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Title: Dark-chilling effects on C4 photosynthesis : comparison between grasses with different decarboxylating mechanisms
Author: Soares, Ana Sofia Contreiras, 1980-
Advisor: Arrabaça, Maria Celeste, 1944-
Keywords: Ácidos gordos foliares
Teses de doutoramento - 2008
Defense Date: 2008
Abstract: Climate changes are expected to occur with increase in the mean global temperature by 1.8-4.0ºC. However, low temperatures at night may occur, increasing the damages on the following warm day metabolism. Therefore this Thesis aims to study the effects of a short-term dark-chilling on photosynthesis of C4 plants from different metabolic subtypes, Paspalum dilatatum Poiret (NADP-ME), Cynodon dactylon (L.) Pers (NAD-ME) and Zoysia japonica Steudel (PEPCK). Results showed that the effects of dark-chilling in photosynthesis and leaf parameters on the subsequent warm period depend on the number of chilling nights and on the species studied. In general, a recovery or a tendency to recover after the second consecutive night-chilling was observed and C. dactylon showed a less sensitive photosynthesis to night-cold. Furthermore, the damages induced by one night-chilling depend on the light intensity on the subsequent warm day. Although the stress did not alter photosynthesis when measured at low light intensity in any of the species, it has altered the P. dilatatum and Z. japonica photosynthesis at moderate and high light intensities. One night-chilling also led to an accumulation of carbohydrates and a tendency to an increase in lipid unsaturation degree in all species. At the membrane level, Z. japonica seems to be the species better prepared to face chilling. Carboxylating enzymes were changed by stress, but the responses were different among species. A deeper study of P. dilatatum photosynthesis revealed a different regulation of photosynthesis and stomatal conductance on each leaf surface, with the adaxial surface presenting a higher decrease of photosynthesis after dark-chilling. Furthermore, differences were also found with light orientation to the leaf, being the photosynthesis on the whole leaf and on the adaxial surface more affected by dark-chilling under adaxial illumination.
Description: Tese de doutoramento em Biologia (Fisiologia e Bioquímica) apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008
Appears in Collections:FC - Teses de Doutoramento

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