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Estructura y función nictinástica de la vaina foliar de Coespeletia Cuatrec.

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Author(s): Torres, Fresia

Journal: Plantula
ISSN 1316-1547

Volume: 3;
Issue: 2;
Start page: 88;
Date: 2003;
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Keywords: Asteraceae | Coespeletia | Superparamo | Anatomy | Pulvínuli | Nictinastic movements.

ABSTRACT
The structure of the foliar sheath of the five studied species of Coespeletia (C. alba, C. lutescens, C. moritziana, C. spicata, and C. timotensis), rosette plants that grown in the superparamos of the State of Mérida (Venezuela) have a pulvinular structure; that possesses a parenchima reservant of water constituted by cells with thin walls and intercellular spaces, surrounded by a compact parenchima constituted by smaller cells with thick walls, colénquima and sometimes with groups of esclereids (C. lutescens, and C. timotensis). The parenchima reservant of water governs the mechanism of the nictinastics movements in the rosette functional leaves by changes of its turgence in response to endogen stimuli like the flow of potasio and exogens like the environmental variations of factors, especially the descent of the nocturnal temperature. This process reinforces the protection of the young leaves to the apical bud as a strategy of adaptation to the adverse environmental conditions propious of páramo. It is presumed that in this process the variation of the angle of insertion of the leaves be related to the volume of reservant water parenchima present in the structure of each one of the foliar sheath.
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