The grass plant—its form and function

Robson, Matthew J.; Ryle, Gilbert; Woledge, Jane

doi:10.1007/978-94-009-1187-1_2

Cited by 78 publications

(63 citation statements)

References 135 publications

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“…Além disso, sob baixa irradiância, o suprimento reduzido de fotoassimilados é alocado preferencialmente para os perfilhos existentes, em detrimento às gemas axilares (Robson et al, 1988), inibindo a produção de novos perfilhos.…”

Section: Resultsunclassified

Características morfológicas, estruturais e produtividade do capim-braquiária e do amendoim forrageiro submetidos ao sombreamento

Gobbi¹,

García²,

Neto

et al. 2009

R. Bras. Zootec.

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RESUMO -As características morfológicas, estruturais e a produção de matéria seca (PMS) do capim-braquiária (Brachiaria decumbens, cv. Basilisk) e do amendoim forrageiro (Arachis pintoi, cv. Amarillo) foram avaliadas em resposta a três níveis de sombreamento artificial (0, 50 e 70%). Utilizou-se o delineamento em blocos casualizados, com três repetições. Foram realizados três e dois cortes, respectivamente, para avaliação do capim-braquiária e do amendoim forrageiro. O amendoim forrageiro apresentou redução significativa na produção de matéria seca com o sombreamento apenas no segundo corte. A produção de matéria seca no capim-braquiária diminuiu linearmente nos dois primeiros cortes.O sombreamento crescente estimulou o aumento da altura média do dossel e do comprimento de pecíolos, colmos e lâminas foliares em todos os cortes das espécies avaliadas. O sombreamento promoveu diminuição linear da densidade populacional de perfilhos no dossel de braquiária em todos os cortes. O peso médio dos perfilhos, no entanto, só foi afetado no terceiro corte, quando aumentou de forma linear de acordo com os níveis de sombreamento. A relação folha:caule da gramínea e da leguminosa não foi afetada pelo sombreamento. A área foliar específica, a área foliar por folíolo e a área foliar por perfilho aumentaram significativamente com o aumento dos níveis de sombreamento. O índice de área foliar (IAF) reduziu de forma linear no segundo corte com o sombreamento do amendoim forrageiro e do capim-braquiária. O amendoim forrageiro e o capim-braquiária são forrageiras com bom potencial para avaliação e uso em sistemas silvipastoris com transmissão luminosa em torno de 50% da radiação fotossinteticamente ativa.Palavras-chave: Arachis pintoi, área foliar, Brachiaria decumbens, perfilhos, relação folha:caule Morphological and structural characteristics and productivity of Brachiaria grass and forage peanut submitted to shading ABSTRACT -The morphological and structural characteristics and dry matter production of signalgrass (Brachiaria decumbens, cv. Basilisk) and forage peanut (Arachis pintoi, cv. Amarillo) were evaluated in response to different shading levels (0, 50 and 70%). A randomized complete block design was used with four replications. Three and two harvests for signalgrass and forage peanut were made, respectively. Forage peanut showed significant reduction in dry matter production with shading, only in the second harvest. Dry matter production of signalgrass decreased linearly in the first and second harvest. In all the harvests evaluated, average sward height, petiole length, and stem and leaf blade length increased significantly with shading. Increasing shade levels promoted linear reduction in the tiller population density of signalgrass, in the three harvests evaluated. On the other hand, mean tiller weight was only affected in the third harvest, showing a linear increment with increasing shade levels. The leaf:stem ratio of signalgrass and forage peanut was not significantly altered by shade. Specific leaf area, leaf area p...

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Section: Resultsunclassified

Características morfológicas, estruturais e produtividade do capim-braquiária e do amendoim forrageiro submetidos ao sombreamento

Gobbi¹,

García²,

Neto

et al. 2009

R. Bras. Zootec.

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“…Furthermore, a shortcoming of the current study was not to differentiate between pseudostem and true stem; both were classified as stem. The level of true stem or pseudostem present is very much dependant on the stage of growth with higher levels of true stem present during reproductive growth (Robson et al, 1988). As pseudostem is a collection of leaf sheaths rolled together (Robson et al, 1988), it is more digestible than true stem.…”

Section: Sward Chemical Compositionmentioning

confidence: 99%

“…The level of true stem or pseudostem present is very much dependant on the stage of growth with higher levels of true stem present during reproductive growth (Robson et al, 1988). As pseudostem is a collection of leaf sheaths rolled together (Robson et al, 1988), it is more digestible than true stem. Evidence suggests that during vegetative growth, the digestibility of pseudostem is not significantly reduced compared with the leaf blade (Terry and Tilley, 1964), offering further explanation for the absence of a relationship between sward structure and chemical composition during the vegetative growth phase.…”

Section: Sward Chemical Compositionmentioning

confidence: 99%

Effect of perennial ryegrass (Lolium perenne L.) cultivars on the milk yield of grazing dairy cows

Wims

McEvoy

Delaby

et al. 2013

Animal

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The objective of this experiment was to investigate the effect of four perennial ryegrass cultivars: Bealey, Astonenergy, Spelga and AberMagic on the milk yield and milk composition of grazing dairy cows. Two 4 3 4 latin square experiments were completed, one during the reproductive and the other during the vegetative growth phase of the cultivars. Thirty-two Holstein-Friesian dairy cows were divided into four groups, with each group assigned 17 days on each cultivar during both experiments. Within each observation period, milk yield and milk composition, sward morphology and pasture chemical composition were measured. During the reproductive growth phase, organic matter digestibility (OMD) was greater for Bealey and Astonenergy (P , 0.001; 11.6%). AberMagic contained a higher stem proportion (P , 0.01; 10.06) and a longer sheath height (P , 0.001; 11.9 cm). Consequently, cows grazing AberMagic recorded a lower milk yield (P , 0.001; 21.5 kg/day) and a lower milk solids yield (P , 0.001; 20.13 kg/day). During the vegetative growth phase, OMD was greater (P , 0.001; 11.1%) for Bealey, whereas the differences between the cultivars in terms of sward structure were smaller and did not appear to influence animal performance. As a result, cows grazing Bealey recorded a higher milk yield (P , 0.001; 10.9 kg/day) and a higher milk solids yield (P , 0.01; 10.08 kg/day). It was concluded that grass cultivar did influence milk yield due to variations in sward structure and chemical composition.Keywords: perennial ryegrass, cultivar, sward structure, dairy cow, grazing ImplicationsThis study investigated the effect of four perennial ryegrass cultivars on dairy cow milk yield and identified the cultivar characteristics responsible for variations in milk yield. The information generated by this study will be of significant use in pasture-based production systems. As the study identified the cultivar characteristics responsible for animal performance, it will allow grass breeders to increase their focus on such traits. Animal performance-orientated breeding programmes should result in grass cultivars becoming available to farmers that will increase animal performance from grazed grass, thereby further improving the economics of pastoral-based animal production systems.

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“…Duru & Ducrocq (2000) reported that as cocksfoot plants grew up to 80 days of regrowth (N and temperature non-limiting conditions), the leaf appearance rate per tiller decreased and the lamina growth duration, lamina length (from 14 to 44 cm), and life-span (from 362 to 580° Cd) increased with its insertion level (sheath length). Similarly, Robson et al (1988) indicated that as a grass tiller ages, the proportion of old to young leaf increases because if the pseudostem in grasses is left intact, the emerging leaves will be relatively long and appear more slowly. Furthermore, because leaf appearance rate decreases and life-span increases during regrowth, the number of living leaves is fairly constant (Duru & Ducrocq 2000).…”

Section: Response Of Photosynthesis To Regrowth Durationmentioning

confidence: 99%

Modelling net photosynthetic rate of field‐grown cocksfoot leaves to account for regrowth duration

Peri

Moot²,

McNeil

et al. 2003

New Zealand Journal of Agricultural Research

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Maximum light-saturated photosynthetic rate (P max ) of field-grown cocksfoot (Dactylis glomerata L.) leaves was measured in a temperate, sub-humid environment (Canterbury, New Zealand). The aim was to derive an individual function for P max of newly expanded leaves against regrowth duration when other environmental factors were nonlimiting. The decrease in P max with regrowth duration was described by a quadratic function. From 20 to 25 days regrowth, P max per unit of leaf was constant and maximal (27.4 µmol CO 2 m -2 s -1 ). It then decreased by 0.42 µmol CO 2 m -2 s -1 per day of regrowth. The decline in P max was attributed to (i) differences in chronological age of the youngest expanded leaf as shown by changes in tiller morphology over time, and (ii) shading within the canopy during leaf expansion. These factors affected P max by decreasing the leaf nitrogen and chlorophyll content, and stomatal conductance. The function for regrowth duration was an additional factor included in a multiplicative model to predict P max with different levels of temperature, nitrogen, and water status, expressed as pre-dawn leaf water potential (Ψ lp ). The only interaction detected was when water stress increased (Ψ lp < -1.2 bar) and leaves had grown for 40-60 days. In this limited situation, stomatal closure at 40-60 days was greater than expected from the non-limiting condition. The inclusion of this function into a simple multiplicative model enabled 80% of the variation in P max for individual cocksfoot leaves to be explained by their temperature, nitrogen, water, and regrowth status. These functions could then be used to develop a canopy photosynthesis model for the prediction of cocksfoot pasture production.

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The grass plant—its form and function

Cited by 78 publications

References 135 publications

Características morfológicas, estruturais e produtividade do capim-braquiária e do amendoim forrageiro submetidos ao sombreamento

Características morfológicas, estruturais e produtividade do capim-braquiária e do amendoim forrageiro submetidos ao sombreamento

Effect of perennial ryegrass (Lolium perenne L.) cultivars on the milk yield of grazing dairy cows

Modelling net photosynthetic rate of field‐grown cocksfoot leaves to account for regrowth duration

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