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Registro Completo |
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Biblioteca(s): |
Embrapa Cerrados. |
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Data corrente: |
14/02/2000 |
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Data da última atualização: |
14/02/2000 |
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Autoria: |
OLIVEIRA, P. R. P. de. |
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Título: |
Effects of level and timing of shading on seed production in Panicum maximum cv. Gatton. |
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Ano de publicação: |
1981 |
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Fonte/Imprenta: |
St. Lucia: University of Queensland, 1981. |
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Páginas: |
132p. |
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Idioma: |
Inglês |
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Notas: |
M.Sc. |
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Conteúdo: |
The effects of shading on the seed production of Panicum maximum cv. (Gatton panic ) were studied at the University of Queensland, St. Lucia. Artificial swards were shaded to 25 ( L25 ) or 54 (L54 ) per cent of the sunlight received in a glasshouse for various periods related to the floral initiation (I), exsertion (E), anthesis (A) and ripening (R) stages of the first formed heads, or were unshaded. Inflorescences were identified according to their time of commencing anthesis from c. December 14 to c. February 11, and components of seed yield recorded. Spikelets were collected by hand shaking each inflorescence on ten occasions from 6 to 24 days after anthesis commencement. Head exsertion was continuous during the datum period and was slightly faster in the early phase. The number of branches differentiated on an inflorescence and (to a lesser extent ) the 100-seed weight were insensitive to the time of inflorescence appearance, but earlier formed inflorescences exhibited greater length, greater spikelet number per branch, and a higher ratio of florets forming caryopses. The rate of seed formation was therefore much higher in inflorescences commecing anthesis up to c. 21 days after the first heads appeared than in subsequent heads. The rate of spikelet sheldding from an individual inflorescence was linear on a number basis, but as barren spikelets tended to shed earlier than spikelets forming caryopses, the rate of caryopsis shedding showed a sigmoid relationnship with time. Because of the continuous head exsertion there was no single optimum harvest time; good seed recovery requires repeated harvesting procedures which collect the ripe caryopses as they are formed. Unshaded swards yielded 1510 gm--_2 shoots, and shading did not significantly reduce shoot yield. Shading reduced seed yield according to its intensity and duration . Total seed yield was 93 gm-2 in the control treatment, relative to 32-48gm-2 in the L54 series; in the L25 series yields varied from 4 in the continuously shaded IR treatment to 29 gm-2- in the late shaded AR treatment. Seed yield was reduced more through effects of shade on the processes determining the amount of seed formed per inflorescence than on the density of inflorescences, although plants shaded deeply from floret initiation orwards showed an apparent reduction in inflorescence density, associated with reduced tiller fertility, and delayed onset of anthesis.The number of branches differentiated on an inflorescence increased slightly with degree of shading. Deep shade slightly reduced 100-seed weight, the effect tending to increase with crop development whereas floret number per branch was more sensitive and to shade and the negative effects of shade were more pronounced in treatments shaded early in crop development. The component of yield most sensitive to shade was the ratio of florets forming seed; shade had persistent effects on inflorescences at all stages of development, including the period before head exsertion.There was also evidence of a slight increase in the rate of spikelet shedding in plants deeply shaded after anthesis. These findings require testing under field conditions. It is postulated that higher seed production potential of Gatton panic exists at sites receiving high levels of illuminance, and that crop management should be directed to promoting the flowering and seed ripening phase in periods which are not cloudy. MenosThe effects of shading on the seed production of Panicum maximum cv. (Gatton panic ) were studied at the University of Queensland, St. Lucia. Artificial swards were shaded to 25 ( L25 ) or 54 (L54 ) per cent of the sunlight received in a glasshouse for various periods related to the floral initiation (I), exsertion (E), anthesis (A) and ripening (R) stages of the first formed heads, or were unshaded. Inflorescences were identified according to their time of commencing anthesis from c. December 14 to c. February 11, and components of seed yield recorded. Spikelets were collected by hand shaking each inflorescence on ten occasions from 6 to 24 days after anthesis commencement. Head exsertion was continuous during the datum period and was slightly faster in the early phase. The number of branches differentiated on an inflorescence and (to a lesser extent ) the 100-seed weight were insensitive to the time of inflorescence appearance, but earlier formed inflorescences exhibited greater length, greater spikelet number per branch, and a higher ratio of florets forming caryopses. The rate of seed formation was therefore much higher in inflorescences commecing anthesis up to c. 21 days after the first heads appeared than in subsequent heads. The rate of spikelet sheldding from an individual inflorescence was linear on a number basis, but as barren spikelets tended to shed earlier than spikelets forming caryopses, the rate of caryopsis shedding showed a sigmoid relationnship with time... Mostrar Tudo |
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Palavras-Chave: |
Cultivar Gatton; Panicum maximu; Seed production; Shading. |
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Thesagro: |
Capim Colonião; Produção de Sementes; Sombreamento; Variedade. |
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Thesaurus Nal: |
varieties. |
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Categoria do assunto: |
-- |
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Marc: |
LEADER 04089nam a2200241 a 4500
001 1559617
005 2000-02-14
008 1981 bl uuuu m 00u1 u #d
100 1 $aOLIVEIRA, P. R. P. de
245 $aEffects of level and timing of shading on seed production in Panicum maximum cv. Gatton.
260 $aSt. Lucia: University of Queensland$c1981
300 $a132p.
500 $aM.Sc.
520 $aThe effects of shading on the seed production of Panicum maximum cv. (Gatton panic ) were studied at the University of Queensland, St. Lucia. Artificial swards were shaded to 25 ( L25 ) or 54 (L54 ) per cent of the sunlight received in a glasshouse for various periods related to the floral initiation (I), exsertion (E), anthesis (A) and ripening (R) stages of the first formed heads, or were unshaded. Inflorescences were identified according to their time of commencing anthesis from c. December 14 to c. February 11, and components of seed yield recorded. Spikelets were collected by hand shaking each inflorescence on ten occasions from 6 to 24 days after anthesis commencement. Head exsertion was continuous during the datum period and was slightly faster in the early phase. The number of branches differentiated on an inflorescence and (to a lesser extent ) the 100-seed weight were insensitive to the time of inflorescence appearance, but earlier formed inflorescences exhibited greater length, greater spikelet number per branch, and a higher ratio of florets forming caryopses. The rate of seed formation was therefore much higher in inflorescences commecing anthesis up to c. 21 days after the first heads appeared than in subsequent heads. The rate of spikelet sheldding from an individual inflorescence was linear on a number basis, but as barren spikelets tended to shed earlier than spikelets forming caryopses, the rate of caryopsis shedding showed a sigmoid relationnship with time. Because of the continuous head exsertion there was no single optimum harvest time; good seed recovery requires repeated harvesting procedures which collect the ripe caryopses as they are formed. Unshaded swards yielded 1510 gm--_2 shoots, and shading did not significantly reduce shoot yield. Shading reduced seed yield according to its intensity and duration . Total seed yield was 93 gm-2 in the control treatment, relative to 32-48gm-2 in the L54 series; in the L25 series yields varied from 4 in the continuously shaded IR treatment to 29 gm-2- in the late shaded AR treatment. Seed yield was reduced more through effects of shade on the processes determining the amount of seed formed per inflorescence than on the density of inflorescences, although plants shaded deeply from floret initiation orwards showed an apparent reduction in inflorescence density, associated with reduced tiller fertility, and delayed onset of anthesis.The number of branches differentiated on an inflorescence increased slightly with degree of shading. Deep shade slightly reduced 100-seed weight, the effect tending to increase with crop development whereas floret number per branch was more sensitive and to shade and the negative effects of shade were more pronounced in treatments shaded early in crop development. The component of yield most sensitive to shade was the ratio of florets forming seed; shade had persistent effects on inflorescences at all stages of development, including the period before head exsertion.There was also evidence of a slight increase in the rate of spikelet shedding in plants deeply shaded after anthesis. These findings require testing under field conditions. It is postulated that higher seed production potential of Gatton panic exists at sites receiving high levels of illuminance, and that crop management should be directed to promoting the flowering and seed ripening phase in periods which are not cloudy.
650 $avarieties
650 $aCapim Colonião
650 $aProdução de Sementes
650 $aSombreamento
650 $aVariedade
653 $aCultivar Gatton
653 $aPanicum maximu
653 $aSeed production
653 $aShading
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