The effects of simulated spring goose grazing on the growth rate and protein content of Phleum pratense leaves

The effects of simulated goose grazing on Phleum pratense plants were tested in an Iceland hayfield during the spring goose staging period (19 April–11 May 1997). Plants in an area exclosed from the influence of grazing and the nutrient effects of goose faeces were subject to the removal of the youngest lamina once, three and four times during this period. Clipping three and four times resulted in 25–41% increases in cumulative elongation of youngest laminae compared with unclipped plants. Total cumulative lamina growth of entire plants showed no significant difference between unclipped plants and those clipped three and four times, hence no overcompensation occurred. Sequential clipping elevated the protein content of the youngest laminae from 20% to 27–33%, whereas there was no change amongst shoots clipped only once. Because geese only consume the youngest lamina of each Phleum plant, measurements from this experiment showed that regular physical removal of growing biomass doubled the biomass of preferred tissue available to geese and increased the potential protein intake 3.5 times at experimental clipping frequencies similar to levels of sequential harvesting observed amongst staging geese compared to less frequent harvesting. These increases were achieved without any fertilising effects of goose faeces implicated in such effects in previous studies. Received: 26 January 1998 / Accepted: 20 March 1998     

A function of the preprophase band of microtubules in Phleum pratense

Summary A study has been made of the microtubules of the preprophase band and the mitotic spindle in the meristematic cells of the root of Phleum pratense. The preprophase band in these cells is placed symmetrically round the nucleus although a great many of the cells divide asymmetrically. It is suggested that the function of the preprophase band is to orient the nucleus prior to mitosis. The function and formation of the tubules which are found in close association with profiles of smooth endoplasmic reticulum is discussed.     

Experimental control of flowering and vivipary in timothy (Phleum pratense)

Environmental and hormonal control of flowering and vivipary in four Norwegian timothy ( Phleum pratense L.) cultivars has been studied in phytotron and by aseptic culture of inflorescence explants. The critical photoperiod for flowering increased with increasing temperature (12–18°C) and it was 13 to 15 h for the southern and 14 to 16.5 h for the northern cultivars. Diurnal temperature fluctuation significantly stimulated flower formation compared to the corresponding constant temperature treatment. Plants grown in 16-h photoperiod contained normal sexual flowers, but a high percentage of spikes developed in 12- or 14-h photoperiod contained viviparous plantlets. One- to four-weeks in continuous light before treatment with 12-h photoperiod increased the number of spikes per plant, but did not enhance the frequency of vivipary. Experiments with aseptic cultures showed that generative versus vegetative development of timothy inflorescence was affected by plant hormones. Kinetin stimulated the vegetative development and induced proliferation both in inflorescence initials and in spikelets isolated at heading time.     

Effect of partial defoliation during the vegetative phase on subsequent growth and grain yield of maize

Maize was grown in two densities, 2–47 or 4–94 plants m^-2, and the following treatments imposed: untreated, plants partly defoliated 51 days after sowing, and alternate plants in a row partly defoliated 44 days after sowing. Plants flowered about 82 days after sowing. Leaf area was decreased by 60–64% by defoliation on day 51. Defoliation resulted in decreases in grain yield and grain number of 6–17%, though when alternate plants were defoliated in the higher density there was a substantial decrease in yield and number of grains in defoliated plants, which was largely offset by an increase in adjacent intact plants. When plants were defoliated on day 51 subsequent growth in leaf area was similar to, and that in leaf weight nearly as large as that in untreated plants, while increase in stem weight was substantially less than in untreated plants. By the time of flowering untreated and defoliated plots differed by c. 30% in leaf area. Increments of dry matter after flowering differed by c. 15% between untreated and defoliated plots. The fraction of these increments which entered the grain was c. 90% in both untreated and defoliated plots. When alternate plants in the row were partly defoliated on day 44 their subsequent increase in leaf area was probably 5–16% less than that of the adjacent intact plants. Increments of dry matter after flowering of plots with alternate plants defoliated were 93–95 % of those of untreated plots; leaf efficiency after flowering was slightly greater than in untreated plots. The fraction of the dry matter increment after flowering which entered the grain was c. 88 % in both intact and defoliated plants of the small density, but was 94% in intact plants and 86% in defoliated plants of the large density.     

Gamahonolides A,B, and Gamahorin,Novel Antifungal Compounds from Stromata of Epichloe typhina on Phleum pratense

Four novel antifungal compounds, gamahonolides A and B, gamahorin, and 5-hydroxyl-4-phenyl-2(5H)-furanone, were isolated from stromata of Epichloe typhina on Phleum pratense. Their structures were determined by spectroscopic methods. The absolute configuration of gamahonolide A was determined by its ORD spectrum and ¹H-NMR shift difference between the diastereomeric pair of its O-methylmandelates. The stereochemistry of gamahorin was determined by NOE difference spectra and its CD spectrum.     

Polysaccharide production in liquid cell suspension cultures of Phleum pratense L.

The production of carbohydrates by cell suspension cultures of Phleum pratense (timothy grass) is described. Extracellular polysaccharides similar in monosaccharide composition to native cell wall polymers were accumulated, together with polymers of fructose (fructans). The fructans had similar properties to the intracellular reserve polymers found in intact plants, and were found in both cells and media of young, slow-growing cultures.Production of extracellular polysaccharides differed in cultures grown on sucrose or equimolar glucose/fructose as carbon source. These differences were observed only when autoclaved media were used, and were not related to changes in either pH or osmolarity. Autoclaving medium containing radioactive glucose and fructose produced a novel, unidentified labelled compound which was absent in medium containing labelled sucrose.     

Allocation of carbon to growth, storage and respiration in the vegetative barley plant

Abstract. It is proposed that the growing plant can be divided into three compartments with reference to carbon: soluble, storage and structural. Experiments carried out at 10, 15, 20 and 30°C in the light followed changes in size of these compartments in barley plants 10–24 days old. The redistribution of ^I4C photo-assimilated by 10 day old plants was monitored simultaneously. The soluble and storage compartments are a higher percentage of plant weight at lower temperatures, and are turned over rapidly at all temperatures; they form the source of respired ¹⁴C. About 30% of the ¹⁴C fixed enters structural material; in the first 24 h after labelling, for each unit of ¹⁴C entering the structural compartment, between 0–9 (at 15°C) and 3.2 (at 30°C) units of ¹⁴C are lost by respiration. At 15°C in the dark, respiratory loss of ¹⁴C is initially from soluble and storage compartments; thereafter respiration of ^I4C occurs at the expense of structural material.     

Effects of heat stress on growth,photosynthetic pigments,oxidative damage and competitive capacity of three submerged macrophytes

There is an information gap regarding heat stress-induced oxidative damage and the species-specific behavior of plants under stress conditions. The present study was designed with the hypothesis that heat stress may induce species-specific oxidative damage that determines the competitive capacity of common submerged macrophytes. We conducted two laboratory experiments to simulate mono- and mixed cultures of three submerged macrophytes with the application of two heat shock treatments. The results showed that both heat shocks had significant effects on growth, photosynthetic pigments and the ability to induce strong oxidative damage for all three species. The comparative results of mono- and mixed cultures showed that P. crispus had an advantage in both the control and high-temperature treatments over the other two species as a strong competitor in the mixed culture. Further, the competitive capacity of P. crispus increased in the moderately high-temperature condition compared to the control.     

The use of internal nitrogen stores in the rhizomatous grass Calamagrostis epigejos during regrowth after defoliation

BACKGROUND AND AIMS: The regrowth dynamics after defoliation of the invasive grass Calamagrostis epigejos were studied. As nitrogen (N) reserves have been shown to play an important role during plant regrowth, the identity, location and relative importance for regrowth of N stores were determined in this rhizomatous grass. METHODS: Plant growth, nitrate uptake and root respiration were followed during recovery from defoliation. Water soluble carbohydrates, nitrate, free amino acids and soluble proteins were analysed in the remaining organs. KEY RESULTS: Nitrate uptake and root respiration were severely reduced during the first days of regrowth. Roots were the main net source of mobilized N. The quantitatively dominant N storage compounds were free amino acids. Free amino acids and soluble proteins in the roots decreased by 55 and 50%, respectively, and a substantial (approximately 38%) decrease in stubble protein was also observed. Although the relative abundance of several soluble proteins in roots decreased during the initial recovery from defoliation, no evidence was found for vegetative storage protein (VSP). Furthermore, rhizomes did not act as a N storage compartment. CONCLUSIONS: Production of new leaf area was entirely reliant, during the first week after defoliation, on N stores present in the plant. Mobilized N originated mainly from free amino acids and soluble proteins located in roots, and less so from proteins in stubble. Presence of VSP in the roots was not confirmed. The data suggest that rhizomes played an important role in N transport but not in N storage.     

Assessment of genetic variation in timothy (Phleum pratense L.) using RAPD and UP-PCR

DNA-based fingerprinting technologies including random amplified polymorphic DNA (RAPD) and universally primed PCR (UP-PCR), a novel method for studying genetic variation, were employed as genetic markers for assessing genetic diversity and relationships in timothy (Phleum pratense L.). This study sought to identify the genetic background of the genotypes used in timothy breeding. Thirty eight genotypes from fifteen countries were used as test materials. RAPD and UP-PCR dendrograms based on 132 (from 3 primers) and 44 highly reproducible bands, respectively, were analyzed. The electrophoretic gels showed that the PCR products were informative and polymorphic. Different geographic genotype groups were distinguished according to the combined RADP and UP-PCR results. The results demonstrate that methods based on molecular fingerprinting can be used for timothy identification.     

Pattern of storage and regrowth in ragwort

Ragwort plants were damaged experimentally by removing the whole shoot. Within about 1 month the original allocation pattern of biomass to root and shoot was reestablished to a large extent. If left undisturbed for a longer period, plant growth accelerated into compensatory growth. Intraspecific variation in storage and tolerance (shoot weight), 1 month after damage, was significant. We could not detect a trade-off between storage or tolerance and relative growth rate of control plants. Consequently there are no indications for costs involved in storage of resources or in tolerating damage. Although tolerance is thought to be dependent upon storage of resources, we detected no effect of storage on tolerance after one event of damage. Storage is genotype specific, but at the same time highly plastic. We hypothesize that the value of storage in ragwort only becomes evident after repeated disturbances. Competition, history of herbivory and change of season all affected storage radically. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interactive effects of mechanical stress,sand burial and defoliation on growth and mechanical properties in Cynanchum komarovii

In drylands, wind, sand burial and grazing are three important factors affecting growth and mechanical properties of plants, but their interactive effects have not yet been investigated. Plants of the semi‐shrub Cynanchum komarovii, common in semi‐arid parts of NE Asia, were subjected to brushing, burial and defoliation. We measured biomass allocation and relative increment rates of dry mass (RGR_m), height (RGR_h) and basal diameter (RGR_d). We also measured the stem mechanical properties, Young’s modulus (E), second moment of area (I), flexural stiffness (EI) and breaking stress (σ_b), and scaled these traits to the whole‐plant level to determine the maximum lateral force (F_lateral) and the buckling safety factor (BSF). Brushing increased RGR_m; neither burial nor defoliation independently affected RGR_m, but together they reduced it. Among buried plants, brushing positively affected stem rigidity and strength through increasing RGR_d, E, I and EI, and at whole plant level this resulted in a larger BSF and F_lateral. However, among unburied plants this pattern was not observed. Our results thus show that effects of mechanical stress and grazing on plants can be strongly modified by burial, and these interactions should be taken into account when considering adaptive significance of plant mechanical traits in drylands.     

Characterization of Phleum pratense pollen extracts by 2-D DIGE and allergen immunoreactivity

The allergen content of standardized pollen material is crucial for an effective diagnosis and treatment. However, variations in IgE reactivities of allergic patients to different preparations of Phleum pratense pollen have been reported. In order to define and directly compare the allergen composition of pollen preparations provided by different suppliers, a comprehensive proteome analysis of three different timothy grass pollen extracts was performed. More than 140 proteins were annotated comprising the pollen proteome/allergome in a global 2-D map. With regard to the individual pollen preparations, several major differences in the overall protein composition were detected that also affected known Phleum allergens and their isoforms. Importantly, these differences were also reflected at the level of antibody reactivities in 1-D and 2-D immunoblots. As a consequence, it is suggested that the observed differences should be taken into consideration aiming for a standardized diagnosis and therapy of grass pollen allergies as recommended by international medical agencies.     

Vernalization response of Phleum pratense and its relationships to stem lignification and floral transition

Background

Timothy is a long-day grass species well adapted for cultivation in northern latitudes. It produces elongating tillers not only in spring growth but also later in summer. As the quantity and quality of harvested biomass is dictated by canopy architecture and the proportion of stem-forming flowering tillers, the regulation of flowering is of great interest in forage grass production.

Methods

Canopy architecture, stem morphology and freezing tolerance of vernalized timothy were investigated in greenhouse and field experiments. The molecular control of development was examined by analysing the relationship between apex development and expression of timothy homologues of the floral inducer VRN1 and repressor VRN2.

Key Results

True stem formation and lignification of the sclerenchyma ring occur in both vernalized and regrowing stems irrespective of the developmental stage of the apex. The stems had, however, divergent morphology. Vernalization enhanced flowering, and the expression of the VRN1 homologue was elevated when the apex had passed into the reproductive stage. High VRN1 homologue expression was not associated with reduction in freezing tolerance and the expression coincided with increased levels of the floral repressor VRN2 homologue. Field experiments supported the observed linkage between the upregulation of the VRN1 homologue and the transition to the reproductive stage in vernalized tillers. The upregulation of putative VRN1 or VRN2 genes was restricted to vernalized tillers in the spring yield and, thus, not detected in non-vernalized tillers of the second yield; so-called regrowth.

Conclusions

The formation of a lignified sclerenchyma ring that efficiently reduces the digestibility of the stem was not related to apex development but rather to a requirement for mechanical support. The observed good freezing tolerance of reproductive timothy tillers could be one important adaptation mechanism ensuring high yields in northern conditions. Both VRN1 and VRN2 homologues required a vernalization signal for expression so the development of yield-forming tillers in regrowth was regulated independently of the studied genes.