for the extra genetic load was only marginal, if any.     

Nutrient content of Abutilon theophrasti seeds and the competitive ability of the resulting plants

Summary Siblings of Abutilon theophrasti, were grown on a nutrient gradient. The plants grown at higher nutrient levels were larger and produced larger and more seeds than plants grown at lower soil nutrient concentrations. There were no differences in germinability of seeds, but the competitive abilities of resulting plants were markedly different.In two different competition experiments designed to eliminate the effects of genotype, seed size, and germination time, by using synchronously germinated seedlings derived from similar size seed from plants grown at different nutrient levels, we found that plants from seeds produced at higher nutrient levels consistently, outperformed plants from seeds produced at the lower nutrient levels. The dominance of seeds produced at higher nutrient levels may be explained by the fact that they had markedly higher concentrations of nitrogen than did seeds produced at lower soil nutrient levels. The additional advantage of increased seed quality to plants controlling more of the nutrient resource than their neighbors would be expected to accelerate their contributions to the gene pool of the population.     

Effect on the Progeny of Applying Different Day Length and Hormone Treatments to Parent Plants of Lactuca scariola

Seedlings of the self-fertilizing species Lactuca scariola L. grown continuously in 8 h days did not flower even one year from sowing. Seedlings grown in 16 h days uatil flower buds appeared 96 days after germination were either transferred to 8 h days or treated weekly with gibberellic acid (GA₃), abscisic acid (ABA) or chlormequat (CCC) and retained, together with untreated control plants, in 16 h days. Each growth regulator caused characteristic morphological changes in the treated plants. All these plants flowered and produced seeds but the seeds showed distinct differences in weight, in their time to germination and in the seedlings which they produced. Germination and seedling characters depended on the light regime during germination as well as on the chemical applied to the parent plant and the rate of application. The parental treatment also affected the shape and size of the seedlings on a given day after germination, and certain treatments of the parent plant (transfer from long to short days and treatment with CCC in long days) advanced the flowering date of the seedlings. The gibberellin level in the seeds was raised, in increasing order, by treatment of the parent plant with 100 mg/1 GA₃, transfer from long to short days, 10 mg/1 GA₃, and 5000 mg/l CCC. It is suggested that the effect of day length on plant performance is mediated by the level of growth regelating substances within the plant and that the behaviour of seeds can be modified by the parental environment via the accumulation of different levels of certain growth factors in the seeds. A rise of one growth substance in the parent plant can result in the accumulation of a different one in the seeds.     

Effect of laser light treatment on some biochemical and physiological processes in seeds and seedlings of white lupine and faba bean

The aim of present study was to determine the changes of some biochemical and physiological processes, which occurred in seeds and seedlings of white lupine and faba bean after pre-sowing treatment with laser beams. It was found this treatment of seeds considerably increased the activity of amylolytic enzymes in seeds of both plants. The greatest differentiation of the enzymatic activity was noticed after 120?h from the time of sowing but the activity of these enzymes in the seeds of both tested plants was similar and it had the same course in time. The irradiated seeds of white lupine and faba bean had higher fresh weight at the time of imbibition than the seeds which were not treated with laser beams. It resulted in earlier and more uniform germination. The concentration of free radicals increased considerably in the seeds pre-treated with laser beams and the largest increase in seeds of both plant species was noticed after five exposures to laser beams. Treating seeds with laser beams considerably increased the amount of indole-3-acetic acid (IAA) in the germinating seeds. Three exposures of seeds caused the largest increase of this plant hormone content in the seeds. The activity of IAA in faba bean was slightly higher than in white lupine seeds. Pre-sowing stimulation with laser had a positive influence on the growth and development of seedlings, which had longer hypocotyl and roots in comparison to seedlings which grew from non irradiated seeds.     

The relative proportions of the chloroplast pigments as influenced by different levels of iron and potassium supply

Summary 1. Potato plants were grown in pot sand cultures at different levels of iron and potassium supply. Plants grown at the lowest level of iron developed iron deficiency chlorosis and potassium deficiency symptoms when maintained at the lowest level of potassium but not at the highest level.2. Rapid procedures were developed for the extraction and estimation of chloroplast pigments from small samples of lamina—usually less than 1 g of fresh material.3. The expression of pigment content on an area basis gave results which were in better agreement with visual observations than those expressed on either fresh or dry weight basis.4. Both iron and potassium additions increased the chloroplast pigment content. Leaves exhibiting iron deficiency contained reduced quantities of all pigments per unit area of lamina.5. A linear relationship existed between chlorophyll and carotene, chlorophyll and xanthophyll, and carotene and xanthophyll contents.6. The results suggested that laminae completely deficient in chlorophyll would contain no carotene but might still contain xanthophyll.7. The relative proportions of chlorophyll, carotene and xanthophyll do not remain constant under varying conditions of iron status. When iron is deficient the proportion of xanthophyll increased in relation to the chlorophyll and carotene contents.