Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 25 of 25
Full-Text Articles in Entire DC Network
Determination Of Nitrogen Sources (Mineral, Atmospheric Or Endogenous) Used By Lucerne During Regrowth, K Tae Hwan, A Ourry, G Lemaire, J Boucaud
Determination Of Nitrogen Sources (Mineral, Atmospheric Or Endogenous) Used By Lucerne During Regrowth, K Tae Hwan, A Ourry, G Lemaire, J Boucaud
IGC Proceedings (1993-2023)
Although for forage legumes such as Medicago saliva, ii is established that nitrogenase activity is very low during the 2 fust weeks of regrowth, there are no data on the amount d nitrogen in regrowin g shoots derived from N1 fixation. In order to ascertain the orisin of N used for regrowth of lucerne, several experiments were unde,taken usin g 15N labellin g to distinguish between endogenous, mineral and atmospheric N recovered' in regrowing shoots of nodulated or non-nodulated lucerne. Calculation of N fluxes from ISN data showed that both N uptake from the medium and N2 fixation strongly decreased …
Influence Of The Photochemical Air Pollutant, Ozone, On Grass-Clover Plots Using An Open Air Fumigation System, S Wilbourn, A Davison, J Ollerenshaw
Influence Of The Photochemical Air Pollutant, Ozone, On Grass-Clover Plots Using An Open Air Fumigation System, S Wilbourn, A Davison, J Ollerenshaw
IGC Proceedings (1993-2023)
Fumigation of perennial ryegrass-white clover (Lolirim perenne - Trifolium repens) plots with moderate ozone (03) concentrations caused a decline in the clover content and a reduction in total seasonal yield of the swards. There was no significant interaction between defoliation treatment and 03 fumigation. The ryegrass population benefited from the reduction in competition from the clover in 03-treated plots. These results, obtained from an open air field fumigation system confirm the findings of other experiments which used different grass-legume mixtures grown in open-top chambers or in controlled environments. Fumigation with 03 in summer caused a significant reduction in …
Defoliation Of Grass (Cut Or Grazed) And Its Effect On Forage Quantity, H C. Hughes
Defoliation Of Grass (Cut Or Grazed) And Its Effect On Forage Quantity, H C. Hughes
IGC Proceedings (1993-2023)
All grassland farmers should try to optimise their grassland output during the growing season. Grassland farmers would improve their production results if they paid more attention to plant defoliation processes. Careful management of the grass ley will increase outputs by more than one third, without needing further inputs. Most grassland farmers need to have this improvement with no additional cost, especially in the present world economy.
Response To Defoliation Of Tall Fescue, H Tavakoli, J Hodgson, P D. Kemp
Response To Defoliation Of Tall Fescue, H Tavakoli, J Hodgson, P D. Kemp
IGC Proceedings (1993-2023)
An experiment studying the behaviour of toll fescue (Fesutca anrundinacea Schreb,) was conducted under steady stale grazing on a sward dominated by this plant. The swards were grazed lo maintain a surface height of 30-40 mm (H), 50-60 mm (M) and 90-100 mm (L). These treatments were applied on swards with and without white clover (Trifolium repens L.) from November 1990 to April 1991. Results showed that leaf growth decreased as the severity of grazing increased. Tiller number was less under H grazing than under M or L grazing, but tiller size remained constant over time in this …
Accumulation Of Dry Matter, Protein And Total Available Carbohydrate In Berseem Under Different Cutting Regimes, P Martinello, G De Santis, A Iannucci, N Di Fonzo
Accumulation Of Dry Matter, Protein And Total Available Carbohydrate In Berseem Under Different Cutting Regimes, P Martinello, G De Santis, A Iannucci, N Di Fonzo
IGC Proceedings (1993-2023)
The effect of different cutting regimes on physiology and morphology of aerial parts and roots in 6 bcrseem (Trifolium alexadrium L.) genotypes was evaluated. Observations were carried out on individual plants at 4 stages of development: fourth and eighth internode elongation, early flowering and physiological seed maturity. The results showed that the genotypes were characterised by highest values of dry matter in the aerial and root parts at the early flowering stage. Variability among genotypes was observed.
Prediction Of Plant Mortality Under Grazing- A Conceptual Approach, J J. Mott, G K. Mckeon, K A. Day
Prediction Of Plant Mortality Under Grazing- A Conceptual Approach, J J. Mott, G K. Mckeon, K A. Day
IGC Proceedings (1993-2023)
Based on the concept of biological thresholds, there is growing acceptance 0£ the importance o£ episodic events in the determination of rangeland condition trend. The variable rainfall occurring within Australian rangelands means that overstocking during droughts is a major cause of these Australian rangeland vegetation complexes exceeding these thresholds. Recently plant production models and simplistic estimates of the relationship between animal utilisation and plant mortality became available. Accurate estimates will be developed only with the incorporation of a sound mechanistic understanding of the relationship between utilisation of forage and plant mortality for different conditions of species and soils. Detailed studies …
Morphogenetic And Structural Determinants Of Plant Regrowth After Defoliation, D F. Chapman, G Lemaire
Morphogenetic And Structural Determinants Of Plant Regrowth After Defoliation, D F. Chapman, G Lemaire
IGC Proceedings (1993-2023)
Responses of forage plants to defoliation can be delineated at two levels: physiological responses and morphological responses. Physiological responses are generally defined as occurring over short time-scales, whereas morphological responses are generally considered as being long-t<;rm. The extent to which physiological and morphological responses influence pasture characteristics and production depends on the defoliation regime, and the balance obtained between the supply and demand of growth resources by plants. Where defoliation is relatively infrequent and lax, plants may maintain balanced growth of root and shoot purely through shortterm physiological responses. However, as defoliation severity increases, morphological adjustments are needed to ensure homeostatic, whole-plant growth. The adaptability of forage species to various points on the continuum of defoliation pressure from lenient to severe depends on their inherent morphological and physiological characteristics. We concentrate on morphogenetic and structural determinants of plant regrowth following defoliation, drawing out the important linkages with the physiological responses. We examine the relationships between plant morphogenesis and sward structure, placing particular emphasis on phcnotypic plasticity as a process whereby plant and population structure can alter to maintain homeostatic growth in response to variation in defoliation management. The imporlnnce of meristem positioning within the sward and of meristem activity, interacting with defoliation management, as determinants of plant production and persistence is discussed. Relationships between plant morphogenesis, herbage growth dynamics and barvestable herbage production are examined and we identify the collection of fundamental physiological and morphological information for a wider array of forage species as an important research goal for improving the productivity and sustainability of the world's grasslands.
Physiology Of Plants Recovering From Defoliation, J H. Richards
Physiology Of Plants Recovering From Defoliation, J H. Richards
IGC Proceedings (1993-2023)
Short-term, whole-plant physiological responses of forage plants to defoliation and the characteristics that allow them to rapidly replace lost tissues are the focus of this review. The physiology of defoliationtolerant plants after moderate to severe defoliation has two distinct phases; the first is a transient period of one to a few days and the second is a readjustment of physiological activity and plant morphogenetic Integration that occurs over several weeks. When whole-plant photosynthetic capacity is reduced by substantial defoliation the effects of reduced carbon supply rapidly propagate through a growing plant, affecting shoot growth, root respiration, nutrient uptake and root …
Effects Of Regrowth Interval In The Autumn On Growth Of Grass In The Autumn/Winter Period, Edward G. O'Riordan
Effects Of Regrowth Interval In The Autumn On Growth Of Grass In The Autumn/Winter Period, Edward G. O'Riordan
IGC Proceedings (1993-2023)
The effect of Autumn grass regrowth interval on herbage production was studied during the Autumn/Winter periods of 1992/93 and 1993/ 94. Treatments, consisting of continual grass growth intervals ranging from 3 to 22 weeks after September 1, were used to examine the effects of Autumn grass regrowth intervals on herbage production. Herbage dry matter accumulation increased linearly from weeks 3 to 12, then plateaued and began to decrease after week 15 (mid- December). Dead material increased over time. Repeatedly harvested swards (every, 3, 4 or 5 weeks) generally produced less (P<0.05) herbage dry matter than corresponding continual growth treatments. Sward digestibility remained high (780 g/kg) for 9 to 10 weeks) and then declined. Highest digestibilities were seen on the more frequently defoliated treatments. Spring herbage production was highest in treatments which had been harvested under a long regrowth interval during the previous autumn.
Effect Of White Clover Defoliation On Seed Production And Maturity, Slepetys, R Dapkus
Effect Of White Clover Defoliation On Seed Production And Maturity, Slepetys, R Dapkus
IGC Proceedings (1993-2023)
Experiments were carried out in Lithuania over the period 1990- 1995. They involved white clover (Trifolium repens L.) cultivars Atoliai (large - leaved) and Bitunai (intermediate - leaved). Different defoliation treatments were carried out at a height of 5, 10 and 15 cm every week over the period from 7 May to 18 June. On 21-28 May, two more treatments consisting of an application with 0.5 and 1.0 l ha-1 reglone were added. When defoliation was carried out on 11-18 June, the seed of cv. Bitunai and cv. Atoliai matured 7 d and 13 d later, respectively than the …
Utilization Of Regrowth For Forage In Seed Stands Of Meadow Fescue (Festuca Pratensis Huds.), Lars T. Havstad
Utilization Of Regrowth For Forage In Seed Stands Of Meadow Fescue (Festuca Pratensis Huds.), Lars T. Havstad
IGC Proceedings (1993-2023)
Intensive utilization of autumn regrowth for forage production was compared to other autumn treatments in nine seed production fields of meadow fescue (Festuca pratensis) during 1993-96. Uncut plots without a N application in autumn always had the lowest number of reproductive tillers and the lowest subsequent year seed yields. Intensive utilization of regrowth, by application of 80 kg N ha-1 immediately after seed harvest and forage harvests in September or October, did not have any negative impact on the following yearsí seed yields. Delaying forage harvest from 10 September to 10 October increased forage yields, but lowered the …
Biomass Partitioning In Grasses Subjected To Defoliation, M Gutman, I Noy-Meir, D Pluda, S Rothman
Biomass Partitioning In Grasses Subjected To Defoliation, M Gutman, I Noy-Meir, D Pluda, S Rothman
IGC Proceedings (1993-2023)
Containerized plants of Perennial wild barley (Hordeum bulbosum) grown from corms and of Wild emmer wheat (Tritium diccocoides) grown from seeds, were grown in environmental conditions comparable to those encountered under field conditions. Both species were subjected to 3 defoliation frequencies ( once, twice and three times during the season) each at 3 different clipping heights (1, 2.5 and 5 cm above ground level ) plus a control treatment (10 treatments in all). Wild emmer wheat control plants had significantly higher cumulative total and reproductive biomass over all harvests than all clipped plants. Clipping height and …
Effect Of Frequency And Intensity Of Defoliation On Oat- Vetch Mixture, M J. Arzadun, M H. Vallejos, M M. Piersanti
Effect Of Frequency And Intensity Of Defoliation On Oat- Vetch Mixture, M J. Arzadun, M H. Vallejos, M M. Piersanti
IGC Proceedings (1993-2023)
An experiment was conducted to evaluate the effect of different cutting regimes on productivity and complementarity between oat and vetch in a mixture. The treatments were allocated in a factorial design on a split-split-plot disposition: they were 3 cutting frequencies (each 35, 70 and 105 days), 3 cutting heights (2, 8 and 14 cm above ground) and 3 crops (oat, vetch and the 1:1 mixture). Forage production (dry matter per hectare) and complementarity between species Relative Yield Total (RYT) were evaluated. The highest forage production (p- 0.05) was obtained with a cutting height of 2 cm and a frequency of …
Defoliation Frequency And Intensity Of Arrhenathherum Elatius, G H. D'Angelo, E B. Postulka, L Ferrari
Defoliation Frequency And Intensity Of Arrhenathherum Elatius, G H. D'Angelo, E B. Postulka, L Ferrari
IGC Proceedings (1993-2023)
This experiment was conducted with the aim of studying whether the frequency and intensity of defoliation of the temperate grass fromental (Arrhenatherum elatius (L.) Presl.) affected its total dry matter (DM)/ha yield as well as the seasonal distribution of forage. Plots were seeded in 1988 and data collected from 1989 to 1991. Two frequencies and two intensities of defoliation were combined in a two factor randomized complete block design with six replications. Treatment plots were cut each year from early autumn to late spring. ANVA, Tukey and Dunnett tests were applied to find out differences between treatments and between …
Carbohydrate Reserves Of Perennial Grasses: Effect Of Drought And Defoliation Intensity, S P. Boschma, M J. Hill, J M. Scott, J J. Lutton
Carbohydrate Reserves Of Perennial Grasses: Effect Of Drought And Defoliation Intensity, S P. Boschma, M J. Hill, J M. Scott, J J. Lutton
IGC Proceedings (1993-2023)
The carbohydrate reserves of six perennial grasses were measured during exposure to drought and defoliation over spring-summer and summer-autumn seasons. Of the six species assessed, tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) had the highest level of reserves while wallaby grass (Danthonia richardsonii) had the lowest levels. The results indicate that during the spring-summer period drought intensity had a greater effect on plant reserves than defoliation intensity. However, defoliation had a greater effect on reserves during the summer-autumn period. It is suggested that tiller reserves may be most affected when drought is …
Tiller Dynamic Of Dwarf Elephantgrass (Pennisetum Purpureum Cv. Mott) Under Defoliation, T Clavero
Tiller Dynamic Of Dwarf Elephantgrass (Pennisetum Purpureum Cv. Mott) Under Defoliation, T Clavero
IGC Proceedings (1993-2023)
A field study was conducted at the Animal Production Research Center of the University of Zulia, Venezuela. The objective of this experiment was to evaluate the tiller dynamic of dwarf elephantgrass (Pennisetum purpureum cv. Mott) under three cutting frequencies (CF) 28, 42 and 56 days and three cutting heights (CH) 10, 20 and 40 cm in order to estimate basal (BT), aerial (AT) and dead tillers (DT). The experiment was laid out as a split-plot trial with three replications. The number of basal tillers increased as CF was shortened and CH was increased. The intensity of defoliation independent of CF …
Phosphorus Availability, Defoliation Tolerance, And Genetic Differentiation In White Clover, D F. Chapman
Phosphorus Availability, Defoliation Tolerance, And Genetic Differentiation In White Clover, D F. Chapman
IGC Proceedings (1993-2023)
The genetic composition of mixed populations of white clover growing in low fertility, grass-dominant hill pastures was estimated four and eight years after populations were established. Populations were based on an adapted ('Grasslands Tahora') or poorly adapted ('Grasslands Huia') cultivar, and received either no fertiliser, or 35kg P /ha /year. The P response curve of surviving plants was also determined, and compared with plants grown from 'standard' seedlines of the respective cultivars. Between years 4 and 8, the proportion of the populations constituted by plants true-to-type for the sown cultivar remained steady at 56 - 58% for Tahora, but fell …
Nitrogen And Co2 Effects On Remobilization Of Root And Crown Reserves For Regrowth Following Defoliation, R H. Skinner, J A. Morgan, J D. Hanson
Nitrogen And Co2 Effects On Remobilization Of Root And Crown Reserves For Regrowth Following Defoliation, R H. Skinner, J A. Morgan, J D. Hanson
IGC Proceedings (1993-2023)
The effect of carbohydrate and nitrogen reserve remobilization during the first 4 d following defoliation on subsequent regrowth was studied under different soil nitrogen and atmospheric CO2 conditions. On a structural dry matter basis, elevated CO2 increased carbohydrate concentration without affecting total nitrogen in roots and crowns. High soil nitrogen had the opposite effect, increasing nitrogen concentration with no effect on nonstructural carbohydrates. Regrowth was significantly correlated with total nitrogen concentration at the time of defoliation. Carbohydrate concentration was not related to subsequent regrowth, nor was there a consistent correlation between carbohydrate or nitrogen remobilization and regrowth. No nitrogen remobilization …
An Overview Of The Physiology And Biochemistry Of N Reserves Mobilization In Forage Species, F Le Dily, A Ourry, J Boucaud
An Overview Of The Physiology And Biochemistry Of N Reserves Mobilization In Forage Species, F Le Dily, A Ourry, J Boucaud
IGC Proceedings (1993-2023)
Recent works focusing on the physiological and biochemical events associated to perennial forages sustainability (re-growth after defoliation, winter survival), provided evidence that vegetative storage proteins (VSPs, ca proteins stored in remaining organs and specifically mobilized) were key organic compounds for shoot regrowth. Attempts to elucidate environmental conditions involved in VSPs deposit ability of different species are under progress today. In contrast, mechanisms of spring- or cut-induced proteolysis are investigated at a lesser extend. This contribution is an opportunity to summarize our knowledge of N-reserves mobilization and to set the question of VSPs breakdown regulation.
Intraspecific Competition In Lucerne And Relationships With Reserve Availability, Jean Christophe Avice, Alain Ourry, Gilles Lemaire, Jeffrey J. Volenec, Jean Boucaud
Intraspecific Competition In Lucerne And Relationships With Reserve Availability, Jean Christophe Avice, Alain Ourry, Gilles Lemaire, Jeffrey J. Volenec, Jean Boucaud
IGC Proceedings (1993-2023)
Below-ground reserves are thought to provide an indication of a forage potential for shoot regrowth after defoliation. The aim of this work was to re-evaluate the causal relationships existing between organic reserves (non-structural carbohydrates and N reserves) and shoot regrowth of alfalfa. The variations brought about by cultivar differences (cv Lodi or Europe), length of the previous regrowth period (30 or 45 d), or by intraspecific competition for light within a dense canopy, were studied. Field grown plants were harvested at weekly intervals, and separated as dominant, intermediate and suppressed plants. Shoot regrowth yield was determined and taproot were analyzed …
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds, Lars T. Havstad
Effects Of Light Intensity And Defoliation On The Receptiveness For Primary Induction In Festuca Pratensis Huds, Lars T. Havstad
IGC Proceedings (1993-2023)
Seedlings of Festuca pratensis Huds. (cv. Salten) were raised at three different light intensities (141, 85 or 28 (mol m-2s-1 ) for 7 weeks after emergence and then either left uncut or defoliated 40 or 80% of total leaf area, before transfer to primary induction (6°C, natural short days) for 12, 15 or 18 weeks. Percentage of heading plants was more affected by the duration of primary induction than by light intensity and defoliation prior to induction. The results lend no support to the existence of a juvenile stage in seedlings of Festuca pratensis. Defoliation had less influence on …
Leaf Anatomy And Ultrastructure Of Poa Ligularis After Defoliation And Water Stress, M G. Klich, R E. Brevedan, S C. Villamil
Leaf Anatomy And Ultrastructure Of Poa Ligularis After Defoliation And Water Stress, M G. Klich, R E. Brevedan, S C. Villamil
IGC Proceedings (1993-2023)
The objective of this study was to determine the effect of defoliation and water stress on leaf anatomy and the mesophyll cell ultrastructure of Poa ligularis. Anatomical differences were detected mainly at epidermal level. Under water stress, leaf roughness was enhanced since the epidermal-cell surface contours became conspicuous. Under defoliation the microscopic roughness decreased as a result of fewer epicuticular wax crystals being formed. Defoliation produced an enhancement of the interlamellar spaces in the irrigated plantís chloroplast. Under no defoliation conditions, chloroplast structure was not affected by water stress. When subjected to water stress, lightly defoliated plants presented chloroplasts …
Root Nitrogen Cycling And Alfalfa Stress Tolerance, J J. Volenec, B C. Joern, L D. Barber, S M. Cunningham, A Ourry
Root Nitrogen Cycling And Alfalfa Stress Tolerance, J J. Volenec, B C. Joern, L D. Barber, S M. Cunningham, A Ourry
IGC Proceedings (1993-2023)
Our hypothesis is that certain root N pools are utilized preferentially during the early shoot regrowth. Our objective was to determine the relative contribution of crown N, root N, and specific root N pools to shoot regrowth after defoliation. We used 15N to follow N into and out of crowns, roots, and specific root N pools, to regrowing shoots after defoliation. The low molecular weight N pool (amino acids, inorganic N,...) acquired 15N rapidly within 2 d of N application. Movement of 15N into the protein-N and insoluble-N pools was delayed initially, but continued until 8 d after N application. …
Effect Of Species Horizontal Distribution On Defoliation Of Ryegrass-Clover Swards Grazed By Sheep, P C. De Faccio Carvalho, F Louault, M Lafarge
Effect Of Species Horizontal Distribution On Defoliation Of Ryegrass-Clover Swards Grazed By Sheep, P C. De Faccio Carvalho, F Louault, M Lafarge
IGC Proceedings (1993-2023)
Defoliation events on labelled white clover (Trifolium repens) growing points or ryegrass (Lolium perenne) tillers were measured during grazing tests by sheep with swards consisting of mixed ryegrass-clover (MIX) or alternate strips of clover and ryegrass (STRIP). Sward surface height was maintained at 6.4 cm by lawnmower cuts in order to obtain a similar surface height for both species. On average, during 13 grazing tests in STRIP and 11 in MIX swards, clover was the more defoliated species : 23.3% of the growing points in STRIP and 26.5% in MIX swards were defoliated compared to 16.2% …
Effects Of Defoliation Frequency On Foraging Selective Behaviour In Pasture With Paspalum Dilatatum, G L. Acosta, A T. Ayala Torales, V A. Deregibus
Effects Of Defoliation Frequency On Foraging Selective Behaviour In Pasture With Paspalum Dilatatum, G L. Acosta, A T. Ayala Torales, V A. Deregibus
IGC Proceedings (1993-2023)
The objective was to assess defoliation effects exerted by sheep grazing on a pasture composed by falaris and dallisgrass, at two phenological stages during spring and summer. A sown pasture of Phalaris aquatica and Paspalum dilatatum were grazed at two phenological stages: stage I (SI), with no more than 5% of reproductive tillers, and stage II (SII), with at least 70% of reproductive tillers. Tillers of both grass species were marked with plastic colour rings along two transects in each plot. Phenological stage of tillers, and the number, age and length of each leaf per tiller were registered. Tiller defoliation …