| Titre : |
Turnover and conservation of nutrients in the pachycaul Senecio keniodendron |
| Type de document : |
texte imprimé |
| Auteurs : |
E. Beck, Auteur |
| Importance : |
pp. 215-221 |
| Langues : |
Anglais (eng) |
| Catégories : |
[Espèces (in biblio)] Senecio
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| Résumé : |
"Pachycaul senecios from the upper Afroalpine zone produce stems up to 11 m tall which are coated with marcescent leaves. Each stem or branch is terminated by a huge leaf rosette composed of 30–120 leaves which surround the central cone-shaped leaf-bud. During the course of a year about 50–60 leaves are produced from the bud (Beck et al. 1980) and in principle the same number of mature leaves at the outer periphery of therosette become senescent and die. The leaves are up to 50 cm long and 15–20 cm wide. Senescence commences at the tip which becomes yellow and subsequently necrotic. Yellowing of the lamina spreads from the tip downwards to the base. A senescing leaf, the upper part of which was already partially necrotic, was found to be still capable of photosynthesis in the lower part (E. Beck, unpublished data). This mode of gradual senescence suggests that a substantial portion of the nutrients can be mobilized and exported from the leaf before it dies. Table 11.1 shows the disappearance of nitrogen in the senescing leaf. The plant was located at 4200 m elevation in the Teleki Valley, Mount Kenya. The prolonged viability of the midribs presumably facilitates this mobilization. This type of internal recycling of nitrogen and other nutrients is common in higher plants. However, unlike the majority of the higher plants the pachycaul groundsels do not shed the dead leaves but maintain them as a dense collar around the stem." (source : auteur) |
| Type de publication : |
article de livre |
| Référence biblio : |
Beck E., 1994 - Turnover and conservation of nutrients in the pachycaul Senecio keniodendron. In : 1994 - Tropical alpine environments : plant form and function. Cambridge University Press, 215-221. |
| ID PMB : |
7608 |
| Permalink : |
http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=7608 |
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Turnover and conservation of nutrients in the pachycaul Senecio keniodendron