Effects of Temperature and Photoperiod on Growth and Development of Tillers and Rhizomes in Poa pratensis L. Ecotypes

The vegetative growth of four Norwegian ecotypes of Poa pratensisL. was compared at day/night temperatures of 21/12, 21/6, 12/12and 12/6 °C and at photoperiods of 12, 16, 20 and 24 h,the irradiation being approximately equal in all treatments.Tillering within tufts was most abundant in short days and atthe large temperature amplitude. Rhizome formation and elongationwere stimulated by long days and, more strongly, by high daytemperature, but a greater proportion of the rhizomes formedaerial tillers in short days. Long day stimulation of heightgrowth and dry matter accumulation differed between ecotypesbut was generally most pronounced at low temperatures. The NorthNorwegian ecotype ‘Lavang’ had a higher relativegrowth rate and developed two to three times as many rhizomesas its South Norwegian counterparts. Day/night temperature, growth rate, leaf area, photoperiodicity, Poa pratensis L., rhizomes, roots, smooth meadow grass, tillering, weight gain     

Change in total phenolic content and antibacterial activity in regenerants of Vitex negundo L.

A valuable medicinal plant, Vitex negundo L. has been investigated for its regeneration potential using shoot tip explants. Out of a range of concentrations of cytokinins [6-benzyl adenine (BA), 6-furfurylaminopurine, 2-isopentenyl adenine] used as supplement to Murashige and Skoog medium (MS), BA at 5.0 μM concentration proved best for multiple shoot induction yielding 3.60 ± 0.50 shoots after 8 weeks of culture. Inclusion of a low concentration of an auxin with optimal cytokinin concentration favoured shoot multiplication and the optimum response was observed on MS medium supplemented with BA (5.0 μM) along with α Naphthalene acetic acid (0.5 μM), where 65.0 ± 1.73 % cultures responded with a mean number of 4.80 ± 0.58 shoots per explants after 8 weeks of culture. Ex vitro rooting of in vitro derived microshoots was achieved upon dipping the cut ends of microshoots in 500 μM indole-3-butyric acid for 10 min followed by transfer to thermocol cups containing sterile soilrite. About 95 % of the plantlets survived the acclimatization procedure and were transferred to greenhouse and finally to field. Screening of the antibacterial activity and estimation of total phenolic content of ethanolic extracts of micropropagated plants were also carried out and compared with that of the mother plant.     

雾灵山草地早熟禾多胚囊和多胚的研究

无融合生殖是指未经炷卵事例而产生后代的特殊生殖方式,它可以分为单倍体无融合生殖和二倍体无融合生殖;对于作物意义更大的是二倍体无融合生殖。多胚囊和多胚现象ＳＨＩ是无融合生殖的表现形式。本文运用石蜡切片法、子房整体透明法研究了雾灵山草地早熟禾（Ｐｏａ ｐｒａｔｅｎｓｉｓ Ｌ．）多胚囊和多胚现象。结果表明,（１）草地早熟禾多胚囊来源有两种：一是自大孢子母细胞,二是来自珠心细胞;（２）草地早熟禾多 来源有     

Metabolic rate of acidic complex saccharides in rabbit uterus under estrogenic condition.

Uterine slices obtained from estrogen-treated rabbits were incubated in vitro with N-acetyl-D-[1-3H]glucosamine together with D-[U-14C]glucose. The isotope-labelled acidic complex saccharides were then isolated by pronase digestion, Dowex 1 column chromatography and preparative electrophoresis on cellulose acetate membrane, in succession. In this way, individual acidic complex saccharides (hyaluronic acid, heparan sulfate, chondroitin sulfate A, chondroitin sulfate C, dermatan sulfate, sulfated glycopeptide, and sialoglycopeptide) were separated into 2-5 subfractions. The specific radioactivity of hexosamine in the subfractions indicated that the metabolic rate of the uterine complex saccharides as follows: hyaluronic acid greater than sulfated glycopeptide greater than heparan sulfate greater than chondroitin sulfate C greater than dermatan sulfate. In addition, metabolic heterogeneity of heparan sulfate, chondroitin sulfate A, chondroitin sulfate C, and dermatan sulfate was suggested.     

Growth of bifidobacteria and clostridia on human and cow milk saccharides

For healthy infants, which were born normally and fully breastfed, the dominant component of the intestinal microflora are bifidobacteria. However, infants born by caesarean section possess clostridia as a dominant intestinal bacterial group. The aim of the present study was to determine whether bifidobacteria and clostridia are able to grow on human milk oligosaccharides (HMOs) and other carbon sources - lactose, cow milk (CM) and human milk (HM). Both bifidobacteria and clostridia grew on lactose and in CM. Bifidobacteria grew in HM and on HMOs. In contrast, 3 out of 5 strains of clostridia were not able to grow in HM. No clostridial strain was able to utilise HMOs. While both bifidobacterial strains were resistant to lysozyme, 4 out of 5 strains of clostridia were lysozyme-susceptible. It seems that HMOs together with lysozyme may act as prebiotic-bifidogenic compounds inhibiting intestinal clostridia.     

N uptake and growth responses to sub-lethal freezing in the grass Poa pratensis L.

Background and aims

Climate warming has the potential to increase both the exposure and vulnerability of grass roots to frost in temperate regions by reducing snow cover and altering the timing of cold acclimation. Despite a strong research focus on the direct effects of freezing on grass mortality, the direct sub-lethal effects of freezing on grass performance have not been well-characterized. We examined sub-lethal responses of the grass Poa pratensis to variation in the timing, severity, rate and length of freezing.

Methods

We assessed short term root functional responses (¹⁵N uptake) and longer term plant growth responses to freezing administered both under controlled conditions in a refrigerated incubator, and in the field by manipulating snow and litter cover.

Results

In fall and spring, ¹⁵N uptake declined in response to 1?day of freezing down to ?10?°C or to 3?days of freezing at ?5?°C, whereas in winter, ¹⁵N uptake was insensitive to freezing. Long term growth responses were similar, with reduced growth only occurring for grasses frozen for 3?days at ?5?°C in spring, but not for grasses frozen in fall or winter. Snow and litter removal intensified soil freezing over winter, but did not significantly affect plant growth.

Conclusions

Our results demonstrate that while P. pratensis is relatively tolerant to frost damage over winter, it may be vulnerable to sub-lethal frost effects in fall, and particularly in spring. These sub-lethal effects occur at temperatures approximately 15–20?°C warmer than the published LT₅₀ values for this species.     

Growth characteristics and total N content of a Leucaena/Sorghum agroforestry system

The growth characteristics and total N content of the woody legume Leucaena leucocephala and the companion crop Sorghum bicolor grown in the greenhouse with N-limiting (NH₄ ⁺ concentration = 447 mM) nutrient medium in sole and mixed cropping were examined. Plant height, dry weight, and total N content increased significantly in sorghum grown intercropped with nodulated Leucaena over the control, sole sorghum. Evidence is presented to indicate that in mixed culture, sorghum gains an average of 0.03 mg N day^–1 plant^–1 relative to sole-cropped sorghum in N-limiting sand culture. The gain in N content of intercropped sorghum, however, represented less than 1% of the N budget of N-fixing Leucaena and was inadequate to sustain normal physiological development of sorghum.     

Growth Studies on Natural Hybrids between Lolium perenne and Festuca pratensis

The growth-rates and chromosome numbers of plants taken froma natural population of hybrids between perennial rye grassand meadow fescue were determined. The growth-rates of diploidhybrids resembled that of rye grass while those of the triploidswere similar to that of meadow fescue. Experiments on plantsgrown singly and in competition showed that fescue was adverselyaffected by low temperature and rye grass by low light and alsoby the reduced nutrient supply arising from competition. The persistence of the sterile hybrids is explained by theirrecurrent formation coupled with greater longevity and vegetativespread, arising from growth characteristics intermediate betweenthose of their parents. The persistence of rye grass and thedisappearance of fescue when periodically grazed appear to resultfrom the earlier growth and more rapid rate of tillering ofthe former. However, rye grass has fewer and smaller meristemsavailable for regrowth if allowed to grow until anthesis, andunder these conditions fescue dominates. The intermediate growthcharacters of the hybrids allow them to survive spring grazingmore readily than meadow fescue and cutting for hay more readilythan rye grass.     

Growth rate, IAA and cytokinin content of wheat seedling after root pruning

Root pruning of wheat seedlings resulted in 2–10 foldincrease in the concentration of IAA in roots ascompared to the control level, which might beresponsible for the observed initiation of lateralroot growth. Cytokinin concentration in xylem sap wasdecreased initially by 60% by pruning in accordancewith the reduction in the hormone-producing organ.Nevertheless cytokinin content in the shoots remainedhigh, which might be due to a decrease in cytokinindecay registered in vitro. A subsequent increasein the export of cytokinins from roots up to thecontrol level demonstrated an elevated ability of thepruned organ to synthesise the hormone. The highcytokinin content in the shoots correlated with theability of the plants to maintain their transpirationand growth at the level of intact plants. Both IAA andcytokinins seem to be important in the restoration ofthe shoot/root balance disturbed by root pruning.     

雾灵山草地早熟禾多胚囊和多胚现象的研究

无融合生殖是指未经精卵融合而产生后代的特殊生殖方式,它可以分为单倍体无融合生殖和二倍体无融合生殖;对于作物改良意义更大的是二倍体无融合生殖。多胚囊和多胚现象SHI是无融合生殖的表现形式。本文运用石蜡切片法、子房整体透明法研究了雾灵山草地早熟禾〖WTBX〗（Poa pratensis〖WTBZ〗 L.）多胚囊和多胚现象。结果表明,（1）草地早熟禾多胚囊来源有两种：一是来自大孢子母细胞,二是来自珠心细胞;（2）草地早熟禾多胚来源有四个：其一是有性生殖胚,其二是孤雌生殖胚,其三是无配子生殖胚,其四是珠心胚。     

Increased rate of drying reduces metabolic inequity and critical water content in radicles of Cicer arietinum L.

Orthodox seed serves as easily accessible model to study desiccation-sensitivity in plant tissues because once they undergo germination, they become sensitive to desiccation imposed injuries. In the proposed study, effects of rate of drying on the viability, electrolyte leakage, superoxide accumulation, lipid-protein oxidation and antioxidant enzymes were explored in excised radicles of Cicer arietinum L. under dehydration and wet storage. For both the drying conditions, desiccation could be explained by exponential and inverse functions. Under rapid drying tissue viability as scored by germination efficiency and tetrazolium staining remained 100 % all through the analysis (24 h) but declined remarkably after 0.30 g g⁻¹ fresh mass water content (4 days) under slow drying. Moreover, precipitous fall in tissue viability was observed after 2 weeks of wet storage. Rapid drying was also accompanied with limited amounts of electrolyte leakage, superoxide radical, malondialdehyde and protein hydroperoxide, together with enhanced level of protein. Additionally, activities of both superoxide dismutase and ascorbate peroxidase were increased in rapidly dried radicles, but guaiacol peroxidase was declined. In contrary, above referred biomarkers were observed to perform either inversely or poorly during slow drying and wet storage suggesting that above documented alterations might be the resultant of ageing and not desiccation. Gathered data demonstrated that increased drying lowers the critical water content for tissue survival and also reduces the risk of damage resulting from aqueous-based deleterious reactions. Additionally, it also showed that growing radicles are a popular model to explore desiccation-sensitivity in plant tissues and/or seeds.     

Variation in body condition, fat content and growth rate of Icelandic summer-spawning herring Clupea harengus L.

Interannual variation in Fulton's condition factor ( K ), total body-fat content and growth rate were investigated for the Icelandic summer-spawning herring Clupea harengus over the period from 1963 to 1999. The results show a close relationship between K and the body-fat content in the autumn, both of which correlated to the growth rate in the same calendar year. A relationship was also found between K during the prespawning season (February to June) and K in the autumn (September to December) in the same year. The different measures of body condition were not found to be related to sea temperature or zooplankton indices, while the spawning stock biomass had negative effects on the fish condition. The results imply that the body condition in the autumn is representative of the feeding success over the whole foregoing year and is therefore related to the growth rate that year. The growth rate appears to be relatively uniform throughout the year.     

The effects of hormones and saccharides on growth and flowering of green and herbicides-treatedChenopodium rubrum L. plants

The medium forin vitro culture of green and SANDOZ herbicides-treatedChenopodium rubrum L. plants contained saccharides and hormones in different concentrations. Five days after sowing, the plants were exposed to non-inductive (15 long days—LD) or inductive (6 short days—SD + 9 LD) photoperiodic conditions. The length of hypocotyl and cotyledon blade were measured and percentage of flowering was scored. Gibberellic acid (GA₃) stimulated hypocotyl growth of green and photobleached plants under SD and inhibited under LD conditions. Indole-3-acetic acid (IAA) slightly stimulated hypocotyl growth of green plants only under LD conditions. Benzylaminopurine (BAP) inhibited hypocotyl growth regardless of photoperiodic regime. The optimal concentration of glucose or saccharose for flowering in green and SANDOZ-treated plants was 5%. In green SAN 9785-treated plants exogenous saccharides compensated lack of photosynthates to bring about full flowering, but SAN 9789-treated plants needed in addition GA₃.     

Growth characteristics and proline content in relation to water status in twoZea mays L. Cultivars during rehydration

Growth behaviour, proline changes and water saturation deficit (WSD) changes were studied in two maize cultivars, Agati-76, a drought resistant oultivar, and cv. Vijay, a susceptible one after stress conditions were removed. Plants of both the cultivars showed a tendency to recover during rehydration. Phenotypically the plants appeared just normal on 7th day of rehydration, although recovery was never complete. Significant positive correlation existed between free proline content and concomitant change in water saturation deficit. Significantly higher proline content in cv. Agati-76 was reoorded in cv. Vijay, immediately after the stress was released, thereafter continuous decline was observed up to 7th day of rehydration in both the cultivars. Proline changes in relation to recovery of plants from stress conditions are discussed.     

The effects of long-term exposures to SO2 and NO2 pollution on the growth of Dactylis glomerata L. and Poa pratensis L.

An investigation was conducted over 20 weeks during winter to determine the effects of 6·8 pphm (194 μg m⁻³) SO₂ and 6·8 pphm NO₂, applied both singly and in combination, on the growth of Dactylis glomerata L. and Poa pratensis L. The combination of SO₂ + NO₂, and singly applied SO₂, caused significant reductions in the leaf areas and all the dry weight fractions measured of both species. These were associated with reductions in the numbers of tillers and leaves produced by both species in the SO₂ + NO₂ treatment, but only by P. pratensis when SO₂ alone was present. Singly applied NO₂ had little effect on the growth of D. glomerata but caused significant reductions in leaf area and all the measured dry weight fractions of P. pratensis. There was some evidence to suggest that NO₂ was more toxic during the mid-winter months when growth was slow. It is concluded that SO₂ and NO₂ in combination may be more toxic to plants than would be predicted by summing their individual effects on growth.