Data/hora: 09/06/2024 04:26:17

Biblioteca(s): | Embrapa Trigo.
Data corrente: | 03/12/2010
Data da última atualização: | 23/08/2013
Autoria: | BLACKMAN, G. E.; BLACK, J. N.
Título: | Physiological and ecological studies in the analysis of plant environment. XI. A further assessment of the influence of shading on the growth of different species in the vegetative phase.
Ano de publicação: | 1959
Fonte/Imprenta: | Annals of Botany, London, v. 23, n. 1, p. 51-63, 1959.
Idioma: | Inglês

Conteúdo:

In a further analysis of the effects of varying light intensity on growth and development in the vegetative phase the reactions of thirteen herbaceous species have been recorded. In some experiments the degree of shading has been extended to 0.055 daylight, a level near or below the compensation point.

For Lathyrus maritimus, Trifolium pratense, and Vicia faba, the net assimilation rate is directly related to the logarithm of the light intensity, but for Helianthus annuus, T. repent, T. hybridum, Medicago sativa, Phaseolus multiflorus, and Lolium multiflorum the relationship, though curvilinear, is not logarithmic. It is concluded that for all species the assimilation rate of unshaded plants was limited by light even though in high summer the recorded light energy between 4,000–7,000 A averaged 1,900–2,200 foot-candles.

For all these species between daylight and 0.12 daylight the leaf-area ratio rises as the intensity decreases and in general the trend is logarithmic. When the degree of shading is increased to 0.055 daylight the logarithmic relationship still holds for L. maritimus and V. faba though this level is below the compensation point. For other species, such as P. multiflorus andH. annuus the trend may be reversed below 0.12 daylight and the ratio then falls.

When the light intensity is reduced from daylight to 0.5 daylight, then for the species already cited and for Lolium perenne, Phleum pratcnse, and Festuca pratensis the relative growth-rate is invariably depressed. At 0.055 daylight the relative growth-rate never exceeded 1 per cent. per day. For L. perennet, P. pratense, and Dactylis glomerata the reactions to shading of ‘hay’ and ‘grazing’ strains were different.

The ecological and physiological implications of these findings are discussed.

Palavras-Chave: | Plant environment.
Categoria do assunto: | F Plantas e Produtos de Origem Vegetal
Registro original: | Embrapa Trigo (CNPT)
Exemplares: | CNPT - (41554-1) - ADD - SP - PP - 15812 -  - 15812 - DIS