Agronomy and Crop Sciences Commons^™

Effects Of Late Spring Grazing Management On Tiller Age Profiles And Summer Autumn Pasture Growth Rates In A Perennial Ryegrass (Lolium Perenne L.) Sward, C Matthew, J X. Xia, J Hodgson, A.C P. Chu

IGC Proceedings (1977-2023)

In perennial ryegrass (Lolium perenne L.) swards large numbers of new tillers are produced shortly after flowering. This high tiller appearance rate is balanced by a high death rate of tillers produced in early spring so that relatively little change in sward tiller numbers occurs (Colvill and Marshall, 1984, Korte, 1986). Tallowin (1982) showed, however, that differences in grazing management can affect the percentage of early spring tillers surviving, and so result in different tiller age profiles in the following summer. This paper reports the results of an investigation of the effects on tiller age profiles and subsequent pasture …

Matric Potential Of Clay Loam Soils On Arid Rangelands Of The Southwestern United States, C H. Herbel, R P. Gibbens

IGC Proceedings (1977-2023)

Precipication is the major climatic factor affecting plant growth on arid rangelands of the southwestern United States. Soil water on floodplain sites is derived from infiltration of pre­cipitation and run-in water from adjacent slopes. We char­acterized the soil matric potential at three floodplain locations, to help understand the functioning of the soil water component of the floodplains ecosystem of arid rangelands.

Physiological Ageing In Young Leaves Of Digitaria Eriantha (Steud), M M. Wolfson, C F. Cresswell

IGC Proceedings (1977-2023)

In a previous paper, Wolfson and Cresswell (1985) demonstrated that single leaf photosynthetic rates measured on successive leaves near the meristematic tip, in plants treated with different forms and concentrations of nitrogen, decreased reaching very low levels after four month's growth, irrespective of the treatment applied. As the leaves were considered to be young and they were not shaded in any way, it was expected that the photosynthetic rate would remain fairly high throughout the growing period. Therefore it was suggested that the leaves underwent some form of programmed metabolic ageing even though they were still structurally and phy­siologically young. …

Performance Of Cartenoid Pigments Of King Gras (Pennisteum Purperum) Mutants, J Lauzan, R S. Herrera, R O. Martinez, R Cruz

IGC Proceedings (1977-2023)

Previous studies from this series have indicated the varia­bility reached in respect to yields and quality of the king grass clones obtained by in vitro tissue culture. The study of the photosynthetic pigments could contribute to explain the performance of these somaclones in respect to their growth and development. Thus, the objective of the pre­sent experiment was to learn the content and variation of chlorophyll a, chlorophyll b and carotenoids.

Nitrogen And Carbohydrate Mobilizations During Regrowth Of Defoliated Lolium Perenne L., A Ourry, B Gonzalez, J Bigot, J Boucaud, J Salette

IGC Proceedings (1977-2023)

It is generally reported that carbohydrate and organic nitro­gen reserves contribute to re-growth of new foliage in perennial grassland species subjected to clipping management. Only few studies are concerned with the comparative pattern of the mobilization, translocation and recovery of carbohydrate and nitrogen reserves during re-growth following defoliation. Davidson and Milthorpe (1966) have suggested that proteins are mobilized to produce energy in the absence of photosyn­thate whereas non-structural carbohydrates are generally con­sidered as the major organic reserves mobilized during re­growth (White, 1973). The objective of this study was to determine the origin of the mobilized nitrogen compounds and to follow …

Using 13c/12/C Ratio To Discriminate C3 And C4 Plants In Grassland, Lin Xiaoquan

IGC Proceedings (1977-2023)

Smith (1971) had determined the delta13C for plant tissue from 104 species representing 60 families. Higher plants fall into two categories, those (C3) with low delta13C value ( 24 %to 34 %), those (C4) with high delta13C values ( 6 % to 19 %). Now this method and its theoretical basis for plant fraction­ation were developed by many studies (O'Leary, 1981 ; Farquhar et al., 1982), and extensively applied to the domain of the ecology (Tieszen, 1987). In this paper, the delta 13C values of plants were determined by spectrometer and C3 or C4 photosynthetic type was discriminated for 27 …

Stand Characteristics Of Irrigated Cocksfoot Regrowth And Leaf Area Increasing, M Duru, A Langlet, S Rouzies

IGC Proceedings (1977-2023)

For grasses, high leaf area index (LAI) extension rate is necessary to intercept much radiation and to increase the growth rate (Gosse et al., 1986). The LAI extension rate depends on stand status just after the cut : tiller density (Nelson and Zarrough, 1981), residual leaf area and reserves level (Smith, 1974), plant nutrition (nitrogen especially). We study the setting up of LAI for vegetative regrowths according to nitrogen nutrition and different stand status : tiller number and size.

Comparison Of Photosynthetic Enzyme Activity And Identification Of C3 Or C4 Plant For 40 Forages Species Growing On Meadow Steppe In The Northeast Of China, Yin Lijuan, Hou Shuhuai, Shi Decheng, Zhu Ling

IGC Proceedings (1977-2023)

Because the plants with different photosynthetic pathways have distinct photosynthetic or physiological features, the environmental conditions they adapted are different. For example, C4 plant is more adaptable to high temperature, high light intensities and arid area than C3 plant. The characters of C4 plants, such as high light saturation point, low CO2 compen­sation point and so on, make them get higher photosynthetic efficiency than C3 plants, their photosynthetic yield and growth rate are generally over C3 plants. Because the characters of adaptability and the distribution are different for the plants with different photosynthetic pathways, according to the change of ratio …

Levels Of Abscisic In Lateral Buds During Regrowth Of Sorghum Biocolor M., H Nojima, S Fuketa, A Isoda, Y Takasaki

IGC Proceedings (1977-2023)

Lateral bud (tiller) development in grasses is important because tillers may contribute to yield of certain cereal and for­age crops. Especially in herbage grasses, lateral bud release after cutting can result in increased yield and persistence. It is required to elucidate the physiologycal mechanisms controlling tillering. Hormonal regulation for bud release in grasses has been studied by some investigators (Langer et al., 1973; Yeh et al., 1976; Sharif and Dale, 1980; Harrison and Kaufman, 1980, 1982; Isbell and Morgan, 1982; Nojima et al., 1985; Woodward and Marshall, 1988; Richard et al., 1988). Cytokinins are recognized as the hormone which promote …

Ryegrass Herbage Yield Components And Their Response To Water Deficit Stress, D J. Barker, A.C P. Chu, C J. Korte

IGC Proceedings (1977-2023)

The response of grassland production (herbage mass) to factors limiting its production, can be considered the collective response of a number of components. Understanding the impact of factors limiting individual components will aid understanding of factors limiting total production. Pre-requi­site to such an analysis is quantification of the contribution of each component to herbage mass. Perhaps even more import­ant are the dynamics (rate of change with time) of these components and their response to factors such as water stress.

The objectives of this study were : 1) to assess the importance of seven components to herbage mass using principle component …

Variability Of Leaf Area Index Extension Rate On Permanent Grasslands, M Duru

IGC Proceedings (1977-2023)

Canopy growth is related to solar radiation intercepted (PARa), (Greenwood et al., 1986; Gosse et al., 1986). The canopy interception efficiency ( i: i = P ARa/P ARc) is related to leaf area index (LAI). In spring, for grasses i: i = 70 % when LAI = 2 (Lemaire, 1985). The faster the LAI extension rate is, the greater the dry matter yield is. We study nitrogen and grass­land type effects, with phosphopotassic soil fertility level and botanical criterion.

Cinteique De La Croissance Foliarie Et Stolonifere D’Un Peuplement De Digitaria Decumbens Au Cours De La Repousse, P Cruz, G Alexandre, H Baudot

IGC Proceedings (1977-2023)

II existe en climat tropical un grand nombre de graminees fourrageres de type stolonifere. Parmi elles on retrouve de nom­breuses especes dans des genres tels que Digitaria, Cynodon et Brachiaria lesquels representent a eux seuls une tres grande proportion des surfaces herbageres des pays tropicaux, dont Jes iles de la Carai:be Dans ces especes, la production est le resultat de la croissanc de d��ux ense?1ble�� d'organes, feuilles et stolons, dans des pro­portions qm vanent fortement en fonction du temps de repousse et des saisons (Salette, 1971; Crespo, 1985). Connais­sant Jes differences dans la valeur nutritive de ces organes (Her­rera, 1979) …

Distribution Des Assimilats Et Fixation D’Azote Chez Le Trefle Blanc: Influence De La Ramification Du Stolon, C Robin, V Guerin, A Guckert

IGC Proceedings (1977-2023)

Les apex de stolon representent des puits majeurs pour le car­bone chez le trefle blanc (Robin et al., 1987). Ce travail vise a definir !'impact d'une ramification sur la repartition des photo­synthetats. Ce puits supplementaire est susceptible d'induire notamment des relations de competition vis-a-vis des autres apex et des nodosites.

Growth And Gas Exchange Of Rhizoma Peanut (Arachis Glabrata Benth.) Subjected To Water Deficit, K A. Albrecht, J M. Bennett, G M. Prine

IGC Proceedings (1977-2023)

Rhizoma peanut (Arachis glabrata Beuth.) is a long lived per­ennial forage legume adapted to well drained soils of Florida and the humid tropics and subtropics that are prone to both long and short term moisture deficits. The nutritive value of rhizoma peanut is similar to that of alfalfa, thus it is an excel­lent supplement to tropical grass pastures. Prine (1983) reported that yields of 11 t/ha are regularly obtained in north­ern Florida and that yield potentials could be greater in areas with longer growing seaso��and well distributed rainfall. The influence of dryught on yield and physiological responses of rhizoma …

The Effect Of Nitrogen Deficiency On Carbon Partitioning In A Tall Fescue Sward, G Belanger, F Gastal, F R. Warembourg

IGC Proceedings (1977-2023)

Intercepted photosynthetically active radiation (PAR), light­use efficiency and assimilate partitioning are three major determinants of crop growth (Charles-Edwards, 1982). Gastal and Lemaire (1988) reported that the amount of intercepted PAR partly explained the differences in aerial DM yield obtained with contrasting N regimes applied to a tall fescue sward. They also indicated that light-use efficiency and assimi­late partitioning were involved in this N effect on DM yield but they could not differentiate between these two growth determ­inants. Very few field studies of the effect of a N deficiency on assim­ilate partitioning in forage grasses have been reported. Most studies conducted …

Etude Des Deux De La Nutrition Azotee Du Trefle Blanc (Trifolium Repens L.): Activite De La Nitrogenase Et De La Nitrate Reductase, D Schontz, C Robin, A Guckert

IGC Proceedings (1977-2023)

L'importance des deux voies de la nutrition azotee (assimila­tion de l'azote combine et moleculaire) du trefle blanc n'a ete etudiee qu'en terme de bilans 15N (Haystead et Lowe, 1977). L'objet de cette etude est de suivre la cinetique des activites de la nitrate reductase et de la nitrogenase au cours du cycle de developpement en presence de differentes concentrations en nitrates.

Effets Di Nitrate Sur La Croissance Et La Fixation D’Azote Chez Le Trefle Blanc (Trifolium Repens L.): Importance De La Souche De Rhizobium, D Schontz, C Robin, D Laurentie, A Guckert

IGC Proceedings (1977-2023)

Des apports d'azote combine sur des associations graminees­trefle blanc provoquent souvent un desequilibre favorable a la graminee. Cet effet peut etre attribue a une moindre competiti­vite de la legumineuse pour prelever l'azote combine (difference d'exploration du sol par le systeme racinaire) mais aussi a une moindre action de l'azote sur la croissance, du fait de !'inhibi­tion de la fixation. L'objet de cette etude est de tester !'influence de la souche de Rhizobium sur la sensibilite de la fixation d'azote et sur !es consequences de cette sensibilite sur la croissance du trefle en presence de differents niveaux de nitrates.

Leaf Growth In Lolium Perenne L., H Schnyder, S Seo, W Kuhbauch

IGC Proceedings (1977-2023)

Knowledge about the spatial distribution of growth rates within the growth zone of leaves is essential for the study of metabolism associated with the growth process (Silk 1984). Such data have been described for Festuca arundinacea Schreb. during the phase of rapid blade elongation (Schnyder and Nelson 1987, 1988) and Zea mays L. during one developmental stage (Hsiao et al. 1985). No developmental studies appear to have been made. This paper describes the spatial distribution of growth rates within the elongation zone of L. perenne leaves from shortly after tip emergence to shortly before cessation of leaf growth. Special …

Analysis Of The Aerial Part And Roots Of The Lucerne Crop To Improve The Breeding Method, P Rotili, L Zannone, G Gnocchi, S Proietti, C Scotti

IGC Proceedings (1977-2023)

In our research work we consider the lucerne crop as a « system», that means a set of elements with their reciprocal relationships (Rotili 1988). The elements of such a system are the plants ; the whole of their relationships is called the « structure » of the system ; it is expressed by the effects caused by the reciprocal interference among the plants on their mor­phology and physiology. Both these constituents of the system (the plants and the structure) have to be considered by the breeder to improve the lucerne crop. From some hundred experiments established with material genetically …

Relationship Of Leaf Export Of Carbohydrate To Rhizomatous Growth In Panicum Amarum L., D S. Fisher, J C. Burns, D H. Timothy, K R. Pond

IGC Proceedings (1977-2023)

Rhizomatous growth is desirable in pastures, yet many species used for grazing have exceedingly short rhizomes. In damaged pastures, vigorous rhizomes can provide for recovery of areas in which the stand has been lost. In breeding pasture grasses, selecting for high yields in a favorable environment may result in altered partitioning of carbohydrate between shoots and roots to favor above ground growth. In the Panicum genus, this can occur even in spaced plantings in which plants may exceed 2 m in height. The following experiment utilized a high rhizome (HR), an intermediate rhizome (IR), and a low rhizome (LR) accession …